Female BALB/c mice of 6-8 weeks old were immunized subcutaneously with various peptide-KLH conjugates mixed with Freund's Complete Adjuvant (Sigma) at 100 mg per injection. Boost injections were given at 2-week intervals with 50 mg antigen in Freund's Incomplete Adjuvant (Sigma) [49] . The antibodies were collected five days after the third boost. All the animal experiments were carried out in the facilities of the Institute of Laboratory Animal Sciences (ILAS), Chinese Academy of Medical Sciences (CAMS). All the experimental procedures were approved (permit number SLXKJ2009-0007) and supervised by the Animal Protection and Usage Committee of ILAS, CAMS.