Preliminary studies on parasitemia, antibody levels and gIFN production in mice infected with Trypanosoma cruzi Colombian strain

DAVIES CAROLINA; PARODI CECILIA MARIA; BASOMBRÍO MIGUEL ANGEL

Armação dos Búzios, Rio de Janeiro, Brasil

Congreso; XIII International Congress of Protistology, XXV Meeting of the Brazilian Society of Protozoology, XXVI Annual Meeting on Basic Research in Chagas Disease; 2009

Sociedade Brasileira de Protistologia

The treatment of Chagas disease is based on the administration of a single drug, either Benznidazol or Nifurtimox, but does not focus on the host’s immune response. Treatment failure has very seldom been connected with failure of immune response, and with the escape mechanisms of Trypanosoma cruzi. gIFN is a co-adjuvant molecule that modulates the host’s immune response, and its production is induced by associated cytokines such as IL2. Our hypothesis is that the strains of the parasite which are resistant to current treatment with Benznidazole (BZL), such as Colombiana strain, do not activate an immune response strong enough in the host that co-adjuvates the chemotherapy. In a first attempt to test this hypothesis, we intraperitoneally infected 20 mice with 250 trypomastigotes of Colombiana strain. Mice were killed at days 10, 25, 35, and 95 post-infection, and their circulating parasites were measured by optical microscopy twice a week. Serum was extracted to measure levels of gIFN and IgG in response to the infection. This inoculum with few parasites induced a low but continuous parasitemia that was still detectable after 3 months of infection, in contrast with other strains whose parasites are undetectable after a month. gIFN and IgG levels were negative at day 10 post-infection, but progressively increased during days 25 and 35, where gIFN reached its peak. In contrast, antibody levels continued increasing and at day 95 were at their highest point, whereas gIFN became negative. These results show that although a high antibody response was mounted it was not enough to control the infection. In future experiments we will explore the mice response to a higher inoculum, and we will also compare it to the one induced by the susceptible strain Tulahuén. Partially supported by Florencio Fiorini Foundation grant.