Research ArticleInfluence of mutations in hepatitis B virus surface protein on viral antigenicity and phenotype in occult HBV strains from blood donors
Introduction
Hepatitis B virus (HBV) persistently infects over 350 million people worldwide and leads to hepatitis, liver cirrhosis, and hepatocellular carcinoma. The hepatitis B surface protein (HBsAg) is an envelope glycoprotein that currently serves as primary target for diagnosis and immunoprophylaxis of HBV infection. The dominant epitopes of HBsAg, which are the targets of neutralizing B cell responses, reside in the “a” determinant (aa 124–147) within the major hydrophilic region (MHR). Amino acid substitutions in the MHR can cause reduced binding of anti-HBs antibodies, resulting in immune escape. The most common MHR mutation, G145R, was initially described in 1990 [1]. The emergence of single or multiple amino acid (aa) substitutions at this and other positions within the MHR has been observed in infants born to HBsAg(+) mothers who received the HBV vaccine with or without HBIG, in liver transplant recipients who received HBIG, in patients who experienced HBsAg loss after anti-HBV therapy, and in individuals with occult HBV infection (OBI) [2], [3], [4].
Occult HBV infection is an atypical form of HBV infection, which is defined as the long-term persistence of HBV DNA, despite undetectable HBsAg by regular immunoassays [5], [6]. Since its initial description in the late ‘70s, OBI has been a challenge in hepatitis B research, with its unique virological and clinical characteristics. Evidence from different geographical regions has demonstrated that OBI was distributed worldwide and was potentially a major source of HBV transmission by transfusion and organ transplantation [7]. Acute viral reactivation may occur in association with immunosuppressive therapies and/or immunodeficiency [8]. In addition, OBI virus maintains its pro-oncogenic properties [9]. High frequencies of MHR mutations have been observed in OBI strains of individuals from Europe and Africa [10], [11]. Generally, the modified proteins produced by MHR-mutated S genes, which are not well recognized by current HBsAg immunoassays, are considered a key cause of detection failure of HBsAg in OBI. However, the influence of MHR mutations on the characteristics of viral antigenicity and phenotype, which is important for uncovering the mechanism of OBI, has not been systematically investigated.
In this study, we investigated the molecular characteristics of OBI strains from a large cohort of blood donors. Representative MHR mutations were detected and were functionally characterized both in vitro and in vivo.
Section snippets
Specimens
From 2007 to 2010, 38,499 blood donations were collected by the Xiamen Blood Service (Xiamen, China). Among these specimens, 308 were HBsAg(+) and 38,191 were HBsAg(−) by ELISA (Murex-V3, Abbott-Murex, UK). The serum HBsAg levels of HBsAg(+) specimens were determined using CMIA (Architect HBsAg, Abbott Laboratories, USA). Of the 38,191 HBsAg(−) specimens, 70 yielded repeatable positive results by Cobas Taqscreen (Roche Inc., Switzerland) or nested PCR, as described elsewhere [4]. Anti-HBs and
MHR mutants in blood donors with OBI
The MHR (aa 110–160) of the viral S gene was successfully amplified and sequenced in 61 out of 70 OBI samples (OBI group) and in 207 out of 308 HBsAg(+) samples. These specimens were used for further molecular characterization. When HBsAg(+) individuals were divided into two groups according to their HBsAg level by a cut-off value of 100 IU/ml, which was widely recognized as a predictor of HBsAg seroclearance in CHB [14], [15], [16], 153 donors had a HBsAg level ⩽100 IU/ml (HBsAg-L group) and the
Discussion
In the present study, we observed a prevalence of OBI of 0.18% in a large cohort of blood donors in Xiamen (China), a highly HBV-endemic area with a documented HBsAg prevalence of 10.9% [17]. In viral sequences isolated from OBI samples, we observed a high MHR mutation frequency (55.7%), which was significantly higher than in the HBsAg(+) group. High mutation frequencies in the MHR have also been observed in OBI strains from Europe and Africa [10], [11]. Our analyses revealed that the MHR
Financial support
This work was supported by grants from the Excellent Youth Foundation of the Fujian Scientific Committee (Grant No. 2009J06020), the National Science Fund for Distinguished Young Scholars (30925030) and the National Scientific and Technological Major Project (2012ZX10002-005/2012ZX10004-503).
Conflict of interest
The authors who have taken part in this study declared that they do not have anything to disclose regarding funding or conflict of interest with respect to this manuscript.
References (22)
- et al.
Vaccine-induced escape mutant of hepatitis B virus
Lancet
(1990) - et al.
Statements from the Taormina expert meeting on occult hepatitis B virus infection
J Hepatol
(2008) - et al.
A 2010 update on occult hepatitis B infection
Pathol Biol (Paris)
(2010) - et al.
Transfusion-transmitted hepatitis B virus infection
J Hepatol
(2009) - et al.
Characterization of occult hepatitis B virus from blood donors carrying genotype A2 or genotype D strains
J Hepatol
(2008) - et al.
Decreasing levels of HBsAg predict HBsAg seroclearance in patients with inactive chronic hepatitis B virus infection
Clin Gastroenterol Hepatol
(2012) Deficiency in virion secretion and decreased stability of the hepatitis B virus immune escape mutant G145R
Hepatology
(2003)- et al.
T cell responses and viral variability in blood donation candidates with occult hepatitis B infection
J Hepatol
(2012) - et al.
Hepatitis B virus variants
Nat Rev Gastroenterol Hepatol
(2009) - et al.
Emergence of hepatitis B virus S gene mutants in patients experiencing hepatitis B surface antigen seroconversion after peginterferon therapy
Hepatology
(2011)
Molecular characteristics of occult hepatitis B virus from blood donors in southeast China
J Clin Microbiol
Cited by (167)
A potent neutralizing and protective antibody against a conserved continuous epitope on HSV glycoprotein D
2022, Antiviral ResearchCitation Excerpt :Briefly, mAbs were raised in mice using an intraperitoneal injection of 106 PFU equivalents of UV-inactivated HSV-1/2 emulsified in Freund's complete adjuvant, followed by a booster injection in the superficial gluteal muscle one month later. Hybridoma cells were obtained at two months post-immunization as previously reported (Huang et al., 2012). The supernatants of hybridoma cells were screened by the cell-based ELISPOT method and ELISPOT-NT method.
Anti-rheumatic drug-induced hepatitis B virus reactivation and preventive strategies for hepatocellular carcinoma
2022, Pharmacological ResearchAdvances in human monoclonal antibody therapy for HBV infection
2022, Current Opinion in Virology
- †
These authors contributed equally to this work.