Titanium Dioxide Nanoparticles Evoke Proinflammatory Response during Murine Norovirus Infection Despite Having Minimal Effects on Virus Replication.

Noroviruses (NoV) have enhanced tropism for the gastrointestinal (GI) tract and are the major cause of nonbacterial gastroenteritis in humans. Titanium dioxide (TiO2) nanoparticles (NPs) used as food additives, dietary supplements, and cosmetics accumulate in the GI tract. We investigated the effect anatase TiO2 NPs on NoV replication and host response during virus infection, using murine norovirus (MNV-1) infection of RAW 264.7 macrophages. Pretreatment with 20 μg/ml anatase NPs significantly reduced the viability of macrophages alone or during virus infection, but did not alter virus replication. In contrast, pre-incubation with 2 μg/ml anatase NPs reduced virus replication fivefold at 48 h. The presence of anatase NPs during MNV-1 infection evoked a pro-inflammatory response, as measured by a significant increase in expression of cytokines, including IL-6, IFN-γ, TNFα and the TGFβ1. No genotoxic insults due to anatase TiO2 NPs alone or to their presence during MNV-1 infection were detected. This study highlights important safety considerations related to NP exposure of the GI tract in individuals infected with noroviruses or other foodborne viruses.