Nasal immunization of mice with Cryptosporidium parvum DNA induces systemic and intestinal immune responses

DNA immunization offers a novel approach to inducing humoral and cellular i mmunity against infectious pathogens. We examined whether such an approach could be used against cryptosporidiosis, an intestinal disease caused by th e protozoan parasite Cryptosporidium parvum. This infection is a major prob lem for young ruminants and immuno-suppressed individuals in whom cryptospo ridiosis causes life-threatening symptoms. The life cycle of C. parvum take s place in the enterocytes of the intestinal epithelium. We therefore focus ed our attention on a route of immunization their might induce a mucosal im munoglobulin (Ig)A response. Eight-week-old BALB/c mice were immunized intr anasally with DNA encoding a 15-kDa C. parvum sporozoite antigen (CP15-DNA) cloned onto the plasmid pcDNA3. CP15-DNA-immunized mice developed specific and longlasting production of anti-CP15 Ig A in intestinal secretions and specific IgG in sera 3 months and 1 year after the first DNA inoculation CP 15-DNA-immunized,mice also developed an antigen-specific T lymphocyte proli ferative response in both spleen and mesenteric lymph nodes. Control mice t hat received the pcDNA3 plasmid alone did not develop specific humoral and cellular responses. These results indicate that plasmid DNA may provide a p owerful means of eliciting intestinal humoral and cellular responses to C. parvum infections in mammals.