Overexpression of Interleukin-33 in Recombinant Rabies Virus Enhances Innate and Humoral Immune Responses through Activation of Dendritic Cell-Germinal Center Reactions

Recombinant feline herpesvirus-1 (FHV-1) expressing granulocyte colony-stimulating factor (G-CSF) exhibits enhanced protective efficacy in felines

Vaccine efficacy relies not only on antigens but also on immunomodulatory agents/adjuvants that are often used to stimulate the immune system and enhance the immune response. However, current immunomodulatory agents are used to increase the immune response induced by viral or bacterial inactivated vaccine antigens, bacterial toxoids or polysaccharides but not attenuated live viruses. Based on the immunomodulatory functions of G-CSF and the characteristics of feline herpesvirus-1 (FHV-1) as an expression vector, a recombinant virus expressing feline G-CSF (WH2020-ΔTK/gI/gE-G-CSF) was constructed. The growth dynamics of WH2020-ΔTK/gI/gE-G-CSF were similar to those of WH2020-ΔTK/gI/gE. Compared with kittens vaccinated with WH2020 Δ TK/gI/gE, felines inoculated with WH2020 ΔTK/gI/gE-G-CSF produced more neutralizing antibodies and neutrophils, further alleviating clinical symptoms after FHV-1 infection. Taken together, our results revealed the potential of G-CSF as an ideal immune potentiator that can augment immune responses to FHV-1 and even other attenuated live vaccines.

Three in one: An effective and universal vaccine expressing heterologous tandem RBD trimer by rabies virus vector protects mice against SARS-CoV-2

The rapid emergence of Severe Acute Respiratory Syndrome Coronavirus type 2 (SARS-CoV-2) variants, coupled with severe immune evasion and imprinting, has jeopardized the vaccine efficacy, necessitating urgent development of broad protective vaccines. Here, we propose a strategy employing recombinant rabies viruses (RABV) to create a universal SARS-CoV-2 vaccine expressing heterologous tandem receptor-binding domain (RBD) trimer from the SARS-CoV-2 Prototype, Delta, and Omicron strains (SRV-PDO). The results of mouse immunization indicated that SRV-PDO effectively induced cellular and humoral immune responses, and demonstrated higher immunogenicity and broader SARS-CoV-2 neutralization compared to the recombinant RABVs that only expressed RBD monomers. Moreover, SRV-PDO exhibited full protection against SARS-CoV-2 in the challenge assay. This study demonstrates that recombinant RABV expressing tandem RBD-heterotrimer as a multivalent immunogen could elicit a broad-spectrum immune response and potent protection against SARS-CoV-2, making it a promising candidate for future human or veterinary vaccines and offering a novel perspective in other vaccine design.

Clofazimine derivatives as potent broad-spectrum antiviral agents with dual-target mechanism

Thirty-two clofazimine derivatives, of which twenty-two were new, were synthesized and evaluated for their antiviral effects against both rabies virus and pseudo-typed SARS-CoV-2, taking clofazimine (1) as the lead. Among them, compound 15f bearing 4-methoxy-2-pyridyl at the N5-position showed superior or comparable antiviral activities to lead 1, with the EC₅₀ values of 1.45 μM and 14.6 μM and the SI values of 223 and 6.1, respectively. Compound 15f inhibited rabies and SARS-CoV-2 by targeting G or S protein to block membrane fusion, as well as binding to L protein or nsp13 to inhibit intracellular biosynthesis respectively, and thus synergistically exerted a broad-spectrum antiviral effect. The results provided useful scientific data for the development of clofazimine derivatives into a new class of broad-spectrum antiviral candidates.