Cryptosporidiosis has been also reported as a common serious primary cause of outbreaks of diarrhoea in newborn calves, goats and sheep. Presently, there is no effective therapeutic agent for the treatment of infection in immunodeficient individuals. Thus, there have been increasing efforts geared towards development of vaccines to control the disease. Cryptosporidium sp. infection is caused by ingestion of sporulated oocysts transmitted by the faecal-oral Ku-0059436 route. After being ingested, the oocysts excyst and release sporozoites that attach to and invade the microvilli of the epithelial cells
of the small intestine and cause pathology seen in the disease (2). In this process, the surface proteins of the sporozoites play an important role. Therefore, to develop the vaccine against the disease, many studies have focused on the analysis of the surface antigens of sporozoites. Among these antigens, the 15-kDa (Cp15) and 23-kDa (Cp23) are considered immunodominant and relevant to infection, and the most promising candidates for vaccine development (3,4). Cp23 is a glycoprotein, geographically conserved among C. parvum isolates and is present in both the sporozoite and merozoite stages. Cp23 was an immunogenic antigen in domestic isolates
of C. parvum (5). Colostrums from cattle hyperimmunized with recombinant (r) Cp23 provided protection against diarrhoea and significantly reduced oocyst shedding in calves. IgA-isotype Staurosporine supplier monoclonal antibodies to Cp23 orally administered to mice prior to inoculation with oocysts provide protection against C. parvum infection. Studies also have demonstrated cellular responses to Cp23 antigen by cells obtained from mice infected with C. parvum (6) and human peripheral blood mononuclear cells (PBMC)
(7). Wyatt et al. (8) demonstrated Cp23-specific T cell Adenosine triphosphate responses in calves after recovery from C. parvum infection. These observations suggest that the Cp23 antigen is involved in the generation of immune responses to C. parvum and may be a possible vaccine target antigen. The Cp15 protein is present on the surface of sporozoite of C. parvum (9). Studies have shown that Cp15 had strong immunogenicity to C. parvum. Tilley et al. found that this 15 kDa glycoprotein was among the most prominent antigen recognized by hyperimmune bovine colostrum (10). The oral administration of anti-Cp15 IgA monoclonal antibodies (McAbs) to suckling mice also provided protection against infection. Hill et al. noted that it was strongly recognized by both serum antibodies and faecal IgA in colostrum-deprived lambs (11). Spleen-derived McAbs against Cp15 have been shown to decrease infection levels in mouse models.