Intracellular retention of surface protein by a hepatitis B virus mutant that releases virion particles

Xu, Zhichang; Yen, T. S. Benedict

doi:10.1128/jvi.70.1.133-140.1996

Cited by 95 publications

(55 citation statements)

References 33 publications

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“…This was first found after introducing artificial triple-point mutations or by studying a natural-occurring 129-bp deletion in the S-promoter. 6,32 Our experiments demonstrated that a single-point mutation located in this motif had a tremendous effect on S-gene regulation, resulting in unusual nuclear and perinuclear localization of viral proteins.…”

Section: Discussionmentioning

confidence: 75%

The Pre-S region determines the intracellular localization and appearance of hepatitis B virus

et al. 1999

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The functional role of the hepatitis B virus (HBV) pre-S region for assembly and appearance of the virus is not completely understood. In this study, 3 natural-occurring mutants were investigated. Three mutants of the pre-S region-a point mutation in the CCAAT box (MUT1), a 6-bp deletion (MUT2) 3Ј of the CCAAT box, and a 153-bp deletion (MUT3) in the preS2 domain-were cloned alone or in combinations in replication-competent HBV plasmids and transfected in hepatoma cells. The impact on HBV assembly and appearance was studied by Northern Blot, primer extension analysis, immunofluorescence studies, enzyme-linked immunosorbent assay, and electron microscopy. An inversed ratio of pre-S/S mRNA transcripts compared with wild-type (wt) HBV was found when either MUT1 or -2 were included into the plasmid. Intracellular localization with both mutants showed retention of large S-protein in the endoplasmic reticulum and nuclear accumulation of core protein. The extracellular amount of S-protein was reduced with MUT1 and -2 or combinations in which 1 of the mutants was included. However, the extracellular appearance of viral products was comparable with wtHBV. In contrast, MUT3 showed major changes. Virion-like particles had a fried-egg, and filaments a screw-like appearance. The S-promoter mutations MUT1 and MUT2 correlated with viral retention. MUT3 leads to malformed viral particles. Therefore, different regions in the pre-S domain are essential to determine the intracellular localization and extracellular appearance of HBV, and might contribute to the prognosis of chronic HBV infection. (HEPATOLOGY 1999; 30:517-525.)The hepatitis B virus (HBV) is the smallest DNA virus known to be pathogenic for humans. The HBV is a member of the hepadnavirus family, showing a close host tropism. The genome of the HBV consists of a small circular DNA of 3.2 kb in length. Despite its small size, the HBV genome contains 4 open reading frames partly overlapping and generating at least 7 viral gene products. The 4 open reading frames are under the transcriptional control of 4 promoters (preS1, S, C, and X promoter) and 2 enhancer (enhancer I and II) elements. [1][2][3] The envelope gene of the HBV is controlled by 2 different promoters: the pre-S-and the S-promoter, which regulate transcription of a 2.4-and a 2.1-kb mRNA, respectively. The pre-S-promoter is located 5Ј of the first in frame ATG of the large (pre-S1) envelope protein. The S-promoter is found in the coding region of the pre-S gene and is a TATA-less promoter. Mainly, 2 factors control the activity of the Spromoter: Sp 1 and NF-Y. 4-7 NF-Y binds to the so-called CCAAT box and is especially important for the regulation of the S-gene controlling the ratio between the pre-S and S mRNA. 4,8 The 2 mRNAs transcribed from the S-gene code for 3 S-proteins (small, middle, and large) sharing the 226 amino acids at the C-terminus. Translation of the small S-protein starts at the third in-frame ATG of the S-gene, while the other 2 proteins start at the first and second ATG. However, some sub...

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Section: Discussionmentioning

confidence: 75%

The Pre-S region determines the intracellular localization and appearance of hepatitis B virus

et al. 1999

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“…18 Core proteins with internal deletions are able to interact with the wild-type core protein and to form mosaic particles. 19 Finally, deletions in the pre-S1 region may lead to retention of surface proteins in the cell by changing the transcriptional regulation of surface protein expression, [20][21][22] In transgenic mice, HBV surface protein retention is directly toxic to the cell or sensitizes the cell to immune or cytokine-mediated injury. [23][24][25][26][27] Combining the effects of all these types of mutations within 1 virus population or even 1 genome, it is conceivable that the virulence of a corresponding HBV population is increased due to enhanced replication and protein expression as well as retention of virus proteins in the cell.…”

Section: Discussionmentioning

confidence: 99%

Complex HBV populations with mutations in core promoter, C gene, and pre-S region are associated with development of cirrhosis in long-term renal transplant recipients

et al. 2002

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Long-term immunosuppressed renal transplant recipients with chronic hepatitis B virus (HBV) infection often develop liver cirrhosis (LC) and end-stage liver disease (ESLD).This study investigated accumulation and persistence of specific HBV mutants in relation to the clinical course in these patients (n ‫؍‬ 38; mean follow-up, 3.5 years). HBV was analyzed longitudinally via length polymorphism of polymerase chain reaction (PCR) fragments (median, 6.5 serum samples per patient) as well as by cloning and partial sequencing of 346 full-length HBV genomes. Fourteen patients (group 1) developed LC or died from ESLD, whereas 24 patients (group 2) showed no evidence of LC during follow-up. Development of LC and ESLD was associated with persistence of HBV mutant populations characterized by deletions/insertions in core promoter plus deletions in the C gene and/or deletions in the pre-S region (86% of group 1 vs. 17% of group 2; P < .0001). HBV without these mutations or with core promoter mutations alone were predominantly found in group 2 (14% of group 1 vs. 75% of group 2). In patients infected with core promoter mutants, the additional appearance and persistence of deletions in the C gene and/or the pre-S region were accompanied or followed by development of LC and ESLD. The mutations were distributed on individual genomes in various combinations, leading to a high complexity of the virus population. In conclusion, these data suggest that accumulation and persistence of specific HBV populations characterized by mutations in 3 subgenomic regions play a role in pathogenesis of LC and ESLD in long-term renal transplant recipients. (HEPATOLOGY 2002;35: 466-477.)H epatitis B virus (HBV) infection is associated with various courses of liver disease ranging from asymptomatic carrier state to fulminant hepatitis. It is generally accepted that liver injury is immune mediated. However, severe liver disease and liver cirrhosis (LC) are also observed in long-term immunosuppressed patients such as renal transplant recipients with chronic HBV infection, 1-4 which is not fully compatible with immunopathogenesis. In past years, there was increasing evidence that HBV mutants may be involved in hepatopathogenesis in immunosuppressed patients. Mutations in the core promoter/enhancer II (Cp/EnII) that create a novel hepatocyte nuclear factor (HNF) 1 binding site and deletions in the pre-S region were found in a heart transplant recipient who died from fulminant HBV infection under immunosuppression. 5 A liver transplant recipient died from fibrosing cholestatic hepatitis following the accumulation of HBV with deletions in the pre-S1/2 region. 6 In a previous study, we showed that HBV with deletions in the C gene is significantly associated with development of HBV-related end-stage liver disease (ESLD) and death in renal transplant recipients. 7 Whereas the former studies reported just single cases without a control group, the latter was focused on 1 subgenomic region of HBV. Therefore, on the HBV genome level, it is still unclear wh...

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“…Currently, we can only speculate on the potential pathogenic importance of secretion-defective variants for the development of fulminant recurrent hepatitis B: It is well known that malfolded or mutated proteins that are not secreted can cause stress in the ER, affecting cellular transcription via intracellular signaling pathways. [44][45][46] Specifically it was shown 29 that accumulation of L-protein in the ER can activate the genes encoding the ER luminal chaperon proteins grp78 and grp94. Thereby retention of the mutant L-and S-proteins in the ER could affect host cell physiology.…”

Section: Discussionmentioning

confidence: 99%

“…This staining pattern is reminiscent of the localization of proteins retained in the ER. [27][28][29] Additional staining with appropriate antibodies for the ER and Golgi compartment revealed a predominant colocalization of all mutant envelope proteins with the perinuclearly localized ER, but not with the Golgi compartment ( Fig. 5).…”

Section: The Mutant Envelope Proteins Showed An Aberrant Subcellularmentioning

confidence: 92%

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

et al. 2001

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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...

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Intracellular retention of surface protein by a hepatitis B virus mutant that releases virion particles

Cited by 95 publications

References 33 publications

The Pre-S region determines the intracellular localization and appearance of hepatitis B virus

The Pre-S region determines the intracellular localization and appearance of hepatitis B virus

Complex HBV populations with mutations in core promoter, C gene, and pre-S region are associated with development of cirrhosis in long-term renal transplant recipients

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

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