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      The truncated mutant HBsAg expression increases the tumorigenesis of hepatitis B virus by regulating TGF-β/Smad signaling pathway


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          It has been reported that the emergence of HBV rtA181T/sW172* mutant could result in a dominant secretion defect of HBsAg and increase the risk of HCC development. This study was designed to reveal the role and possible pathogenic mechanism of truncated mutant HBsAg in tumorigenesis of HBV rtA181T/sW172* mutant.


          As compared to wide type or substituted mutant HBsAg, the ratio of cell clones was significant higher in L02 cells stable expressing truncated mutant HBsAg. Injection of L02 cells stable expressing truncated mutant HBsAg into the dorsal skin fold of nude mice resulted in increased primary tumor growth compared to L02 cells stable expressing wide-type and substituted mutant HBsAg. In HBV replication L02 cell lines, the key molecular involved in TGF-β/Smad pathway was also investigated. We found that the mRNA and protein levels of Smad3/2, CREB and CyclinD1 were significantly higher and TGFBI level was significantly lower in cells stably expressing truncated mutant HBsAg as compared to cells stably expressing wide-type and substituted mutant HBsAg. Additionally, after administration of TGF-β1 (increasing TGFBI level), the volume of tumor is obviously reduced in nude mice with injection of L02 cells stable expressing truncated HBsAg.


          The emergence of sW172* mutant may increase the tumorigenesis of HBV, and its mechanism may be associated with down-regulated expression of TGFBI in TGF-β/Smad signaling pathway.

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          The antiviral drug selected hepatitis B virus rtA181T/sW172* mutant has a dominant negative secretion defect and alters the typical profile of viral rebound.

          The hepatitis B virus (HBV) mutation that encodes rtA181T is selected in the viral polymerase during antiviral drug therapy and can also encode a stop codon in the overlapping surface gene at amino acid 172 (sW172*) resulting in truncation of the last 55 amino acids of the C-terminal hydrophobic region of the surface proteins. This mutation is usually detected as a mixed population with wild-type HBV. In vitro analysis revealed that the rtA181T/sW172* variant is not only defective in secretion of viral particles causing intracellular retention of surface proteins, it also has a dominant negative effect on virion but not subviral particle secretion when coexpressed with the wild type. This dominant negative effect was attributed to the truncated S protein alone. Furthermore, these truncated surface proteins were less glycosylated, and the truncated L protein was able to support virion secretion. Examination of sequential HBV DNA levels in patients failing lamivudine or adefovir therapy where only the rtA181T change was detected via polymerase chain reaction sequencing revealed that viral load rebound did not occur or was not as large as usually observed with drug-resistant HBV. The rtA181T/sW172* variant has a secretory defect and exerts a dominant negative effect on wild-type HBV virion secretion. The selection of rtA181T/sW172* reduced the typical extent of virological breakthrough, resulting in a missed diagnosis of drug resistance if viral load was used as the only criterion for drug failure, necessitating HBV polymerase chain reaction sequencing or other genotypic methods to diagnose antiviral drug resistance in these cases.
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            Primary resistance, multidrug resistance, and cross-resistance pathways in HBV as a consequence of treatment failure.

            Antiviral resistance is now the single most important factor in treatment failure using nucleos(t)ide analogues (NA). Primary drug resistance mutations refer to amino acid change(s) that result in reduced susceptibility to an antiviral agent. Secondary compensatory mutations restore replication defects associated with primary drug resistance and may be associated with low level reduced susceptibility. Several evolutionary pathways of drug resistant HBV have been observed in patients treated with NAs. It is possible that the drug resistance mutations selected with one agent may affect the efficacy of other NAs. Several major HBV-evolutionary NA-resistance pathways (rtM204I/V, rtN236T and rtA181T/V) have now been characterised. The rtM204V/I pathway is responsible for resistance to the L: -nucleosides, such as lamivudine (LMV), telbivudine (LdT) and clevudine (CLD), and also entecavir (ETV), whilst the rtN236T pathway is responsible for adefovir (ADV) and tenofovir (TFV) resistance. Both pathways are associated with clusters of secondary mutations that can affect subsequent treatment with NAs (rtT184G, rtS202I) such as ETV. The third pathway, rtA181T/V, is associated with resistance to LMV and ADV and is a potential multi-drug resistance pathway and will probably have an impact on TFV sensitivity, either alone or with the rtN236T. In naïve patients treated with ETV, atleast three mutations arising at the same time are required: rtL180M + rtM204V plus either one of rtT184, rtS202 or rtM250 codon changes. Finally, in highly drug-experienced patients, clusters of mutations such as rtA181T/I233V/N236T/M250L, all on the one dominant HBV genome, are being detected which are associated with multi-drug resistance. Sequential treatment with nucleos(t)ide analogue reverse transcriptase inhibitors (NRTI) promotes multidrug resistance. It is likely, therefore, that development of multi-drug resistance could be reduced by combination therapy optimised to individual viral phenotypes.
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              Nucleotide change of codon 182 in the surface gene of hepatitis B virus genotype C leading to truncated surface protein is associated with progression of liver diseases.

              Hepatitis B virus (HBV) genotype C infection is associated with progression of hepatocellular carcinoma (HCC). Specific mutations of the HBV surface (S) gene have been reported to contribute to the development of HCC. In this study, novel nucleotide changes (sW182*) that result in a premature stop at codon 182 in the S gene of genotype C are investigated with regards to the development of HCC. A multi-probe real time PCR that enables rapid and reliable detection of sW182* was developed and applied to 292 DNA samples from Korean patients with diverse chronic liver diseases. sW182* was detected in a total of 73 patients out of the 275 with positive amplification (26.5%). Its prevalence was significantly higher in patients with progressive forms of the disease (HCC and liver cirrhosis) than in patients with less severe forms of the disease (chronic hepatitis and carrier) [31.8% (56/176 patients) vs. 17.2% (17/99 patients); p=0.010]. In addition, an in vitro study using cell lines stable expressing the S protein with sW182* also strongly supported its relationship with HCC. In the present study, we demonstrate that the sW182* of HBV could provide an important contribution to the progression of liver diseases, through molecular epidemiologic and in vitro studies. Copyright © 2011 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

                Author and article information

                Virol J
                Virol. J
                Virology Journal
                BioMed Central (London )
                2 April 2018
                2 April 2018
                : 15
                : 61
                ISNI 0000 0004 1770 1022, GRID grid.412901.f, Center of Infectious Diseases, , West China Hospital, Sichuan University, ; No.37 Guo Xue Xiang, Wuhou District, Chengdu, 610041 People’s Republic of China
                © The Author(s). 2018

                Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

                : 27 December 2017
                : 21 March 2018
                Funded by: FundRef http://dx.doi.org/10.13039/501100001809, National Natural Science Foundation of China;
                Award ID: 81271811
                Award ID: 81772193
                Award Recipient :
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                © The Author(s) 2018

                Microbiology & Virology
                hepatitis b virus mutation,rta181t/sw172* mutation,truncated mutant hbsag,tumorigenises,tgfbi


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