Cloning and expression of a DNA sequence encoding a 41-kilodalton Cryptosporidium parvum oocyst wall protein

This study was conducted to produce a recombinant species-specific oocyst w all protein of Cryptosporidium parvum. Antigens unique to C. parvum were id entified big gradient sodium dodecyl sulfate-polyacrylamide gel electrophor esis and immunoblotting of oocyst proteins from several different Cryptospo ridium species. Antiserum was then prepared against a 41-kDa antigen unique to C. parvum and used to identify a recombinant DNA clone, designated rCP4 1. Expression of CP41 mRNA in C. parvum oocysts was confirmed by reverse tr anscriptase PCR (RT-PCR). Although the CP41 sequence was shown by PCR to be present in the genome of C. baileyi, CP41 mRNA was not detected in this sp ecies by RT-PCR Immunofluorescence staining with antiserum against recombin ant CP41 detected native CP41 antigen on the surface of C. parvum oocysts b ut failed to detect CP41 on C. baileyi oocysts. Immunoelectron microscopy d emonstrated that native CP41 was distributed unevenly on the C. parvum oocy st surface and was associated with amorphous oocyst wall material. In an en zyme-linked immunosorbent assay, purified rCP41 performed as well as native C. parvum oocyst protein in measuring the serological responses of young c alves and adult cows to experimental and natural C. parvum infections. Thes e results indicate that recombinant CP41 antigen may have potential in the immunodiagnosis of cryptosporidiosis.