Stabilization of Murine Norovirus by Bacteria

Enteric viruses encounter various bacteria in the host, which can impact infection outcomes. The interactions between noroviruses and enteric bacteria are not well understood. Previous work determined that murine norovirus (MNV), a model norovirus, had decreased replication in antibiotic-treated mice compared with conventional mice. Although this suggests that the microbiota promotes MNV infection, the mechanisms are not completely understood. Additionally, prior work with other enteric viruses, such as poliovirus and coxsackievirus B3, demonstrated that virions bind bacteria, and exposure to bacteria stabilizes viral particles and limits premature RNA release. Therefore, we examined interactions between MNV and specific bacteria and the consequences of these interactions. We found that the majority of Gram-positive bacteria tested stabilized MNV, while Gram-negative bacteria did not stabilize MNV. Both Gram-positive and Gram-negative bacteria bound to MNV. However, bacterial binding alone was not sufficient for virion stabilization, since Gram-negative bacteria bound MNV but did not stabilize virions. Additionally, we found that bacteria conditioned medium also stabilized MNV and this stabilization may be due to a small heat-stable molecule. Overall, this work identifies specific bacteria and bacterial components that stabilize MNV and may impact virion stability in the environment. IMPORTANCE Enteric viruses are exposed to a wide variety of bacteria in the intestine, but the effects of bacteria on viral particles are incompletely understood. We found that murine norovirus (MNV) virion stability is enhanced in the presence of several Gram-positive bacterial strains. Virion-stabilizing activity was also present in bacterial culture medium, and activity was retained upon heat or protease treatment. These results suggest that certain bacteria and bacterial products may promote MNV stability in the environment, which could influence viral transmission.