HIV variants and hepatitis B surface antigen mutants: diagnostic challenges for immunoassays

Molecular analysis of the hepatitis B virus presurface and surface gene in patients from eastern China with occult hepatitis B

This study was designed to detect and analyze mutations that occur within the presurface and surface (pre-S/S) gene of HBV in patients with occult hepatitis B, and determine their relationship to that disorder. Among 254 HBsAg negative samples of blood collected in eastern China, 183 were positive for anti-HBc alone, 61 were positive for anti-HBe alone, and 10 samples were positive for HBeAg. Within this group, 15 samples were found to be HBV DNA positive by real-time PCR and were designated Group I. A control group of 28 HBsAg positive samples were chosen at random from patients with chronic hepatitis B and designated Group II. The HBV pre-S/S gene was amplified by PCR and subjected to sequencing analysis. Occult hepatitis B was found in 1.6% of the patients with anti-HBc alone and in 3.3% of those with anti-HBe alone. Occult hepatitis B also was found in all HBsAg negative but HBeAg positive samples. Sequencing analysis showed a significant correlation between point mutations within the "a" determinant and occult hepatitis B (P < 0.0001), and a close relationship between pre-S deletion mutations and occult hepatitis B (P = 0.06). There were unique amino acid mutations at the G145 position other than G145R. The HBV DNA levels in patients with occult hepatitis B were significantly lower than those found in the control group. The "a" determinant mutations and pre-S deletions may play important roles in occult hepatitis B by affecting the expression, synthesis and secretion of the S protein and by impeding viral release and replication.

Establishment of an HBsAg mixed titer performance panel and HBsAg working standard for quality control of HBsAg diagnostic kits in Korea

BACKGROUND

International Standards or commercial panels used for performance validation of diagnostic kits might not reflect the viral characteristics common in Korea. Also, continuous use of these materials is difficult because of limited quantity and high cost.

OBJECTIVES

Establishment of HBsAg reference materials to be used as National Standards for validation of HBsAg diagnostic kits.

STUDY DESIGN

568 plasma units with OD less than 2.0 on HBsAg EIA were collected. HBsAg testing with 3 EIAs and 1 CIA was performed on all units. HBsAg positive units were subjected to HBV DNA quantification, genotyping and subtyping. Candidates for the mixed titer performance panel and working standard were confirmed for HBsAg by neutralization. A collaborative study was conducted for the candidates of the mixed titer performance panel and the working standard.

RESULTS

Based on the results of the collaborative study, a working standard (KFDA08/024) consisting of a series of four-fold dilutions of 2 materials, one with genotype/subtype C2/adr and the other with C1/adw, was established. A mixed titer performance panel composed of 2 negative and 16 positive samples was also established. A G1896A and a T/I126S mutant are included in the positive samples.

CONCLUSIONS

An HBsAg mixed titer performance panel and a working standard reflecting HBV genotypes/subtypes prevalent in Korea have been established as National Standards. This will enable consistent supply of validation materials, improve the validation system of HBsAg diagnostic kits in Korea and lead to quality improvement of diagnostic kits.

PreS deletion mutations of hepatitis B virus in chronically infected patients with simultaneous seropositivity for hepatitis-B surface antigen and anti-HBS antibodies

Hepatitis B surface antigen (HBsAg) and anti-HBs antibodies (anti-HBs) may coexist in certain chronic hepatitis B (CHB) patients. This study was designed to further explore the relationship between this coexistence and hepatitis B Virus (HBV) preS deletions. Sera of 28 patients carrying both HBsAg and anti-HBs (Group I) and those of another 28 HBsAg positive but anti-HBs negative patients (Group II) were collected from CHB patients. Direct sequencing of polymerase chain reaction products or sequencing of clones was applied to both groups to determine sequences of HBV preS and S genes. Genotyping of the S gene indicated that all sampled HBVs were either Genosubtype Ba or Genosubtype Ce. Seven samples in Group I harbored HBV preS deletion mutations. Three of the seven samples showed large deletion mutations in 3' terminus of preS1 and co-existence of the mutant type and the full-length wild type, and the remaining four samples showed deletion mutations in 5' terminus of preS2. All mutant strains were found to be genosubtype Ce. Only two samples in Group I showed G145R/A mutation. Only one sample in Group II contained preS deletion mutation. It is therefore concluded that HBV preS deletion mutations are likely to be related to the coexistence of HBsAg and anti-HBs in CHB patients (P-value = 0.024). Some immune reactions may select for the preS deletion in CHB patients with anti-HBs, the possible marker for immune selection.

Molecular virology of hepatitis B virus for clinicians

This article reviews the molecular biology of the hepatitis B virus in an effort to explain its natural history from a molecular perspective. The life cycle of the virus, with special attention to virus replication, polypeptide production, and morphogenesis, is described. The way in which these steps may influence the natural history of viral pathogenesis, as well as the effectiveness of interventions, receives special consideration.