Publications by Year: 2026

In this study, the infection dynamics, replication, and pathogenicity of a recombinant virus containing a deletion of ORF6 (rWA1ΔORF6) on the backbone of the highly virulent SARS-CoV-2 WA1 virus (rWA1) were investigated and compared to the parental rWA1 virus. While both rWA1 and rWA1ΔORF6 viruses replicated efficiently in cultured cells, the rWA1ΔORF6 virus produced smaller plaques, suggesting reduced cell-to-cell spread. Luciferase reporter assays revealed immune-suppressing effects of ORF6 on interferon (IFN) and nuclear factor kappa B (NF-κB) signaling pathways. Pathogenesis assessment in cats revealed that animals inoculated with rWA1 were lethargic and presented with fever on days 2 and 4 post-infection (pi), whereas rWA1ΔORF6-inoculated animals developed subclinical infection. Additionally, animals inoculated with rWA1ΔORF6 presented reduced infectious virus shedding in nasal and oral secretions and broncho-alveolar lavage fluid when compared with the rWA1-inoculated cats. Similarly, the rWA1ΔORF6-inoculated cats presented reduced virus replication in the respiratory tract as evidenced by lower viral loads and reduced lung inflammation on days 3 and 5 pi when compared to rWA1-inoculated animals. Host gene transcriptomic analysis revealed distinct differentially expressed gene (DEG) profiles in the nasal turbinate of animals infected with rWA1 when compared to rWA1ΔORF6. Importantly, type I IFN signaling was significantly upregulated in rWA1ΔORF6-infected cats when compared to rWA1-inoculated animals, which could potentially contribute to the reduced replication of rWA1ΔORF6 in the upper and lower respiratory tracts of infected animals. Collectively, these results demonstrate that the SARS-CoV-2 ORF6 is an important virulence determinant of the virus, contributing to the modulation of host antiviral immune responses.IMPORTANCESARS-CoV-2 encodes several proteins that inhibit host IFN responses. The accessory protein ORF6 antagonizes IFN signaling by blocking the nucleocytoplasmic trafficking of key transcription factors. In this study, we showed that ORF6 plays an important role in SARS-CoV-2 pathogenesis. While both rWA1 and rWA1ΔORF6 viruses replicated efficiently in cell culture, the rWA1ΔORF6 presented impaired cell-to-cell spread and reduced innate immune inhibition compared to the parental rWA1. A pathogenesis study in the feline model revealed an attenuated phenotype of the rWA1ΔORF6, indicating that ORF6 is a major virulence determinant of SARS-CoV-2.

Several mammarenaviruses (MaAv), chiefly Lassa virus (LASV) in Western Africa and Junin virus (JUNV) in the Argentinean Pampas, cause severe disease in humans and pose important public health problems in their endemic regions. In addition, the globally distributed MaAv lymphocytic choriomeningitis virus (LCMV) is an underrecognized human pathogen of clinical significance, especially in congenital infections, and LCMV poses a serious risk for immunocompromised individuals. There are no FDA-approved MaAv vaccines or antivirals, and current anti-MaAv therapy is limited to an off-label use of ribavirin, whose efficacy remains controversial. This highlights an urgent unmet need for developing antivirals against human pathogenic MaAv. Halofuginone (HF), a derivative of the natural alkaloid febrifugine, has been shown to exhibit antiviral activity against several RNA viruses. Here, we present evidence that HF exhibits potent dose-dependent antiviral activity against LCMV, and against the hemorrhagic fever causing MaAv LASV and JUNV. HF binds to the bifunctional enzyme glutamyl-prolyl-tRNA synthetase 1 (EPRS1) and specifically inhibits its prolyl-tRNA synthetase (PRS) activity, resulting in translation inhibition via the amino acid starvation (AAS) response with preferential impact on proline-rich proteins. HF anti-LCMV activity was prevented by the addition of exogenous proline supporting that inhibition of PRS activity plays a critical role in the anti-MaAv activity of HF. We found that HF did not affect LCMV cell entry, modestly (twofold) reduced the activity of the virus ribonucleoprotein (vRNP), but strongly inhibited (>90%) Z budding activity, a process involving the Z proline-rich late domain motifs.

Monkeypox (MPOX) is an emerging zoonotic disease caused by monkeypox virus (MPXV), an orthopoxvirus closely related to smallpox. Initially confined to endemic regions in Central and West Africa, MPOX has recently gained global significance with outbreaks reported across multiple continents. MPXV is maintained in animal reservoirs but is increasingly transmitted from person to person, facilitated by close contact, respiratory droplets, and, in some cases, sexual transmission. Clinically, MPOX presents with fever, lymphadenopathy, and a characteristic vesiculopustular rash, though atypical manifestations have been observed in recent outbreaks, complicating diagnosis. Laboratory confirmation relies on molecular testing, while differential diagnosis must consider varicella, herpes, and other vesicular illnesses. Therapeutic options remain limited; supportive care is the cornerstone of management, but antivirals such as tecovirimat and brincidofovir, as well as smallpox vaccines, have shown efficacy in mitigating disease severity and preventing infection. The unprecedented global outbreak has underscored the importance of surveillance, rapid diagnostics, and coordinated public health responses to contain transmission. This review provides an overview of epidemiology, virology, clinical manifestations, modes of transmission, available diagnostics, and prophylactic and therapeutic strategies against MPOX. We also discuss the role of animal reservoirs, viral evolution, and human-to-human transmission in shaping the dynamics of recent MPOX outbreaks. By summarizing the latest evidence, this review aims to inform clinicians, researchers, and policymakers about key aspects of MPOX biology, clinical management, and prevention, while identifying gaps that warrant future investigation for the control of this and potentially other emerging zoonotic-related pathogens with an impact on human health.

The remaining unacceptably high mortality of influenza-induced acute respiratory distress syndrome underscores the urgent need to identify key cellular drivers of host responses. Endothelial cells (ECs) are increasingly recognized for their immunomodulatory roles, but whether they function as antigen-presenting cells (APCs) following respiratory viral infection remains unknown. Here, we show that influenza A virus H1N1 restrictively infects pulmonary microvascular ECs (PMVECs) during late-stage acute lung injury, triggering robust MHC class I (MHC-I) upregulation in vitro, in vivo, and in ex vivo human precision-cut lung slices. Infected PMVECs present H1N1 antigens via MHC-I and co-stimulatory CD40 to lung-resident CD8⁺ T cells, driving their proliferation and effector function (Granzyme B, IFNγ) to promote viral clearance and resolve inflammation. This process is IFNγ-dependent and STAT1-regulated, forming a positive feedback loop that enhances PMVEC antigen presentation and CD8⁺ T cells activation. By contrast, the emerging H5N1 (A/Texas/37/2024) infect pulmonary ECs earlier and more broadly but elicits weaker pulmonary EC-driven CD8 + T cell responses, potentially contributing to its higher pathogenicity. These findings reveal PMVECs as active APCs in antiviral defense and highlight new avenues for immunotherapeutic intervention.