O-glycosylated HBsAg peptide can induce specific antibody neutralizing HBV infection

Impact of preS1 Evaluation in the Management of Chronic Hepatitis B Virus Infection

Background and Objectives: The measurement of hepatitis B surface antigen (HBsAg) is essential for managing chronic hepatitis B virus infection (CHB). HBsAg consists of three different surface envelope proteins: large, middle, and small HB surface proteins. However, in clinical practice, it is not common to evaluate each of these HB surface proteins separately. Materials and Methods: In this study, we investigated preS1 expression using seven monoclonal antibodies (mAbs) in 68 CHB patients, as well as examining their antigenicity. Results: Although the seven mAbs had been derived from genotype (Gt) C, they could recognize preS1 with Gts A to D. The epitopes were concentrated within the aa33-47 region of preS1, and their antigenicity was significantly reduced by an aa45F substitution. We found that preS1 expression remained consistent regardless of HBsAg levels and different Gts in CHB patients, in contrast to what was observed in SHBs. Conclusions: These results suggest that the antigenic epitope is preserved among different Gts and that the expression pattern of preS1 is altered during CHB, highlighting its vital role in the HBV infection cycle. Our present results suggest preS1 is a promising therapeutic target in CHB.

Hepatitis B surface antigen glycan isomer is a predictor of the development of hepatocellular carcinoma during nucleoside/nucleotide analog therapy

AIM

A recombinant monoclonal antibody against the hepatitis B surface antigen glycan isomer (HBsAgGi) was newly developed using the O-glycosylated PreS2 peptide in M-HBsAg of hepatitis B virus (HBV) genotype C. However, the association between HBsAgGi and the development of hepatocellular carcinoma (HCC) during nucleoside/nucleotide analog (NA) therapy remains unknown.

METHODS

A total of 112 HBV genotype C-infected patients who were treated with NA were included in this study. We assessed the association between HBV markers, including HBsAgGi and other conventional markers, and the development of HCC during NA therapy.

RESULTS

Ten patients developed HCC during the follow-up period. Of the HBV markers, HBsAg (≤3.53 log IU/mL; p = 0.047), HBsAgGi/HBsAg ratio (≥1.10; p = 0.035), and HBV DNA (≤6.3 log copies/mL; p = 0.012) at baseline and HBsAg (≤3.19 log IU/mL; p = 0.033) and HBsAgGi/HBsAg ratio (≥1.09; p = 0.003) at 48 weeks after NA therapy were significantly associated with the development of HCC according to the log rank test. In contrast, no significant association was observed between HBsAgGi and the development of HCC. Multivariate analysis revealed that a platelet count at baseline ≤88 × 103/mm3 (p = 0.026; hazard ratio [HR], 10.577) and an HBsAgGi/HBsAg ratio at 48 weeks after NA therapy ≥1.09 (p = 0.040; HR, 10.099) were independently and significantly associated with the development of HCC.

CONCLUSIONS

Our findings suggest that a combination of on-treatment HBsAgGi and HBsAg predicts the development of HCC during NA therapy.

Hepatitis B surface antigen (HBsAg) glycan isomer is predictive of HBsAg seroclearance in patients with chronic hepatitis B

AIM

Measurement of O-glycosylated middle hepatitis B surface antigen (HBsAg glycan isomer, HBsAgGi) has been developed to quantify hepatitis B virus (HBV) infectious virions and distinguish them from subviral particles. This study aimed to evaluate the association between serum HBsAg seroclearance and serum HBV virions measured by HBsAgGi in patients with chronic hepatitis B (CHB).

METHODS

Serum HBsAgGi levels were quantified in 232 treatment-naïve patients with CHB genotype C. Cox proportional hazards analysis was used to calculate hazard ratios (HRs) for factors associated with HBsAg seroclearance.

RESULTS

Baseline HBsAgGi levels showed significant differences among HBV phenotypes. During a median follow-up period of 7.4 years, 22 of the 232 patients achieved HBsAg seroclearance. Multivariate analysis demonstrated that quantitative HBsAg, nucleoside/nucleotide analog therapy during the follow-up period, and HBsAgGi levels were independent predictors of seroclearance. The adjusted HR indicated that the HBsAg seroclearance probability in patients with low HBsAgGi (≤3.5log ng/mL) was over five times higher than that in patients with high HBsAgGi. Kaplan-Meier analysis indicated that the 10-year probabilities of HBsAg seroclearance were 21.0% and 3.0% in patients with low and high HBsAgGi levels, respectively (p < 0.001), and that patients with high HBsAgGi levels showed low seroclearance probabilities irrespective of the other predictors.

CONCLUSION

Serum HBV infectious virion levels, measured using HBsAgGi, may be a novel predictor of HBsAg seroclearance.

O-glycosylation in viruses: A sweet tango

O-glycosylation is an ancient yet underappreciated protein posttranslational modification, on which many bacteria and viruses heavily rely to perform critical biological functions involved in numerous infectious diseases or even cancer. But due to the innate complexity of O-glycosylation, research techniques have been limited to study its exact role in viral attachment and entry, assembly and exit, spreading in the host cells, and the innate and adaptive immunity of the host. Recently, the advent of many newly developed methodologies (e.g., mass spectrometry, chemical biology tools, and molecular dynamics simulations) has renewed and rekindled the interest in viral-related O-glycosylation in both viral proteins and host cells, which is further fueled by the COVID-19 pandemic. In this review, we summarize recent advances in viral-related O-glycosylation, with a particular emphasis on the mucin-type O-linked α-N-acetylgalactosamine (O-GalNAc) on viral proteins and the intracellular O-linked β-N-acetylglucosamine (O-GlcNAc) modifications on host proteins. We hope to provide valuable insights into the development of antiviral reagents or vaccines for better prevention or treatment of infectious diseases.

Kinetics of serum O-glycosylated M-hepatitis B surface antigen with hepatocellular carcinoma history and nucleos(t)ide analogue therapy in hepatitis B patients

A newly developed O-glycosylated M-hepatitis B surface antigen (HBsAgGi) measurement system can detect hepatitis B surface antigen (HBsAg) associated with infectious particles. We investigated the association of HBsAgGi levels with clinical parameters and a history of hepatocellular carcinoma (HCC) development in a cross-sectional cohort analysis (Study 1) as well as the quantitative changes in HBsAgGi during nucleos(t)ide analogue (NA) therapy in a longitudinal cohort analysis (Study 2). A total of 124 patients with genotype C chronic HBV infection were analysed in Study 1 to evaluate correlations of HBsAgGi with conventional HBV markers and HCC history. Among those, 36 patients receiving NA therapy were enrolled in Study 2 for quantitative comparisons between pre-treatment baseline and 48 weeks of NA therapy. In Study 1, serum HBsAgGi was significantly associated with HBsAg (r = .5857, p < .00001) and weakly but significantly correlated with HBV DNA (r = .2936, p = .001). Although HBsAgGi (p = .111) was comparable between HCC history (+) group and HCC history (-) group, the HBsAgGi/HBsAg ratio (p = .011) was significantly higher in HCC history (+) patients. In Study 2, HBsAgGi was significantly decreased after 48 weeks of NA therapy (p < .001). HBsAg findings were similar (p = .005) along with an HBV DNA reduction (p < .001). In the baseline hepatitis B e antigen (HBeAg) (+) subgroup, HBsAgGi decreased significantly between baseline and 48 weeks of NA (p = .005), while HBsAg was comparable (p = .051). Low HBsAg and high HBsAgGi were associated with a history of HCC development. HBsAgGi decreased significantly by 48-week NA therapy.

Serum O-glycosylated hepatitis B surface antigen levels in patients with chronic hepatitis B during nucleos(t)ide analog therapy

Background

Serum hepatitis B surface antigen (HBsAg) is a component of both hepatitis B virus (HBV) virions and non-infectious subviral particles (SVPs). Recently, O-glycosylation of the PreS2 domain of middle HBsAg protein has been identified as a distinct characteristic of genotype C HBV virions versus SVPs. This study aimed to evaluate serum O-glycosylated HBsAg levels in patients with chronic hepatitis B (CHB) treated with nucleos(t)ide analogs (NAs).

Methods

Forty-seven treatment-naïve patients with genotype C CHB were retrospectively enrolled. Serum O-glycosylated HBsAg levels at baseline and after 48 weeks of NA therapy were quantified by immunoassay using a monoclonal antibody against the O-glycosylated PreS2 domain of middle HBsAg, and their correlations with conventional HBV marker levels were analyzed.

Results

At baseline, the serum O-glycosylated HBsAg levels were significantly correlated with the HBV DNA (P = 0.004), HBsAg (P = 0.005), and hepatitis B-core related antigen (HBcrAg, P = 0.001) levels. Both HBV DNA and O-glycosylated HBsAg levels were decreased after 48 weeks of NA therapy. The significant correlation of the O-glycosylated HBsAg level with the HBsAg or HBcrAg level was lost in patients who achieved undetectable HBV DNA (HBsAg, P = 0.429; HBcrAg, P = 0.065). Immunoprecipitation assays demonstrated that HBV DNA and RNA were detected in the O-glycosylated HBsAg-binding serum fraction, and the proportion of HBV RNA increased during NA therapy (P = 0.048).

Conclusion

Serum O-glycosylated HBsAg levels change during NA therapy and may reflect combined levels of serum HBV DNA and RNA virions. An O-glycosylated HBsAg-based immunoassay may provide a novel means to monitor viral kinetics during NA therapy.

Development and Evaluation of a Robust Sandwich Immunoassay System Detecting Serum WFA-Reactive IgA1 for Diagnosis of IgA Nephropathy

Aberrant glycosylation of IgA1 is involved in the development of IgA nephropathy (IgAN). There are many reports of IgAN markers focusing on the glycoform of IgA1. None have been clinically applied as a routine test. In this study, we established an automated sandwich immunoassay system for detecting aberrant glycosylated IgA1, using Wisteria floribunda agglutinin (WFA) and anti-IgA1 monoclonal antibody. The diagnostic performance as an IgAN marker was evaluated. The usefulness of WFA for immunoassays was investigated by lectin microarray. A reliable standard for quantitative immunoassay measurements was designed by modifying a purified IgA1 substrate. A validation study using multiple serum specimens was performed using the established WFA-antibody sandwich automated immunoassay. Lectin microarray results showed that WFA specifically recognized N-glycans of agglutinated IgA1 in IgAN patients. The constructed IgA1 standard exhibited a wide dynamic range and high reactivity. In the validation study, serum WFA-reactive IgA1 (WFA+-IgA1) differed significantly between healthy control subjects and IgAN patients. The findings indicate that WFA is a suitable lectin that specifically targets abnormal agglutinated IgA1 in serum. We also describe an automated immunoassay system for detecting WFA+-IgA1, focusing on N-glycans.