Interferon-gamma expression in jejunal biopsies in experimental human cryptosporidiosis correlates with prior sensitization and control of oocyst excretion

To investigate the role of interferon (IFN)-gamma in human cryptosporidiosi s, jejunal biopsies from experimentally infected volunteers and chronically infected AIDS patients were examined for IFN-gamma expression by in situ h ybridization, IFN-gamma expression was compared with oocyst excretion, base line serum anti-Cryptosporidium antibody and symptoms. IFN-gamma mRNA was d etected in biopsies from 13 of 26 volunteers after experimental infection b ut not in biopsies taken before C. parvum exposure or in biopsies from pati ents with AIDS-associated cryptosporidiosis, After challenge, 9 of 10 volun teers with baseline C. parvum antibody produced IFN-gamma, compared with 4 of 16 volunteers without baseline antibody (P < .01), Furthermore, IFN-gamm a mRNA was detected in 9 of 13 volunteers who did not excrete oocysts, comp ared with 4 of 13 with organisms (P < .05), Thus, expression of IFN-gamma i n the jejunum was associated with prior sensitization and absence of oocyst shedding. IFN-gamma production may explain the resistance to infection not ed in sensitized persons but may not be involved in control of human primar y infection.