Search Results (227)

Myxoma virus (MYXV), a rabbit-specific poxvirus and non-pathogenic in humans and mice, is an excellent candidate oncolytic virus for cancer therapy. MYXV also has immunotherapeutic benefits. In ovarian cancer (OC), immunosuppressive tumor-associated macrophages (TAMs) are key to inhibiting antitumor immunity while hindering therapeutic benefit by chemotherapy and dendritic cell (DC) vaccine. Because MYXV favors binding/entry of macrophages/monocytes, we examined the therapeutic potential of MYXV against TAMs. We found previously that a replication-defective MYXV with targeted deletion of an essential gene, M062R, designated ΔM062R MYXV, activated both the host DNA sensing pathway and the SAMD9 pathway. Treatment with ΔM062R confers therapeutic benefit comparable to that of wild-type replicating MYXV in preclinical models. Here we found that ΔM062R MYXV, when integrated with cisplatin and DC immunotherapy, further improved treatment benefit, likely through promoting tumor antigen-specific T cell function. Moreover, we also tested ΔM062R MYXV in targeting human immunosuppressive TAMs from OC patient ascites in a co-culture system. We found that ΔM062R treatment subverted the immunosuppressive properties of TAMs and elevated the avidity of cytokine production in tumor antigen-specific CD4⁺ T cells. Overall, ΔM062R presents a promising immunotherapeutic platform as a beneficial adjuvant to chemotherapy and DC vaccine. Full article

Background: Protein kinase R (PKR) inhibits general mRNA translation by phosphorylating the alpha subunit of eukaryotic translation initiation factor 2 (eIF2). PKR also modulates NF-κB signaling during viral infections, but comparative studies of PKR-mediated NF-κB responses across mammalian species and their regulation by viral inhibitors remain largely unexplored. This study aimed to characterize the conserved antiviral and inflammatory roles of mammalian PKR orthologs and investigate their modulation by poxviral inhibitors. Methods: Using reporter gene assays and quantitative RT-PCR, we assessed the impact of 17 mammalian PKR orthologs on general translation inhibition, stress-responsive translation, and NF-κB-dependent induction of target genes. Congenic human and rabbit cell lines infected with a myxoma virus strain lacking PKR inhibitors were used to compare the effects of human and rabbit PKR on viral replication and inflammatory responses. Site-directed mutagenesis was employed to determine key residues responsible for differential sensitivity to the viral inhibitor M156. Results: All 17 mammalian PKR orthologs significantly inhibited general translation, strongly activated stress-responsive ATF4 translation, and robustly induced NF-κB target genes. Inhibition of these responses was specifically mediated by poxviral K3 orthologs that effectively suppressed PKR activation. Comparative analyses showed human and rabbit PKRs similarly inhibited virus replication and induced cytokine transcripts. Amino acid swaps between rabbit PKRs reversed their sensitivity to viral inhibitor M156 and NF-κB activation. Conclusions: Our data show that the tested PKR orthologs exhibit conserved dual antiviral and inflammatory regulatory roles, which can be antagonized by poxviral K3 orthologs that exploit eIF2α mimicry to modulate the PKR-NF-κB axis. Full article

Objectives: Understanding the antibody response in monkeypox virus (MPXV)-infected and uninfected individuals is essential for developing next-generation MPXV vaccines. This study aimed to characterize neutralizing antibody (NAb) and antibody-dependent cellular cytotoxicity (ADCC) responses in both groups, providing insights into immune protection and vaccine design. Methods: A recombinant vaccinia Tian Tan (VTT) virus was utilized to develop high-throughput luciferase-reporter-based neutralization and ADCC assays. These assays were applied to evaluate the presence and levels of poxvirus-specific antibodies in MPXV-infected and uninfected individuals, including those vaccinated with vaccinia-based vaccines. Results: Poxvirus-specific NAbs were detected in MPXV-negative individuals with prior vaccinia vaccination. However, MSM individuals exhibited significantly lower pre-existing NAb levels than non-MSM individuals, potentially contributing to their higher susceptibility to MPXV infection. In individuals with mild MPXV infection, robust NAb and ADCC responses were observed, regardless of vaccination status. Additionally, HIV-positive individuals demonstrated comparable antibody responses following MPXV infection. Conclusions: These findings highlight the potential role of pre-existing NAbs in MPXV susceptibility and the strong immune response elicited by mild MPXV infection. Further research is needed to determine whether MPXV-specific antibodies mitigate disease progression, which could inform the development of effective MPXV vaccines. Full article

Sheep pox (SP) is a contagious viral disease affecting sheep, characterized by fever, respiratory distress, hypogalactia, and skin lesions. In response to a series of outbreaks of pox-like lesions with morbidity (75%) and mortality (37%) rates among sheep in the Upper East Region of Ghana, nasal samples were obtained from affected sheep for diagnosis and characterization. The DNA extracted from these samples was tested using quantitative PCR (qPCR). Positive samples were subjected to further analysis for poxvirus marker genes using conventional PCR. Positive amplicons were sequenced, and phylogenetic analysis was conducted. The characterization and comparison of RPO30, GPCR, EEV glycoprotein, and B22R genes with other isolates demonstrated a close genetic relationship with sheep poxviruses (SPVs) identified in other African and Asian countries. This study represents the first comprehensive characterization of SPV in Ghana, and the data generated will be of significant interest to national and regional veterinary authorities. Full article

The papers introduced in the Commentary present new insights and review aspects of current knowledge concerning the competition between viruses and their hosts for the cellular translation apparatus. Viruses depend on this apparatus and utilize diverse mechanisms to usurp it for the translation of viral mRNAs and to suppress synthesis of cellular proteins. Virus-induced modification of translation factors, selective abrogation of mRNA binding to ribosomes and degradation of cellular mRNAs all impair elements of the innate immune response, thereby undermining host defenses against infection. Various cellular mechanisms prevent translation of viral mRNAs, by modifying components of the translation apparatus to effect a generalized shut-off of translation or by binding of host proteins to viral mRNAs to induce their degradation or to prevent their engagement with the translation apparatus. Viruses have in turn evolved countermeasures to evade these defenses, for example by encoding proteins that impair the activity of host factors or via alterations in the sequence and structure of viral mRNAs. Such changes enable viral mRNAs to avoid recognition by host factors or to support translation initiation by specialized mechanisms that involve only a subset of the factors that are required by cellular mRNAs. Full article

Poxvirus infections, particularly those caused by the monkeypox virus, have emerged as significant public health threats. Ocular manifestations constitute a severe potential clinical complication associated with these infections, potentially resulting in permanent visual impairment in afflicted patients. This review aimed to examine the clinical spectrum of ocular manifestations associated with mpox and other poxvirus infections and to evaluate current management strategies alongside emerging therapeutic interventions and prevention strategies. A comprehensive literature search was performed across major databases to identify studies reporting ocular involvement in poxviral infections. Ocular involvement in poxviral infections ranges from mild conjunctivitis and eyelid lesions to severe keratitis with potential vision loss. Mpox-related ocular manifestations are more prevalent in unvaccinated and immunocompromised individuals. Although early antiviral intervention and supportive care are critical, clinical outcomes vary considerably across viral clades. Emerging evidence indicates that tecovirimat may reduce lesion severity, although its impact on accelerating recovery remains limited. Moreover, vaccine strategies, particularly the MVA-BN (JYNNEOS) vaccine, appear to decrease ocular complications, despite regional disparities in access and implementation. Ocular complications pose a significant clinical challenge in mpox and related poxviral infections. This review highlights the need for early diagnosis and integrated treatment approaches that combine antiviral therapy, supportive care, and targeted vaccination. Further research is essential to refine treatment protocols and assess the long-term outcomes in diverse patient populations. Full article

Background/Objectives: Monkeypox, twice declared a public health emergency of international concern by the WHO, currently lacks approved targeted therapeutics. This study focused on the development of monkeypox virus (MPXV) E8-specific human monoclonal antibodies (mAbs) derived from recipients of the recombinant vaccinia vaccine (rTV), with subsequent evaluation of their cross-neutralizing activity against orthopoxviruses, including the vaccinia virus (VACV) and MPXV. Methods: Three mAbs (C5, C9, and F8) were isolated from rTV vaccinees. Structural mapping characterized their binding domains on the MPXV E8 and VACV D8 proteins. Neutralization potency was assessed against the VACV TianTan strain and MPXV clade IIb. A combo was further evaluated in a VACV-infected mice model for clinical recovery and viral load reduction. Complement-dependent enhancement mechanisms were also investigated in vitro. Results: C9 targets the virion surface region of E8 and both the virion surface region and intravirion region of D8, showing cross-neutralization activity against the MPXV (IC₅₀ = 3.0 μg/mL) and VACV (IC₅₀ = 51.1 ng/mL) in vitro. All three antibodies demonstrated potent neutralization against the VACV in vitro: C5 (IC₅₀ = 3.9 ng/mL), C9 (IC₅₀ = 51.1 ng/mL), and F8 (IC₅₀ = 101.1 ng/mL). Notably, complement enhanced neutralization against the VACV by >50-fold, although no enhancement was observed for the MPXV. In vivo administration accelerated clinical recovery by 24 h and achieved significant viral clearance (0.9-log reduction). Conclusions: E8-targeting mAbs exhibited broad-spectrum neutralization against orthopoxviruses, demonstrating therapeutic potential against both historical (VACV) and emerging (MPXV) pathogens. However, MPXV’s resistance to complement-dependent enhancement highlights the necessity for pathogen-adapted optimization. These findings establish E8 as a critical conserved target for pan-poxvirus VACV and MPXV countermeasure development. Full article

Orf virus (ORFV) is the type species of Parapoxvirus of the Poxviridae family that induces cutaneous pustular skin lesions in sheep and goats, and causes zoonotic infections in humans. Pattern recognition receptors (PRRs) sense pathogen-associated molecular patterns (PAMPs), leading to the triggering of the innate immune response through multiple signalling pathways involving type I interferons (IFNs). The major PAMPs generated during viral infection are nucleic acids, which are the most important molecules that are recognized by the host. The induction of type l IFNs leads to activation of the Janus kinase (JAK)-signal transducer activator of transcription (STAT) pathway, which results in the induction of hundreds of interferon-stimulated genes (ISGs), many of which encode proteins that have antiviral roles in eliminating virus infection and create an antiviral state. Genetic and functional analyses have revealed that ORFV, as found for other poxviruses, has evolved multiple immunomodulatory genes and strategies that manipulate the innate immune sensing response. Full article

The ongoing global outbreak of mpox caused by clade IIb viruses has led to more than 100,000 confirmed cases around the world, highlighting the urgent need for antiviral research to combat current and future mpox outbreaks. Reporter viruses expressing fluorescent proteins to monitor viral replication and virus spreading in cell culture provide a powerful tool for antiviral drug screening. In this work, we engineered two recombinant mpox clade IIb viruses by inserting, under the control of the vaccinia early/late promoter 7.5, the coding sequence of two different fluorescent proteins (EGFP and TurboFP635) in a previously unreported location within the viral genome. These recombinant viruses replicate in BSC-1 cells at rates similar to those of the parental virus. We show how these reporter mpox viruses allow the discrimination of infected cells by cell flow cytometry and facilitate the quantification of viral spread in cell culture. Finally, we validated these reporter viruses with two previously known inhibitors of poxvirus replication, cytosine arabinoside (AraC) and bisbenzimide. Full article

Norovirus is a major etiological agent of nonbacterial gastroenteritis around the world. Due to its in vitro culture complexity, high genome diversity, and the lack of cross-reactive immunity between genogroups, there is an unmet urgent need for polyvalent norovirus vaccines that provide broad-spectrum protection, and no vaccine has gained global approval to date. In this study, we constructed a bivalent norovirus vaccine, based on the highly attenuated poxvirus [strain VG9] vector, expressing the major capsid protein VP1 from genotypes GII.4 and GII.17. VG9-NOR exhibited a comparable replication ability to the authentic virus while preserving good safety. After the intramuscular and intranasal immunization of mice, VG9-NOR induced high IgG- and IgA-binding antibody (Ab) titers against GII.4 and GII.17, increased the secretion of GII.4 and GII.17-specific HGBA-blocking antibodies, and enhanced GII.17-specific mucosal immunity. Furthermore, VG9-NOR also induced a Th1-mediated cellular response. These results demonstrate that the polyvalent poxvirus vector vaccine expressing VP1 variants from different subtypes is able to elicit effective protection. Our study highlights the VG9 vector as a highly promising candidate for the development of polyvalent norovirus vaccines. Full article

Amid the current multi-country mpox outbreak, analyzing monkeypox virus (MPXV) and vaccinia virus (VACV) genomes is vital for understanding evolutionary processes that may impact vaccine efficacy and design. This study aimed to elucidate the phylogenetic relationships and structural features of viral antigens, which are crucial for developing effective vaccines. By aligning 1903 MPXV genomes from the NCBI Virus repository (released between 2022 and 2024), an increase in phylogenetic diversity was observed compared to previous studies. These genomes were grouped into Clade I (25 genomes) and Clade IIB (1898 genomes), with a new Clade I sub-lineage emerging from samples collected in Sud-Kivu province, Democratic Republic of the Congo (DRC). Comparing six key MPXV neutralization determinants (A29, A35, B6, E8, H3, and M1) of a novel 2024 Clade I MPXV isolate to those of the 1996 Zaire isolate revealed remarkable sequence conservation despite spanning 28 years. Homology-based modeling of the Clade I MPXV antigens (A29, A35, E8, H3, and M1) showed high-match identities (84% to 99%) with VACV templates (current mpox vaccine), with several amino acid variants near potential antibody binding sites. Phylogenomic analysis, combined with structural modeling and variant profiling, has yielded valuable insights into the virus and vaccine, guiding vaccine design and functional studies. Full article

Globally, there are two major poxvirus outbreaks: mpox, caused by the monkeypox virus, and lumpy skin disease, caused by the lumpy skin disease virus. While vaccines for both diseases exist, there is a need for improved vaccines. The original vaccines used to eradicate smallpox, which also protect from the disease now known as mpox, are no longer acceptable. This is mainly due to the risk of serious adverse events, particularly in HIV-positive people. The next-generation vaccine for mpox prevention is modified vaccinia Ankara, which does not complete the viral replication cycle in humans and, therefore, has a better safety profile. However, two modified vaccinia Ankara immunizations are needed to give good but often incomplete protection, and there are indications that the immune response will wane over time. A better vaccine that induces a long-lived response with only one immunization is desirable. Another recently available smallpox vaccine is LC16m8. While LC16m8 contains replicating vaccinia virus, it is a more attenuated vaccine than the original vaccines and has limited side effects. The commonly used lumpy skin disease vaccines are based on attenuated lumpy skin disease virus. However, an inactivated or non-infectious vaccine is desirable as the disease spreads into new territories. This article reviews novel vaccine approaches, including mRNA and subunit vaccines, to protect from poxvirus infection. Full article

Avian pox is a globally spread viral disease affecting a wide spectrum of wild and domesticated bird species. The disease is caused by a diverse group of large DNA viruses, namely, avipoxviruses (genus Avipoxvirus, family Poxviridae). In this study, gross pathological examination and histopathological examination of skin lesions and several organs suggested acute poxvirus infection of a Eurasian crane (Grus grus, Linnaeus, 1758). Avipoxvirus infection was confirmed by testing wart-like lesions via gene-specific PCR assay and sequencing the obtained amplicon. Phylogenetic analysis of the gene encoding the DNA polymerase revealed that the crane poxvirus clustered in clade A, subclade A3. A large fragment of the poxvirus genome (306,477 bp in length) was assembled from the DNA of a skin specimen. Our study reaffirms previous findings that even complex virus genomes can be determined from a metagenomic assemblage generated directly from avian tissue samples without prior virus isolation, a promising approach for the epidemiologic surveillance of avipoxvirus infections in wild birds and domestic poultry. Full article

Since its first report in Brazil in 1999, outbreaks of exanthematous diseases caused by vaccinia virus (VACV) have been a recurring concern, particularly impacting rural regions. Minas Gerais (MG) State, Brazil, has emerged as the epicenter of bovine vaccinia (BV) outbreaks. This study presents a comprehensive overview of VACV circulation in MG State over the past two decades, examining the occurrence and distribution of poxvirus cases and outbreaks and the demographic characteristics of affected populations. Analysis of secondary databases from 2000 to 2023 revealed VACV circulation in at least 149 municipalities, particularly expanding in dairy regions. The study underscores BV as an occupational disease, predominantly affecting rural men involved in dairy cattle activities. Laboratory findings indicate high levels of anti-OPXV antibodies in most individuals, with some showing acute infections confirmed by qPCR testing. This analysis informs public health policies, emphasizing the need for enhanced surveillance of and preventive measures for dairy farming communities. Full article

The threespine stickleback iridovirus (TSIV), a double-stranded DNA virus, was the first megalocytivirus detected in wild North American fishes. We report a second occurrence of TSIV in threespine stickleback (Gasterosteus aculeatus) from Stormy Lake, Alaska, and assemble a nearly complete genome of TSIV. The 115-kilobase TSIV genome contains 94 open reading frames (ORFs), with 91 that share homology with other known iridoviruses. We identify three ORFs that likely originate from recent lateral gene transfers from a eukaryotic host and one ORF with homology to B22 poxvirus proteins that likely originated from a lateral gene transfer between viruses. Phylogenetic analysis of 24 iridovirus core genes and pairwise sequence identity analysis support TSIV as a divergent sister taxon to other megalocytiviruses and a candidate for a novel species designation. Screening of stickleback collected from Stormy Lake before and after a 2012 rotenone treatment to eliminate invasive fish shows 100% positivity for TSIV in the two years before treatment (95% confidence interval: 89–100% prevalence) and 0% positivity for TSIV in 2024 after treatment (95% confidence interval: 0 to 3.7% prevalence), suggesting that the rotenone treatment and subsequent crash and reestablishment of the stickleback population is associated with loss of TSIV. Full article