Oral immunization with Salmonella as Cruzipain-DNA delivery system generates a protective immune response against Trypanosoma cruzi infection.

CAZORLA SI,; BECKER PD; FRANK FM,; CORRAL RS; MALCHIODI EL,; GUZMAN CA

Rio do Janeiro, Brasil

Congreso; IMMUNO RIO 2007.; 2007

Our strategy in the design of a vaccine for Chagas’ disease focuses on the use of Salmonella enteric as DNA delivery system for cruzipain (SCz), the major cystein proteinase of T. cruzi.  To improve the performance of this DNA vaccine, we tested the co-administration of SCz and Salmonella carrying the gene encoding the granulocyte-macrophage colony–stimulating factor (SGM-CSF), as well as prime-boost protocols with recombinant cruzipain (rCz) plus different adjuvants. Mice were immunized with: GI- SCz, GII- SCz + SGM-CSF, GIII- SCz +[boost rCz+CpG-ODN], GIV- SCz +[boost  rCz+MALP], GV- PBS. Vaccinated mice displayed enhanced specific antibody titers, particularly GII (35201±10121) and GIII (1.8±0.5x106). Spleen cells of these mice strongly proliferated in vitro upon rCz stimulation. ELISPOT analysis of LTCD4+-depleted splenocytes showed a higher frequency of IFN-ã producing cells, with a GI: 33, GII: 53, GIII: 19 and GIV: 24-fold increase over the control. Trypomastigote challenge of vaccinated mice rendered a significant decrease in parasitemia levels compared with control. After the acute phase of infection, spleen cells were restimulated in vitro with soluble parasite antigens; an enhanced release of IFN-ã and IL-2 was observed in GI and GII.. The activity of CPK, LDH and ASAT (as enzyme markers of muscle injury) in these mice was significantly lower than that observed in the control at the chronic stage of Chagas’ disease.  These results were in agreement with histopathologic studies on skeletal muscle. We conclude that Salmonella as cruzipain-DNA delivery system raises a TH1 immune response able to protect against Chagas’ disease.