T-CELL BLASTOGENIC RESPONSES TO TOXOPLASMA-GONDII TROPHOZOITES AMONG HIV-INFECTED PATIENTS

Objective: To evaluate the cell-mediated immune response to Toxoplasma gondii (T. gondii) among HIV-infected patients. Methods: Forty HIV-in fected patients were studied, Of them, 35 had antibodies to T. gondii and 5 had not, Nine of 35 patients with detectable serum Toxoplasma an tibodies were classified as group A1 (CDC 1993), 10 as group B2, 6 as group B3, and 10 as group C3. Peripheral blood mononuclear cells (PBMC s) were obtained by Ficoll-Hypaque gradient centrifugation, Living Tox oplasma gondii trophozoites, herpes simplex virus (HSV), tetanus toroi d, and phytohemoagglutinin (PHA) were used in standard proliferation a ssays, Toxoplasma-responding blasts were expanded and assayed for anti gen specificity and HLA restriction by proliferation assays, T cell su bsets were analyzed using two-color flow cytometry.Results: Among pati ents with detectable Toxoplasma serum antibodies, significant PBMC pro liferation in response to T. gondii trophozoites was observed in those classified in group Al or B2 but not in those in groups B3 and C3. To xoplasma-induced blasts from five of six patients after 7 days of cult ure and from five patients after 15 days of culture proliferated in re sponse to T. gondii in the presence of either autologous or allogeneic PBMCs as antigen-presenting cells (APCs) and/or also proliferated in response to HSV, The surface markers of T. gondii-induced blasts showe d a variable percentage of CD4 and CD8 activated cells. Conclusions: T cell proliferative response to living trophozoites of T. gondii is lo st only in patients with severe depletion of CD4 cells, PBMC prolifera tion was observed only in patients with previous T. gondii infection, but the T cell blasts generated showed a strong alloreactivity (prolif erating in response to allogeneic irradiated PBMCs) and were apparentl y not antigen specific (proliferating also in response to HSV).