Recombinant Anti-CD3 x Anti-CD4 Bispecific Antibody (Diabody) is designed to be expressed as two polypeptide chains respectively. The two chains are cross-over pairing to form a dimer. It contains a His-tag for affinity purification. This BsAb can retarget T cells to HIV-1 infected cells. It is designed for the research of HIV-1 infection, AIDS therapy.