Replication of human enteric viruses from wastewater in saliva cell lines

Enteric viruses cause significant public health risk and are frequently detected in wastewater at high concentrations. While viral detection and prevalence of enteric viruses from wastewater has been widely studied, infectivity in single cell lines has been challenging, particularly for Human Norovirus (NoV) which has been difficult to culture in the past. Emerging evidence suggests that salivary cell lines could be a potential replication tool for enteric viruses. This study aimed to evaluate the feasibility of saliva cell lines in the replication and infectivity of multiple enteric viruses in wastewater and fecal samples. Our results demonstrated successful replication of all tested viruses in saliva cells, including Adenovirus 41, Astrovirus type 1, Rotavirus, Hepatitis A virus, Coxsackievirus B3 & B1, Enterovirus A71, Reovirus type 1, and NoV genogroups GI and GII, demonstrating mean log increases in viral genome concentrations (GC) ranging from 0.58 to 5.11. Co-infections of different viruses, which included fecal sample, lab adapted and wastewater derived viruses, was demonstrated. Overall, 10/14 (71 %) wastewater samples had replication of at least one virus and 8 samples (80 %) showed co-infection (multiple viruses replicated concurrently). Among these samples, NoV RNA was detected by molecular measurement in 10/14 samples (71 %) samples but only 6/14 samples (42 %), showed evidence of positive NoV infectivity. This study shows that saliva cells can replicate enteric viruses suggesting its role in environmental enteric viral transmission which would inform strategies for public and environmental surveillance interventions.