Recombinant Anti-CD3 x Anti-CD4 Bispecific Antibody (IgG(L)-scFv) is formed by an IgG and two scFv moieties. The scFv fragments from an anti-CD3 antibody are fused to the C terminus of an anti-CD4 IgG light (L) chains, or vice versa. It is a type of appended IgGs, which is bispecific and tetravalent (2+2 antigen-binding valency). This BsAb can retarget T cells to HIV-1 infected cells. It is designed for the research of HIV-1 infection, AIDS therapy.