Although the COVID-19 pandemic was declared no longer a global emergency by the World Health Organization in May 2023, SARS-CoV-2 is still infecting people across the world. Many therapeutic oligonucleotides such as ASOs, siRNAs, or CRISPR-based systems emerged as promising antiviral strategies for the treatment of SARS-CoV-2. In this work, we explored the inhibitory potential on SARS-CoV-2 replication of Polypurine Reverse Hoogsteen Hairpins (PPRHs), CC1-PPRH, and CC3-PPRH, targeting specific polypyrimidine sequences within the replicase and Spike regions, respectively, and previously validated for COVID-19 diagnosis. Both PPRHs are bound to their target sequences in the viral genome with high affinity in the order of nM. In vitro, both PPRHs reduced viral replication by more than 92% when transfected into VERO-E6 cells 24 h prior to infection with SARS-CoV-2. In vivo intranasal administration of CC1-PPRH in K18-hACE2 mice expressing the human ACE receptor protected all the animals from SARS-CoV-2 infection. The properties of PPRHs position them as promising candidates for the development of novel therapeutics against SARS-CoV-2 and other viral infections.

Cyclic GMP-AMP synthase (cGAS) is a DNA sensing cellular receptor that induces IFN-I transcription in response to pathogen and host derived cytosolic DNA and can limit the replication of some RNA viruses. Some viruses have nonetheless evolved mechanisms to antagonize cGAS sensing. In this study, we evaluated the interaction between Bluetongue virus (BTV), the prototypical dsRNA virus of the Orbivirus genus and the Sedoreoviridae family, and cGAS. We found mitochondrial damage and DNA accumulation in the cytoplasm of infected cells. In addition, we show that BTV infection blocks DNA-induced IFN-I transcription and that virus infection prevents DNA sensing by inducing cGAS and STING degradation. We identify BTV-NS3 as the viral protein responsible for cGAS degradation, showing that NS3 physically interacts with cGAS and induces its degradation through an autophagy-dependent mechanism. Taken together, these findings identify for the first time a mechanism by which a dsRNA virus interferes with a DNA sensing pathway to evade the innate immune response.

Peste des petits ruminants (PPR) is a WOAH notifiable disease affecting sheep and goats, caused by Peste des petits ruminants virus (PPRV), a morbillivirus of the Paramyxoviridae family. Infection with PPRV leads to immunosuppression, creating conditions for opportunistic infections that can result in animal mortality. Although goats generally exhibit more severe clinical signs than sheep, the underlying mechanisms driving this species-specific difference remain poorly understood. Dendritic cells (DC), which play a pivotal role in initiating immune responses, are among the immune targets of PPRV in small ruminants. In this study, we examined the impact of PPRV on caprine immune cells, focusing on CD14⁺ monocytes and monocyte-derived dendritic cells (MoDC). Our findings indicate that PPRV infects goat monocytes without preventing their differentiation into DC. Infected MoDC displayed increased expression of maturation markers and reduced phagocytic activity, suggesting a transition toward an activated phenotype. However, mixed lymphocyte reaction assays revealed that PPRV-infected MoDCs have a diminished capacity to promote T cell proliferation. This impaired function was associated with elevated IL-10 production and reduced conjugation between DCs and T cells. Overall, PPRV infection induces an atypical maturation stage in goat MoDCs, characterized by partial activation but impaired antigen presentation. These findings demonstrate that PPRV-driven modulation of DC function contributes to the immunosuppression observed during PPRV infection in goats.

Background/Objectives: Bluetongue virus (BTV) is an emerging arbovirus causing significant economic losses in the ruminant industry. Current vaccines offer limited cross-protection against heterologous serotypes and do not enable differentiation between infected and vaccinated animals (DIVA). Subunit-based vaccines provide a potential DIVA-compatible solution. This study aimed to develop a vaccination protocol expressing BTV structural proteins VP7 or VP2 using antibiotic-resistance-free DNA plasmids and replication-defective adenovirus vectors. Methods: We evaluated homologous DNA prime–boost and heterologous DNA prime–adenovirus boost strategies in a murine model, assessing adaptive immune responses and protection against virulent BTV challenge. Results: The heterologous DNA–adenovirus prime–boost strategy expressing both antigens conferred full protection, preventing viremia, while homologous DNA-DNA prime–boost provided only partial protection. Both VP7 and VP2 elicited cellular and humoral immune responses, but the heterologous strategy significantly enhanced anti-BTV IgG, neutralizing antibody titers, and T cell activation. CD8⁺ T cell responses showed the strongest correlation with viral load reduction, suggesting that cellular immunity to conserved VP7 could serve as a platform for cross-protection against multiple BTV serotypes. Conclusions: These findings highlight the potential of heterologous DNA–adenovirus vaccination as an effective DIVA-compatible strategy for BTV control. By inducing strong and protective immune responses, this approach could improve disease surveillance and management, ultimately reducing the impact of BTV on livestock industries.

Background/Objectives: Bluetongue virus (BTV) is an emerging arbovirus causing significant economic losses in the ruminant industry. Current vaccines offer limited cross-protection against heterologous serotypes and do not enable differentiation between infected and vaccinated animals (DIVA). Subunit-based vaccines provide a potential DIVA-compatible solution. This study aimed to develop a vaccination protocol expressing BTV structural proteins VP7 or VP2 using antibiotic-resistance-free DNA plasmids and replication-defective adenovirus vectors. Methods: We evaluated homologous DNA prime-boost and heterologous DNA prime-adenovirus boost strategies in a murine model, assessing adaptive immune responses and protection against virulent BTV challenge. Results: The heterologous DNA-adenovirus prime-boost strategy expressing both antigens conferred full protection, preventing viremia, while homologous DNA-DNA prime-boost provided only partial protection. Both VP7 and VP2 elicited cellular and humoral immune responses, but the heterologous strategy significantly enhanced anti-BTV IgG, neutralizing antibody titers, and T cell activation. CD8+ T cell responses showed the strongest correlation with viral load reduction, suggesting that immunity to VP7 could offer cross-protection against multiple BTV serotypes. Conclusion: These findings highlight the potential of heterologous DNA-adenovirus vaccination as an effective DIVA-compatible strategy for BTV control. By inducing strong and protective immune responses, this approach could improve disease surveillance and management, ultimately reducing the impact of BTV on livestock industries.