Trypanosoma cruzi: Transfer of Protection by Lymph Node Cells Obtained from Mice Immunized with Exoantigens of PI 4.5

Exoantigens of pI 4.5 (Ea 4.5) of T. cruzi released to the circulation of infected mice are able to induce partial protective immune response in mice (F. Cerbán et al. 1991, International Archives of Allergy and Applied Immunology 96, 35-40). In order to analyze the participation of cellular immunity in the parasitemia control, we i.d. immunized mice with Ea 4.5 plus Bordetella pertussis as adjuvant. The role of immune cells in protective immunity was examined by adoptive transfer experiments. The immune lymph node cells (LNC) transferred the capacity to control the parasitemia, since it was observed that the normal recipients of immune LNC, which were afterward infected, presented a significant decrease in parasite levels with respect to the animals receiving LNC from control mice. This capacity was absent in the spleen cells. In addition, polystyrene nonadherent cells from immune LNC transferred the capacity to control T. cruzi infection. It was observed that Ig+ cells and enriched T cells from immunized mice are able to control the parasitemia. To define epitopes of Ea 4.5 able to stimulate protective immunity, the levels of parasitemia were examined in mice immunized with Ea 4.5 untreated or treated with sodium metaperiodate. These animals presented similar levels of parasitemia and in both cases they are significantly lower than the parasitemias of the control animals, suggesting that the most relevant epitopes for the protective immune response that control the beginning of the infection are not carbohydrates. Later, on Day 30 postinfection only the animals immunized with untreated Ea 4.5 maintained a significant decrease in parasite levels. The animals immunized with Ea 4.5 treated with sodium metaperiodate showed parasitemia levels similar to those from the controls despite that they survive longer. Consequently, it may be possible that the role of the anti-carbohydrate response is more relevant at an advanced stage of the infection.