A bispecific antibody against two different epitopes on hepatitis B surface antigen has potent hepatitis B virus neutralizing activity

Treatment of chronic hepatitis B virus (HBV) infection with interferon and viral reverse transcriptase inhibitor regimens results in poor viral clearance, loss of response, and emergence of drug-resistant mutant virus strains. These problems continue to drive the development of new therapeutic approaches to combat HBV. Here, we engineered a bispecific antibody using two monoclonal antibodies cloned from hepatitis B surface antigen (HBsAg)-specific memory B cells from recombinant HBsAg-vaccinated healthy volunteers. Next, we evaluated its efficacy in neutralizing HBV in HepaRG cells. This bispecific antibody, denoted as C4D2-BsAb, had superior HBV-neutralizing activity compared with the combination of both parental monoclonal antibodies, possibly through steric hindrance or induction of HBsAg conformational changes. Moreover, C4D2-BsAb has superior endocytotic characteristics into hepatocytes, which inhibits the secretion of HBsAg. These results suggest that the anti-HBsAg bispecific antibody may be an effective treatment method against HBV infection.