Characterization of a thermal stable poliovirus mutant reveals distinct mechanisms of virion stabilization

Enteric viruses, including poliovirus, are spread by the fecal-oral route. In order to persist and transmit to a new host, enteric virus particles must remain stable once they are in the environment. Environmental stressors such as heat and disinfectants can inactivate virus particles and prevent viral transmission. It has been previously demonstrated that bacteria or bacterial surface glycans can enhance poliovirus virion stability and limit inactivation from heat or bleach. While investigating the mechanisms underlying bacterial-enhanced virion thermal stability, we identified and characterized a poliovirus mutant with increased resistance to heat inactivation. This poliovirus mutant, M132V, harbors a single amino acid change in the VP1 capsid-coding that is sufficient to confer heat resistance. M132V was comparable to wild-type virus for replication in vitro, as well as for replication and pathogenesis in orally-inoculated mice. Although the M132V virus was stable in the absence of bacteria or feces at most temperatures, M132V virus was stabilized by feces at very high temperatures. Additionally, the M132V virus does not have enhanced stability during bleach treatment, suggesting that thermal and bleach inactivation mechanisms are separable. Our results suggest that different mechanisms underlie virion stabilization by bacteria and the M132V mutation. Overall, this work sheds light on factors that influence virion stability.