RARE DISEASE
Human infection by orthopoxvirus
Human infection by orthopoxvirus
Human infection by orthopoxvirus
Drug discovery
7
drugs
With orphan designations
Overview
Human infection by orthopoxvirus, primarily caused by monkeypox virus (MPXV) and cowpox virus, manifests as a febrile illness with lymphadenopathy and a centrifugal maculopapular rash progressing to pustules. Transmission occurs via zoonotic exposure or close human contact, particularly through skin lesions or respiratory droplets. Post-smallpox eradication, declining population immunity has increased susceptibility, with MPXV emerging as the most clinically significant orthopoxvirus globally. Recent outbreaks highlight expanded human-to-human transmission, particularly in men who have sex with men (MSM), necessitating heightened clinical vigilance [1][6][12][19].
Burden
Clade I (Congo Basin) mortality: ≤10%; clade II (West African): 1–5% [6][12][19].
90,000 global cases (2022–2024), with complications including secondary infections, keratitis, and psychosocial stigma [6][15][19].
Economic and healthcare strain in endemic regions due to limited diagnostics and vaccine access [2][5][15].
Therapies
Antivirals: Tecovirimat (first-line, FDA-approved for smallpox/mpox) and brincidofovir (reserved for severe cases); cidofovir used off-label [3][13][17].
Supportive care: Pain management, hydration, and infection control.
Combination therapies: Investigational use of tecovirimat with ACAM2000 vaccine or brincidofovir in high-risk cases [3][8][17].
Categories: rare infectious diseases
Research Papers
1,917 drug discovery papers about Human infection by orthopoxvirus, with 2 first-in-class and 6 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
1,917 drug discovery papers about Human infection by orthopoxvirus, with 2 first-in-class and 6 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
categories:
Small molecules
proteins
2026-05-17 | Molecular mechanism of 2',3'-cGAMP degradation by monkeypox virus poxin-schlafen protein.
The World Health Organization had declared the multiregional outbreak of monkeypox a global public health emergency twice since 2022. Poxin from orthopoxviruses degrades the second messenger 2',3'-cGAMP of the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway to evade innate immune surveillance. Monkeypox virus (MPXV) poxin is fused to schlafen and the mechanism of how it catalyzes the degradation of 2',3'-cGAMP remains unclear. Here, we show that MPXV poxin-schlafen degrades 2',3'-cGAMP into Gp[2'-5']Ap[3'], suppressing interferon-β (IFN-β) induction mediated by the cGAS-STING pathway. The schlafen domain has no impact on the degradation of 2',3'-cGAMP mediated by the poxin domain. Crystal structures of MPXV poxin domain and its complex with Gp[2'-5']Ap[3'] reveal that 2',3'-cGAMP binds to a pocket formed by two monomers of the poxin dimer and induces closure of the pocket to trigger degradation. MPXV poxin exhibits a strict substrate specificity and does not degrade 3',3'-cGAMP, c-di-AMP, and c-di-GMP that also activate STING-mediated immune responses. These results unveil the molecular mechanism for 2',3'-cGAMP degradation by MPXV poxin-schlafen protein and provide the structural basis for the development of inhibitors against MPXV infection.
2026-03-06 | Lactoferrin blocks orthopoxvirus entry via heparan sulphate and regulates host antiviral pathways.
Current antiviral therapies for orthopoxviruses face critical challenges, including limited efficacy and significant toxicity, which impede outbreak containment and clinical management. Here, we identify lactoferrin as a potent antiviral agent against multiple orthopoxvirus strains. Combination administration of lactoferrin with brincidofovir or tecovirimat demonstrated additive efficacy, suggesting a potential clinical strategy to reduce individual drug toxicity. Mechanistically, lactoferrin blocks viral entry by competitively binding to heparan sulphate proteoglycans (HSPGs). It also suppresses viral replication by regulating host antiviral pathways, including down-regulating cytokines and upregulating TGF-β-dependent antiviral signalling pathways. We identify TGFBI as a virus-responsive target regulated by lactoferrin. Lactoferrin treatment restores TGFBI expression and activates downstream MAPK/ERK and JAK2/STAT3 signalling cascades, leading to enhanced interferon production and interferon-stimulated gene (ISG) expression. In a murine vaccinia virus (VACV) infection model, lactoferrin treatment reduced lung viral loads and histological damage. These results underscore lactoferrin's distinctive dual antiviral mechanism and highlight its translational potential as a safe and cost-effective prophylactic or therapeutic agent. It is particularly beneficial for immunocompromised populations in resource-limited settings during orthopoxvirus outbreaks.
2026-02-05 | Structural basis of mpox virus A30/H2 subcomplex formation.
The continuous spread of mpox disease caused by mpox virus (MPXV) has posed great threat to global public health. The postattachment membrane fusion process of MPXV is mediated by a multimeric protein machinery, termed as entry-fusion complex (EFC). Among EFC components, A30 and H2 are the earliest identified interaction pair and play important roles in virus entry. Here, we determine the crystal structure of MPXV A30/H2 subcomplex via the tandem-fusion strategy, and show that A30 undergoes large conformational rearrangements upon H2 binding. Structural analysis reveals extended intersubunit interface and highly conserved intermolecular interactions. In vitro binding data further clarify key residues and elements involved in the A30/H2 subcomplex formation. Finally, we show that the H2-A30 fusion protein, superior to A30 ectodomain alone or the ectodomain-mixture of H2+A30, can induce more potent neutralizing-antibody responses which could inhibit viral infection. These data provide valuable information for the understanding of poxvirus EFC assembly and the H2-A30-based immunogen design and optimization.
2026-02-01 | Immunological response patterns in human cowpox infection: A clinical analysis
Approximately 73% of documented human cowpox infections in Europe during the past decade have occurred in individuals born after the cessation of routine smallpox vaccination programs, highlighting a growing immunological vulnerability within these populations. This research examined the immunological response patterns in 86 patients diagnosed with human cowpox virus (CPXV) infection at a tertiary referral center in Amsterdam, Netherlands, between March 2020 and September 2023. Clinical immunological assessments included serial measurements of orthopoxvirus-specific IgG and IgM antibodies, cytokine profiling encompassing TNF-alpha, IL-6, IFN-gamma, and IL-10, and flow cytometric analysis of lymphocyte subpopulations. Patients were stratified into mild, moderate, and severe clinical categories based on lesion count, systemic involvement, and duration of illness. The results demonstrated that severe cases exhibited significantly elevated IFN-gamma concentrations with a mean of 168.4 pg/mL compared to 82.6 pg/mL in mild cases at day 14 post-infection. CD8-positive T lymphocyte expansion was most pronounced in severe infections, reaching 720 cells per microliter compared to 420 cells per microliter in mild presentations. Treatment with interferon-alpha supplementation in moderate and severe cases was associated with a 34.2% reduction in time to clinical resolution. These findings provide evidence supporting the clinical utility of immunological monitoring and interferon-based interventional strategies in managing human cowpox infections of varying severity.
2025-07-28 | The vaccinia virus protein, C16, promotes the ubiquitylation and relocalization of the antiviral E3 ubiquitin-ligase, TRIM25.
Poxviruses co-opt the ubiquitin (Ub)-proteasome system (UPS) to facilitate virus replication, evade the innate immune response, and block programmed cell death of infected cells. Moreover, the UPS is an integral component of innate immune signaling pathways used by the host to respond to infection. To further elucidate how the UPS is engaged early during poxvirus infection, we quantified viral and cellular peptides with a Ub remnant motif (diGly peptides) from lysates of uninfected and vaccinia virus Copenhagen strain (VACV-Cop)-infected HeLa cells. Of note, we identified several ubiquitylated peptides from the cellular antiviral protein, TRIM25, that were enriched for, or exclusively found, in VACV-Cop-infected cells. TRIM25 is an E3 ligase for Ub and the Ub-like protein, ISG15, and TRIM25 performs several functions including activating the type I interferon response. Higher-molecular weight, ubiquitylated TRIM25 species were evident as early as 1 h post-infection of HeLa cells with VACV-Cop, and they persisted throughout infection. Proteasomal or lysosomal degradation did not appear to be a major consequence of this ubiquitylation; however, TRIM25 ubiquitylation correlated with its relocalization to punctate structures in infected cells. C16, a Bcl-2 family-like protein encoded by identical genes on both arms of the VACV-Cop genome, was both necessary and sufficient to promote TRIM25 ubiquitylation and relocalization. These phenomena were not evident in cells infected with Orthopoxviruses lacking the genes encoding for C16. We postulate that the ubiquitylation and/or relocalization of TRIM25 induced by C16 could represent a novel mechanism for poxviruses to subvert the host antiviral response.IMPORTANCEUbiquitylation is a versatile post-translational modification that is required for poxviruses to replicate their genomes and evade host cell defenses to infection. At the same time, both degradative and non-degradative protein ubiquitylation are critical components of the innate and adaptive immune responses to infection. In this study, we opted for a proteomics approach to examine changes in protein ubiquitylation early after vaccinia virus infection with the goal of identifying novel ways by which ubiquitylation is exploited during infection. We demonstrate that many Orthopoxviruses utilize the Bcl-2 family-like protein C16 to promote the ubiquitylation and relocalization of the cellular E3 ubiquitin/ISG15-ligase, TRIM25, which we hypothesize represents a novel strategy by which these viruses evade the host cell antiviral response. Moreover, our findings hint that Orthopoxviruses may also have C16-independent strategies to interfere with the function of TRIM25.
vaccines
2026-08-11 | ACAM2000 vaccine safety and immunogenicity considerations for smallpox and mpox.
Smallpox, eradicated globally in 1980, remains a major biodefense concern due to retained Variola virus stocks and the absence of population immunity following cessation of routine vaccination. Monkeypox virus (MPXV), a related orthopoxvirus, has reemerged as a global public health threat, with major outbreaks in 2022 and renewed spread from 2024 onward. This review evaluates ACAM2000®, a second-generation live smallpox vaccine, summarizing its development, immunogenicity, efficacy, safety, regulatory status, and potential role in mpox prevention. ACAM2000 remains a critical medical countermeasure for smallpox preparedness and a valuable, though selective, tool for mpox prevention. Its high immunogenicity, rapid protection, and broad orthopoxvirus coverage must be balanced against a well-characterized safety risk profile.
2026-07-12 | Vaccinia virus and Monkeypox virus neutralizing and antigen-binding antibodies following subcutaneous and reduced intradermal doses of an MVA vaccine.
To expand the supply of the modified vaccinia Ankara (MVA) smallpox/mpox vaccine, fractional doses administered intradermally (ID) have been considered as alternatives to the standard dose given subcutaneously (SC). In a recent clinical trial, participants received the standard 108 infectious units of vaccine SC or a one-fifth (IDH) or a one-tenth (IDL) dose ID twice 28-days apart. Two weeks after the second dose, sera were analyzed using a vaccinia virus (VACV) strain Western Reserve plaque-reduction test (PRNT) with the conclusion that IDH but not IDL was non-inferior to SC. The present study extends the latter by quantifying neutralizing antibodies to the MVA vaccine and to monkeypox virus (MPXV) in the absence and presence of added complement and by assessing multiplex binding antibodies to individual VACV antigens (A27, A33, B5, D8 and L1) and the MPXV homologs (A29, A35, B6, E8 and M1). The main conclusions of the study are that the titers of MVA neutralizing antibodies induced by SC and IDH were not significantly different, whereas MVA neutralizing antibody titers induced by IDL were lower like the previous PRNT results. However, the titers of complement-enhanced MPXV neutralizing antibodies induced by SC were significantly higher than for both IDH and IDL immunizations, suggesting that the standard SC dose and reduced dose ID immunizations may not be equivalent. Additional analyses suggested that antibody binding to VACV B5 and D8 and MPXV B6 and E8 may serve as surrogates for neutralizing antibodies.
2026-06-22 | Pan-genome and reverse vaccinology for a multi-epitope vaccine against circulating post-2022 Monkeypox virus strains.
Since the 2022 outbreak, the number of Monkeypox cases worldwide has been increasing at an alarming rate. As of August 2024, approximately 99,000 people have been infected with the virus. The severity of this situation is further highlighted by the World Health Organization's (WHO) classification of the Mpox virus as a Public Health Emergency of International Concern (PHEIC) due to the increased fatality rate of approximately 3.6% in clade I. Targeting the virus's membrane-bound, enveloped, and extracellular proteins, our goal was to computationally develop and assess a broad-spectrum multi-epitope vaccine that elicits humoral and adaptive immune responses against Monkeypox virus (MPXV) infection. During an outbreak, a pan-genome-based reverse vaccinology approach can offer rapid, practical solutions to enduring problems in experimental vaccine design. The method involved screening 16 monkeypox genomes to identify viral targets, from which viral proteins were selected based on their antigenicity, location, and solubility. Immunoinformatics methods and algorithms were used to extract the proteins' putative T-cell and B-cell epitopes, which were combined to form several vaccine constructions. The tertiary structure of the chimeric vaccine construct's interaction with Toll-like receptor 4 (TLR4) was thoroughly assessed using the advanced techniques of molecular docking and molecular dynamics simulation. A pan-genomic analysis identified 80 core genes, which were then screened for proteins suitable for epitope-based vaccine design. From four of these selected proteins, T-cell and B-cell epitopes were extracted to create four distinct vaccine constructs. Appropriate adjuvants and linkers were incorporated into each construct to enhance its potential efficacy. Stability and immunogenicity analyses of each vaccine design yielded promising results. These findings suggest that the vaccine constructs could be effective in preventing monkeypox, warranting further experimental validation and supporting the application of similar strategies to combat other viral illnesses.
2026-06-16 | Tracking the Trail of Monkeypox: From Origins to Outbreak Control.
Monkeypox virus (MPXV), a zoonotic viral disease first identified in 1958, has re-emerged as a major global health concern. The first human case was reported in 1970 in the Democratic Republic of Congo (DRC), and since then, MPXV has demonstrated a clinical resemblance to smallpox, with transmission occurring through both animal-to-human and human-to-human contact. In 2022, the largest recorded outbreak resulted in over 30,000 cases across the Western Pacific, Asia, Europe, and the Americas. Subsequently, between 2022 and 2024, more than 100,000 confirmed cases were documented worldwide, leading the World Health Organization to declare MPXV a Public Health Emergency of International Concern (PHEIC) in August 2024. This review provides a comprehensive, up-to-date overview of MPXV, including its viral structure, life cycle, clinical manifestations, diagnostic strategies, vaccines, and emerging therapeutics. Furthermore, it examines current challenges in disease detection and control and identifies opportunities to strengthen surveillance, prevention, and treatment strategies. Overall, this article aims to serve as a consolidated resource on MPXV, highlighting its epidemiology, clinical significance, and implications for global public health preparedness.
2026-05-07 | Immunoinformatics driven multi-epitope vaccine design targeting clade IIb Mpox variant.
The Monkeypox virus (MPXV), an emerging zoonotic orthopoxvirus, has reemerged as a major global health threat, with the 2022 outbreak predominantly associated with Clade IIb lineages. The surface glycoprotein B21R (OPG210), a major virulence and immune-evasion factor, contains three lineage-defining amino acid substitutions (D209N, P722S, and M1741I) that distinguish Clade IIb from other variants, emphasizing its relevance as a vaccine target. In this study, an integrated immunoinformatics and molecular dynamics-based approach was employed to design a multi-epitope vaccine (MEV) targeting the B21R glycoprotein. Comprehensive B-cell, helper T-lymphocyte (HTL), and cytotoxic T-lymphocyte (CTL) epitopes were screened based on their immune-eliciting potential, non-allergenicity, cytotoxicity and global immunogenic coverage, and were subsequently assembled into a rationally engineered MEV construct. The modeled vaccine displayed potential affinity and conformational integrity in complex with immune receptors, as confirmed by molecular docking, normal mode analysis, and molecular dynamics simulations, which indicated favorable flexibility and compactness conducive to immune activation. By integrating clade-specific sequence variations, this study introduces a strain adapted vaccine design framework capable of addressing viral evolution and immune escape in contemporary MPXV strains. These findings highlight the potential of computational vaccinology as a rapid and cost-effective strategy for mpox vaccine design; however, further experimental and preclinical validation is required.
gene therapies
2026-06-19 | Epidemiology and characteristics of cases with monkeypox virus clade I in the WHO European Region, 2024 to 2025.
BACKGROUNDA public health emergency of international concern (PHEIC) was declared in August 2024 following a sharp increase in mpox cases linked to the emergence of monkeypox virus (MPXV) clade Ib.AIMWe aimed to characterise imported and locally acquired mpox clade I cases reported in the WHO European Region (WHO/Europe) since August 2024 and assess transmission patterns and response measures.METHODSWe collected data on MPXV clade I infections reported by countries in WHO/Europe through the International Health Regulations. We contacted reporting countries to collect age, sex, travel history, most likely route of transmission, clinical course, contacts and type of exposure, and implemented control and prevention measures.RESULTSBetween 14 August 2024 and 23 November 2025, 82 cases of MPXV clade I infection were reported; 45 were imported and 37 were infected in reporting countries. Seventy-nine were typed as clade Ib and two as clade Ia. Most imported cases reported heterosexual (n = 26) or close physical contact (n = 5) as possible exposure. Secondary transmission occurred in six households. One healthcare worker was infected. Since October 2025, further 17 autochthonous male cases were most likely infected through sex with other men.CONCLUSIONImported cases of MPXV clade I infection were associated with limited household transmission. The increase in autochthonous infections among men with recent sexual contact with other men suggests undetected spread in Europe, that may become sustained. Continued surveillance, case and contact investigation are needed to understand MPXV clade I epidemiology and drivers of MPXV clade I transmission in Europe.
2026-04-27 | Mpox (Monkeypox) in Pregnant Women, the Placenta and Fetus: Correlation with Maternal-Fetal Transmission, Pathology and Strain Differences from MPXV Clades Ia, Ib, IIa, and IIb.
Since the elimination of smallpox, mpox (monkeypox) is the most medically significant orthopoxvirus infection. As a result of numerous regional, national and global outbreaks of MPXV (mpox virus), there is an abundance of new data available on the effects of the different viral clades on clinical obstetrical and perinatal outcomes when infection occurs in pregnancy. In addition, there have been additional placentas from cases of congenital MPXV infection available for study. These recent data indicate that there are prominent differences between viral strains and their effects on the fetus, with MPXV Clade I strains (Ia, Ib) having the greatest risk for an adverse outcome in pregnancy, and Clade II strains (IIa, IIb) having far less risk. In particular, the ongoing outbreak of MPXV Clade Ib in the DRC indicates that there is a significant risk for adverse perinatal outcomes associated with infection in pregnancy, especially during the first trimester. These outcomes include spontaneous abortion, stillbirth, neonatal death and congenital mpox. The placenta in cases of congenital infection demonstrates abundant virus in the chorionic villi, with prominent involvement of Hofbauer cells. Similar to smallpox, transplacental transmission and adverse pregnancy outcomes are an important feature of certain strains of this orthopoxvirus infection when occurring in pregnant women.
2026-04-01 | Dynamic shift in the dominant transmission route of clade Ib monkeypox virus across networks with sexual and nonsexual contacts.
The intensifying outbreaks of the novel monkeypox virus clade Ib in the Democratic Republic of the Congo have raised global concern about the potential for wider epidemic spread. Some clade Ib mpox outbreaks have shown a distinct transmission pattern in which transmission associated with both sexual and nonsexual contacts coexist. Here, we characterize these outbreaks in a network epidemic model, which incorporates sexual and nonsexual contacts, and project age- and route-specific transmission potentials under a wide range of scenarios. Our analyses suggest that the dominant route of transmission may shift over time from sexual to nonsexual contacts, which leads to larger epidemics. The age groups contributing most to overall infections and mortality also change over time, suggesting that target groups for intervention should be adjusted accordingly. For countries at risk of travel-associated mpox outbreaks, these findings highlight the importance of monitoring evolving monkeypox virus transmission patterns and interacting transmission routes to support timely and effective control measures.
2026-03-30 | Emergence and diversity of monkeypox virus Clade IIb sub-lineages in Nigeria (1971-2023) and its role in the 2022 global outbreak.
The exact role played by Nigeria in the global monkeypox virus (MPXV) outbreak of 2022 remains unclear, despite exported cases to Singapore, the United Kingdom (UK), the United States of America (USA), and Israel from 2018 to 2022. We sought to resolve the origin of the 2022 MPXV global outbreak. All Nigerian MPXV whole genomes deposited in the EpiPox™ database were aligned using Nextclade v3.13.3 against the reference genome (NC_063383.1) for lineage and mutation analyses. Multiple sequence alignments were performed using MAFFT version 7, followed by maximum likelihood trees in IQ-TREE for clades A.3 and B.1 and visualised in iTOL viewer. We quantified total C → T substitutions as APOBEC3-related mutations. Seven clades or sub-lineages, namely: A (2017-2023), A.1 (2018 and 2019), A.2 and A.3 (2019), A.2.2 (2022), A.2.3 (2022 and 2023), and B.1 (2022) were observed. There was a gradual buildup of total substitution events (APOBEC3-related mutations) from 1978 to 2023, with a slight decline in 2020 but most pronounced in 2019, 2021, and 2022. Furthermore, total substitutions events were widespread across both variable and core regions of the MPXV genomes. The B.1 and A.3 maximum likelihood trees points to Nigerian ancestral roots, supporting our hypothesis that the B.1 sub-lineage originated in Nigeria. Our phylodynamics analyses showed peak distributions for the A.3 clade around 2013, while that of B.1 showed rapid spread of the virus in May 2022. The evolution rates of the for A.3 and B.1 were 6.94 × 10-5 and ∼ 3.091 × 10-4 substitutions/site/year, while their molecular clock signals were moderate with respective values of R2 = 0.56 and 0.56. Overall, our findings indicate that the B.1 sub-lineage, which triggered the 2022 outbreak, potentially evolved from A.3, with both lineages having their ancestral roots in Nigeria.
2026-03-14 | Genomic diversity of Clade Ia monkeypox virus in the Central African Republic, 2019-2024.
Monkeypox virus (MPXV) is a zoonotic pathogen known to be endemic to the Congo basin and West Africa, and which causes characteristic lesions disseminated on all skin surfaces of infected cases. Multiple MPXV outbreaks have been reported in the Central African Republic (CAR), a country in the Congo basin, at an increased frequency since 2020. The genomic history of these outbreaks in CAR is poorly characterized due to undersampling, with only a recent expansion in the number of sequences from CAR. Here, we report twenty-six new near-complete genomes from six prefectures of CAR, selected to represent outbreaks that occurred in the country between 2019 and 2024. Our analysis shows the sustained homogeneity of genomes in CAR, as all of them belonged to Clade Ia, but with an expansion of sub-lineages and therefore increased MPXV diversity within CAR. We highlight the introduction into CAR of a lineage previously known to occur only in Gabon and Cameroon, as well as the apparent regional clustering of MPXV genomes in CAR. Our analysis reveals limited APOBEC3-mediated activity, which is consistent with recent zoonotic origins and short human-to-human transmission chains observed in CAR. These analyses provide an in-depth view of the genomic diversity of MPXV in the Central African region.
small molecules
2026-07-10 | Severe mpox in an immunocompromised, non-traveller South African male.
Mpox is a zoonotic orthopoxvirus infection historically linked to being in endemic regions, travel and close physical contact, including within men who have sex with men (MSM) communities. We report a case of severe mpox in a heterosexual man with advanced human immunodeficiency virus (HIV) disease and no travel history to endemic areas. The patient developed extensive cutaneous disease and transmitted mpox to household contacts, illustrating non-sexual transmission. Management included supportive care and tecovirimat under Section 21 authorisation (a regulatory mechanism in South Africa permitting access to an unregistered medicine) with good clinical response. This case highlights the changing epidemiology of mpox, the risk of severe disease in immunocompromised patients, household and non-sexual transmission. We also emphasise the importance of early diagnosis, infection control and antiviral therapy when indicated.
2026-07-06 | Functional characterization of the poxvirus poly(A) polymerase
Poxvirus infections can result in human diseases, most notably smallpox, caused by variola virus (VARV), and mpox, caused by monkeypox virus (MPXV). Smallpox was eradicated in 1980 through vaccination; however, the discontinuation of vaccination programs has left the population vulnerable to emergent zoonotic MPXV or the potential reappearance of VARV. Part I of this thesis characterizes the orthopoxvirus poly(A) polymerase VP55 as a candidate antiviral target, using vaccinia virus (VACV) as the model system. The VACV poly(A) polymerase is a heterodimer composed of VP55 and VP39. This work demonstrates that VP55 selectively polyadenylates cellular noncoding RNAs (ncRNAs), targeting those involved in host regulation while sparing ncRNAs essential for translation. Moreover, VP55 expression inhibited host cell translation. VP55 also exhibited a distinct subcellular distribution compared to its known partner VP39 and, unexpectedly, associated with translation-related proteins. Based on these observations, a working model has been proposed in which VP55-mediated polyadenylation acts as a decoy mechanism for PABP, thereby rendering mRNAs transcriptionally inactive and establishing the importance of VP55 in viral infection. Poxviruses replicate entirely in the cytoplasm of infected cells. Efficient infection relies on the host translation machinery and, intriguingly, also requires nuclear host proteins. In Part II of this thesis, nuclear heterogeneous ribonucleoprotein (hnRNP) K was identified as essential for VACV replication, as its absence reduced viral protein and RNA levels. Upon infection, hnRNP K can translocate from the nucleus to the cytoplasm, where it shifts its RNA-binding preference toward viral transcripts. Although its protein-protein interactions remain unchanged, this redistribution suggests a functional repurposing. hnRNP K has been implicated in non-canonical translation initiation, and this work opens new avenues to investigate how VACV sustains translation under conditions of host translational shutdown.
2026-07-02 | Exploring drug repurposing for monkeypox virus: A structural and computational approach.
The increasing global threat posed by viral infections that are transmitted to humans from animals has intensified interest in emerging pathogens such as monkeypox virus (MPV). This study investigated the potential of drug repurposing as an efficient therapeutic strategy against MPV, focusing on its close genetic relationships with vaccinia and variola viruses. Due to the structural and evolutionary similarities among these orthopoxviruses, the Food and Drug Administration (FDA)-approved smallpox drug tecovirimat was selected as a reference drug. A descriptive-analytical approach was used to assess the binding energies of 38 FDA-approved drugs from four therapeutic classes. Molecular docking was performed against key target proteins from the genus Orthopoxvirus. Several compounds exhibited stronger binding energies than the reference drug tecovirimat, indicating their potential repurposing as anti-MPV agents. To further validate the stability and interaction dynamics of the top performing drug-protein complexes, molecular dynamics (MD) simulations were conducted, which supported their potential as viable candidates for future therapeutic development. These findings provide promising leads for the development of new therapeutic applications, thereby enhancing both the public health response and commercial value of repurposed treatments. MD simulations also supported the stability and feasibility of these promising drug-protein complexes.
2026-06-09 | Non-cyclic dinucleotide STING agonists abrogate MPXV infection
Abstract Mpox has emerged as a global threat to public health following several national and international outbreaks from 2022. Poxviruses deploy multiple strategies to counteract host immune defences including pathways leading to interferon (IFN) production. Here we demonstrate that depleting the viral 2’3’-cGAMP nuclease poxin restores activation of STING and IRF3 during MPXV infection despite the presence of other viral antagonists. We then demonstrate that non-cyclic dinucleotide (non-CDN) STING agonists are resistant to poxin; activate STING and IRF3 during infection; and potently suppress MPXV and orthopoxvirus replication in human primary fibroblasts and differentiated monocytes, where replication is completely abrogated. Mechanistically, non-CDN restriction requires STING, IFNAR and STAT signalling, and induces a unique transcriptional signature over IFNβ, enabling expression of additional cytokines. In vivo, non-CDN activity effectively reduces signs of illness and enhances survival in wild-derived castaneous mice inoculated with the virulent clade I MPXV. Our study reveals poxin as an Achilles’ heel of MPXV, that when bypassed by direct STING agonism, provides a promising novel anti-mpox therapeutic strategy with reduced risk of antiviral resistance.
2026-05-01 | Structural Modification of Tranilast against Poxvirus Based on α, β-Unsaturated Acrylamide Covalent Warhead and Confirmation of the Targets and Mode of Action.
The recurrent mpox outbreak has raised widespread global concern, yet specific antiviral therapies remain unavailable. Based on the α, β-unsaturated acrylamide covalent warhead of tranilast (TRA), we designed and synthesized 24 new TRA derivatives and evaluated their anti-orthopoxvirus activity using a VTT-Fluc assay. Compound 8l exhibited the most potent antipoxvirus activity and moderate activity against monkeypox clade IIb, with EC50 values of 6.1 and 47.1 μM, respectively, significantly outperformed TRA. In a VTT-Fluc nude mouse model, oral administration of 8l at 90 mg/kg achieved an 88.2% viral inhibition rate. Mechanistic studies revealed 8l exerted dual-target inhibition by acting on viral A17L and mRNA methyltransferase, thereby blocking membrane fusion and intracellular biosynthesis. The acrylamide warhead in 8l forms covalent adducts with serine residues of both targets via Michael addition. This work provides a promising covalent lead and identifies potential targets for the development of broad-spectrum anti-orthopoxvirus agents.
other
2026-07-28 | Rapid protection from lethal Orthopoxvirus infection following vaccination with mRNA-LNP encoding the Type I Interferon Binding Protein 2259797
Abstract Introduction Orthopoxviruses (OPVs), such as monkeypox, pose ongoing public health threats, especially since the global herd immunity has declined following the cessation of routine smallpox vaccination. Current vaccine strategies have limitations due to safety and short-lived immunity. Most anti-viral vaccines aim to induce antibodies (Abs) that bind to structural viral proteins, preferentially those that can neutralize the viral particle. The Type I IFN-binding protein (IFN-I bp) is a highly conserved non-structural protein present in all OPVs, an immune evasion protein, and is essential for their pathogenicity. It has been previously shown that mice vaccinated with recombinant IFN-I bp or passively immunized with anti-IFN-I bp monoclonal antibodies (Abs), are protected from lethal challenge with the mouse OPV ectromelia virus (ECTV), a classic model for human smallpox and monkeypox infections. Methods We made mRNA-lipid nanoparticle (mRNA-LNP) vaccine encoding IFN-I bp. We evaluated Abs responses by ELISA, and protective efficacy by challenging the immunized mice with ECTV in the footpad or with the OPV vaccinia virus intranasally. Results We found that a single immunization of 5 ug of mRNA-LNPs encoding ECTV’s IFN-I bp induced much higher titers of IgG antibodies (as opposed to IgM) as early as six days post-immunization than control mRNA-LNP vaccines. Notably, vaccinated BALB/c and TLR9-deficient mice challenged with ECTV or VACV eight days post-immunization were fully protected from viral lethality. Conclusion These data indicate that the IFN-I bp is a promising antigen for OPV vaccines, particularly when rapid protection is crucial, such as during an epidemic. Ongoing studies aim to determine the mechanisms underlying rapid IgG induction. Funding Source grant Topic Categories Vaccines and Immunotherapy (VAC)
2026-07-25 | An experimentally validated structure-based computational framework for humanisation of anti-orthopoxvirus antibodies.
The re-emergence of orthopoxviruses, most notably mpox virus (MPXV), poses a growing global public health threat. Well-characterised murine anti-orthopoxvirus antibodies are clinically limited by anti-mouse antibody responses, while traditional sequence-based humanisation often impairs antigen-binding activity. We developed an experimentally validated structure-guided computational humanisation framework prioritising 3D architectural congruence over sequence identity, integrating Foldseek-based structural alignment and interface-residue constraints. We applied this framework to humanise two murine anti-orthopoxvirus antibodies (7D11, A27D7), with comprehensive in vitro and in vivo validation. Structural superimposition confirmed high conformational conservation between the humanised variants (POX1.1 and POX2.1) and their parental mAbs, with root mean square deviation (RMSD) values below 0.6 Å for all variable domains. Both humanised variants retained full epitope specificity with natural humanness profiles. POX1.1 showed enhanced neutralisation potency against vaccinia virus (VACV) and MPXV, compared with the parental 7D11. POX2.1 preserved the broad cross-reactive binding and the extracellular enveloped virion neutralising activity of the parental A27D7. In the lethal VACV mouse model, both monotherapies conferred significant prophylactic and therapeutic protection, reducing pulmonary viral loads and improving survival. The dual-targeting combination of POX1.1 and POX2.1 achieved markedly improved in vivo efficacy compared with individual antibodies, delivering 100% survival even when administered 2 days post-challenge. In the MPXV CAST/EiJ mouse model, the combination significantly reduced splenomegaly and MPXV DNA loads in plasma, spleen and lung tissues, effectively suppressing systemic viral dissemination. These findings establish that the structure-centric workflow enables efficient humanisation of well-characterised murine anti-orthopoxvirus antibodies, providing a validated framework to support the development of countermeasures for orthopoxvirus pandemic. This work was supported by the National Natural Science Foundation of China, the Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences, the Scientific Research Innovation Capability Support Project for Young Faculty and the National Science and Technology Major Project.
2026-06-22 | Human monoclonal antibodies from donors vaccinated with recombinant vaccinia vaccine targeting A35 and B6 effectively inhibit orthopoxvirus spread and infection.
The global Monkeypox (Mpox) outbreak remains ongoing, yet specific therapeutics are still limited. Monkeypox virus (MPXV) proteins A35 and B6 are known to mediate viral cell-to-cell spread within the host. Here, we isolated human monoclonal antibodies (mAbs) targeting MPXV A35 and B6 proteins from the donors received recombinant vaccinia vaccine (rTV). Both A35 mAbs (A35A3, A35A9) and B6 mAbs (B6H1, B6G1) exhibited cross-binding activity against vaccinia virus(VACV) and MPXV, and inhibited cell-to-cell spread of both viruses in vitro. In murine VACV challenge models, A35A3, A35A9, B6H1, and B6G1 conferred significant protection in therapeutic administration. In summary, this study identified four promising candidate mAbs, providing valuable insights for the treatment of orthopoxvirus infections, warranting further validation in MPXV challenge models.
2026-05-27 | Circular RNA vaccines encoding fusion proteins of Mpox Virus A35R-M1R and B6R-A29L induce robust and durable protective immunity in mice.
Developing a safe and effective vaccine is crucial to control the recent worldwide outbreaks of mpox. Here, building upon our previously established lipid nanoparticle (LNP)-encapsulated circRNA vaccine platform, we constructed two bivalent mpox virus (MPXV) circRNA vaccines: cirBA encoding a B6R-A29L tandem antigen and cirAM encoding an A35R-M1R fusion antigen. Both bivalent MPXV circRNA vaccines, whether administered alone or in combination (designated cirMix), could induce robust and durable MPXV antigen-specific humoral and cellular immune responses in mice, conferring complete protection against lethal vaccinia virus Tian Tan strain (VTT) challenge. Moreover, even at low doses (2 µg for cirBA and cirAM, 4 µg for cirMix), all circRNA vaccines could provide 100% protection against lethal VTT challenge. Furthermore, at a higher dose (20 µg), all three vaccine groups induced potent long-term protective immunity lasting for at least 40 weeks, with cirBA achieving 100% protection, a level higher than that observed in the other groups. Collectively, our MPXV multivalent circRNA vaccines exhibit robust immunogenicity and represent promising candidates for further use in humans. The circRNA-based multivalent vaccine platform, capable of co-expressing multiple antigens, can be utilized for prevention of various infectious diseases.
2026-01-21 | Poxvirus dsDNA genomes differentially activate AIM2 or NLRP3 inflammasomes in human primary cells.
The innate immune system is known for its ability to recognize cytosolic DNA as evidence of infection, but detailed studies of this process have been mostly limited to mice and cell lines. To investigate inflammasome responses in human primary cells, we used engineered viruses encoding the inflammasome reporter caspase-1CARD-EGFP. We show that released genomes of vaccinia virus and monkeypox virus trigger robust inflammasome assembly in human primary cells. To determine the involved inflammasome sensors, we generated nanobodies against AIM2. Three of them inhibit AIM2 inflammasome assembly by blocking the polymerization of the AIM2 Pyrin domain, most potently as bivalent nanobodies. Utilizing an engineered vaccinia virus expressing bivalent AIM2 nanobodies, we demonstrate that inflammasomes in primary human macrophages and keratinocytes are nucleated by AIM2, while CD14+ monocytes assemble NLRP3 inflammasomes. This finding resolves the discrepancy between the previously reported activation of AIM2 inflammasomes in mice and NLRP3 inflammasomes in humans, and provides the first evidence for cell-type-specific regulation of DNA-triggered inflammasome activation. The newly developed AIM2-specific nanobodies offer a precise tool to dissect and potentially target AIM2 inflammasome assembly in other disease contexts.
proteins
2026-05-17 | Molecular mechanism of 2',3'-cGAMP degradation by monkeypox virus poxin-schlafen protein.
The World Health Organization had declared the multiregional outbreak of monkeypox a global public health emergency twice since 2022. Poxin from orthopoxviruses degrades the second messenger 2',3'-cGAMP of the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway to evade innate immune surveillance. Monkeypox virus (MPXV) poxin is fused to schlafen and the mechanism of how it catalyzes the degradation of 2',3'-cGAMP remains unclear. Here, we show that MPXV poxin-schlafen degrades 2',3'-cGAMP into Gp[2'-5']Ap[3'], suppressing interferon-β (IFN-β) induction mediated by the cGAS-STING pathway. The schlafen domain has no impact on the degradation of 2',3'-cGAMP mediated by the poxin domain. Crystal structures of MPXV poxin domain and its complex with Gp[2'-5']Ap[3'] reveal that 2',3'-cGAMP binds to a pocket formed by two monomers of the poxin dimer and induces closure of the pocket to trigger degradation. MPXV poxin exhibits a strict substrate specificity and does not degrade 3',3'-cGAMP, c-di-AMP, and c-di-GMP that also activate STING-mediated immune responses. These results unveil the molecular mechanism for 2',3'-cGAMP degradation by MPXV poxin-schlafen protein and provide the structural basis for the development of inhibitors against MPXV infection.
2026-03-06 | Lactoferrin blocks orthopoxvirus entry via heparan sulphate and regulates host antiviral pathways.
Current antiviral therapies for orthopoxviruses face critical challenges, including limited efficacy and significant toxicity, which impede outbreak containment and clinical management. Here, we identify lactoferrin as a potent antiviral agent against multiple orthopoxvirus strains. Combination administration of lactoferrin with brincidofovir or tecovirimat demonstrated additive efficacy, suggesting a potential clinical strategy to reduce individual drug toxicity. Mechanistically, lactoferrin blocks viral entry by competitively binding to heparan sulphate proteoglycans (HSPGs). It also suppresses viral replication by regulating host antiviral pathways, including down-regulating cytokines and upregulating TGF-β-dependent antiviral signalling pathways. We identify TGFBI as a virus-responsive target regulated by lactoferrin. Lactoferrin treatment restores TGFBI expression and activates downstream MAPK/ERK and JAK2/STAT3 signalling cascades, leading to enhanced interferon production and interferon-stimulated gene (ISG) expression. In a murine vaccinia virus (VACV) infection model, lactoferrin treatment reduced lung viral loads and histological damage. These results underscore lactoferrin's distinctive dual antiviral mechanism and highlight its translational potential as a safe and cost-effective prophylactic or therapeutic agent. It is particularly beneficial for immunocompromised populations in resource-limited settings during orthopoxvirus outbreaks.
2026-02-05 | Structural basis of mpox virus A30/H2 subcomplex formation.
The continuous spread of mpox disease caused by mpox virus (MPXV) has posed great threat to global public health. The postattachment membrane fusion process of MPXV is mediated by a multimeric protein machinery, termed as entry-fusion complex (EFC). Among EFC components, A30 and H2 are the earliest identified interaction pair and play important roles in virus entry. Here, we determine the crystal structure of MPXV A30/H2 subcomplex via the tandem-fusion strategy, and show that A30 undergoes large conformational rearrangements upon H2 binding. Structural analysis reveals extended intersubunit interface and highly conserved intermolecular interactions. In vitro binding data further clarify key residues and elements involved in the A30/H2 subcomplex formation. Finally, we show that the H2-A30 fusion protein, superior to A30 ectodomain alone or the ectodomain-mixture of H2+A30, can induce more potent neutralizing-antibody responses which could inhibit viral infection. These data provide valuable information for the understanding of poxvirus EFC assembly and the H2-A30-based immunogen design and optimization.
2026-02-01 | Immunological response patterns in human cowpox infection: A clinical analysis
Approximately 73% of documented human cowpox infections in Europe during the past decade have occurred in individuals born after the cessation of routine smallpox vaccination programs, highlighting a growing immunological vulnerability within these populations. This research examined the immunological response patterns in 86 patients diagnosed with human cowpox virus (CPXV) infection at a tertiary referral center in Amsterdam, Netherlands, between March 2020 and September 2023. Clinical immunological assessments included serial measurements of orthopoxvirus-specific IgG and IgM antibodies, cytokine profiling encompassing TNF-alpha, IL-6, IFN-gamma, and IL-10, and flow cytometric analysis of lymphocyte subpopulations. Patients were stratified into mild, moderate, and severe clinical categories based on lesion count, systemic involvement, and duration of illness. The results demonstrated that severe cases exhibited significantly elevated IFN-gamma concentrations with a mean of 168.4 pg/mL compared to 82.6 pg/mL in mild cases at day 14 post-infection. CD8-positive T lymphocyte expansion was most pronounced in severe infections, reaching 720 cells per microliter compared to 420 cells per microliter in mild presentations. Treatment with interferon-alpha supplementation in moderate and severe cases was associated with a 34.2% reduction in time to clinical resolution. These findings provide evidence supporting the clinical utility of immunological monitoring and interferon-based interventional strategies in managing human cowpox infections of varying severity.
2025-07-28 | The vaccinia virus protein, C16, promotes the ubiquitylation and relocalization of the antiviral E3 ubiquitin-ligase, TRIM25.
Poxviruses co-opt the ubiquitin (Ub)-proteasome system (UPS) to facilitate virus replication, evade the innate immune response, and block programmed cell death of infected cells. Moreover, the UPS is an integral component of innate immune signaling pathways used by the host to respond to infection. To further elucidate how the UPS is engaged early during poxvirus infection, we quantified viral and cellular peptides with a Ub remnant motif (diGly peptides) from lysates of uninfected and vaccinia virus Copenhagen strain (VACV-Cop)-infected HeLa cells. Of note, we identified several ubiquitylated peptides from the cellular antiviral protein, TRIM25, that were enriched for, or exclusively found, in VACV-Cop-infected cells. TRIM25 is an E3 ligase for Ub and the Ub-like protein, ISG15, and TRIM25 performs several functions including activating the type I interferon response. Higher-molecular weight, ubiquitylated TRIM25 species were evident as early as 1 h post-infection of HeLa cells with VACV-Cop, and they persisted throughout infection. Proteasomal or lysosomal degradation did not appear to be a major consequence of this ubiquitylation; however, TRIM25 ubiquitylation correlated with its relocalization to punctate structures in infected cells. C16, a Bcl-2 family-like protein encoded by identical genes on both arms of the VACV-Cop genome, was both necessary and sufficient to promote TRIM25 ubiquitylation and relocalization. These phenomena were not evident in cells infected with Orthopoxviruses lacking the genes encoding for C16. We postulate that the ubiquitylation and/or relocalization of TRIM25 induced by C16 could represent a novel mechanism for poxviruses to subvert the host antiviral response.IMPORTANCEUbiquitylation is a versatile post-translational modification that is required for poxviruses to replicate their genomes and evade host cell defenses to infection. At the same time, both degradative and non-degradative protein ubiquitylation are critical components of the innate and adaptive immune responses to infection. In this study, we opted for a proteomics approach to examine changes in protein ubiquitylation early after vaccinia virus infection with the goal of identifying novel ways by which ubiquitylation is exploited during infection. We demonstrate that many Orthopoxviruses utilize the Bcl-2 family-like protein C16 to promote the ubiquitylation and relocalization of the cellular E3 ubiquitin/ISG15-ligase, TRIM25, which we hypothesize represents a novel strategy by which these viruses evade the host cell antiviral response. Moreover, our findings hint that Orthopoxviruses may also have C16-independent strategies to interfere with the function of TRIM25.
vaccines
2026-08-11 | ACAM2000 vaccine safety and immunogenicity considerations for smallpox and mpox.
Smallpox, eradicated globally in 1980, remains a major biodefense concern due to retained Variola virus stocks and the absence of population immunity following cessation of routine vaccination. Monkeypox virus (MPXV), a related orthopoxvirus, has reemerged as a global public health threat, with major outbreaks in 2022 and renewed spread from 2024 onward. This review evaluates ACAM2000®, a second-generation live smallpox vaccine, summarizing its development, immunogenicity, efficacy, safety, regulatory status, and potential role in mpox prevention. ACAM2000 remains a critical medical countermeasure for smallpox preparedness and a valuable, though selective, tool for mpox prevention. Its high immunogenicity, rapid protection, and broad orthopoxvirus coverage must be balanced against a well-characterized safety risk profile.
2026-07-12 | Vaccinia virus and Monkeypox virus neutralizing and antigen-binding antibodies following subcutaneous and reduced intradermal doses of an MVA vaccine.
To expand the supply of the modified vaccinia Ankara (MVA) smallpox/mpox vaccine, fractional doses administered intradermally (ID) have been considered as alternatives to the standard dose given subcutaneously (SC). In a recent clinical trial, participants received the standard 108 infectious units of vaccine SC or a one-fifth (IDH) or a one-tenth (IDL) dose ID twice 28-days apart. Two weeks after the second dose, sera were analyzed using a vaccinia virus (VACV) strain Western Reserve plaque-reduction test (PRNT) with the conclusion that IDH but not IDL was non-inferior to SC. The present study extends the latter by quantifying neutralizing antibodies to the MVA vaccine and to monkeypox virus (MPXV) in the absence and presence of added complement and by assessing multiplex binding antibodies to individual VACV antigens (A27, A33, B5, D8 and L1) and the MPXV homologs (A29, A35, B6, E8 and M1). The main conclusions of the study are that the titers of MVA neutralizing antibodies induced by SC and IDH were not significantly different, whereas MVA neutralizing antibody titers induced by IDL were lower like the previous PRNT results. However, the titers of complement-enhanced MPXV neutralizing antibodies induced by SC were significantly higher than for both IDH and IDL immunizations, suggesting that the standard SC dose and reduced dose ID immunizations may not be equivalent. Additional analyses suggested that antibody binding to VACV B5 and D8 and MPXV B6 and E8 may serve as surrogates for neutralizing antibodies.
2026-06-22 | Pan-genome and reverse vaccinology for a multi-epitope vaccine against circulating post-2022 Monkeypox virus strains.
Since the 2022 outbreak, the number of Monkeypox cases worldwide has been increasing at an alarming rate. As of August 2024, approximately 99,000 people have been infected with the virus. The severity of this situation is further highlighted by the World Health Organization's (WHO) classification of the Mpox virus as a Public Health Emergency of International Concern (PHEIC) due to the increased fatality rate of approximately 3.6% in clade I. Targeting the virus's membrane-bound, enveloped, and extracellular proteins, our goal was to computationally develop and assess a broad-spectrum multi-epitope vaccine that elicits humoral and adaptive immune responses against Monkeypox virus (MPXV) infection. During an outbreak, a pan-genome-based reverse vaccinology approach can offer rapid, practical solutions to enduring problems in experimental vaccine design. The method involved screening 16 monkeypox genomes to identify viral targets, from which viral proteins were selected based on their antigenicity, location, and solubility. Immunoinformatics methods and algorithms were used to extract the proteins' putative T-cell and B-cell epitopes, which were combined to form several vaccine constructions. The tertiary structure of the chimeric vaccine construct's interaction with Toll-like receptor 4 (TLR4) was thoroughly assessed using the advanced techniques of molecular docking and molecular dynamics simulation. A pan-genomic analysis identified 80 core genes, which were then screened for proteins suitable for epitope-based vaccine design. From four of these selected proteins, T-cell and B-cell epitopes were extracted to create four distinct vaccine constructs. Appropriate adjuvants and linkers were incorporated into each construct to enhance its potential efficacy. Stability and immunogenicity analyses of each vaccine design yielded promising results. These findings suggest that the vaccine constructs could be effective in preventing monkeypox, warranting further experimental validation and supporting the application of similar strategies to combat other viral illnesses.
2026-06-16 | Tracking the Trail of Monkeypox: From Origins to Outbreak Control.
Monkeypox virus (MPXV), a zoonotic viral disease first identified in 1958, has re-emerged as a major global health concern. The first human case was reported in 1970 in the Democratic Republic of Congo (DRC), and since then, MPXV has demonstrated a clinical resemblance to smallpox, with transmission occurring through both animal-to-human and human-to-human contact. In 2022, the largest recorded outbreak resulted in over 30,000 cases across the Western Pacific, Asia, Europe, and the Americas. Subsequently, between 2022 and 2024, more than 100,000 confirmed cases were documented worldwide, leading the World Health Organization to declare MPXV a Public Health Emergency of International Concern (PHEIC) in August 2024. This review provides a comprehensive, up-to-date overview of MPXV, including its viral structure, life cycle, clinical manifestations, diagnostic strategies, vaccines, and emerging therapeutics. Furthermore, it examines current challenges in disease detection and control and identifies opportunities to strengthen surveillance, prevention, and treatment strategies. Overall, this article aims to serve as a consolidated resource on MPXV, highlighting its epidemiology, clinical significance, and implications for global public health preparedness.
2026-05-07 | Immunoinformatics driven multi-epitope vaccine design targeting clade IIb Mpox variant.
The Monkeypox virus (MPXV), an emerging zoonotic orthopoxvirus, has reemerged as a major global health threat, with the 2022 outbreak predominantly associated with Clade IIb lineages. The surface glycoprotein B21R (OPG210), a major virulence and immune-evasion factor, contains three lineage-defining amino acid substitutions (D209N, P722S, and M1741I) that distinguish Clade IIb from other variants, emphasizing its relevance as a vaccine target. In this study, an integrated immunoinformatics and molecular dynamics-based approach was employed to design a multi-epitope vaccine (MEV) targeting the B21R glycoprotein. Comprehensive B-cell, helper T-lymphocyte (HTL), and cytotoxic T-lymphocyte (CTL) epitopes were screened based on their immune-eliciting potential, non-allergenicity, cytotoxicity and global immunogenic coverage, and were subsequently assembled into a rationally engineered MEV construct. The modeled vaccine displayed potential affinity and conformational integrity in complex with immune receptors, as confirmed by molecular docking, normal mode analysis, and molecular dynamics simulations, which indicated favorable flexibility and compactness conducive to immune activation. By integrating clade-specific sequence variations, this study introduces a strain adapted vaccine design framework capable of addressing viral evolution and immune escape in contemporary MPXV strains. These findings highlight the potential of computational vaccinology as a rapid and cost-effective strategy for mpox vaccine design; however, further experimental and preclinical validation is required.
gene therapies
2026-06-19 | Epidemiology and characteristics of cases with monkeypox virus clade I in the WHO European Region, 2024 to 2025.
BACKGROUNDA public health emergency of international concern (PHEIC) was declared in August 2024 following a sharp increase in mpox cases linked to the emergence of monkeypox virus (MPXV) clade Ib.AIMWe aimed to characterise imported and locally acquired mpox clade I cases reported in the WHO European Region (WHO/Europe) since August 2024 and assess transmission patterns and response measures.METHODSWe collected data on MPXV clade I infections reported by countries in WHO/Europe through the International Health Regulations. We contacted reporting countries to collect age, sex, travel history, most likely route of transmission, clinical course, contacts and type of exposure, and implemented control and prevention measures.RESULTSBetween 14 August 2024 and 23 November 2025, 82 cases of MPXV clade I infection were reported; 45 were imported and 37 were infected in reporting countries. Seventy-nine were typed as clade Ib and two as clade Ia. Most imported cases reported heterosexual (n = 26) or close physical contact (n = 5) as possible exposure. Secondary transmission occurred in six households. One healthcare worker was infected. Since October 2025, further 17 autochthonous male cases were most likely infected through sex with other men.CONCLUSIONImported cases of MPXV clade I infection were associated with limited household transmission. The increase in autochthonous infections among men with recent sexual contact with other men suggests undetected spread in Europe, that may become sustained. Continued surveillance, case and contact investigation are needed to understand MPXV clade I epidemiology and drivers of MPXV clade I transmission in Europe.
2026-04-27 | Mpox (Monkeypox) in Pregnant Women, the Placenta and Fetus: Correlation with Maternal-Fetal Transmission, Pathology and Strain Differences from MPXV Clades Ia, Ib, IIa, and IIb.
Since the elimination of smallpox, mpox (monkeypox) is the most medically significant orthopoxvirus infection. As a result of numerous regional, national and global outbreaks of MPXV (mpox virus), there is an abundance of new data available on the effects of the different viral clades on clinical obstetrical and perinatal outcomes when infection occurs in pregnancy. In addition, there have been additional placentas from cases of congenital MPXV infection available for study. These recent data indicate that there are prominent differences between viral strains and their effects on the fetus, with MPXV Clade I strains (Ia, Ib) having the greatest risk for an adverse outcome in pregnancy, and Clade II strains (IIa, IIb) having far less risk. In particular, the ongoing outbreak of MPXV Clade Ib in the DRC indicates that there is a significant risk for adverse perinatal outcomes associated with infection in pregnancy, especially during the first trimester. These outcomes include spontaneous abortion, stillbirth, neonatal death and congenital mpox. The placenta in cases of congenital infection demonstrates abundant virus in the chorionic villi, with prominent involvement of Hofbauer cells. Similar to smallpox, transplacental transmission and adverse pregnancy outcomes are an important feature of certain strains of this orthopoxvirus infection when occurring in pregnant women.
2026-04-01 | Dynamic shift in the dominant transmission route of clade Ib monkeypox virus across networks with sexual and nonsexual contacts.
The intensifying outbreaks of the novel monkeypox virus clade Ib in the Democratic Republic of the Congo have raised global concern about the potential for wider epidemic spread. Some clade Ib mpox outbreaks have shown a distinct transmission pattern in which transmission associated with both sexual and nonsexual contacts coexist. Here, we characterize these outbreaks in a network epidemic model, which incorporates sexual and nonsexual contacts, and project age- and route-specific transmission potentials under a wide range of scenarios. Our analyses suggest that the dominant route of transmission may shift over time from sexual to nonsexual contacts, which leads to larger epidemics. The age groups contributing most to overall infections and mortality also change over time, suggesting that target groups for intervention should be adjusted accordingly. For countries at risk of travel-associated mpox outbreaks, these findings highlight the importance of monitoring evolving monkeypox virus transmission patterns and interacting transmission routes to support timely and effective control measures.
2026-03-30 | Emergence and diversity of monkeypox virus Clade IIb sub-lineages in Nigeria (1971-2023) and its role in the 2022 global outbreak.
The exact role played by Nigeria in the global monkeypox virus (MPXV) outbreak of 2022 remains unclear, despite exported cases to Singapore, the United Kingdom (UK), the United States of America (USA), and Israel from 2018 to 2022. We sought to resolve the origin of the 2022 MPXV global outbreak. All Nigerian MPXV whole genomes deposited in the EpiPox™ database were aligned using Nextclade v3.13.3 against the reference genome (NC_063383.1) for lineage and mutation analyses. Multiple sequence alignments were performed using MAFFT version 7, followed by maximum likelihood trees in IQ-TREE for clades A.3 and B.1 and visualised in iTOL viewer. We quantified total C → T substitutions as APOBEC3-related mutations. Seven clades or sub-lineages, namely: A (2017-2023), A.1 (2018 and 2019), A.2 and A.3 (2019), A.2.2 (2022), A.2.3 (2022 and 2023), and B.1 (2022) were observed. There was a gradual buildup of total substitution events (APOBEC3-related mutations) from 1978 to 2023, with a slight decline in 2020 but most pronounced in 2019, 2021, and 2022. Furthermore, total substitutions events were widespread across both variable and core regions of the MPXV genomes. The B.1 and A.3 maximum likelihood trees points to Nigerian ancestral roots, supporting our hypothesis that the B.1 sub-lineage originated in Nigeria. Our phylodynamics analyses showed peak distributions for the A.3 clade around 2013, while that of B.1 showed rapid spread of the virus in May 2022. The evolution rates of the for A.3 and B.1 were 6.94 × 10-5 and ∼ 3.091 × 10-4 substitutions/site/year, while their molecular clock signals were moderate with respective values of R2 = 0.56 and 0.56. Overall, our findings indicate that the B.1 sub-lineage, which triggered the 2022 outbreak, potentially evolved from A.3, with both lineages having their ancestral roots in Nigeria.
2026-03-14 | Genomic diversity of Clade Ia monkeypox virus in the Central African Republic, 2019-2024.
Monkeypox virus (MPXV) is a zoonotic pathogen known to be endemic to the Congo basin and West Africa, and which causes characteristic lesions disseminated on all skin surfaces of infected cases. Multiple MPXV outbreaks have been reported in the Central African Republic (CAR), a country in the Congo basin, at an increased frequency since 2020. The genomic history of these outbreaks in CAR is poorly characterized due to undersampling, with only a recent expansion in the number of sequences from CAR. Here, we report twenty-six new near-complete genomes from six prefectures of CAR, selected to represent outbreaks that occurred in the country between 2019 and 2024. Our analysis shows the sustained homogeneity of genomes in CAR, as all of them belonged to Clade Ia, but with an expansion of sub-lineages and therefore increased MPXV diversity within CAR. We highlight the introduction into CAR of a lineage previously known to occur only in Gabon and Cameroon, as well as the apparent regional clustering of MPXV genomes in CAR. Our analysis reveals limited APOBEC3-mediated activity, which is consistent with recent zoonotic origins and short human-to-human transmission chains observed in CAR. These analyses provide an in-depth view of the genomic diversity of MPXV in the Central African region.
small molecules
2026-07-10 | Severe mpox in an immunocompromised, non-traveller South African male.
Mpox is a zoonotic orthopoxvirus infection historically linked to being in endemic regions, travel and close physical contact, including within men who have sex with men (MSM) communities. We report a case of severe mpox in a heterosexual man with advanced human immunodeficiency virus (HIV) disease and no travel history to endemic areas. The patient developed extensive cutaneous disease and transmitted mpox to household contacts, illustrating non-sexual transmission. Management included supportive care and tecovirimat under Section 21 authorisation (a regulatory mechanism in South Africa permitting access to an unregistered medicine) with good clinical response. This case highlights the changing epidemiology of mpox, the risk of severe disease in immunocompromised patients, household and non-sexual transmission. We also emphasise the importance of early diagnosis, infection control and antiviral therapy when indicated.
2026-07-06 | Functional characterization of the poxvirus poly(A) polymerase
Poxvirus infections can result in human diseases, most notably smallpox, caused by variola virus (VARV), and mpox, caused by monkeypox virus (MPXV). Smallpox was eradicated in 1980 through vaccination; however, the discontinuation of vaccination programs has left the population vulnerable to emergent zoonotic MPXV or the potential reappearance of VARV. Part I of this thesis characterizes the orthopoxvirus poly(A) polymerase VP55 as a candidate antiviral target, using vaccinia virus (VACV) as the model system. The VACV poly(A) polymerase is a heterodimer composed of VP55 and VP39. This work demonstrates that VP55 selectively polyadenylates cellular noncoding RNAs (ncRNAs), targeting those involved in host regulation while sparing ncRNAs essential for translation. Moreover, VP55 expression inhibited host cell translation. VP55 also exhibited a distinct subcellular distribution compared to its known partner VP39 and, unexpectedly, associated with translation-related proteins. Based on these observations, a working model has been proposed in which VP55-mediated polyadenylation acts as a decoy mechanism for PABP, thereby rendering mRNAs transcriptionally inactive and establishing the importance of VP55 in viral infection. Poxviruses replicate entirely in the cytoplasm of infected cells. Efficient infection relies on the host translation machinery and, intriguingly, also requires nuclear host proteins. In Part II of this thesis, nuclear heterogeneous ribonucleoprotein (hnRNP) K was identified as essential for VACV replication, as its absence reduced viral protein and RNA levels. Upon infection, hnRNP K can translocate from the nucleus to the cytoplasm, where it shifts its RNA-binding preference toward viral transcripts. Although its protein-protein interactions remain unchanged, this redistribution suggests a functional repurposing. hnRNP K has been implicated in non-canonical translation initiation, and this work opens new avenues to investigate how VACV sustains translation under conditions of host translational shutdown.
2026-07-02 | Exploring drug repurposing for monkeypox virus: A structural and computational approach.
The increasing global threat posed by viral infections that are transmitted to humans from animals has intensified interest in emerging pathogens such as monkeypox virus (MPV). This study investigated the potential of drug repurposing as an efficient therapeutic strategy against MPV, focusing on its close genetic relationships with vaccinia and variola viruses. Due to the structural and evolutionary similarities among these orthopoxviruses, the Food and Drug Administration (FDA)-approved smallpox drug tecovirimat was selected as a reference drug. A descriptive-analytical approach was used to assess the binding energies of 38 FDA-approved drugs from four therapeutic classes. Molecular docking was performed against key target proteins from the genus Orthopoxvirus. Several compounds exhibited stronger binding energies than the reference drug tecovirimat, indicating their potential repurposing as anti-MPV agents. To further validate the stability and interaction dynamics of the top performing drug-protein complexes, molecular dynamics (MD) simulations were conducted, which supported their potential as viable candidates for future therapeutic development. These findings provide promising leads for the development of new therapeutic applications, thereby enhancing both the public health response and commercial value of repurposed treatments. MD simulations also supported the stability and feasibility of these promising drug-protein complexes.
2026-06-09 | Non-cyclic dinucleotide STING agonists abrogate MPXV infection
Abstract Mpox has emerged as a global threat to public health following several national and international outbreaks from 2022. Poxviruses deploy multiple strategies to counteract host immune defences including pathways leading to interferon (IFN) production. Here we demonstrate that depleting the viral 2’3’-cGAMP nuclease poxin restores activation of STING and IRF3 during MPXV infection despite the presence of other viral antagonists. We then demonstrate that non-cyclic dinucleotide (non-CDN) STING agonists are resistant to poxin; activate STING and IRF3 during infection; and potently suppress MPXV and orthopoxvirus replication in human primary fibroblasts and differentiated monocytes, where replication is completely abrogated. Mechanistically, non-CDN restriction requires STING, IFNAR and STAT signalling, and induces a unique transcriptional signature over IFNβ, enabling expression of additional cytokines. In vivo, non-CDN activity effectively reduces signs of illness and enhances survival in wild-derived castaneous mice inoculated with the virulent clade I MPXV. Our study reveals poxin as an Achilles’ heel of MPXV, that when bypassed by direct STING agonism, provides a promising novel anti-mpox therapeutic strategy with reduced risk of antiviral resistance.
2026-05-01 | Structural Modification of Tranilast against Poxvirus Based on α, β-Unsaturated Acrylamide Covalent Warhead and Confirmation of the Targets and Mode of Action.
The recurrent mpox outbreak has raised widespread global concern, yet specific antiviral therapies remain unavailable. Based on the α, β-unsaturated acrylamide covalent warhead of tranilast (TRA), we designed and synthesized 24 new TRA derivatives and evaluated their anti-orthopoxvirus activity using a VTT-Fluc assay. Compound 8l exhibited the most potent antipoxvirus activity and moderate activity against monkeypox clade IIb, with EC50 values of 6.1 and 47.1 μM, respectively, significantly outperformed TRA. In a VTT-Fluc nude mouse model, oral administration of 8l at 90 mg/kg achieved an 88.2% viral inhibition rate. Mechanistic studies revealed 8l exerted dual-target inhibition by acting on viral A17L and mRNA methyltransferase, thereby blocking membrane fusion and intracellular biosynthesis. The acrylamide warhead in 8l forms covalent adducts with serine residues of both targets via Michael addition. This work provides a promising covalent lead and identifies potential targets for the development of broad-spectrum anti-orthopoxvirus agents.
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2026-07-28 | Rapid protection from lethal Orthopoxvirus infection following vaccination with mRNA-LNP encoding the Type I Interferon Binding Protein 2259797
Abstract Introduction Orthopoxviruses (OPVs), such as monkeypox, pose ongoing public health threats, especially since the global herd immunity has declined following the cessation of routine smallpox vaccination. Current vaccine strategies have limitations due to safety and short-lived immunity. Most anti-viral vaccines aim to induce antibodies (Abs) that bind to structural viral proteins, preferentially those that can neutralize the viral particle. The Type I IFN-binding protein (IFN-I bp) is a highly conserved non-structural protein present in all OPVs, an immune evasion protein, and is essential for their pathogenicity. It has been previously shown that mice vaccinated with recombinant IFN-I bp or passively immunized with anti-IFN-I bp monoclonal antibodies (Abs), are protected from lethal challenge with the mouse OPV ectromelia virus (ECTV), a classic model for human smallpox and monkeypox infections. Methods We made mRNA-lipid nanoparticle (mRNA-LNP) vaccine encoding IFN-I bp. We evaluated Abs responses by ELISA, and protective efficacy by challenging the immunized mice with ECTV in the footpad or with the OPV vaccinia virus intranasally. Results We found that a single immunization of 5 ug of mRNA-LNPs encoding ECTV’s IFN-I bp induced much higher titers of IgG antibodies (as opposed to IgM) as early as six days post-immunization than control mRNA-LNP vaccines. Notably, vaccinated BALB/c and TLR9-deficient mice challenged with ECTV or VACV eight days post-immunization were fully protected from viral lethality. Conclusion These data indicate that the IFN-I bp is a promising antigen for OPV vaccines, particularly when rapid protection is crucial, such as during an epidemic. Ongoing studies aim to determine the mechanisms underlying rapid IgG induction. Funding Source grant Topic Categories Vaccines and Immunotherapy (VAC)
2026-07-25 | An experimentally validated structure-based computational framework for humanisation of anti-orthopoxvirus antibodies.
The re-emergence of orthopoxviruses, most notably mpox virus (MPXV), poses a growing global public health threat. Well-characterised murine anti-orthopoxvirus antibodies are clinically limited by anti-mouse antibody responses, while traditional sequence-based humanisation often impairs antigen-binding activity. We developed an experimentally validated structure-guided computational humanisation framework prioritising 3D architectural congruence over sequence identity, integrating Foldseek-based structural alignment and interface-residue constraints. We applied this framework to humanise two murine anti-orthopoxvirus antibodies (7D11, A27D7), with comprehensive in vitro and in vivo validation. Structural superimposition confirmed high conformational conservation between the humanised variants (POX1.1 and POX2.1) and their parental mAbs, with root mean square deviation (RMSD) values below 0.6 Å for all variable domains. Both humanised variants retained full epitope specificity with natural humanness profiles. POX1.1 showed enhanced neutralisation potency against vaccinia virus (VACV) and MPXV, compared with the parental 7D11. POX2.1 preserved the broad cross-reactive binding and the extracellular enveloped virion neutralising activity of the parental A27D7. In the lethal VACV mouse model, both monotherapies conferred significant prophylactic and therapeutic protection, reducing pulmonary viral loads and improving survival. The dual-targeting combination of POX1.1 and POX2.1 achieved markedly improved in vivo efficacy compared with individual antibodies, delivering 100% survival even when administered 2 days post-challenge. In the MPXV CAST/EiJ mouse model, the combination significantly reduced splenomegaly and MPXV DNA loads in plasma, spleen and lung tissues, effectively suppressing systemic viral dissemination. These findings establish that the structure-centric workflow enables efficient humanisation of well-characterised murine anti-orthopoxvirus antibodies, providing a validated framework to support the development of countermeasures for orthopoxvirus pandemic. This work was supported by the National Natural Science Foundation of China, the Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences, the Scientific Research Innovation Capability Support Project for Young Faculty and the National Science and Technology Major Project.
2026-06-22 | Human monoclonal antibodies from donors vaccinated with recombinant vaccinia vaccine targeting A35 and B6 effectively inhibit orthopoxvirus spread and infection.
The global Monkeypox (Mpox) outbreak remains ongoing, yet specific therapeutics are still limited. Monkeypox virus (MPXV) proteins A35 and B6 are known to mediate viral cell-to-cell spread within the host. Here, we isolated human monoclonal antibodies (mAbs) targeting MPXV A35 and B6 proteins from the donors received recombinant vaccinia vaccine (rTV). Both A35 mAbs (A35A3, A35A9) and B6 mAbs (B6H1, B6G1) exhibited cross-binding activity against vaccinia virus(VACV) and MPXV, and inhibited cell-to-cell spread of both viruses in vitro. In murine VACV challenge models, A35A3, A35A9, B6H1, and B6G1 conferred significant protection in therapeutic administration. In summary, this study identified four promising candidate mAbs, providing valuable insights for the treatment of orthopoxvirus infections, warranting further validation in MPXV challenge models.
2026-05-27 | Circular RNA vaccines encoding fusion proteins of Mpox Virus A35R-M1R and B6R-A29L induce robust and durable protective immunity in mice.
Developing a safe and effective vaccine is crucial to control the recent worldwide outbreaks of mpox. Here, building upon our previously established lipid nanoparticle (LNP)-encapsulated circRNA vaccine platform, we constructed two bivalent mpox virus (MPXV) circRNA vaccines: cirBA encoding a B6R-A29L tandem antigen and cirAM encoding an A35R-M1R fusion antigen. Both bivalent MPXV circRNA vaccines, whether administered alone or in combination (designated cirMix), could induce robust and durable MPXV antigen-specific humoral and cellular immune responses in mice, conferring complete protection against lethal vaccinia virus Tian Tan strain (VTT) challenge. Moreover, even at low doses (2 µg for cirBA and cirAM, 4 µg for cirMix), all circRNA vaccines could provide 100% protection against lethal VTT challenge. Furthermore, at a higher dose (20 µg), all three vaccine groups induced potent long-term protective immunity lasting for at least 40 weeks, with cirBA achieving 100% protection, a level higher than that observed in the other groups. Collectively, our MPXV multivalent circRNA vaccines exhibit robust immunogenicity and represent promising candidates for further use in humans. The circRNA-based multivalent vaccine platform, capable of co-expressing multiple antigens, can be utilized for prevention of various infectious diseases.
2026-01-21 | Poxvirus dsDNA genomes differentially activate AIM2 or NLRP3 inflammasomes in human primary cells.
The innate immune system is known for its ability to recognize cytosolic DNA as evidence of infection, but detailed studies of this process have been mostly limited to mice and cell lines. To investigate inflammasome responses in human primary cells, we used engineered viruses encoding the inflammasome reporter caspase-1CARD-EGFP. We show that released genomes of vaccinia virus and monkeypox virus trigger robust inflammasome assembly in human primary cells. To determine the involved inflammasome sensors, we generated nanobodies against AIM2. Three of them inhibit AIM2 inflammasome assembly by blocking the polymerization of the AIM2 Pyrin domain, most potently as bivalent nanobodies. Utilizing an engineered vaccinia virus expressing bivalent AIM2 nanobodies, we demonstrate that inflammasomes in primary human macrophages and keratinocytes are nucleated by AIM2, while CD14+ monocytes assemble NLRP3 inflammasomes. This finding resolves the discrepancy between the previously reported activation of AIM2 inflammasomes in mice and NLRP3 inflammasomes in humans, and provides the first evidence for cell-type-specific regulation of DNA-triggered inflammasome activation. The newly developed AIM2-specific nanobodies offer a precise tool to dissect and potentially target AIM2 inflammasome assembly in other disease contexts.
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Drug Discovery Landscape
7 orphan drug designations for Human infection by orthopoxvirus, including 2 approved therapies.
7 orphan drug designations for Human infection by orthopoxvirus, including 2 approved therapies.
Drug | Therapy type | Regulator | Orphan designation | Approval | Sponsor |
|---|---|---|---|---|---|
brincidofovir [Tembexa] | small molecules | FDA | 2018-06-05 | 2021-06-04 | Emergent BioDefense Operations Lansing LLC |
Brincidofovir | small molecules | EMA | 2016-11-18 | — | Emergent Operations Ireland Limited |
Tecovirimat | small molecules | EMA | 2010-10-01 | — | SIGA Pharmaceuticals (Europe) Limited |
tecovirimat | small molecules | FDA | 2010-09-29 | — | SIGA Technologies, Inc. |
tecovirimat [TPOXX] | small molecules | FDA | 2006-12-27 | 2018-07-13 | SIGA Technologies, Inc. |
tecovirimat | small molecules | FDA | 2006-12-18 | — | SIGA Technologies, Inc. |
polyinosinic-polycytidilic acid (Poly-ICLC) | oligonucleotides | FDA | 2002-11-19 | — | Oncovir |
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