Ionic surfactants alter virus surface properties and electrostatic interactions in aqueous systems

Interactions between viruses and sub-inhibitory concentrations of surfactants in water systems are understudied. At concentrations below the minimum inhibitory concentration (MIC), surfactants may interact with virus surface proteins without virus inactivation and alter virus surface properties. This study determined the MIC of benzyldimethyldodecylammonium chloride (BAC) and sodium dodecyl sulfate (SDS) on human adenovirus (ADV, non-enveloped, dsDNA) and mouse hepatitis virus (MHV, enveloped, ssRNA), and how sub-MIC surfactants influence virus isoelectric point (IEP), hydrated diameter, and interact with virus surface proteins. Both surfactants had MICs of 1 mg/L over 60 minutes. Experimental IEPs were lower than IEPs estimated based on amino acid structures. The ADV IEP was 3.8 without surfactants and dropped to 3.3 with BAC and lower than 3 with SDS. The MHV IEP was 4.2 without surfactants and decreased to 4.1 with SDS and 3.4 with BAC. Dynamic light scattering showed SDS and BAC decreased ADV hydrated diameter from 142 ± 8 nm (no surfactant) to 109-116 nm, while MHV decreased from 150 ± 10 nm (no surfactants) to 132-140 nm upon surfactant exposure. Molecular dynamics simulations revealed that SDS, due to its multivalent sulfate headgroup, forms numerous intimate contacts with the MHV spike protein that markedly perturb its electrostatic environment. In contrast, BAC engages only sporadically and diffusely with the protein, indicating a much weaker influence on its structure and electrostatics. Overall, this study showed that ionic surfactants can influence virus properties thus altering virus interactions with surfaces in engineered and natural systems.