Resolution of cryptosporidial infection in mice correlates with parasite-specific lymphocyte proliferation associated with both Th1 and Th2 cytokine secretion.

This study was designed to investigate and characterize T-cell responses which lead to elimination of a primary infection of Cryptosporidium muris in BALB/c mice. The proliferative response of spleen cells to parasite antigen was measured by uptake of 3H-thymidine and, in parallel, supernatants were removed from cells to measure levels of IFN-gamma, TNF, IL-2 and IL-4 by ELISA. Oocyst excretion in faeces was first detected on day 10 post infection (p.i.); the level of shedding subsequently increased until day 14 and then declined until no oocysts were detected by day 25. The proliferative response of spleen cells from infected animals was similar to control levels up to day 14 p.i. but increased significantly on day 21 and was even greater on day 26. IFN-gamma and IL-2 were detected initially on day 14 p.i. and significantly higher concentrations were found on days 21 and 26. IL-4 secretion was also detected, but not until day 21 p.i., and production of TNF was not found at any time. Depletion of T-cells or CD4+ cells from spleen cells cultured with antigen resulted in a significant decrease in the levels of cytokine detected. These results indicated, therefore, that in BALB/c mice there was a correlation between the development of immunity to C. muris infection and both a parasite antigen-specific proliferative response and Th1 and Th2 cytokine production by spleen cells.