STUDIES RELATED TO IMMUNOSUPPRESSION IN MICE WITH CHRONIC TOXOPLASMOSIS

Mice chronically infected with Toxoplasma gondii were treated with cyc lophosphamide, obiopeptide-1 (Obi-1) and/or anti-CD4 monoclonal antibo dy to determine the effect of these immunosuppressive agents on the cy sts in the brain. In the brain of non-treated, and infected cyclophosp hamide-Obi-1 treated mice, with hematoxylin-eosin, and anti-Toxoplasma avidin-biotin-conjugate labelling techniques, large typically rounded tissue cysts were mostly detected, and sometimes with dividing microc ysts. In contrast, brain tissue from cyclophosphamide only or anti-CD4 treated infected mice had multiple degenerate cysts of varied size in some brain regions, as well as clusters of microcysts, however, such change was more striking in the anti-CD4 treated group. Infected mice treated with a combination of cyclophosphamide and Obi-1 showed a sign ificantly higher survival of 80% compared to 20% survival in mice trea ted with cyclophosphamide only. Percent neutrophilic leucocytes, monoc ytes and lymphocytes in mice treated with a combination of Obi-1 and a nti-CDL4, or Obi-1 and cyclophosphamide were higher compared to those groups treated with anti-CD4 antibody, or cyclophosphamide only. The i ncrease in neutrophilic leucocyte and lymphocyte counts after a combin ed cyclophosphamide and Obi-1 treatment may, likewise, contribute to t he induction of resistance in mice against T. gondii. Furthermore, the se results seem to suggest that the reactivation or rupture of tissue cysts in mice chronically infected with T. gondii is not principally c orrelated with the death of cyclophosphamide treated mice.