EFFECT OF SURFACE ANTIGEN-1 (SA-1) IMMUNE LYMPHOCYTE SUBSETS AND NAIVE CELL SUBSETS IN PROTECTING SCID MICE FROM INITIAL AND PERSISTENT INFECTION WITH CRYPTOSPORIDIUM-PARVUM

We tested the hypothesis that adoptive transfer of immune spleen cell subsets from Cryptosporidium parvum antigen immunized, immunocompetent BALB/c mice would prevent initial infection or terminate persistent i nfection in severe combined immunodeficient (scid) mice. Cell donor mi ce were immunized with either solubilized C-parvum oocysts and sporozo ites (positive control) or a surface antigen-1 (SA-1) enriched C-parvu m antigen fraction. Both groups of BALB/c cell donor mice immunized wi th C-parvum antigens had increased antibody titers and lymphoprolifera tive responses when compared with negative control mice injected with phosphate buffered saline and adjuvant. Intravenous adoptive transfer of 5x10(6) cells of each cell subset (spleen cells, CD4 T and B lympho cytes, CD4 T lymphocytes or B lymphocytes) derived from immunized adul t BALB/c donor mice did not protect scid mice against initial infectio n of the gastrointestinal epithelium with C-parvum, despite flow cytom etric evidence of CD4 T lymphocyte engraftment in the spleen and detec table levels of C-parvum-specific serum antibody. In contrast, intrave nous injection of either naive or immune CD4 T and B lymphocytes combi ned, or CD4 T lymphocytes alone, terminated persistent C-parvum infect ion in scid mice. Intestinal infectivity scores were significantly red uced by 9 days post-engraftment in all groups and continued to decline throughout the remainder of the experiment. Flow cytometric analysis demonstrate significantly increased CD4 T lymphocytes in the spleens o f recipient scid mice when compared with infected scid mice receiving no cells. Cryptosporidium parvum-specific antibody was detected on day 12 post engraftment in mice receiving SA-1 immune CD4 T and B lymphoc ytes but was not detectable in mice receiving naive cell subsets.