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.