Direct ex vivo evaluation of long-lived protective antiviral memory B cell responses against hepatitis B virus

Background. The frequency of protective antiviral memory B cells after hepatitis B virus (HBV) vaccination is unknown. Methods. A novel 2-step immunomagnetic protocol to assess the ex vivo frequency of protective HBV surface antigen (HBsAg) -specific memory B cells was used. Results. HBsAg-specific memory B cells were detected in vaccinated individuals, although at very low frequency (median, 0.2% of CD19 (+) cells [range, 0% -4% of CD19 (+) cells]). No correlation existed between the frequency of HBsAg-specific memory B cells and the corresponding serum antibody titer or B cell enzyme-linked immunosorbent spot findings. Conclusion. Our results indicate sustained B cell -mediated protection against HBV despite waning antibody titers, which is consistent with clinical observations.