Cryptosporidium parvum:: The contribution of Th1-inducing pathways to the resolution of infection in mice

The contribution of cytokines IL-12, IL-18, IL-23, and IFN-gamma, and Stat1 signaling molecules involved in Th1 responses associated with host resistance to Cryptosporidium parvum infection was investigated in adult IL-12p40(-/-) mice. Host resistance to C parvum infection was assessed in different mouse strains lacking IL-12, IL-18, and IL-23 genes. We found that as in IL-12p40(-/-) mice (which lack both IL12 and IL-23), IL-12p35(-/-) mice (which lack IL-12) and IL-18 deficient mice were also susceptible to infection with C parvum. Varied levels of resistance were observed when mice were treated with cytokines like IL-18, IL-23 and IFN-gamma. Mice treated with IL-12, as expected, were completely resistant to infection until day 5 post infection, and had significantly decreased (85%) parasite loads at peak infection (day 7), whereas rIL-23 had a lesser effect, decreasing parasite load by approximately 45%. Interestingly, IL-18 appears to play a significant role in initial immune response, even in the absence of IL-12, since treatment with IL-18 in IL-12p40(-/-) knockout mice decreased parasite load by approximately 70%. In addition, the establishment of C parvum infection in mice lacking the Stat1 gene demonstrated the involvement of this pathway in resolution of infection. These observations indicate a strong requirement for Th1 response in the development of immunity to C parvum in the adult IL-12p40(-/-) mice, information that will be essential to further investigate the immune responses during infections and in the development of potential vaccine candidates. (c) 2006 Elsevier Inc. All rights reserved.