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

Abstract

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

Humoral immunity in hepatitis B virus infection: Rehabilitating the B in HBV

“…Liver T cell infiltration was low, overall supporting the notion of a T-cell independent germline encoded B cell response towards HBcAg in HBV-ALF which leads to ADCC and massive necrosis [83,84]. Recently this phenomenon was also found to occur in experimental fulminant HBV infections with precore HBV mutants in chimpanzees [85]. It is unclear whether a similar mechanism may be involved -albeit partly-in ALT flares during CHB infections, which have been ascribed to CD8 T cell and innate immune responses but are still not fully understood [86].…”

Distinct Cytokine Profiles Correlate with Disease Severity and Outcome in Longitudinal Studies of Acute Hepatitis B Virus and Hepatitis D Virus Infection in Chimpanzees

“…Interestingly, this silent cytokine profile in the same animal at the time of the ALT peak (week 6) correlated with a limited inflammatory infiltrate within the liver and a positive staining for caspase 3 activation, a marker of hepatocyte death (8). In contrast, caspase 3 staining was negative in classic AHB infected with the wild-type HBV, where at the time of ALT peak there was an extensive inflammatory infiltrate, particularly of T cells (8). Thus, the difference in the necroinflammatory reaction strongly suggests that the mechanisms of disease pathogenesis induced by the precore mutant differ from that induced by the wild-type HBV.…”

“…Strikingly, severe AHB was associated with a silent cytokine profile with respect to IFN-␣2, IFN-␥, IL-12 p70, and IL-17A at all time points throughout the course of the disease. Interestingly, this silent cytokine profile in the same animal at the time of the ALT peak (week 6) correlated with a limited inflammatory infiltrate within the liver and a positive staining for caspase 3 activation, a marker of hepatocyte death (8). In contrast, caspase 3 staining was negative in classic AHB infected with the wild-type HBV, where at the time of ALT peak there was an extensive inflammatory infiltrate, particularly of T cells (8).…”

“…Indeed, both animals developed an equally severe form of AHB, which suggests that the precore HBV mutant carries an inherently higher pathogenicity that is independent of the host and the inoculum size. In a recent study (8), we characterized the intrahepatic antibody response in the same two chimpanzees by using phage display library and next-generation sequencing (NGS) technologies and compared the results with those seen in classic AHB and in HBVassociated ALF in humans (8). We found that severe AHB was characterized by a limited inflammatory reaction at the time of the ALT peak relative to the degree of hepatocellular damage, associated with B-cell infiltration, albeit less extensive than that in HBV-associated ALF (8).…”

“…We recently demonstrated that in chimpanzees infected with a precore HBV mutant, hepatocellular damage at the time of ALT peak (up to 1,468 IU/liter) was associated with limited inflammatory infiltrates and the presence of B cells (8), although the B-cell infiltration was less extensive than that seen in HBV-associated acute liver failure (9). Thus, liver pathology data showed a remarkable difference between severe AHB and classic AHB, as typically observed following infection with the wild-type HBV, where the ALT peak usually coincided with an extensive inflammatory reaction, especially T-cell infiltration (8). Another clinical observation derived from these historical studies was the remarkably high degree of necroinflammation following HBV/HDV coinfection, or even higher after HDV superinfection.…”