Recombinant Cryptosporidium parvum p23 as a target for the detection of Cryptosporidium-specific antibody in calf sera.

Cryptosporidium parvum is a widely distributed coccidian parasite and causes enteric disease in humans and animals. In addition to being a cause of life-threatening disease in immunodeficient people, mostly AIDS patients, C. parvum has been reported as a common serious primary cause of outbreaks of diarrhea in newborn calves, especially newborn ruminants (De Graaf et al. in Int J Parasitol 29:1269-1287, 1999). To obtain the recombinant P23 protein, we isolated the mRNA from oocyst of C. parvum and amplified the cDNA of P23 gene by reverse transcriptase PCR. Sequencing of cDNA showed 100% homology to the known P23 sequences. The double strand P23-cDNA was then cloned in pGEX-5X-2 expression vector. Western blot analysis of recombinant P23 showed that it could be recognized by the positive C. parvum serum. Since P23 is an immunodominant surface glycoprotein expressed in the early phase of infection (Jakobi and Petry in Microbes Infect 8:2186-2194, 2006) and the immunogenic epitopes are also found in the residual chain of amino acid sequence of this glycoprotein, the recombinant P23 was used for the screening of 437 serum samples collected from calves (#264) and cattle (#173). The dot blot analysis showed that from 264 calf and 173 cattle sera, 33% and 37% sera were positive, respectively. Due to the simple handling and equipment, dot blot analysis with P23 could be recommended for calves screening against cryptosporidiosis.