Prevalence of S gene mutations within the major hydrophilic region of hepatitis B virus in patients in Dongguan, southern China

Frequency of HBsAg variants in occult hepatitis B virus infected patients and detection by ARCHITECT HBsAg quantitative

Objective

To analyze the amino acid substitution caused by mutations in the major hydrophilic region (MHR) of the S-region genes in the serum samples of occult hepatitis B virus infection (OBI), and to explore the reasons for the missed detection of HBsAg.

Method

The full-length gene of the S-region in hepatitis B virus(HBV) in the chronic hepatitis B virus(CHB)(10 samples) and OBI groups(42 samples) was amplified using a lab-developed, two-round PCR amplification technology. The PCR amplification products were sequenced/clone sequenced, and the nucleotide sequences of the S-region gene in HBV were compared to the respective genotype consensus sequence.

Results

Only 20 of the 42 samples in the OBI group had the S-region genes successfully amplified, with the lowest HBV DNA load of 20.1IU/ml. As S-region genes in HBV, 68 cloned strains were sequenced. In the OBI and CHB groups MHR region, with a mutation rate of 3.21% (155/4828) and 0.70% (5/710). The genetic mutation rate was significantly higher in the OBI group than in the CHB group (P<0.05). The common mutation types in the MHR region were: I126T, L162R, K122E, C124R, and C147Y.Mutations at s122, s126, and s162 were associated with subgenotypes, most of which being C genotypes. The high-frequency mutation sites L162R and K122E found in this study have not been reported in previous literature.

Conclusion

The results of this study confirmed that MHR mutations can cause the missed detection of HBsAg, giving rise to OBI.

Natural variability in surface antigen and reverse transcriptase domain of hepatitis B virus in treatment-naïve chronic HBV-infected Egyptian patients

Hepatitis B virus (HBV) infection is a serious health problem not only in Egypt, but also worldwide. We collected 57 serum samples from treatment-naïve chronic HBV-infected Egyptians. The DNA segment encoding HBV surface antigen (HBsAg) and reverse transcriptase (RT) domain was partially sequenced. Our data revealed that all viral isolates belonged to genotype D with ayw2 as the predominant serotype (89 %). Regarding HBsAg, 45 substitutions were detected in the collected isolates. Eleven substitutions were found in the major hydrophilic region, including two novel ones (M103T and G130E) that were not correlated before with genotype D. Additionally, 11 occult samples (19 %) were detected, in which the predominant mutations of HBsAg were S143L (7 samples) followed by D144A and T125M (4 samples each). Concerning the RT domain, 26 isolates (45 %) harbored 19 natural mutations that were reported to be associated with antiviral resistance. Eleven different mutations were not correlated previously with genotype D. The most predominant mutation was Y124H (47 samples, 82 %). Interestingly, such mutation was detected in 91 % of the previous reported sequences of HBV isolates collected in Egypt (157 sequences). Furthermore, our study illustrated the presence of viral quasispecies in the HBsAg (10 samples, 17.5 %) and RT domain (9 samples, 15.7 %). In conclusion, we elucidated the presence of natural substitutions in HBsAg and RT domain of HBV isolates obtained from treatment-naïve chronic HBV-infected Egyptian patients. Additionally, we detected viral quasispecies and revealed Y124H as a characteristic substitution in the RT domain for HBV isolates in Egypt. Moreover, novel substitutions in HBsAg and RT domain were reported with genotype D.

Analysis of clinical characteristics and S gene sequences in chronic asymptomatic HBV carriers with low-level HBsAg

BACKGROUND

During the natural hepatitis B virus (HBV) infection process, some infected subjects are characterized by a sustained low serum HBV surface antigen (HBsAg) expression level. Most members in this population are chronic asymptomatic HBV carriers (ASCs). To elucidate the mechanism underlying low-level HBsAg expression in ASCs, we sequenced the HBV S gene in these patients to reveal specific sequence characteristics.

METHODS

Overall, 1308 cases of chronic ASCs were grouped according to their HBsAg serum expression levels (10 IU/mL). The clinical characteristics of the population were analysed in detail. The HBV S gene was sequenced from 276 ASC cases with low-level HBsAg expression. Additionally, 100 of 1032 ASC cases with high-level HBsAg expression were randomly selected for HBV S gene sequencing based on age matching according to the low-level HBsAg group. A comparative analysis was conducted with the HBV S gene sequences from ASCs with low HBsAg expression and the HBV reference S gene sequences from ASCs with high HBsAg expression.

RESULTS

The population with low-level HBsAg expression displayed the following primary clinical characteristics: mostly chronic asymptomatic HBV carriers, older age (mean age 55.09 years), HBsAg/anti-HBe/anti-HBc (core) positivity as the main serological pattern (97.1%), low HBV DNA replication (1.32 ± 1.60 log₁₀ IU/mL), a low HBV-DNA positive rate (45.65%) and primarily genotype B (82.54%) and serotype adw (84.13%). The comparative analysis of the HBV S gene sequences from ASCs with low-level HBsAg showed significant mutations (including co-mutations) on both sides of the main hydrophilic region (MHR).

CONCLUSION

Significant mutations in multiple regions and at multiple sites (including co-mutations) on both sides of the MHR may be one cause of the low HBsAg expression level in this population.

Mutations within the major hydrophilic region (MHR) of Hepatitis B virus from individuals with simultaneous HBsAg and anti-HBs in Guangzhou, Southern China

The mechanism of the coexistence of HBsAg and anti-HBs is still unclear. This study investigated the variations located in the major hydrophilic region (MHR) of HBV from individuals with simultaneous HBsAg and anti-HBs in Guangzhou, southern China. Among 4455 samples analyzed, 179 (4.02%) patients were discovered with both HBsAg and anti-HBs. Finally, 44 individuals with concurrent HBsAg and anti-HBs (defined as group I), and 88 patients with positive HBsAg and negative anti-HBs (defined as group II, served as control) were enrolled in the study. The number of residue changes per 100 residues within the MHR in group I was 7.1 times more frequent than group II (P < 0.001) and was discovered mostly in the MHR1 (aa99-119) (P < 0.001). Two or more residue changes in the MHR were discovered in 15 patients (34.1%) of group I, but were found in only one (1.1%) patient of group II (P < 0.001). The most common variants in group I were at positions s101Q, s133M, s126T/I, s131T, s145G, s120P, and s129Q. In addition, sQ101 K, sT131N, and sM133L were more frequently discovered in group I with significant difference (P < 0.05). In chronic hepatitis B (CHB) patients, the simultaneous of HBsAg and anti-HBs were accompanied with an increase of MHR variants, and suggested that the HBsAg mutants were selected by naturally acquired anti-HBs during chronic carriage.