A CLONED GENE OF CRYPTOSPORIDIUM-PARVUM ENCODES NEUTRALIZATION-SENSITIVE EPITOPES

Two mAb, C6B6 and 7D10, each significantly reduced infection of mice b y Cryptosporidium parvum and reacted with a 23-kDa glycoprotein (p23) of geographically disperse C. parvum isolates. The antibodies were use d to identify plaques in a cDNA library prepared from C. parvum sporoz oite mRNA. cDNA insert sequences from positive plaques were determined and used to isolate additional clones encoding p23 coding sequences. A consensus open reading frame of 333 base pairs, encoding 111 amino a cids, was identified in this collection of cDNAs. The predicted amino acid sequence contained one N-glycosylation site, but lacked hydrophob ic membrane spanning regions. Epitope mapping revealed that mAb 7D10 d efines the linear epitope QDKPAD which occurs twice in the C terminal region of the peptide encoded by the ORF. This same C terminal peptide region contains a non-linear epitope bound by mAb C6B6. Serum from mi ce immunized with synthetic C terminal peptide reacted with sporozoite p23. The occurrence of neutralization-sensitive epitopes encoded by d efined regions of the C. parvum genome suggests that recombinant prote ins or synthetic peptides containing these epitopes may prove useful f or inducing immune responses that diminish infection.