Abstract: 　Objective To clone and sequence the gp23 gene encoding a surface antigen on the sporozoites of Cryptosporidium parvum . Methods Genomic DNA was isolated from oocysts of Cryptosporidium parvum . The gp23 gene was amplified by polymerase chain reaction (PCR) and cloned into pMD18 T vector and sequenced by the methods of dideoxy mediated chain termination. Results and Conclusion The gp23 gene was 345 bp in length and included an open reading frame encoding a protein of 114 amino acid residues. The homology of the nucleotide and amino acid sequences of the gp23 gene was 97.3% and 98.2% to that in the GenBank, respectively. The gp23 gene cloned contained 6 nucleotides more than that in the GenBank.

Key words: Cryptosporidium parvum, gp23 gene, gene cloning, sequence analysis