A time-course study of circulating antigen and parasite-specific antibody in cotton rats infected with Leishmania donovani.

Levels of circulating antigen in a group of cotton rats infected with Leishmania donovani were followed over a 28-week period, using a modified, polyethylene-glycol (PEG) ELISA. Circulating antigen could be detected from 1 week post-infection and gradually increased over time. In infected cotton rats treated with a curative dose of Pentostam at 12 weeks post-infection, antigen levels peaked and then declined. Antigen was still detected in some of the treated animals at 28 weeks post-infection. The antibodies used in the PEG-ELISA were also used in a capture ELISA to detect parasite antigens in urine. Urine samples which were positive by capture ELISA were also analysed by western blotting, in an attempt to identify the parasite antigens present. Three components, of 45, 47 and 58 kDa, were detected.