Observed Kinetics of Enterovirus Inactivation by Free Chlorine Is Host Cell-Dependent

Abstract

The virucidal efficacy of disinfectants is typically assessed by infectivity assay utilizing a single type of host cell. Enteroviruses infect multiple host cells via different entry routes, and each entry route may be impaired to a varying extent by a given disinfectant. Yet, it is not known how the choice of host cells for titration affects the observed inactivation kinetics. Here, we evaluated the inactivation kinetics of echovirus 11 (E11) by free chlorine, ultraviolet (UV) irradiation, and heat, using three different host cells (BGMK, RD, and A549). E11 inactivation by free chlorine occurred at a two-fold greater rate when enumerated on BGMK cells compared to RD and A549 cells. Conversely, a comparable inactivation rate was observed for UV and heat independent of the host cell used. Host cell-dependent inactivation kinetics by free chlorine were also observed for echovirus 7, 9 and 13, and coxsackievirus A9, confirming that this phenomenon is not serotype-specific. Inactivation of E11 was partly caused by a loss in host cell attachment, which was most pronounced for BGMK cells, and which may be promoted by a lack of CD55 attachment receptors on this cell type. Additionally, BGMK cells lack a key subunit of the uncoating receptor, β2M, which may further contribute to the differential inactivation kinetic for this cell type. Consequently, inactivation kinetics of enteroviruses should be assessed using host cells with different receptor profiles. This will yield a more complete understanding of the inactivating power of disinfectants targeting the viral attachment and/or uncoating.