Identification and Mapping of HBsAg Loss-Related B-Cell Linear Epitopes in Chronic HBV Patients by Peptide Array

Abstract

Identification of immunogenic targets against hepatitis B virus (HBV)-encoded proteins will provide crucial advances in developing potential antibody therapies. In this study, 63 treatment-naïve patients with chronic HBV infection and 46 patients who achieved hepatitis B surface antigen loss (sAg loss) following antiviral treatment were recruited. Moreover, six patients who transitioned from the hepatitis B e antigen-positive chronic infection phase (eAg+CInf) to the hepatitis phase (eAg+CHep) were enrolled from real-life clinical practice. Additionally, telbivudine-treated eAg+CHep patients and relapsers or responders from an off-treatment cohort were longitudinally studied. The frequencies and function of B cells were assessed by flow cytometry. We devised a peptide array composed of 15-mer overlapping peptides of HBV-encoded surface (S), core (C), and polymerase (P) proteins and performed a screening on B-cell linear epitopes with sera. Naïve B cells and plasmablasts were increased, whereas total memory, activated memory (AM), and atypical memory (AtM) B cells were reduced in sAg- patients compared with sAg+ patients. Importantly, longitudinal observations found that AtM B cells were associated with successful treatment withdrawal. Interestingly, we identified six S-specific dominant epitopes (S33, S34, S45, S76, S78, and S89) and one C-specific dominant epitope (C37) that reacted with the majority of sera from sAg- patients. Of note, more B-cell linear epitopes were detected in CHep patients with alanine aminotransferase (ALT) flares than in nonflare CInf patients, and five B-cell linear epitopes (S4, S5, S10, S11, and S68) were overwhelmingly recognized by ALT flare patients. The recognition rates of epitopes on C and P proteins were significantly increased in CHep patients relative to CInf patients. Strikingly, a statistically significant elevation in the number of positive epitopes was observed when ALT nonflare patients shifted into the flare phase. Moreover, S76 identified at baseline was confirmed to be associated with a complete response after 48 weeks of telbivudine therapy. Taken together, we identified several functional cure-related B-cell linear epitopes of chronic HBV infection, and these epitopes may serve as vaccine candidates to elicit neutralizing antibodies to treat HBV infection.

Longitudinal mapping of hepatitis B vaccine‐induced B‐cell linear epitopes in healthy individuals

“…The increasing epitopes occupancy could forecast enhanced antibodies neutralization and functional cure in patients with chronic HBV infection after nucleos(t)ide analog treatment 29 . In addition, our previous study also identified several functional cure‐related B‐cell linear epitopes, which were different from the candidate epitope S29 in our study 30 . The seemingly paradox may result from discrepant immunological mechanism of vaccine and natural HBV infection.…”

“…29 In addition, our previous study also identified several functional cure-related B-cell linear epitopes, which were different from the candidate epitope S29 in our study. 30 The seemingly paradox may result from discrepant immunological mechanism of vaccine and natural HBV infection. On all accounts, both studies strengthened the necessity of "a determinant region" in inducing neutralizing antibodies.…”

An Ideal Hallmark Closest to Complete Cure of Chronic Hepatitis B Patients: High-sensitivity Quantitative HBsAg Loss

“…The dominant B cell epitopes (S76 and S78) in patients with negative HBsAg may be significant candidates for treatment to achieve a functional cure. 49 During PegIFNα treatment, the proportion of total B cells and plasma B cells in the HBsAg-negative group was higher than that in the HBsAgpositive group, when other factors including age, sex, and treatment duration were completely matched. 50…”

Role of CXCR5+CD8+ T cells in human hepatitis B virus infection

“…It is progressively recognized that B cells play an extremely important role in the continuous control of HBV, and the generation of HBsAb is not only a mark of acute infection resolution but also the ultimate goal of the functional cure of CHB 57 . HBsAg‐specific B cells persist in the blood and liver of many patients with CHB, however, these cells are substantially defective in antibody production, which was consistent with undetectable levels of anti‐HB antibodies in vivo 58 . The dysfunctional HBsAg‐specific and global B cells cluster CD21/CD27 atypical memory B cells (ATM‐Bs) with high expression of inhibitory receptors (including PD‐1); in turn, blocking PD‐1 could partially restore B‐cell function and increases antibody generation 59 .…”

“…57 HBsAg-specific B cells persist in the blood and liver of many patients with CHB, however, these cells are substantially defective in antibody production, which was consistent with undetectable levels of anti-HB antibodies in vivo. 58 The dysfunctional HBsAg-specific and global B cells cluster CD21/CD27 atypical memory B cells (ATM-Bs) with high expression of inhibitory receptors (including PD-1); in turn, blocking PD-1 could partially restore B-cell function and increases antibody generation. 59 Importantly, longitudinal observation showed that ATM-B cells were related to the successful treatment of CHB.…”