Secretory IgA antibodies to Cryptosporidium parvum in AIDS patients with chronic cryptosporidiosis.

Immune mechanisms that may control Cryptosporidium parvum infection remain unknown. The role of T cell-mediated immunity is suggested by the chronic disease observed in AIDS patients and in athymic or CD4+ T cell-depleted mice. The role of specific antibodies is also unclear. This study sought to determine serum and secretory antibodies to C. parvum in patients infected with human immunodeficiency virus type 1 (HIV-1) with or without chronic cryptosporidiosis. C. parvum-specific antibodies and specific secretory antibodies were determined by ELISA in saliva and sera from 50 HIV-1-infected patients, 27 healthy adults, and 21 healthy children. Despite lower CD4+ lymphocyte counts, patients with chronic cryptosporidiosis had increased levels of C. parvum-specific antibodies in saliva and serum and higher specific secretory antibody levels in saliva than did controls. Persistence of protracted diarrhea despite high levels of both serum and secretory antibodies suggests that specific secretory antibodies are not sufficient to control this protozoan parasite infection of intestinal mucosa.