Chronic hepatitis associated with GB virus B persistence in a tamarin after intrahepatic inoculation of synthetic viral RNA

Abstract

Progress in understanding the pathogenesis of hepatitis C virus (HCV) has been slowed by the absence of tractable small animal models. Whereas GB virus B (GBV-B, an unclassified flavivirus) shares a phylogenetic relationship and several biologic attributes with HCV, including hepatotropism, it is not known to cause persistent infection, a hallmark of HCV. Here, we document persistent GBV-B infection in one of two healthy tamarins (Saguinus oedipus) inoculated intrahepatically with infectious synthetic RNA. High-titer viremia (10 8 to 10 9 genome equivalents per ml) and transiently elevated serum alanine transaminase activities were present from weeks 4 to 12 postinoculation in both animals. However, whereas GBV-B was eliminated from one animal by 20 weeks, the second animal remained viremic (10 3 to 10 7 genome equivalents per ml) for >2 years, with alanine transaminase levels becoming elevated again before spontaneous resolution of the infection. A liver biopsy taken late in the course of infection demonstrated hepatitis with periportal mononuclear infiltrates, hepatocellular microvesicular changes, cytoplasmic lipid droplets, and disordered mitochondrial ultrastructure, findings remarkably similar to chronic hepatitis C. GBV-B-infected hepatocytes contained numerous small vesicular membranous structures resembling those associated with expression of HCV nonstructural proteins, and sequencing of GBV-B RNA demonstrated a rate of molecular evolution comparable to that of HCV. We conclude that GBV-B is capable of establishing persistent infections in healthy tamarins, a feature that substantially enhances its value as a model for HCV. Mitochondrial structural changes and altered lipid metabolism leading to steatosis are conserved features of the pathogenesis of chronic hepatitis caused by these genetically distinct flaviviruses.

Signal Peptide Peptidase Cleavage of GB Virus B Core Protein Is Required for Productive Infection in Vivo

“…GBV-B has been a paradigm for HCV infection, given the close similarity of the two viruses and the ability of GBV-B to readily infect New World monkeys (12,14,16,17). Our aim was to determine whether SPP, which is required for maturation of HCV core protein (10,11), also processed the corresponding GBV-B protein and thereafter to examine the need for SPP cleavage in productive GBV-B infection in animals.…”

“…To assess the infectivity of transcribed RNA in tamarins (Saguinus mystax), ϳ100 g of RNA was inoculated directly into the liver, and at 7-14-day intervals post-inoculation, serum was collected and assayed for alanine aminotransferase (ALT) activity and viral RNA levels. In the latter case, RNA was isolated using a QiaAmp viral RNA extraction kit (Qiagen) and quantitated by real-time, 5Ј-exonuclease, reverse transcription-PCR (TaqMan) using a one-step procedure with the TaqMan EZ core reagent kit (PerkinElmer Life Sciences) and primers located within the GBV-B NS5A sequence as described previously (16 …”

“…GB virus B (GBV-B) can act as a surrogate model of HCV infection, because the two viruses have identical genome organizations and share significant sequence similarity (12)(13)(14)(15)(16)(17)(18)(19). GBV-B establishes an acute infection in several species of New World monkeys including tamarins (Saguinus sp.)…”

Characterization of GB Virus B Polyprotein Processing Reveals the Existence of a Novel 13-kDa Protein with Partial Homology to Hepatitis C Virus p7 Protein

“…GBV-B was iden-tified in 1995 in a tamarin (Saguinus species) that developed acute hepatitis after inoculation with serum from the 11th tamarin passage of the original, human GB inoculum (16,17). GBV-B infection is typically self-limited and associated with acute hepatitis (18,19), although persistent infection can lead to chronic hepatitis in tamarins (20). The natural host for GBV-B remains unknown since this virus has never been isolated directly from tamarins or humans (21,22), but the fact that GBV-B appears to be incapable of replicating in chimpanzees argues against a human origin (23).…”

A comparative cell biological analysis reveals only limited functional homology between the NS5A proteins of hepatitis C virus and GB virus B

“…It shares the hepatotropism of HCV. Although GBV-B has been reported to lead to persistent infections in some cases in tamarins (Saguinus species) (Martin et al, 2003;Nam et al, 2004), unlike the human virus, GBV-B primarily causes an acute, resolving hepatitis in tamarins and other New World monkeys such as common marmosets (Callithrix jacchus) (Bukh et al, 2001;Jacob et al, 2004;Lanford et al, 2003). In contrast, HCV is a major cause of chronic hepatitis, liver cirrhosis and hepatocellular carcinoma, affecting an estimated 3 % of the world's population.…”