A dominant hepatitis B virus population defective in virus secretion because of several S-gene mutations from a patient with fulminant hepatitis

Abstract

There is increasing evidence that certain pathogenic hepatitis B virus (HBV) variants may play a role in the pathogenesis of fulminant hepatitis (FHB). Recently, we isolated from a patient with fulminant recurrent hepatitis B after liver transplantation variants with enhanced replication competence and a possible defect in viral particle secretion. Both viral features may have contributed to the severity of the disease. The aim of this study was to prove the secretion defect of these variants, to analyze the consequences, and to identify the responsible viral mutations. The variant genomes and appropriate wild-type/variant hybrid genomes were functionally characterized after transfection in human hepatoma cells. Two cloned genomes and the polymerase chain reaction (PCR)-amplified mixture of full-length genomes showed a block in viral particle secretion. This was caused by a combination of amino acid changes in the Sprotein including the mutation G145R frequently emerging after hyperimmunoglobulin treatment. The mutations induced retention of the surface proteins in an endoplasmic reticulum (ER)-like compartment, but no intracellular accumulation. These data provide evidence for the in vivo existence of a dominant HBV population with a severe defect in The occurrence of hepatitis B virus (HBV) variants as minor or major viral populations in infected patients with fulminant, acute, and chronic hepatitis B was amply documented in the past. 1-5 HBV variants can differ from wild-type virus (WT) both in the DNA and viral protein sequences. Sequence variability and mutations were found in regulatory regions as well as in structural and nonstructural proteins. There is increasing evidence for a role of specific hepadnaviral variants in establishing chronic infection, virus/host cell interaction, and hepatopathogenesis. 4,5 In addition, several epidemic outbreaks of fulminant hepatitis B infections, which could be traced back to one chronically infected carrier, argue for an impact of viral variants in the pathogenesis of fulminant hepatitis (FHB). 6-9 Furthermore, it was shown that viral strains isolated from patients with FHB are particularly pathogenic for chimpanzees. 10 Three animals that were infected with serum of a child who transmitted FHB to 2 pediatricians developed severe hepatitis with unusually high transaminases for these animals. Based on the hypothesis that certain pathogenic HBV strains may cause or contribute to FHB several studies tried to identify structural characteristics of viral variants of these patients by determining the DNA and amino acid sequences of certain regions or the complete HBV genomes. 11-14 These experiments revealed that certain mutations, such as the precore stop codon mutation A-1896 and the core promoter mutations T-1762 and A-1764 occur more frequently in patients with FHB compared with chronic carriers, but no mutation specific for this disease course could be identified. However, this does not exclude a role of HBV variants in the pathogenesis of FHB because several differen...

Reduced Secretion of Virions and Hepatitis B Virus (HBV) Surface Antigen of a Naturally Occurring HBV Variant Correlates with the Accumulation of the Small S Envelope Protein in the Endoplasmic Reticulum and Golgi Apparatus

“…Previously, HBsAg of HBV variants 9a and 9b, which contained multiple mutations, colocalized with calnexin in ER but not with the G58K protein in Golgi (21). In contrast, in our L77R small S protein, it colocalized with both calnexin (Fig.…”

“…This domain is important for the secretion of virions (29). Naturally occurring mutations in the group a determinant, which is located in the lumen of the endoplasmic reticulum, have been found to exhibit reduced secretions of virions or HBsAg (21,22,23). However, naturally occurring mutations in the core-envelope interaction domain, which is on a cytosolic loop of the small S envelope protein, have not been functionally characterized.…”

Modulation of Hepatitis B Virus Secretion by Naturally Occurring Mutations in the S Gene

“…Considering that liver injury associated with HBV infection is mediated in large part by the host immune response, the secretion efficiency of an HBV strain may greatly affect viral pathogenicity. In support of this view, an HBV genome associated with fulminant hepatitis was found to be impaired in virion secretion (12). During the characterization of naturally occurring core promoter mutants of genotype A (22), we identified clones with a high-virion-secretion phenotype (4B and 5.2) as well as those with impaired virion secretion (3.4 and 4C) ( Table 1).…”

Pathogenesis of hepatitis B virus infection

“…Furthermore, a recent study demonstrates evidence that patients with progressive liver disease have a higher frequency of pre-S deletion [76] . HBsAg variants resulting in a defect or impairment in virion secretion have also been described in severe and fulminant hepatitis B [56,77] .…”