Ž . Parasitology International 48 2000 233242 Cloning and molecular characterization of calpain, a calcium-activated neutral proteinase, from different strains of Schistosoma japonicum  Renli Zhang a , Takashi Suzuki a , Satoru Takahashi b , Ayako Yoshida a , Hitoshi Kawaguchi a , Haruhiko Maruyama a , Yoshisada Yabu a , Jun Fu a,c , Tomoyuki Shirai b , Nobuo Ohta a,  a Department of Medical Zoology, Nagoya City Uni  ersity Medical School, 1 Azakawasumi, Mizuhocho, Mizuhoku, Nayoga 467-8601, Japan b First Department of Pathology, Nagoya City Uni  ersity Medical School, Nagoya, Japan c Department of Medical Zoology, Mie Uni  ersity School of Medicine, Tsu, Japan Received 1 March 1999; accepted 8 September 1999 Abstract cDNA coding for calpain of Schistosoma japonicum were cloned and sequenced, and serological basis of host responses to calpain were analyzed. cDNA of calpain from S. japonicum of two different isolates, Yamanashi strain Ž . Ž . Ž . Sj-J and Hunan strain Sj-C , were 2, 468 bp and 2, 465 bp in length, including the same number 2, 274 of open reading frame. Nucleotide sequence and amino acid sequence between the two calpains are 99.1% and 98.8% identity, respectively. Sj-J and Sj-C calpains were considered to be translated as a preproenzyme, and a 746-amino acid mature enzyme contains eight motifs without a signal peptide at the N-terminal based on the deduced amino acid sequences. mRNA for calpain were detectable in different developmental stages, however, sera obtained from mice immunized with recombinant calpain showed enhanced binding to cercarial antigen. Human sera from S. japonicum-infected individuals recognized the large subunit of schistosomal calpain, and light-infected sera showed stronger reactivities to the recombinant calpain than moderatehigh infection cases. When we tested synthetic Abbre  iations: APM, apical plasma membrane; CAP, cercarial antigen preparation; CTP, cytosine nucleotide triphosphate; ELISA, enzyme linked immunosorbent assay; EPG, eggs per gram stool; GSP, gene-specific primer; NTP, nucleotide triphosphate; PCR, polymerase chain reaction; RACE, rapid amplification cDNA ends; RT-PCR, reverse transcription PCR; SEA; soluble egg antigen; SSC, standard saline citrate; SWAP, schistosomal worm antigen preparation  The nucleotide sequence data reported in this paper will appear in the EMBL, GenBank and DDJB data bases under the accession numbers AB016725 and AB016726.  Corresponding author. Tel.: 81-52-853-8184; fax: 81-52-842-0149. Ž . E-mail address: nohta@med.nagoya-cu.ac.jp N. Ohta 1383-576900$ - see front matter  2000 Elsevier Science Ireland Ltd. All rights reserved. Ž . PII: S 1 3 8 3 - 5 7 6 9 99 00024-0