Distinct disease features in chimpanzees infected with a precore HBV mutant associated with acute liver failure in humans.

Transmission to chimpanzees of a precore hepatitis B virus (HBV) mutant implicated in acute liver failure (ALF) in humans did not cause ALF nor the classic form of acute hepatitis B (AHB) seen upon infection with the wild-type HBV strain, but rather a severe AHB with distinct disease features. Here, we investigated the viral and host immunity factors responsible for the unusual severity of AHB associated with the precore HBV mutant in chimpanzees. Archived serial serum and liver specimens from two chimpanzees inoculated with a precore HBV mutant implicated in ALF and two chimpanzees inoculated with wild-type HBV were studied. We used phage-display library and next-generation sequencing (NGS) technologies to characterize the liver antibody response. The results obtained in severe AHB were compared with those in classic AHB and HBV-associated ALF in humans. Severe AHB was characterized by: (i) the highest alanine aminotransferase (ALT) peaks ever seen in HBV transmission studies with a significantly shorter incubation period, compared to classic AHB; (ii) earlier HBsAg clearance and anti-HBs seroconversion with transient or undetectable hepatitis B e antigen (HBeAg); (iii) limited inflammatory reaction relative to hepatocellular damage at the ALT peak with B-cell infiltration, albeit less extensive than in ALF; (iv) detection of intrahepatic germline antibodies against hepatitis B core antigen (HBcAg) by phage-display libraries in the earliest disease phase, as seen in ALF; (v) lack of intrahepatic IgM anti-HBcAg Fab, as seen in classic AHB, but at variance with ALF; and (vi) higher proportion of antibodies in germline configuration detected by NGS in the intrahepatic antibody repertoire compared to classic AHB, but lower than in ALF. This study identifies distinct outcome-specific features associated with severe AHB caused by a precore HBV mutant in chimpanzees, which bear closer resemblance to HBV ALF than to classic AHB. Our data suggest that precore HBV mutants carry an inherently higher pathogenicity that, in addition to specific host factors, may play a critical role in determining the severity of acute HBV disease. Author summary While the pathogenesis of classic acute hepatitis B (AHB) is believed to be mediated by hepatitis B virus (HBV)-specific T-cell responses, the pathogenesis of HBV-associated acute liver failure (ALF), one of the most rapid and lethal liver diseases, remains largely unknown. Our previous work demonstrated that ALF is associated with an uncommon B-cell response with the intrahepatic production of antibodies in germline configuration directed against the hepatitis B core antigen (HBcAg). Previous reports also documented an association of ALF with HBV variants containing precore or core promoter mutations. Here, we studied chimpanzees experimentally infected with a precore HBV mutant implicated in human ALF with the aim of getting new insights into ALF pathogenesis. Although these chimpanzees did not develop ALF, they had an unusually severe AHB with distinct disease features, including the highest alanine aminotransferase (ALT) peaks ever seen in HBV transmission studies, a shorter incubation period with an earlier ALT peak, an earlier HBsAg clearance and antibody seroconversion compared to classic AHB, and intrahepatic B-cell infiltration. Remarkably, the ALT peak correlated with extensive hepatocellular damage, but very limited inflammatory reaction. As previously documented in ALF, anti-HBcAg antibodies in germline configuration were present in the liver in the earliest disease phase. Thus, although chimpanzees did not develop ALF, infection with a precore HBV mutant caused a severe AHB with several analogies with ALF, suggesting that precore HBV mutants carry an inherently higher pathogenicity.