Molecular Cloning and Expression of a Gene EncodingCryptosporidium parvumGlycoproteins gp40 and gp15

Abstract

Cryptosporidium parvumis a significant cause of diarrheal disease worldwide. The specific molecules that mediateC. parvum-host cell interactions and the molecular mechanisms involved in the pathogenesis of cryptosporidiosis are unknown. In this study we have shown that gp40, a mucin-like glycoprotein, is localized to the surface and apical region of invasive stages of the parasite and is shed from its surface. gp40-specific antibodies neutralize infection in vitro, and native gp40 binds specifically to host cells, implicating this glycoprotein inC. parvumattachment to and invasion of host cells. We have cloned and sequenced a gene designatedCpgp40/15that encodes gp40 as well as gp15, an antigenically distinct, surface glycoprotein also implicated inC. parvum-host cell interactions. Analysis of the deduced amino acid sequence of the 981-bpCpgp40/15revealed the presence of an N-terminal signal peptide, a polyserine domain, multiple predictedO-glycosylation sites, a single potentialN-glycosylation site, and a hydrophobic region at the C terminus, a finding consistent with what is required for the addition of a GPI anchor. There is a single copy ofCpgp40/15in theC. parvumgenome, and this gene does not contain introns. Our data indicate that the twoCpgp40/15-encoded proteins, gp40 and gp15, are products of proteolytic cleavage of a 49-kDa precursor protein which is expressed in intracellular stages of the parasite. The surface localization of gp40 and gp15 and their involvement in the host-parasite interaction suggest that either or both of these glycoproteins may serve as effective targets for specific preventive or therapeutic measures for cryptosporidiosis.