Inactivation Mechanisms of Human and Animal Rotaviruses by Solar UVA and Visible Light Elbashir Araud,* ,† Joanna L. Shisler, ‡ and Thanh H. Nguyen † † Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States ‡ Department of Microbiology and Department of Pathobiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States * S Supporting Information ABSTRACT: Two rotavirus (RV) strains (sialidase-resistant Wa and sialidase-sensitive OSU) were irradiated with simulated solar UVA and visible light in sensitizer-free phosphate buffered solution (PBS) (lacking exogenous reactive oxygen species (ROS)) or secondary effluent wastewater (producing ROS). Although light attenuated for up to 15% through the secondary effluent wastewater (SEW), the inactivation efficacies increased by 0.7 log 10 for Wa and 2 log 10 for OSU compared to those in sensitizer- free phosphate buffered solution (PBS) after 4 h of irradiation. A binding assay using magnetic beads coated with porcine gastric mucin containing receptors for rotaviruses (PGM-MB) was developed to determine if inactivation influenced RV binding to its receptors. The linear correlation between the reduction in infectivity and the reduction in binding after irradiation in sensitizer-free solution suggests that the main mechanism of RV inactivation in the absence of exogenous ROS was due to damage to VP8*, the RV protein that binds to host cell receptors. For a given reduction in infectivity, greater damage in VP8* was observed with sialidase-resistant Wa compared to sialidase-sensitive OSU. The lack of correlation between the reduction in infectivity and the reduction in binding, in SEW, led us to include RNase treatment before the binding step to quantify virions with intact protein capsids and exclude virions that can bind to the receptors but have their capsid permeable after irradiation. This assay showed a linear correlation between the reduction in RV infectivity and RV-receptor interactions, suggesting that RV inactivation in SEW was due to compromised capsid proteins other than the VP8* protein. Thus, rotavirus inactivation by UVA and visible light irradiation depends on both the formation of ROS and the stability of viral proteins. ■ INTRODUCTION Group A rotaviruses (RVs) are the major etiological agent of acute gastroenteritis in infants worldwide and accounted for 215 000 deaths in children in 2013. 1 They have a low infectious dose of fewer than 10 particles, and they shed at high titers (10 10 -10 12 particles per gram of stool) from infected persons. 2-4 Despite the success of vaccines against RVs in the reduction of severe gastroenteritis among infants, RVs are still of major public health importance and the leading cause of diarrhea in children younger than five years old, globally. 2,5 RV outbreaks still occur worldwide due to the high genetic diversity of RVs and the lack of cross-protection. 2,5 There are eight groups of RVs referred to as A, B, C, D, E, F, G, and H. Humans are primarily infected by the group A RV, which can be further divided into different serotypes. 6 The outer capsid glycoprotein (VP7) and the spike protein (VP4) differentiate RVs into 14 G (glycoprotein) serotypes and 27 different P (protease sensitive) genotypes. 6 Currently, five serotypes (G1-G4, and G9) are the predominant circulating viruses, accounting for almost 95% of strains worldwide. 7 In addition, reassortment of RV strains between animal and human has been reported. 8-13 Thus, RVs are highly diverse, both antigenically and genetically. RV-contaminated water and food are the main source of RV outbreaks. 14 In both developed and developing countries, infectious particles or genomes of human or animal RV are found in drinking water sources. 15-19 The contamination of the drinking water source is attributed to inadequately treated wastewater. 20 Also, it is troublesome that RV is detected on lettuce irrigated with surface water in the US. 21 Thus, the risk of RV outbreaks may increase when contaminated surface water comes into contact with vegetables and seafood. To complicate matters, newly emerging RV strains due to intragenogroup reassortment are reported constantly and may also add to current or future RV outbreaks. 8,22 Therefore, prevention of RV infection and outbreaks can be achieved by improving waste- Received: December 20, 2017 Revised: April 13, 2018 Accepted: April 19, 2018 Published: April 19, 2018 Article pubs.acs.org/est Cite This: Environ. Sci. Technol. 2018, 52, 5682-5690 © 2018 American Chemical Society 5682 DOI: 10.1021/acs.est.7b06562 Environ. Sci. Technol. 2018, 52, 5682-5690 Downloaded via US EPA OFFICE OF ENVIRONMENTAL INFO on December 13, 2018 at 12:17:37 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.