Specific Cryptosporidium antigens associate with reinfection immunity and protection from cryptosporidiosis.

There is no vaccine to protect from cryptosporidiosis, a leading cause of diarrhea in infants in low and middle income countries. Here we comprehensively identified parasite antigens associated with protection from reinfection. A Cryptosporidium protein microarray was constructed by in vitro transcription and translation of 1761 C. parvum, C. hominis or C. meleagridis antigens, including proteins with a signal peptide and/or a transmembrane domain. Plasma IgG and/or IgA from Bangladeshi children longitudinally followed for cryptosporidiosis from birth to three years of age, identified 233 seroreactive proteins. Seven of these were associated with protection from reinfection. These included Cp23 and Cp17, Gp900 and four additional antigens (CpSMP1, CpMuc8, CpCorA and CpCCDC1). Infection in the first year of life however often resulted in no detectable antigen-specific antibody response, and antibody responses, when detected, were (i) specific to the infecting parasite genotype, and (ii) decayed in the months post-infection. In conclusion humoral immune responses against specific parasite antigens were associated with acquired immunity. While antibody decay over time and parasite genotype-specificity may limit natural immunity, this work serves as a foundation for antigen selection for vaccine design.