Recombinant Anti-pre S2 protein x Anti-S protein Bispecific Antibody (Tandem scFv-Fc) is designed to be expressed as a homodimer, which has 2+2 antigen-binding valency. This format consists of one Fc region and two tandem scFv fragments, in which the anti-pre S2 protein/S protein tandem scFv is fused to the Fc domain. The engineered fragment format is used to extend the half-life. This BsAb can bind two antigens simultaneously. It is designed for the research of HBV infection therapy.