Novel pre-C/C gene mutants of hepatitis B virus in chronic active hepatitis: naturally occurring escape mutants

Lee, Young Ik; Hur, Gang Min; Suh, Dae-Shik; Kim, Sun Hee

doi:10.1099/0022-1317-77-6-1129

Cited by 26 publications

(21 citation statements)

References 16 publications

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“…In addition to mutants 38 and 60 ( Fig. 1 and 2), a highly frequent naturally occurring mutation at codon 5 (P5T) was also included in this study (14,18,22). In addition to P5T, several other codon 5 mutants (P5S and P5A) were constructed and characterized in parallel.…”

Section: Resultsmentioning

confidence: 99%

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Low-Level Secretion of Human Hepatitis B Virus Virions Caused by Two Independent, Naturally Occurring Mutations (P5T and L60V) in the Capsid Protein

Pogam

Yuan

Sahu

et al. 2000

J Virol

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The functional significance of naturally occurring variants of human hepatitis B virus (HBV) remains largely unknown. Previously, we reported an immature secretion phenotype caused by a highly frequent mutation at amino acid 97 of the HBV core (capsid) protein (HBcAg). This phenotype is characterized by a nonselective and excessive secretion of virions containing an immature genome of single-stranded viral DNA. To extend our study of virion secretion to other naturally occurring variants, we have characterized mutations at HBcAg codons 5, 38, and 60 via site-directed mutagenesis. Although the phenotype of the mutation at codon 38 is nearly identical to that for the wild-type virus, our study reveals that a single mutation at codon 5 or 60 exhibits a new extracellular phenotype with significantly reduced virion secretion yet maintains normal intracellular viral DNA replication. A complementation study indicates that the mutant core protein alone is sufficient for the "lowsecretion" phenotype. Furthermore, the low-secretion phenotype of the codon 5 mutant appears to be induced by the loss of a parental proline residue, rather than by the gain of a new amino acid. Our study underscores the core protein as another crucial determinant in virion secretion, in addition to the known envelope proteins. Our present results suggest that a very precise structure of both ␣-helical and nonhelical loop regions of the entire HBcAg molecule is important for virion secretion. The low-secretion variants may contribute to the phenomenon of gradually decreasing viremia in chronic carriers during the late phase of persistent infection.Hepatitis B virus (HBV) is an important human infectious agent. Worldwide, at least 300 million individuals are chronic HBV carriers. Chronic infection with HBV leads to the development of cirrhosis and liver cancer (31, 32). Naturally occurring variants have been found frequently in chronic HBV carriers. The potential role of these variants in chronicity and pathogenesis remains unclear, since no universal assay is available to evaluate these diverse HBV variants. For example, naturally occurring variants of HBV core antigen (HBcAg) have been frequently reported. This 183-amino-acid protein has multiple functions, including interaction with the pregenomic RNA and polymerase during encapsidation, polymerization with itself to form the nucleocapsid, import of relaxed circular DNA to the nucleus, and targeting to the endoplasmic reticulum for envelope formation (3,7,16,25,26,37). In addition, HBcAg is structurally related to the secreted e antigen (27), and thus certain mutations in HBcAg should also be present in the e antigen. Because of the highly versatile nature of the HBV core protein, it is difficult to predict which functional assays should be used for the study of HBcAg variants in order to yield more informative results. Therefore, the biological significance of these mutations remains unclear.Previously, we described several missense mutations in HBcAg which coincide with major histocompatibili...

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Section: Resultsmentioning

confidence: 99%

“…14,15,18,28,29,36). Finally, a very frequent mutation of HBcAg occurs at codon 5, changing a conserved proline (P) to a threonine (T) (1,2,6,11,13,14,18,22,33,38). While the most common mutation found at HBcAg codon 5 is from P to T, other less frequent changes have also been reported, such as proline to serine (S).…”

mentioning

confidence: 99%

Low-Level Secretion of Human Hepatitis B Virus Virions Caused by Two Independent, Naturally Occurring Mutations (P5T and L60V) in the Capsid Protein

Pogam

Yuan

Sahu

et al. 2000

J Virol

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“…Interestingly the C-terminus of the core-protein (aa 150-171) seems to tolerate mutations easily in spite of its replicative functions [12]. The Ser-169 frequently was changed into Pro.…”

Section: Mutations Of the Core-regionmentioning

confidence: 99%

“…These experiments might allow the conclusion that mutants with additional Cys or change of the Cys-61 can alter the conformation of the HBeAg or the HBcAg. The newly developed proteins could no longer be recognized by antibodies [12,107].…”

Section: Mutations Of the Precore-regionmentioning

confidence: 99%

Molecular, immunological and clinical properties of mutated hepatitis B viruses

Kreutz¹

2002

J Cellular Molecular Medi

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Hepatitis B virus (HBV) is at the origin of severe liver diseases like chronic active hepatitis, liver cirrhosis and hepatocellular carcinoma. There are some groups of patients with high risk of generation of HBV mutants: infected infants, immunosupressed individuals (including hemodialysis patients), patients treated with interferon and lamivudine for chronic HBV infection. These groups are the target for molecular investigations reviewed in this paper. The emergence of lamivudine‐ or other antiviral‐resistant variants, rises concern regarding long term use of these drugs. Infection or immunization with one HBV subtype confers immunity to all subtypes. However, reinfection or reactivation of latent HBV infection with HBV mutants have been reported in patients undergoing transplant and those infected with HIV. Mutations of the viral genome which are not replicative incompetent can be selected in further course of infection or under prolonged antiviral treatment and might maintain the liver disease. Four open reading frames (ORF) which are called S‐gene, C‐gene, X‐gene and P‐gene were identified within the HBV genome. Mutations may affect each of the ORFs. Mutated S‐genes were described to be responsible for HBV‐infections in successfully vaccinated persons, mutated C‐genes were found to provoke severe chronic liver diseases, mutated X‐genes could cause serious medical problemes in blood donors by escaping the conventional test systems and mutated P‐genes were considered to be the reason for chemotherapeutic drug resistance. This paper reviews molecular, immunological and clinical aspects of the HBV mutants.

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“…In the literature, out of 65 sequences containing 97L mutations, 10 (15.4%) have concurrent P5T mutations (1,2,5,9,12,13,15,25,27,28). Previously, we reported a compensatory core mutation, P130T, which also can rescue the immature secretion phenotype induced by the I97L mutation (32).…”

mentioning

confidence: 99%

Coexistence of Two Distinct Secretion Mutations (P5T and I97L) in Hepatitis B Virus Core Produces a Wild-Type Pattern of Secretion

Chua

Wen

Shih

2003

J Virol

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Unlike a Tokyo isolate of hepatitis B virus variants, we found a Shanghai isolate that secretes few virions with an immature genome despite its core I97L mutation. Core mutations P5T and I97L were found to be mutually compensatory in offsetting their respective distinct effects on virion secretion.Hepatitis B virus (HBV) replicates by using reverse transcriptase (11,24). Due to the low fidelity of the polymerase, error-prone replication and natural selection in vivo lead to the accumulation of multiple mutations in HBV variants predominant in chronic carriers (20,22). The most frequent natural mutation in the HBV core protein occurs at amino acid 97 (5, 6, 9, 10, 13). It remains a challenge to elucidate the functional significance of these prevalent and predominant mutations, since there is no a priori knowledge about what kind of assays should be used. Recently, a so-called "immature secretion" phenotype was demonstrated to be a global phenotype in tissue culture by introducing a 97L mutation into the core gene of a wild-type HBV genetic background of subtype adr and ayw origins (31,33). This phenotype of HBV variant 97L is interesting, because it represents an exception to the dogma of preferential export of virions containing mature genomes (highermolecular-weight viral DNA in relaxed circle form) in wild-type hepadnaviruses (24). Unlike the wild-type HBV, the 97L mutant secretes similar amounts of mature and immature genomes (lower-molecular-weight viral DNA in single-strand form). This phenotype is not caused by any deficiency in reverse transcription (33) or any instability of core proteins and particles (31, 33; M. Newman, F. M. Suk, and C. Shih, unpublished results).Although an immature secretion-like phenotype has also been found to occur in vivo in woodchuck and snow goose hepadnaviruses (4, 26), it is puzzling that it has not been found so far in natural infection in humans (F. M. Suk, M. H. Lin, and C. Shih, unpublished results). Furthermore, it remains unclear whether an immature secretion phenotype can still be observed in the genetic context of naturally occurring variants, which often contain multiple mutations throughout the genome. To address these issues, we took a reciprocal approach by reverting the natural mutation at amino acid 97 in a naturally occurring HBV variant from leucine back to isoleucine (L97I) and asked whether the predicted immature secretion phenotype can be abolished by eliminating the leucine residue at position 97 of the HBV core antigen (HBcAg).This parental HBV variant clone of adr subtype origin was isolated from a hepatocellular carcinoma patient from Shanghai, China (clone 14 in references 18 and 19). In addition to the hot spot mutation I97L, it contains multiple frequent mutations, including core mutations P5T and S87G, enhancer II mutations at nucleotides 1762 and 1764, and mutations truncating the X protein and abrogating the production of the pre-S2-containing M envelope protein (18). The 3.2-kb monomeric HBV genome in clone 14 was released from the pUC18 vector ...

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Novel pre-C/C gene mutants of hepatitis B virus in chronic active hepatitis: naturally occurring escape mutants

Cited by 26 publications

References 16 publications

Low-Level Secretion of Human Hepatitis B Virus Virions Caused by Two Independent, Naturally Occurring Mutations (P5T and L60V) in the Capsid Protein

Low-Level Secretion of Human Hepatitis B Virus Virions Caused by Two Independent, Naturally Occurring Mutations (P5T and L60V) in the Capsid Protein

Molecular, immunological and clinical properties of mutated hepatitis B viruses

Coexistence of Two Distinct Secretion Mutations (P5T and I97L) in Hepatitis B Virus Core Produces a Wild-Type Pattern of Secretion

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