Due to the urgent need of a therapeutic treatment for coronavirus (CoV) disease 2019 (COVID-19) patients, a number of FDA-approved/repurposed drugs have been suggested as antiviral candidates at clinics, without sufficient information. Furthermore, there have been extensive debates over antiviral candidates for their effectiveness and safety against severe acute respiratory syndrome CoV 2 (SARS-CoV-2), suggesting that rapid preclinical animal studies are required to identify potential antiviral candidates for human trials. To this end, the antiviral efficacies of lopinavir-ritonavir, hydroxychloroquine sulfate, and emtricitabine-tenofovir for SARS-CoV-2 infection were assessed in the ferret infection model. While the lopinavir-ritonavir-, hydroxychloroquine sulfate-, or emtricitabine-tenofovir-treated group exhibited lower overall clinical scores than the phosphate-buffered saline (PBS)-treated control group, the virus titers in nasal washes, stool specimens, and respiratory tissues were similar between all three antiviral-candidate-treated groups and the PBS-treated control group. Only the emtricitabine-tenofovir-treated group showed lower virus titers in nasal washes at 8 days postinfection (dpi) than the PBS-treated control group. To further explore the effect of immune suppression on viral infection and clinical outcome, ferrets were treated with azathioprine, an immunosuppressive drug. Compared to the PBS-treated control group, azathioprine-immunosuppressed ferrets exhibited a longer period of clinical illness, higher virus titers in nasal turbinate, delayed virus clearance, and significantly lower serum neutralization (SN) antibody titers. Taken together, all antiviral drugs tested marginally reduced the overall clinical scores of infected ferrets but did not significantly affect in vivo virus titers. Despite the potential discrepancy of drug efficacies between animals and humans, these preclinical ferret data should be highly informative to future therapeutic treatment of COVID-19 patients. IMPORTANCE The SARS-CoV-2 pandemic continues to spread worldwide, with rapidly increasing numbers of mortalities, placing increasing strain on health care systems. Despite serious public health concerns, no effective vaccines or therapeutics have been approved by regulatory agencies. In this study, we tested the FDA-approved drugs lopinavir-ritonavir, hydroxychloroquine sulfate, and emtricitabine-tenofovir against SARS-CoV-2 infection in a highly susceptible ferret infection model. While most of the drug treatments marginally reduced clinical symptoms, they did not reduce virus titers, with the exception of emtricitabine-tenofovir treatment, which led to diminished virus titers in nasal washes at 8 dpi. Further, the azathioprine-treated immunosuppressed ferrets showed delayed virus clearance and low SN titers, resulting in a prolonged infection. As several FDA-approved or repurposed drugs are being tested as antiviral candidates at clinics without sufficient information, rapid preclinical animal studies should proceed to identify therapeutic drug candidates with strong antiviral potential and high safety prior to a human efficacy trial.

While pregnancy increases the risk for severe COVID-19, the clinical and immunological implications of COVID-19 on maternal-fetal health remain unknown. Here, we present the clinical and immunological landscapes of 93 COVID-19 mothers and 45 of their SARS-CoV-2-exposed infants through comprehensive serum proteomics profiling for >1,400 cytokines of their peripheral and cord blood specimens. Prenatal SARS-CoV-2 infection triggers NF-κB-dependent proinflammatory immune activation. Pregnant women with severe COVID-19 show increased inflammation and unique IFN-λ antiviral signaling, with elevated levels of IFNL1 and IFNLR1. Furthermore, SARS-CoV-2 infection re-shapes maternal immunity at delivery, altering the expression of pregnancy complication-associated cytokines, inducing MMP7, MDK, and ESM1 and reducing BGN and CD209. Finally, COVID-19-exposed infants exhibit induction of T cell-associated cytokines (IL33, NFATC3, and CCL21), while some undergo IL-1β/IL-18/CASP1 axis-driven neonatal respiratory distress despite birth at term. Our findings demonstrate COVID-19-induced immune rewiring in both mothers and neonates, warranting long-term clinical follow-up to mitigate potential health risks.

Tick-borne diseases have become a growing threat to public health. SFTSV, listed by the World Health Organization as a prioritized pathogen, is an emerging phlebovirus, and fatality rates among those infected with this virus are high. Infected Haemaphysalis longicornis ticks are the major source of human SFTSV infection. In particular, the recent spread of this tick to over 12 states in the United States has increased the potential for outbreaks of this disease beyond Far East Asia. Due to the lack of therapies and vaccines against SFTSV infection, there is a pressing need to understand SFTSV pathogenesis. As the Nrf2-mediated antioxidant response affects viral life cycles, a number of viruses deregulate Nrf2 pathways. Here we demonstrate that the SFTSV NSs inhibits the TRIM21 function to upregulate the p62-Keap1-Nrf2 antioxidant pathway for efficient viral pathogenesis. This study not only demonstrates the critical role of SFTSV NSs in viral pathogenesis but also suggests potential future therapeutic approaches to treat SFTSV-infected patients.

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a highly lethal tick-borne bunyavirus, and its nonstructural protein NSs is the engine driving viral pathogenesis. Far beyond a simple accessory protein, NSs acts as a master manipulator of the host: it shuts down interferon defenses, rewires inflammatory signaling, and creates an immunosuppressive environment that favors viral survival. At the same time, NSs reshapes cellular physiology by halting the cell cycle, reprogramming stress and antioxidant pathways, dismantling antiviral granules, and hijacking metabolic organelles such as lipid droplets and autophagosomes to build replication-permissive niches. Remarkably, NSs also functions as a cross-kingdom suppressor of RNA interference, disarming antiviral defenses in both mammalian hosts and tick vectors to ensure efficient replication and transmission. This convergence of immune evasion, cellular reprogramming, and vector adaptation underscores NSs as the central determinant of SFTSV virulence and a striking example of how a single viral protein can orchestrate complex host-pathogen interactions.

Patients with immune-mediated inflammatory diseases (IMIDs) like rheumatoid arthritis (RA) are at higher risk for severe COVID-19 and long-term complications in bone health. Emerging clinical evidence demonstrated that SARS-CoV-2 infection reduces bone turnover and promotes bone loss, but the mechanism underlying worsened bone health remains elusive. This study sought to identify specific immune mediators that exacerbated preexisting IMIDs after SARS-CoV-2 exposure. Plasma samples from 4 groups were analyzed: healthy, IMID only, COVID-19 only, and COVID-19 + IMID. Using high-throughput multiplexed proteomics, we profiled 1,500 protein biomarkers and identified 148 unique biomarkers in COVID-19 patients with IMIDs, including elevated inflammatory cytokines (e.g., IL-17F) and bone resorption markers. Long-term circulating SARS-CoV-2 ORF8, a virulence factor for COVID-19, was detected in the COVID + IMID group. RA was one of the most common IMIDs in our study. ORF8 treatment of RA-derived human osteoblasts (RA-hOBs) increased levels of inflammatory ( TNF , IL6 , CCL2 ) and bone resorption ( RANKL /osteoprotegerin ratio) markers compared with healthy controls. Supernatants from ORF8-treated RA-hOBs drove the differentiation of macrophages into osteoclast-like cells. These findings suggest that SARS-CoV-2 exposure can exacerbate IMIDs through ORF8-driven inflammation and osteoclastogenesis, highlighting potential therapeutic targets for managing COVID-19–induced bone pathologies.

RNA interference (RNAi) is a posttranscriptional gene silencing mechanism acting as an antiviral defense in eukaryotes. During viral replication, intermediate double-stranded RNAs are processed into virus-derived small interfering RNAs (vsiRNAs) by the host enzyme, DICER. These vsiRNAs are incorporated into the RNA-induced silencing complex (RISC), where AGO2 cleaves viral genomic RNAs. However, viruses have evolved mechanisms to suppress this pathway. Here, we report that the nonstructural protein (NSs) of severe fever with thrombocytopenia syndrome virus (SFTSV) interacts with RISC to suppress the RNAi pathway. NSs forms a ternary complex by interacting with both DICER and AGO2 of the RNAi pathway. The interaction between NSs and DICER, facilitated by the two RNase III domains of DICER, is disrupted in the absence of AGO2 or the DICER-interacting domain (PIWI) of AGO2, indicating a direct interaction between NSs and AGO2. Functional assays using shRNA- and siRNA-mediated silencing of GFP signal, along with co-localization studies, demonstrated that NSs competes with siRNA to interact with AGO2, thereby abolishing RNAi activity. Mutational analysis identified an NSs-A26 mutant that no longer interacts with AGO2 and is unable to suppress RNAi activity, suggesting that NSs acts as a viral suppressor of RNAi (VSR) for SFTSV. Viral infection led to the generation of vsiRNA and showed higher replication in AGO2 ^-/- cells compared to wild-type (WT) cells, confirming the antiviral role of the RNAi pathway against SFTSV infection. These data suggest that the NSs–AGO2 interaction suppresses RNAi, counteracting the antiviral RNAi pathway, thereby facilitating SFTSV infection and pathogenesis. IMPORTANCE: RNA interference (RNAi) is the main antiviral defense pathway in plants and insects but is not predominant in mammals. While RNAi’s role in countering severe fever with thrombocytopenia syndrome virus (SFTSV) infection has been studied in ticks, its role in humans is unknown. The SFTSV nonstructural protein (NSs) forms inclusion bodies (IBs) in the host, sequestering multiple antiviral proteins and facilitating pathogenesis, contributing to SFTSV’s high mortality rate. Our study found that SFTSV NSs directly interacts with AGO2, a key RNAi protein, hindering its function. A novel NSs mutant failed to interact with AGO2 and lost its RNAi suppression ability, highlighting NSs as a viral suppressor of RNAi (VSR). Infection studies confirmed the RNAi pathway’s critical role in combating SFTSV infection. This study demonstrates NSs’s role in viral infection and suggests potential therapeutic approaches.