Mice chronically infected with
toxoplasma gondii were treated with cyclophosphamide, obiopeptide-1 (Obi-1) and/or anti-CD4 monoclonal antibody to determine the effect of these immunosuppressive agents on the cysts in the brain. In the brain of non-treated, and infected cyclophosphamide-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 microcysts. 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 significantly higher survival of 80% compared to 20% survival in mice treated with cyclophosphamide only. Percent neutrophilic leucocytes, monocytes and lymphocytes in mice treated with a combination of Obi-1 and anti-CD4, or Obi-1 and cyclophosphamide were higher compared to those groups treated with anti -CD4 antibody, or cyclophosphamide only. The increase in neutrophilic leucocyte and lymphocyte counts after a combined cyclophosphamide and Obi-1 treatment may, likewise, contribute to the induction of resistance in mice against
T. gondii. Furthermore, these results seem to suggest that the reactivation or rupture of tissue cysts in mice chronically infected with
T. gondii is not principally correlated with the death of cyclophosphamide treated mice.
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