In developing countries,
cryptosporidiosis causes moderate-to-severe
diarrhea and kills thousands of infants and toddlers annually. Drinking and recreational water contaminated with Cryptosporidium spp. oocysts has led to waterborne outbreaks in developed countries. A competent immune system is necessary to clear this
parasitic infection. A better understanding of the immune responses required to prevent or limit
infection by this protozoan parasite is the cornerstone of development of an effective
vaccine. In this light, lessons learned from previously developed
vaccines against Cryptosporidium spp. are at the foundation for development of better next-generation
vaccines. In this review, we summarize the immune responses elicited by naturally and experimentally-induced Cryptosporidium spp.
infection and by several experimental
vaccines in various animal models. Our aim is to increase awareness about the immune responses that underlie protection against
cryptosporidiosis and to encourage promotion of these immune responses as a key strategy for
vaccine development. Innate and mucosal immunity will be addressed as well as adaptive immunity, with an emphasis on the balance between TH1/TH2 immune responses. Development of more effective
vaccines against
cryptosporidiosis is needed to prevent Cryptosporidium spp.-related deaths in infants and toddlers in developing countries.