Rhesus rotavirus NSP1 mediates extra-intestinal infection and is a contributing factor for biliary obstruction

We previously demonstrated that in Ifnar1-/-Ifngr1-/- or Stat1-/- suckling mice lacking intact type I and type II interferon (IFN) signaling, rhesus rotavirus (RRV) infection causes a lethal disease with clinical manifestations similar to biliary atresia, including acholic stools, oily fur, growth retardation, and excess mortality. Elevated levels of viral RNA are detected in the bile ducts and liver of diseased pups together with severe inflammatory responses in these tissues. However, the viral determinants and the molecular mechanisms driving this process remain incompletely understood. Using an optimized rotavirus (RV) reverse genetics system, we generated a panel of recombinant RVs that encode non-structural protein 1 (NSP1) derived from different RV strains. We found that compared to the parental simian SA11 strain that is less biliary pathogenic, SA11 containing an RRV-derived NSP1 resulted in severe biliary obstructive disease comparable to that associated with RRV infection, reflected by high levels of viral RNA and inflammation in the biliary tract, liver, and pancreas. In contrast, RRV containing an SA11-originated NSP1 showed only mild biliary obstruction comparable to what was observed during SA11 infection. Infection with a monoreassortant RRV virus carrying NSP1 from the bovine RV UK strain also showed substantially reduced viral replication in extra-intestinal organs and did not develop clinical biliary diseases. Mechanistically, RRV NSP1 seemed to promote active viral replication in hepatocytes and this expanded tropism led to enhanced infiltration of CD4 and CD8 T cells, causing immunopathology and damage in the hepatobiliary system. These results highlight an unexpectedly important role of RV NSP1 in viral replication and disease progression in extra-intestinal tissues.