Trypanosoma cruzi Enoyl-CoA Hydratase Knockouts are non-persistent and Confer Protection Against Virulent Parasite Challenge

DAN XU, CECILIA PÉREZ BRANDÁN, RICK TARLETON

New Orleans, USA

Congreso; 57th American Society of Tropical Medicine and Hygiene Annual Meeting; 2008

Trypanosoma cruzi ech1 and ech2 genes encode putative enoyl-CoA hydratase/isomerase family proteins. Transcriptome analysis and quantitative RT-PCR data of T. cruzi revealed that whereas the transcript for ech2 was upregulated in amastigotes, ech1 transcripts were most abundant in the epimastigote stage. Using a Multisite Gateway-based approach, we generated parasites with 1 copy of ech1 gene and both copies of the ech2 gene deleted. These ech KO parasites grew slightly slower than WT parasites as epimastigotes and did not efficiently grow as amastigotes in Vero cells. The ech KO parasites also failed to establish persistent infections in mice, as evidenced by the inability of immunosuppression with cyclophosphamide to reveal parasites in C57Bl/6J mice exposed to up to 5 x 105 metacyclic trypomastigote form of the ech KO parasites.  However, exposure of C57 mice to ech KO parasites induced a substantial T. cruzi specific CD8+ T cell response.  Furthermore, mice vaccinated with the ech KO parasites were significantly  protected against  challenge infection with WT parasites. This study demonstrates that the selective KO of genes in T. cruzi can generate attenuated parasites useful as an effective vaccine for Chagas disease.