Sulfur-containing class of broad-spectrum antivirals improves influenza virus vaccine development.

Enveloped viruses are significant zoonotic disease threats with the potential to cause global pandemics. We identified a class of small-molecule sulfur-containing antiviral compounds (XM series) that broadly inhibit enveloped viruses. Multidisciplinary approaches revealed that XM compounds alter the viral membrane lipid chemical composition, enhance membrane order within the hydrophobic bilayer, and increase membrane phase transition temperatures. This mechanism inhibits membrane fusion and viral entry, while leaving the viral glycoproteins and genomes largely unaffected. Leveraging these unique properties, we develop a proof-of-concept whole inactivated influenza virus (IIV) vaccine using XM-01 (XM-01-IIV). In a mouse model, XM-01-IIV elicit significantly enhanced neutralizing antibody responses against hemagglutinin and neuraminidase compared to traditional paraformaldehyde-inactivated vaccines. Further, XM-01-IIV reduces morbidity and mortality following influenza challenge, achieving protection comparable to live virus vaccination. This promising class of broadly acting antivirals can be highly impactful in the development of highly potent inactivated vaccines for enveloped viruses.