Brief Reports
Copyright ©2005 Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. May 21, 2005; 11(19): 2960-2966
Published online May 21, 2005. doi: 10.3748/wjg.v11.i19.2960
Phage displaying peptides mimic schistosoma antigenic epitopes selected by rat natural antibodies and protective immunity induced by their immunization in mice
Min Wang, Xin-Yuan Yi, Xian-Ping Li, Dong-Ming Zhou, McReynolds Larry, Xian-Fang Zeng
Min Wang, Xian-Ping Li, Department of Clinical Laboratory, The Second Xiangya Hospital of Central South University, Changsha 410011, Hunan Province, China
Xin-Yuan Yi, Xian-Fang Zeng, Dong-Ming Zhou, Department of Parasitology, Xiangya Medical College of Central South University, Changsha 410078, Hunan Province, China
McReynolds Larry, Molecular Parasitology Group, New England Biolabs, Inc., Beverly, MA 01915, USA
Author contributions: All authors contributed equally to the work.
Supported by the WHO/TDR, No. 980255 and the Science Commission of Hunan Province, No. 00jzy2115
Correspondence to: Min Wang, Department of Clinical Laboratory, The Second Xiangya Hospital of Central South University, Changsha 410011, Hunan Province, China. wangmin0000@yahoo.com.cn
Telephone: +86-731-5550258
Received: June 28, 2004
Revised: June 29, 2004
Accepted: July 22, 2004
Published online: May 21, 2005
Abstract

AIM: To obtain the short peptides mimic antigenic epitopes selected by rat natural antibodies to schistosomes, and to explore their immunoprotection against schistosomiasis in mice.

METHODS: Adults worm antigens (AWA) were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and enzyme-linked transferred immunoblotting methods with normal SD rat sera (NRS). The killing effects on schistosomula with fresh and heat-inactivated sera from SD rats were observed. Then the purified IgG from sera of SD rats was used to biopan a phage random peptide library and 20 randomly selected positive clones were detected by ELISA and 2 of them were sequenced. Sixty female mice were immunized thrice with positive phage clones (0, 2nd, 4th wk). Each mouse was challenged with 40 cercariae, and all mice were killed 42 d after challenge. The worms and the liver eggs were counted.

RESULTS: NRS could specifically react to the molecules of 75000, 47000, 34500 and 23000 of AWA. Sera from SD rats showed that the mortality rate of schistosomula was 76.2%, and when the sera were heat-inactivated in vitro, the mortality rate was decreased to 41.0% after being cultured for 48 h. The specific phages bound to IgG were enriched about 300-folds after three rounds of biopanning. Twenty clones were detected by ELISA, 19 of them bound to the specific IgG of rat sera. Immunization with these epitopes was carried out in mice. Compared with the control groups, the mixture of two mimic peptides could induce 34.9% (P = 0.000) worm reduction and 67.6% (P = 0.000) total liver egg reduction in mice. Two different mimic peptides could respectively induce 31.0% (P = 0.001), 14.5% (P = 0.074) worm reduction and 61.2% (P = 0.000), 35.7% (P = 0.000) total liver egg reduction. The specific antibody could be induced by immunization of the mimic peptides, and the antibody titer in immunized mice reached more than 1:6400 as detected by ELISA.

CONCLUSION: Specific peptides mimic antigenic molecules can be obtained by biopanning the phage random peptide library and a partially protective immunity against schistosome infection can be stimulated by these phage epitopes in mice.

Keywords: Schistosome, Phage peptide library, Epitope, Mimic peptide, Protective immunity, Vaccine