Bacterial lipopolysaccharide reduces the stability of avian and human influenza viruses

Commensal bacteria can promote or reduce the severity of viral infection and disease progression in their hosts depending on the specific viral pathogen 1 . Influenza A virus (IAV) has a broad host-range, comprises many subtypes, and utilizes different routes of transmission including the fecal-oral route in wild birds 2 . It has been previously demonstrated that commensal bacteria can interact with the host’s immune system to protect against IAV pathogenesis 3,4 . However, it is unclear whether bacteria and their products may be interacting directly with IAV to impact virion stability. Herein we show that gastrointestinal (GI) tract bacterial isolates in an in vitro system significantly reduce the thermal stability of IAV. Moreover, bacterial lipopolysaccharide (LPS), found on the exterior surfaces of bacteria, was sufficient to significantly decrease the stability of both human and avian viral strains at the physiological temperatures of their respective hosts, as well as in the aquatic environment. Subtype and host-origin of the viruses were shown to affect the extent to which IAV was susceptible to LPS. Furthermore, using a receptor-binding assay and transmission electron microscopy, we observed that LPS binds to and affects the morphology of influenza virions.