Molecular targets for detection and immunotherapy in Cryptosporidium parvum.

Cryptosporidium parvum is an obligate protozoan parasite responsible for the diarrheal illness cryptosporidiosis in humans and animals. Although C. parvum is particularly pathogenic in immunocompromised hosts, the molecular mechanisms by which C. parvum invades the host epithelial cells are not well understood. Characterization of molecular-based antigenic targets of C. parvum is required to improve the specificity of detection, viability assessments, and immunotherapy (treatment). A number of zoite surface (glyco)proteins are known to be expressed during, and believed to be involved in, invasion and infection of host epithelial cells. In the absence of protective treatments for this illness, antibodies targeted against these zoite surface (glyco)proteins offers a rational approach to therapy. Monoclonal, polyclonal and recombinant antibodies represent useful immunotherapeutic means of combating infection, especially when highly immunogenic C. parvum antigens are utilized as targets. Interruption of life cycle stages of this parasite via antibodies that target critical surface-exposed proteins can potentially decrease the severity of disease symptoms and subsequent re-infection of host tissues. In addition, development of vaccines to this parasite based on the same antigens may be a valuable means of preventing infection. This paper describes many of the zoite surface glycoproteins potentially involved in infection, as well as summarizes many of the immunotherapeutic studies completed to date. The identification and characterization of antibodies that bind to C. parvum-specific cell surface antigens of the oocyst and sporozoite will allow researchers to fully realize the potential of molecular-based immunotherapy to this parasite.