2650. Evaluating Antiviral Agents for Human Noroviruses Using a Human Intestinal Enteroid Model

BACKGROUND: Norovirus can cause chronic infections with serious morbidity and mortality in immunocompromised patients. While there are no FDA-approved medications for these infections, nitazoxanide, ribavirin, and enterally administered pooled immunoglobulin (IVIG) are used off-label on the basis of expert opinion. Nitazoxanide and ribavirin show antiviral activity in a murine norovirus infection model and an in vitro replicon model of genotype GI.I human norovirus RNA expression, respectively. However, these drugs have not been evaluated in in vitro infections with GII.4 human noroviruses, responsible for most human norovirus disease. We used the stem cell-derived nontransformed human intestinal enteroid (HIE) system, which supports GII.4 human norovirus replication, to evaluate the antiviral activities of nitazoxanide, ribavirin, and IVIG. METHODS: We inoculated HIEs with GII.4 human norovirus in the presence of half-log dilutions of nitazoxanide (3 µM to 100 µM), ribavirin (10 µM to 10 mM), or IVIG (1:100 to 1:3,000) and a media control. One and 48 hours after inoculation, we extracted and quantified GII.4 norovirus RNA from the HIEs. To demonstrate that replication inhibition was not due to cytotoxicity, we performed quantitative lactate dehydrogenase release assays on the HIEs across the therapeutic range of each compound. RESULTS: Nitazoxanide reduced GII.4 replication at 48 hours in a dose-dependent manner, achieving a >90% reduction in viral replication at 10 µM without cytotoxicity. These findings were confirmed in multiple HIE lines representing different intestinal segments and established from different donors. IVIG completely inhibited GII.4 replication at up to a 1:1,000 dilution and was not cytotoxic at therapeutic concentrations. Ribavirin did not reduce GII.4 replication at concentrations up to 10 mMµM, well in excess of levels achieved in human sera with standard doses. CONCLUSION: Nitazoxanide and IVIG, but not ribavirin, potently inhibit GII.4 human norovirus replication in a biologically relevant in vitro model of human norovirus infection. These data highlight the use of HIEs as a new pre-clinical model for developing therapeutics for human norovirus disease. DISCLOSURES: All authors: No reported disclosures.