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-naive 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.

Automated summary

This study evaluated the changes in serum HBsAg levels in patients with chronic hepatitis B (CHB) treated with nucleos(t)ide analogs (NAs). The results showed that the serum levels of O-glycosylated HBsAg were correlated with viral load markers and changed after NA therapy. This suggests that an O-glycosylated HBsAg-based immunoassay may serve as a novel approach to monitor viral kinetics during treatment.