Dietary nucleosides and nucleotides reduce Cryptosporidium parvum infection in dexamethasone immunosuppressed adult mice

Numerous studies have demonstrated that dietary sources of nucleosides and nucleotides are important for the maintenance of cellular and humoral immun e responses. To determine the immunological effects of feeding a nucleoside -nucleotide mixture to dexamethasone-immunosuppressed C57BL/6 adult mice in fected with Cryptosporidium parvum, we examined fecal oocyst shedding, lymp hoproliferative responses to concanavalin (Con) A, and C. parvum antigen, i nterleukin (IL-2), and gamma-interferon (IFN-gamma) production by cultured spleen cells. Mice were fed a nucleotide-free 20% casein diet (control grou p) or this diet supplemented with a 0.5% nucleoside-nucleotide mixture befo re and after inoculation with C. parvum. Spleens from mice receiving the su pplemented diet had higher (P < 0.05) Con A and antigen-specific induced ce ll proliferation than those from control mice. In addition to the increased cell proliferation, the spleen cells from the supplemented mice produced s ignificantly more IL-2 (P < 0.002) and significantly more IFN-gamma (P < 0. 004) than cells from the control mice. Mice fed the supplemented diet excre ted fewer (P < 0.05) C. parvum oocysts in the feces than control mice. The cumulative survival rate in the nucleoside-nucleotide mixture-fed group was higher compared with the control group (P < 0.05). We conclude that nucleo sides and nucleotides may partially counteract the immunosuppressive effect s of dexamethasone in C. parvum-challenged mice. (C) 1999 Academic Press.