HBsAg sT123N mutation induces stronger antibody responses to HBsAg and HBcAg and accelerates in vivo HBsAg clearance

Host immunity and HBV S gene mutation in HBsAg-negative HBV-infected patients

Background

Clinically, some patients whose HBsAg becomes negative owing to antiviral therapy or spontaneously still show a low level of HBV DNA persistence in serum. T-lymphocyte subsets, cytokine levels and HBV S gene sequences were analyzed in this study.

Methods

A total of 52 HBsAg-negative and HBV DNA-positive patients(HBsAg-/HBV DNA+ patients), 52 persistently HBsAg-positive patients(HBsAg+/HBV DNA+ patients) and 16 healthy people were evaluated. T-lymphocyte subsets of these patients were detected by flow cytometry, serum cytokines and chemokines were detected by the Luminex technique, and the HBV S region was evaluated by Sanger sequencing. T%, T-lymphocyte, CD8+ and CD4+T lymphocyte were lower in the HBsAg-negative group than in the HC group. Compared with the HBsAg-positive group, the HBsAg-negative group had lower levels in T lymphocyte %, CD8+T lymphocyte %, CD8+T lymphocyte and CD4/CD8. These difference were statistically significant (P<0.05). Serum IFN-γ, IFN-α and FLT-3L levels were significantly higher in the HBsAg-negative group than in the HBsAg-positive group (P<0.05). However, levels of many cytokines related to inflammation (i.e., IL-6, IL-8, IL10, IL-12, IL-17A) were lower in the HBsAg-negative group. Fifty-two HBsAg-negative samples were sequenced, revealing high-frequency amino acid substitution sites in the HBV S protein, including immune escape mutations (i.e., Y100C, S114T, C124Y, P127L, G130R, T131N, M133T, C137S, G145A) and TMD region substitutions (i.e., E2K/R/D, G7D/R, G10D, A17R, F20L/S, L21V, L22V).

Conclusions

According to the results of T-lymphocyte subsets and serum cytokines, it can be deduced that the cellular immune function of HBsAg-negative patients is superior to that of HBsAg-positive patients, with attenuation of liver inflammation. HBsAg-negative patients may show a variety of mutations and amino acid replacement sites at high frequency in the HBV S region, and these mutations may lead to undetectable HBsAg, HBsAg antigenic changes or secretion inhibition.

Functional Cure of Hepatitis B Virus Infection in Individuals With HIV-Coinfection: A Literature Review

In individuals infected with hepatitis B virus (HBV), the loss of hepatitis B surface antigen (HBsAg) is the ultimate therapeutic goal, which defines "functional cure." For individuals living with human immunodeficiency virus (HIV), functional cure occurs roughly 2 per 100 person-years during potent anti-HBV containing antiretroviral therapy. Although this rate may be higher than expected in treated HBV mono-infected individuals, rates of functional cure widely vary between studies (0.6-10.5 per 100 person-years). Similar to HBV mono-infection, the phase of HBV infection, HBV (sub-)genotypes and hepatitis B "e" Ag-negative variants are associated with functional cure in treated HIV-HBV co-infection. In specifically HIV-HBV co-infected individuals, strong increases in CD4+ T cell counts after treatment initiation have also been linked to functional cure, yet this finding is inconsistent across studies. Several markers directly or indirectly reflecting HBV activity are being developed to predict functional cure, such as quantification of HBsAg, hepatitis B core-related antigen, HBsAg protein composition, anti-hepatitis B core antibodies and interferon-gamma-inducible protein 10. Few have been assessed during treatment in HIV-HBV co-infected individuals and none have been validated to predict functional cure. Novel therapeutics for HBV cure are essential for individuals with HIV-HBV co-infection and need to be separately evaluated in this population.

Plasma Fibronectin Levels Identified via Quantitative Proteomics Profiling Predicts Hepatitis B Surface Antigen Seroclearance in Chronic Hepatitis B

BACKGROUND

Seroclearance of hepatitis B surface antigen (HBsAg) is a potentially achievable target of chronic hepatitis B (CHB). Plasma proteins relevant to HBsAg seroclearance remain undetermined.

METHODS

We prospectively recruited treatment-naive CHB patients with spontaneous HBsAg seroclearance and matched HBsAg-positive controls. Plasma protein profiling was performed using isobaric tags for relative and absolute quantitation-based proteomics, with the expression of candidate proteins validated in a separate cohort. The predictive value of fibronectin was assessed at 3 years, 1 year (Year -1) before, and at the time (Year 0) of HBsAg seroclearance.

RESULTS

Four hundred eighty-seven plasma proteins were identified via proteomics, with 97 proteins showing altered expression. In the verification cohort (n = 90), median plasma fibronectin levels in patients with HBsAg seroclearance was higher than in controls (P = .009). In the longitudinal cohort (n = 164), patients with HBsAg seroclearance, compared with controls, had a higher median fibronectin levels at Year -1 (413.26 vs 227.95 µg/mL) and Year 0 (349.45 vs 208.72 µg/mL) (both P < .001). In patients with an annual HBsAg log reduction >0.5, Year -1 fibronectin level achieved an area under the receiving operator characteristic of 0.884 in predicting HBsAg seroclearance.

CONCLUSIONS

Using proteomics-based technology, plasma fibronectin may be associated with HBsAg seroclearance and a potential predictor of "functional cure".

Complementation of Wild-Type and Drug-Resistant Hepatitis B Virus Genomes to Maintain Viral Replication and Rescue Virion Production under Nucleos(t)ide Analogs

As the open reading frames of hepatitis B virus (HBV) genomes are overlapping, resistance mutations (MTs) in HBV polymerase may result in stop codon MTs in hepatitis B surface proteins, which are usually detected as a mixed population with wild-type (WT) HBV. The question was raised how the coexistence of nucleos(t)ide analogs (NAs) resistance MTs and WT sequences affects HBV replication. In the present study, HBV genomes with frequently detected reverse transcriptase (RT)/surface truncation MTs, rtA181T/sW172*, rtV191I/sW182* and rtM204I/sW196*, were phenotypically characterized alone or together with their WT counterparts in different ratios by transient transfection in the absence or presence of NAs. In the absence of NAs, RT/surface truncation MTs impaired the expression and secretion of HBV surface proteins, and had a dose-dependent negative effect on WT HBV virion secretion. However, in the presence of NAs, coexistence of MTs with WT maintained viral replication, and the presence of WT was able to rescue the production of MT HBV virions. Our findings reveal that complementation of WT and MT HBV genomes is highly effective under drug treatment.

Hepatitis B core antigen regulates dendritic cell proliferation and apoptosis through regulation of PKC/NF‑κB signaling pathway

Hepatitis B core antigen (HBcAg) possesses unusual immunologic features. However, the biological roles and mechanisms of HBcAg in dendritic cell proliferation and apoptosis remain to be elucidated. In the present study, DC2.4 cells were treated with different concentrations of HBcAg (10, 20 and 30 µg/ml). MTT assay and flow cytometry (Annexin V/propidium iodide analysis) were performed to investigate changes in cell proliferation and apoptosis. Western blot analysis was conducted to examine the changes in nuclear factor (NF)‑κB and protein kinase C (PKC) signaling pathways. NF‑κB inhibitor pyrrolidine dithiocarbamate (PDTC) and PKC inhibitor Chelerythrine were used to block these two signaling pathways. It was identified that HBcAg increased proliferation and decreased apoptosis in a dose‑dependent manner. Western blotting results demonstrated that HBcAg upregulated p‑PKC, p‑IκB, p‑P65, tumor necrosis factor‑α and B‑cell lymphoma 2 (Bcl‑2) levels, and downregulated cleaved caspase 3, demonstrating that HBcAg activated the PKC and NF‑κB signaling pathways. NF‑κB inhibitor PDTC reduced the effects of HBcAg on DC2.4 proliferation (0.6 fold vs. 0.25 fold) and apoptosis (0.43 fold vs. 0.17 fold), and on Bcl‑2 expression levels. PKC inhibitor Chelerythrine reduced the biological effects of HBcAg; it reduced proliferation (0.67 fold vs. 0.23 fold) and upregulated apoptosis (0.43 fold vs. 0.13 fold). Chelerythrine also blocked NF‑κB activity and the HBcAg‑induced Bcl‑2 increase, suggesting the effect on Bcl‑2 from HBcAg was dependent on the PKC/NF‑κB signaling pathway. In conclusion, HBcAg promoted proliferation and inhibited apoptosis through the PKC/NF‑κB/Bcl‑2 signaling pathway in DC2.4 cells.

Amino acid substitutions Q129N and T131N/M133T in hepatitis B surface antigen (HBsAg) interfere with the immunogenicity of the corresponding HBsAg or viral replication ability

Variants of hepatitis B surface antigen (HBsAg) influenced its antigenicity and immunogenicity. In our study, we aim to investigate biological significance of amino acid (aa) substitutions in HBsAg, Q129 N and T131 N/M133 T, for glycosylation, antigenicity and immunogenicity of variant HBsAg (vtHBsAg) and viral replication. Expression plasmids of vtHBsAg with aa substitutions Q129 L, T123 N, Q129 N and T131 N/M133 T were constructed. Immunofluorescence (IF) staining and Western blot were simultaneously utilized to examine expression of vtHBsAg proteins in Huh7 cells transfected with vtHBsAg constructs. vtHBsAg of Q129 N and T131 N/M133 T created new N-glycosylation and displayed perinuclear distribution by IF staining with the anti-HA. Antigenicity of vtHBsAg of Q129 N and T131 N/M133 T was reduced compared with wild type (wt) HBsAg. In addition, we discovered impaired ability to induce anti-HBs responses against wtHBsAg in mice immunized with plasmids pHBsAg- Q129 N and T131 N/M133 T. Even so, efficient protective response toward wild type HBV can be primed by the two vtHBsAgs in mice. Further, we discovered that vtHBsAg with Q129 N distinctly impaired HBV replication capacity, but vtHBsAg with T131 N/M133 T had no impact on viral replication. Thus, we conclude that vtHBsAg with Q129 N or T131 N/M133 T creates new N-glycosylation and interferes with both the antigenicity and immunogenicity of vtHBsAg. And vtHBsAg with Q129 N impaired HBV replication ability.

Hepatitis B virus infection: Defective surface antigen expression and pathogenesis

Hepatitis B virus (HBV) infection is a global public health concern. HBV causes chronic infection in patients and can lead to liver cirrhosis, hepatocellular carcinoma, and other severe liver diseases. Thus, understanding HBV-related pathogenesis is of particular importance for prevention and clinical intervention. HBV surface antigens are indispensable for HBV virion formation and are useful viral markers for diagnosis and clinical assessment. During chronic HBV infection, HBV genomes may acquire and accumulate mutations and deletions, leading to the expression of defective HBV surface antigens. These defective HBV surface antigens have been found to play important roles in the progression of HBV-associated liver diseases. In this review, we focus our discussion on the nature of defective HBV surface antigen mutations and their contribution to the pathogenesis of fulminant hepatitis B. The relationship between defective surface antigens and occult HBV infection are also discussed.

MITA/STING and Its Alternative Splicing Isoform MRP Restrict Hepatitis B Virus Replication

An efficient clearance of hepatitis B virus (HBV) requires the coordinated work of both the innate and adaptive immune responses. MITA/STING, an adapter protein of the innate immune signaling pathways, plays a key role in regulating innate and adaptive immune responses to DNA virus infection. Previously, we identified an alternatively spliced isoform of MITA/STING, called MITA-related protein (MRP), and found that MRP could specifically block MITA-mediated interferon (IFN) induction while retaining the ability to activate NF-κB. Here, we asked whether MITA/STING and MRP were able to control the HBV replication. Both MITA/STING and MRP significantly inhibited HBV replication in vitro. MITA overexpression stimulated IRF3-IFN pathway; while MRP overexpression activated NF-κB pathway, suggesting these two isoforms may inhibit HBV replication through different ways. Using a hydrodynamic injection (HI) mouse model, we found that HBV replication was reduced following MITA/STING and MRP expression vectors in mice and was enhanced by the knockout of MITA/STING (MITA/STING^-/-). The HBV specific humoral and CD8⁺ T cell responses were impaired in MITA/STING deficient mice, suggesting the participation of MITA/STING in the initiation of host adaptive immune responses. In summary, our data suggest that MITA/STING and MRP contribute to HBV control via modulation of the innate and adaptive responses.