Development of Trypanosoma cruzi genetically attenuated knockout lines with potential use as transmission blocking vaccines

JUAN M. BUSTAMANTE; ASHLEY HARTLEY; CECILIA PÉREZ BRANDAN; ELLEN DOTSON; RICK L. TARLETON

Atlanta

Encuentro; ASTMH 61st Annual Meeting; 2012

ASTMH

Chagas disease, caused by the protozoan Trypanosoma cruzi, is the most important parasitic burden in Latin America. There are no effective vaccines to prevent this infection. In endemic areas, dogs are important sources of infection for the insect vector and therefore represent a critical control point for T. cruzi transmission. A transmission-blocking vaccine for dogs would greatly reduce the prevalence of T. cruzi infection in the canine and consequently, in the human population. Live attenuated parasites can be used as experimental vaccines. In this work we report on the generation of T. cruzi attenuated lines (KO5: Serine/threonine protein phosphatase like-protein; KO10: Hypothetical protein; KO121: Protein kinase and ECH: Enoyl-CoA hydratase/isomerase family protein) by disruption of genes, whose products are predicted to be critical for parasite replication in mammals. We evaluated whether C57BL/6 mice immunized with these attenuated parasites would develop protective immune responses that would prevent the establishment of vector transmittable infection upon rechallenge with T. cruzi. Mice immunized with any of the attenuated lines elicited strong T. cruzi-specific CD8+ T cells responses. However, the frequencies of T. cruzi-specific CD8+ T cells in mice immunized with the KO10 line decreased to undetectable levels in the blood after ~70 days post immunization (dpi). At 300 dpi, parasite-specific CD8+ T cells from mice immunized with KO5 and ECH showed relatively high expression of the central memory marker CD127 and low expression of recent activation marker KLRG1 compared with their wild type and KO121 counterparts. The magnitude and the phenotype of T. cruzi-specific CD8+ T cells suggest that these lines could be ideal for a transmission blocking vaccine for dogs. Current studies are focused on determining parasite persistence and on whether mice immunized with these attenuated lines and rechallenged with a virulent T. cruzi strain will not develop blood parasite levels sufficiently high to infect the insect vectors and therefore block the transmission of the infection.