Survival of the fittest: Selection of hepatitis C virus variants during liver graft reinfection

Abstract

End-stage liver disease caused by chronic hepatitis C virus (HCV) infection is a leading cause for liver transplantation (LT). Due to viral evasion from host immune responses and the absence of preventive antiviral strategies, reinfection of the graft is universal. The mechanisms by which the virus evades host immunity to reinfect the liver graft are unknown. In a longitudinal analysis of six HCV-infected patients undergoing LT, we demonstrate that HCV variants reinfecting the liver graft were characterized by efficient entry and poor neutralization by antibodies present in pretransplant serum compared with variants not detected after transplantation. Monoclonal antibodies directed against HCV envelope glycoproteins or a cellular entry factor efficiently cross-neutralized infection of human hepatocytes by patient-derived viral isolates that were resistant to autologous host-neutralizing responses. These findings provide significant insights into the molecular mechanisms of viral evasion during HCV reinfection and suggest that viral entry is a viable target for prevention of HCV reinfection of the liver graft. CommentRecurrent hepatitis C after orthotopic liver transplantation (OLT) for hepatitis C-associated end-stage liver disease or hepatocellular carcinoma is a vexing clinical problem. Rapid reinfection of the liver graft by hepatitis C virus (HCV) particles in the blood is nearly universal, and the ensuing disease often runs an accelerated course quickly progressing to graft cirrhosis and retransplantation or death.1 In contrast to hepatitis B, no passive immunoprophylaxis is currently available. The first potent, directly acting antiviral drugs are expected to be licensed only in 2011, and they have not been evaluated in individuals with end-stage liver disease or in the peritransplant setting. The difficulties in creating efficient immunoprophylaxis are in large part due to the high genetic variability of HCV: this relatively small enveloped virus with an approximately 10-kb nonsegmented, plus-strand RNA genome has a highly error-prone RNA-dependent RNA polymerase.2 As a result, HCV exists in the infected host not as a homogeneous population but rather as a large number of variants that are collectively called the quasispecies swarm.3 Therefore, HCV can rapidly respond to selective pressures to which it is subjected by antiviral drugs or cellular and humoral immune responses; this is conceivably a prerequisite for establishing and maintaining a chronic infection. 4 For HCV to infect target cells, the viral envelope glycoproteins, E1 and E2, must interact with at least four (co)receptors on the hepatocyte surface: scavenger receptor BI, the tetraspanin CD81, and two components of the hepatic tight junction (claudin 1 and occludin).5 It has been shown that the humoral immune response is a major driver of HCV E1E2 evolution during chronic infection because antibodies capable of neutralizing most viral variants in the swarm are continuously generated, but neutralization-resistant minor variants pres...

Entry inhibitors: New advances in HCV treatment

“… 4 Unfortunately, the reinfection of a graft is difficult to avoid due to the lack of preventive strategies. 5 …”