Antibody response of healthy adults to recombinant thrombospondin-related adhesive protein of cryptosporidium 1 after experimental exposure to cryptosporidium oocysts.

Thrombospondin-related adhesive protein of Cryptosporidium 1 (TRAP-C1) belongs to a group of proteins that are also found in Toxoplasma gondii, Eimeria tenella, and Plasmodium species. TRAP-related proteins are needed for gliding motility, host-cell attachment, and invasion. The objective of this study was to characterize the antibody response to recombinant TRAP-C1 (rTRAP-C1) in healthy volunteers exposed to C. parvum and their association with clinical illness. A total of 31 healthy adult volunteers participated. Seven volunteers received the C. parvum TAMU isolate (inocula, 10 to 300 oocysts), and 24 volunteers received the C. parvum UCP isolate (500 to 10(5) oocysts). The total antibody (immunoglobulin M [IgM], IgG, and IgA) response to rTRAP C-1 was measured by enzyme-linked immunosorbent assays prior to and after exposure to Cryptosporidium parvum (days 0 to 45). Results of this study showed that individuals who were uninfected demonstrated higher reactivity at baseline compared to those who became infected. After challenge, increases in antibody reactivity were seen on days 30 and 45 compared to the results seen on days 0 to 5. The increases in antibody reactivity were statistically significant in subjects with diarrhea and with or without detectable oocysts compared to the results seen with those who were uninfected and asymptomatic. These findings suggest that increases in antibody reactivity to rTRAP-C1 occur after recent exposure to C. parvum.