Effects of disinfectants against norovirus virus-like particles predict norovirus inactivation

Human noroviruses (NoVs) are a major cause of epidemic and sporadic acute gastroenteritis worldwide. Public and personal hygiene is one of the most important countermeasures to prevent the expansion of NoV infection. However, initial tests of the virucidal effectiveness of anti-NoV disinfectants and sanitizers have been performed using surrogate viruses because of the lack of a practicable cell culture system for NoV. In this study, we used NoV virus-like particles (VLPs) as a new surrogate for NoVs, and developed a method to evaluate NoV inactivation. Our method is based on morphological changes in VLPs after treatment with sodium hypochlorite. We found VLP specimens were deformed and degraded in a concentration-dependent manner. Based on these results, we classified the effects of sodium hypochlorite on VLPs according to morphological changes and number of particles in four phases. Using these criteria, we evaluated the efficacy of ethanol, carbonates, and alkali solutions against VLPs. Deformation and aggregation of VLPs were observed after treatment with the disinfectants under specific conditions. To determine the degradation mechanism, VLPs were examined by SDS-PAGE and immunoblotting after treatment with sodium hypochlorite and ethanol. The band corresponding to the major capsid protein, VP1, was not detected after treatment with sodium hypochlorite at concentrations greater than 500 ppm, but remained after treatment with ethanol. These results suggest that VLPs have excellent potential as a surrogate marker for NoVs and can be used in initial virucidal effectiveness tests to determine the mechanism of chemical agents on NoVs.