Chemical inactivation of two non-enveloped viruses follows distinct molecular pathways

Non-enveloped viruses, which lack a lipid envelope, typically display higher resistance to disinfectants, soaps and sanitizers compared to enveloped viruses. The capsids of these viruses are highly stable and symmetric protein shells that resist inactivation by commonly employed virucidal agents. This group of viruses include highly transmissible human pathogens such as Rotavirus, Poliovirus, Foot and Mouth Disease Virus, Norovirus and Adenovirus; thus, devising appropriate strategies for chemical disinfection is essential. We tested a mild combination of a denaturant, alcohol, and organic acid on two representative non-enveloped viruses – Human Adenovirus 5 (HAdV5) and Feline Calicivirus (FCV)– and evaluated the molecular pathway of capsid neutralization using biophysical methods. The transition temperatures signifying conformational shifts in the capsid were established in the presence and absence of chemical treatment using Differential Scanning Calorimetry (DSC), while the corresponding morphological alterations were visualized and correlated using Transmission Electron Microscopy (TEM). We found that while chemical treatment of purified HAdV5 particles resulted in increased thermal instability, followed by large scale particle aggregation; similar treatment of FCV particles resulted in complete collapse of the capsids. The distinct effects of the chemical treatment on the morphology of HAdV5 and FCV suggests that non-enveloped viruses with icosahedral geometry can follow different molecular pathways to inactivation. Further, while individual components of the chemical formulation caused significant damage to the capsids, a synergistic action of the whole formulation was evident against both non-enveloped viruses tested. Molecular level understanding of inactivation pathways may result in the design and development of effective mass-market formulations for rapid neutralization of non-enveloped viruses.