The present invention provides can be in conjunction with the antibody or its antigen-binding fragment of the antigen binding pocket of AP33 antibody, wherein the antibody or its antigen-binding fragment include VL CDR1 (L1), VL CDR2 (L2) and the VL CDR3 (L3) being made of respectively the amino acid sequence of SEQ ID NO:1, SEQ ID NO:2 and SEQ ID NO:23, and include the VH CDR1 (H1), VH CDR2 (H2) and VH CDR3 (H3) being made of respectively the amino acid sequence of SEQ ID NO:24, SEQ ID NO:25 and SEQ ID NO:26. The present invention also provides composition, method, nucleic acid and purposes.
