Glycochenodeoxycholic acid and ceramide suppress the antiviral effect of 25-hydroxycholesterol against human norovirus infection in human intestinal enteroids

The human intestinal enteroid (HIE) cell culture system with the support of glycine-conjugated bile acid glycochenodeoxycholic acid (GCDCA) and ceramide (C2) facilitate successful replication of several norovirus strains. Here we investigate how the presence of GCDCA/C2 impacts gene expression of norovirus-infected HIE and the impact of 25 hydroxycholesterol (25-HC), a key regulator of cholesterol homeostasis and bile acid production on norovirus replication. In absence of GCDCA/C2, 0.01 and 0.1 M 25-HC suppressed virus (GII.4 Sydney[P16]) replication by 1.3 log and 1.1 log respectively (p<0.05). In the presence of GCDCA/C2, 5 M 25-HC was required to achieve a 1 log decrease (p<0.05) in viral titers demonstrating that 25-HC restricts norovirus replication in HIE. RNA sequence analysis showed that during human norovirus infection, 25-HC downregulated expression of genes (CYP3A4, APOB, APOA1, and ABCG1) involved in cholesterol metabolism and transport as well as interferon stimulated genes such as ISG15 and IFIT1. GCDCA/C2 counteracts the suppressive effect of 25-HC expression of some genes related to these pathways including APOA4 and CYP27A1 however, other cholesterol genes such as APOA1 were further suppressed in the presence of GCDCA/C2. ImportanceNorovirus is the leading cause of epidemic and endemic acute gastroenteritis worldwide and currently, there are no effective therapeutic strategies against this highly contagious pathogen. Our study provides insights into the effect of bile during norovirus infection, highlight the role of the cholesterol/oxysterol pathways during human norovirus replication, and demonstrate the potential utility of oxysterols in developing norovirus therapeutics.