Rhesus rotavirus receptor‐binding site affects high mobility group box 1 release, altering the pathogenesis of experimental biliary atresia

Biliary atresia (BA) is a neonatal inflammatory cholangiopathy that requires surgical intervention by Kasai portoenterostomy to restore biliary drainage. Even with successful portoenterostomy, most patients diagnosed with BA progress to end‐stage liver disease, necessitating a liver transplantation for survival. In the murine model of BA, rhesus rotavirus (RRV) infection of neonatal mice induces an inflammatory obstructive cholangiopathy that parallels human BA. The model is triggered by RRV viral protein (VP)4 binding to cholangiocyte cell‐surface proteins. High mobility group box 1 (HMGB1) protein is a danger‐associated molecular pattern that when released extracellularly moderates innate and adaptive immune response. In this study, we investigated how mutations in three RRV VP4‐binding sites, RRVVP4‐K187R (sialic acid‐binding site), RRVVP4‐D308A (integrin α2β1‐binding site), and RRVVP4‐R446G (heat shock cognate 70 [Hsc70]‐binding site), affects infection, HMGB1 release, and the murine model of BA. Newborn pups injected with RRVVP4‐K187R and RRVVP4‐D308A developed an obstruction within the extrahepatic bile duct similar to wild‐type RRV, while those infected with RRVVP4‐R446G remained patent. Infection with RRVVP4‐R446G induced a lower level of HMGB1 release from cholangiocytes and in the serum of infected pups. RRV infection of HeLa cells lacking Hsc70 resulted in no HMGB1 release, while transfection with wild‐type Hsc70 into HeLa Hsc70‐deficient cells reestablished HMGB1 release, indicating a mechanistic role for Hsc70 in its release. Conclusion: Binding to Hsc70 contributes to HMGB1 release; therefore, Hsc70 potentially serves as a therapeutic target for BA. Utilizing novel single amino acid mutant strains of Rhesus rotavirus (RRV) corresponding to known cellular receptor binding sites (Heat shock cognate protein 70 (Hsc70), sialic acid, and integrin alpha2beta1) it was demonstrated that strains capable of binding to Hsc70 resulted in increased levels of HMGB1 and obstruction of the extrahepatic bile duct similar to that seen in wild‐type RRV injection while ducts from mice infected with a mutant strain unable to bind to Heat shock cognate 70 (Hsc70) remained patent with lower levels of HMGB1. RRV infection of WT‐HeLa cells resulted in HMGB1 release while HeLa Hsc70 KO cells were unable to release HMGB1; however, release was reestablished following transfection with WT‐Hsc70. This data suggests that Hsc70 binding is integral in HMGB1 release potential