Association of HBsAg mutation patterns with hepatitis B infection outcome: Asymptomatic carriers versus HCC/cirrhotic patients

INTRODUCTION AND OBJECTIVES

The hepatitis B virus (HBV) surface antigen (HBsAg) variations suggested having some effects on infection outcome. Due to some controversial issues, the aim of this study was to compare the pattern of HBsAg variation between asymptomatic carriers and HCC/cirrhosis patients.

MATERIALS AND METHODS

In this cross-sectional study, 19 HCC/cirrhotic and 26 asymptomatic patients were enrolled. After viral DNA extraction, HBs gene was amplified using an in-house nested-PCR. Then, PCR products were introduced into bi-directional Sanger sequencing. The retrieved sequences were compared with references, to investigate the variation of immunologic sites, major hydrophilic region (MHR) of HBsAg as well as reverse transcriptase (RT), and also to determine genotype/subtype.

RESULTS

The analysis of MHR and epitopes on HBsAg showed dozens of substitution, which occurred more prevalently in I110, P120, Y134, G159, S193, Y206, S207, I208, L213 and P214 positions. However, Y134N/F/L (P=0.04) and P120T/S (P=0.009) were significantly detected in MHR and B-cell epitope of HCC/Cirrhotic group. A number of truncation-related mutations were higher in HCC/Cirrhotic group (P>0.001), albeit only C69* stop codon was statistically significant (P=0.003). In RT, some potentially resistant substitutions such as Q215S, V191I and V214A, were revealed. Phylogenetic analysis showed that all of isolates belonged to genotype D, and the major serotype was ayw1.

CONCLUSION

The higher frequency of substitutions in MHR and immune epitopes at positions such as Y134 and P120 as well as stop codons such as C69* in HCC/cirrhotic group might candidate them as predictive factors for infection outcome.

Conformational analysis of hepatitis B virus surface antigen mutations among HIV-positive patients diagnosed with occult hepatitis B virus

Aim: We analyzed the role of mutations on the conformational structure of hepatitis B surface antigen (HBsAg) among HIV-1 positive patients who were infected with occult hepatitis B. Methods: The effects of the potential impact of amino-acid substitutions on the 3D structures of the HBsAg and molecular ducking were investigated using bioinformatics software. Results: Mutations classified in seven groups in accordance with their positions in occult hepatitis B virus infection patients. Some substitutions of residues could linearize the ‘a’ determinant loops. The affinity of binding in mutant HBsAg structures to MAb 12 was lower compared with the wild ones. T123I and P127L substitutions were undergone decrease in HBsAg antigenicity. Conclusion: These findings could be beneficial for a better understanding of hepatitis B virus antigen/antibody interactions.

Hepatitis B immunopathogenesis and immunotherapy

Worldwide there are over 248 million chronic carriers of HBV of whom about a third eventually develop severe HBV-related complications. Due to the major limitations of current therapeutic approaches, the development of more effective strategies to improve therapeutic outcomes in chronic hepatitis B (CHB) patients seems crucial. Immune activation plays a critical role in spontaneous viral control; therefore, new modalities based on stimulation of the innate and adaptive immune responses could result in the resolution of infection and are promising approaches. Here, we summarize the HBV immunopathogenesis, and discuss the encouraging results obtained from the promising immune-based innovations, such as therapeutic vaccination, cytokine therapy, cell-based therapies and blocking inhibitory receptors, as current and future immunotherapeutic interventions.

Naturally Occurring Surface Antigen Variants of Hepatitis B Virus in Tunisian Patients

In Tunisia, the prevalence of naturally occurring surface (S) gene variants of hepatitis B virus (HBV) has not been determined. In the present study, the prevalence of these variants was examined in terms of the clinical and viral state in a series of 99 Tunisian patients with HBV infection. The S genes were amplified and directly sequenced. Genotype D was predominant (98%), 40.4% isolates belonged to subgenotypes D7 and 1 to subgenotype D2. The most common subtype was ayw2 (95.9%). In total, 60.6% of the studied strains harbored S mutations. Several novel mutation patterns were detected. Interestingly, the presence of S mutations was significantly correlated with the D7 subgenotype, low HBV DNA and advancing age (≥35 years), and tended to be higher in liver cirrhosis than in chronic infection. The global prevalence of the major hydrophilic region variants was 12.1%, with substitution S143L/T as the most frequent (4%). Only 33.9% of S substitutions produced amino acid changes in the polymerase gene. In conclusion, a high prevalence of naturally occurring HBsAg variants was observed among Tunisian HBV carriers. Natural viral variability in a geographical region and duration of infection are among the major factors associated with the occurrence of S mutations.

Impacts of the G145R Mutation on the Structure and Immunogenic Activity of the Hepatitis B Surface Antigen: A Computational Analysis

BACKGROUND

Vaccine-escaped hepatitis B virus (HBV) mutations occur within the "a" determinant area, which is located in the major hydrophilic region (MHR) of the hepatitis B surface antigen (HBsAg) protein. It is now well established that the common G145R mutation is highly capable of escaping from HBsAg immune recognition. However, the impacts of this mutation on the structure and immunogenic activity of HBsAg have been poorly investigated.

OBJECTIVES

The present study analyzed the effects of the G145R mutation on the structure and immunogenic activity of the HBsAg.

MATERIALS AND METHODS

Three-dimensional (3D) structure of HBsAg for both the wild-type and G145R mutant were predicted and refined using several web tools. After quantitative evaluations, the effects of the G145R mutation on the secondary and 3D structures of the HBsAg were investigated. In parallel, the immunogenic activity of the wild-type and mutant HBsAg was also analyzed using a ClusPro docking server as well as the IEDB web tool. Further analyses were performed via molecular dynamics (MD) simulations using the GROMACS v5.0.2 simulation package.

RESULTS

The G145R mutation causes a considerable reduction in the immunogenic activity of the HBsAg through a conformational change in the HBsAg antigenic loops. This mutation inserts a new β-strand in the "a" determinant region of the HBsAg, leading to a reduced binding affinity to its monoclonal antibody, MAb12. The G145R mutation also increased the compactness and stability of the HBsAg by enhancing the rigidity of the "a" determinant.

CONCLUSIONS

These data will be beneficial for designing more advanced antibodies for the recognition of the HBsAg in diagnostics. In addition, the results of this study may assist in the design or development of more effective hepatitis B vaccines.

A strategical re-thinking on National Blood Donor Pool: Anti-HBc positivity related re-entry mechanisms

BACKGROUND AND OBJECTIVES

Screening of blood donations for antibodies against hepatitis B core antigen (anti-HBc) is used to prevent transfusion transmitted hepatitis B virus (HBV) infection. In this study, we studied the magnitude of blood donor gain by using a re-entry mechanism in our Blood Bank of Gulhane Military Academy of Medicine.

MATERIALS AND METHODS

Between January and May 2013, 5148 voluntary blood donors were screened by ELISA method for HBsAg, anti-HBc total and other screening markers, prospectively. Samples with repeated reactivity for the presence of anti-HBc were further tested with four supplemental assays.

RESULTS

We detected 515 (10%) anti-HBc positive and 4612 (90%) anti-HBc negative cases in 5127 HBsAg negative serum samples. A total of 461 (89.5%) blood units were reactive for at least one additional serologic parameter and 54 were (10.5%) negative. Isolated anti-HBc positivity rate was 1.3% (69/5127). In the isolated anti-HBc positive samples, 54 were also anti-HBe and HBeAg negative. HBV DNA was not detected in any of the samples.

CONCLUSION

Applying the EDQM criteria would decrease our blood donor loss from 10% to 5.4%. As alternative re-entry mechanisms have already been presented in the literature, institution of a new policy is needed to enhance the limited blood donor pool in our system.

Characterization of overt and occult hepatitis B virus infection among HTLV-1 positive healthy carriers in the Northeast of Iran; AN HTLV-I endemic area

To date, no studies have provided data on hepatitis B virus (HBV) prevalence among asymptomatic, healthy human T-lymphotropic virus (HTLV-I) positive carriers. This sero- and molecular epidemiology study was performed on patients in the Northeast of Iran, which is an endemic area for HTLV-I infection. A total of 109 sera were collected from HTLV-I positive healthy carriers who were admitted to Ghaem Hospital, Mashhad City. All were tested for HBV serology and subsequently, real time PCR was carried out on the samples, regardless of the results of the serology. Standard PCR and direct sequencing were applied on positive samples. All cases were negative for HBsAg, Anti-HBc, and anti-HBs were positive in 34 (31.1%), and 35 (32%) individuals, respectively. There were 19 (17.4%) cases that were positive only for anti-HBs, and they had already received HBV vaccine. 16 (15%) were positive for both anti-HBs and anti-HBc, indicating a past-resolved HBV infection. 18 (16.5%) were isolated as anti-HBc, and 56 (51.3%) were negative for all HBV serological markers. Only one subject (0.9%) had detectable HBV DNA (2153 copy/ml), and assigned as being an occult HBV infection. The low prevalence of HBsAg, despite the high percentage of anti-HBc positive cases, might be related to the suppression effect of HTLV-I on surface protein expression. The low prevalence of HBV infection among HTLV-I positive healthy carriers from an endemic region, indicates that the epidemiology of HTLV-I and HBV coinfection is related to the endemicity of HBV in that region, rather than HTLV-I endemicity.

Hepatitis B virus surface protein mutations clustered mainly in CTL immune epitopes in chronic carriers: results of an Iranian nationwide study

Mutations within the coding region of hepatitis B surface antigen (HBsAg) have been found naturally in chronic carriers. To characterize the mutations of HBsAg from Iranian chronic carriers who were vaccine and/or medication naive. The surface genes from 360 patients were amplified and directly sequenced. The distribution of amino acid substitutions was classified according to different immune epitopes of the surface protein. All isolates belonged to genotype D. 222 (61.6%) of 360 patients contained at least one amino acid substitution. 404 (74.5%) of 542 amino acid changes occurred in different immune epitopes of HBsAg, of which 112 (27.7%) in 32 residues of B-cell epitopes (62 in the 'a' determinant); 111 (27.4%) in 32 residues of T helper; and 197 (48.7%) in 32 residues inside cytotoxic T lymphocyte (CTL) epitopes. One Th (186-197) and two CTL (28-51 and 206-215) epitopes were found to be hotspot motifs for the occurrence of 213 (52.7%) substitutions. 20 stop codons were identified in different epitopes. There was a significant association between amino acid substitutions and anti-HBe seropositivity; however, the correlation between such changes with viral load and ALT levels was not significant. In chronic hepatitis B virus(HBV) carriers, positive selection in particular outside the 'a' determinant appeared to exert influence on the surface proteins. These changes could be immune escape mutations naturally occurring due to the host immune surveillance especially at the T-cell level.