Identification of the critical regions in hepatitis B virus preS required for its stability

Maternal A90V mutation in the PreS1 gene of sub-genotype C2 hepatitis B virus is associated with intrauterine transmission

PreS/S gene mutations could impact virus secretion, infection and immune evasion. However, the relationship between PreS/S mutations and intrauterine transmission has not yet been clarified. Thus, we aimed to explore the associations between PreS/S gene mutations of HBV isolated from mothers and intrauterine transmission. We analyzed the mutations of PreS/S regions of the HBV genome in mothers with HBV DNA levels ≥ 106 IU/mL whose neonates experienced HBV intrauterine transmission (transmission group, GT) and those whose neonates did not experience intrauterine transmission (control group, GC) analyzed using clone-based sequencing. In total, 206 sequences were successfully amplified, including 98 sequences (from 21 mothers) from GT and 108 sequences (from 20 mothers) from GC of genotype C for mutational analysis. Among the 1203 nucleotides of PreS/S regions, there were 219 (18.20%) base substitutions, of which 103 (47.03%) base mutations caused amino acid changes. F80S, A90V and I68T were mutation hotspots. Mothers in GT had a higher mutation rate of A90V in the PreS1 gene than mothers in GC. The A90V mutation increased the risk of HBV intrauterine transmission after adjusting the maternal age and the mode of delivery (OR = 6.23, 95% CI: 1.18-32.97). Moreover, the area under the ROC curve (AUC) for intrauterine transmission due to A90V and a combination of A90V with the mode of delivery were 0.723 (95% CI: 0.575 to 0.891, P = 0.011) and 0.848 (95% CI: 0.723 to 0.972, P < 0.001), respectively. Mothers with the A90V mutation in the PreS1 gene may be a potential risk factor for HBV intrauterine transmission.

Pre-S Deletions are Predominant Quasispecies in HIV/HBV Infection: Quasispecies Perspective

Background

Combined HIV infection can accelerate HBV-induced liver disease. It is known that HBV Pre-S deletion is closely related to HBV-associated terminal liver disease in HBV mono-infection. Currently, data on HBV Pre-S quasispecies feature deletion in HIV/HBV co-infected patients are lacking.

Methods

The characteristics and blood samples of patients with chronic HBV infection were collected and classified into an HIV/HBV co-infection group and an HBV mono-infection group according to HIV antibody results before treatment. HBV DNA in serum was extracted. The HBV Pre-S region was amplified by nested-PCR and was further T-A cloned. Using the standard sequence of the matched genotype HBV as a reference, BioEdit 7.0 software was employed for sequence alignment.

Results

HBV Pre-S regions were successfully amplified from 147 patients, including 71 cases in the HIV/HBV co-infected group and 76 cases in the HBV mono-infected group. The proportion of the HIV/HBV co-infected group with Pre-S quasispecies deletion was lower than that of the HBV mono-infected group. By analyzing the frequency of Pre-S quasispecies in the two groups, the frequency of Pre-S quasispecies in HIV/HBV co-infected patients with Pre-S quasispecies was higher than HBV mono-infected patients. The frequency of Pre-S quasispecies deletion of the S protein promoter region in the HIV/HBV co-infected group was significantly higher than that in the HBV mono-infected group.

Conclusion

High-frequency Pre-S quasispecies deletions are predominant in HIV/HBV co-infected patients; however, low-frequency Pre-S deletions are predominant in HBV mono-infected patients, providing a reference for the pathogenesis of the accelerated progression of liver disease in HIV/HBV co-infection.

The Hepatitis B Surface Antigen Binding Protein: An Immunoglobulin G Constant Region-Like Protein That Interacts With HBV Envelop Proteins and Mediates HBV Entry

Hepatitis B virus (HBV) infection is a leading cause of liver cirrhosis, liver cancer, and liver failure, affecting 350 million people worldwide. Currently available anti-HBV drugs include (PEGylated-) interferon-α and nucleos(t)ide analogs, which can cause significant side effects and drug-resistance in many cases of long-term treatment. The lack of a reliable and robust in vitro infection system is a major barrier for understanding the HBV life cycle and discovering novel therapeutic targets. In the present study, we demonstrate that overexpression of the hepatitis B surface antigen binding protein (SBP) in HepG2 cells (HepG2-SBP) resulted in their susceptibility to HBV infection. HepG2-SBP cells supported the uptake of the viral surface protein (HBsAg-preS), HBV-pseudotyped virus, and live HBV in patient sera. Moreover, SBP-mediated HBsAg-preS uptake, and HBV pseudotyped virus infections were efficiently blocked by preS1- and SBP-specific antibodies. These observations suggest that SBP is involved in HBV entry and that HepG2-SBP cells can serve as a cellular model to study the post-binding steps of HBV infection.

Generation of hepatitis B virus PreS2-S antigen in Hansenula polymorpha

Despite the long availability of a traditional prophylactic vaccine containing the HBV surface antigen (HBsAg) and aluminum adjuvant, nearly 10% of the population remains unable to generate an effective immune response. Previous studies have indicated that hepatitis B virus (HBV) PreS2-S is abundant in T/B cell epitopes, which induces a stronger immune response than HBsAg, particularly in terms of cytotoxic T lymphocyte (CTL) reaction. In the current study, the HBV PreS2-S gene encoding an extra 26 amino acids (PreS2 C-terminus) located at the N-terminus of HBsAg was cloned into the pVCH1300 expression vector. PreS2-S expressed in the methylotrophic yeast, Hansenula polymorpha, was produced at a yield of up to 250 mg/L. Subsequent purification steps involved hydrophobic adsorption to colloidal silica, ion-exchange chromatography and density ultracentrifugation. The final product was obtained with a total yield of ∼ 15% and purity of ∼ 99%. In keeping with previous studies, ∼ 22 nm viruslike particles were detected using electron microscopy. The generated PreS2-S antigen will be further studied for efficacy and safty in animals.

Construction and expression of a recombinant eukaryotic expression plasmid containing the preS1-preS2-S genes of hepatitis B virus and the granulocyte-macrophage colony stimulating factor gene: A study of its immunomodulatory effects

A total of 10-20% of the population remains unresponsive or weakly responsive to hepatitis B vaccine, which is composed of hepatitis B surface antigen HBsAg (S protein). Therefore, it is necessary to develop a hepatitis B vaccine with a better penetrating and responsive rate. In the present study, a plasmid pVAX1-L-GM was constructed and its immunomodulatory effect of as hepatitis B virus (HBV) DNA vaccine was analyzed through the immunization of BALB/c mice. Immune responses were measured after immunization by anti-HBsAg, proliferation of splenocytes, the number of CD4⁺ and CD8⁺ molecules, CTL cytotoxicity, cytokines of IFN-γ and IL-2 secretion assays. Following the immunization, mice in the pVAX1-L-GM group produced antibody 2 weeks earlier compared to the control plasmid pVAX1 and pVAX1HBsAg groups and antibody levels showed significant differences. Enhanced HBsAg-specific splenocyte proliferation as well as specific cytotoxic activities of splenic CTLs were also detected. Furthermore, pVAX1-L-GM plasmid increased the number of CD4⁺ and CD8⁺ molecules on the surface of the spleen T cell and the level of IFN-γ, IL-2 secretion. pVAX1-L-GM induced a specific immune response in mice and enhanced the immune effect. Thus, a foundation was laid for developing immunogenicity of a better prevention and treatment of HBV via a hepatitis B vaccine.

Correlation between pretreatment viral sequences and the emergence of lamivudine resistance in hepatitis B virus infection

The emergence of amino acid or nucleotide substitutions leads to lamivudine resistance in hepatitis B virus (HBV) infected patients. The aim of this study was to investigate whether viral sequences help predict the emergence of lamivudine resistance. The study subjects comprised 59 consecutive patients infected with HBV treated with daily therapy of 100 mg lamivudine. Among those, 32 patients with adequate pretreatment serum preservation were investigated for the correlation between viral amino acid substitutions and the appearance of lamivudine resistance with consideration of clinical background by determining dominant HBV full open reading frames. Viral resistance to lamivudine emerged in 28 of 59 patients (47%) in a median period of 2.45 years. Sequence comparisons of HBV genomes between patients who later developed lamivudine resistance and patients who did not revealed the existence of significant differences between the two groups in the pre-S1 84 (P = 0.042), pre-S2 1 (P = 0.017) and 22 (P = 0.015), and polymerase tp 95 (P = 0.046), judged by a log-rank test. Viral sequence analyses revealed the presence of amino acid substitutions in HBV pre-S1 and pre-S2 that may be associated with the emergence of lamivudine resistance during chronic HBV infection.

Anti-preS responses influence the anti-HBs response in newborns after vaccination with the third generation Sci-B-Vac vaccine

We analysed the specificity and significance of the antibody response towards the linear preS1 sequence that has been shown to represent the "hepatocyte binding site" comprising amino acids preS1 (21-47) or the specific preS2 (131-140) antibody response to the "polymerised albumin receptor" in relation to the antibody response to hepatitis B surface antigen during immunisation of healthy children with the preS-containing Sci-B-Vac vaccine. Twenty-eight healthy newborns received three doses of the Sci-B-Vac vaccine according to a 0-, 1-, and 6-month scheme. Seventeen (61%) of the 28 newborns had detectable levels of anti-preS1 (21-47) antibodies and 14 (50%) were anti-preS2 (131-140) reactive at 6 and/or 9 months after initiation of the vaccination. The mean levels of anti-HBs were significantly higher in the anti-preS2 (131-140) non-reactive (24580+/-7815IU/l, mean+SEM) compared with the reactive sera (7287+/-2317IU/l, p<0.025). The highest anti-HBs levels were found in newborns who exhibited reactivity towards the aa 21-47 of the preS1 but lacked anti-preS2 (131-140) reactivity.

PreS1 epitope recognition in newborns after vaccination with the third-generation Sci-B-Vac vaccine and their relation to the antibody response to hepatitis B surface antigen

Background

Sci-B-Vac™ is a recombinant, hepatitis B vaccine derived from a mammalian cell line and containing hepatitis B surface antigen (HBsAg) as well as preS1 and preS2 antigens. Few studies have been performed on the antibody responses to preS1 in relation to the antibody to hepatitis B surface antigen (anti-HBs) response during immunisation of healthy children with preS-containing vaccines.

Results

In this study 28 healthy newborns were randomly selected to receive either 2.5 ug or 5.0 ug of the Sci-B-Vac vaccine. Children received three doses of vaccine according to a 0-, 1-, 6-month scheme. Antibodies against the S-protein and three synthetic peptides mimicking three B-cell preS1 epitopes, (21–32 amino acid epitope), (32–47 amino acid epitope) and the C-terminal (amino acid epitope 94–117) were determined at 6 and 9 months. Fourteen (50%) of the 28 newborns had detectable levels of anti-preS1 (21–32) antibodies; 15 (54%) were anti-preS1 (32–47) reactive and 12 (43%) were anti-preS1 (94–117) reactive at 6 or 9 months after initiation of the vaccination. Significantly higher levels of anti-HBs were observed in the sera of patients with detectable anti-preS1 (32–47) reactivity (24 550 ± 7375 IU/L, mean ± SEM) as compared with the non-reactive sera (5991 ± 1530 IU/L, p < 0.05). The anti-HBs levels were significantly lower if none (p < 0.05) or one (p < 0.025) of the preS1 (21–32, 32–47, 94–117) peptides were recognised compared with the anti-HBs levels if two or three peptides were recognised.

Conclusion

Recognition of several preS1 epitopes, and in particular, the epitope contained within the second half of the hepatocyte binding site localised in the hepatitis B surface protein of the third-generation hepatitis B vaccine is accompanied by a more pronounced antibody response to the S-gene-derived protein in healthy newborns.