Expression of the eukaryotic Trypanosoma cruzi CRA gene in Yersinia enterocolitica and induction of an immune response against CRA in mice

The 70-kb plasmid pYV of Yersinia enterocolitica directs the secretion of a set of proteins, called Yops, that are produced during infection of humans and animals. Trypanosoma cruzi, the agent of American trypanosomiasis, synthesizes a cytoplasmic protein termed CRA that is considered to be T. cruzi specific. To produce CRA in Y. enterocolitica, we constructed a hybrid yopE-CRA gene that we integrated into plasmid pYV by homologous recombination. Recombinant Y. enterocolitica produced a chimeric Yop-CRA protein that was secreted in large amounts in the surrounding medium. This protein reacted with sera directed against either CRA or YopE. To test the ability of the recombinant strain to induce an immune response against CRA, we inoculated C57BL/6J mice by gastric intubation with live recombinant bacteria. A clear antibody response directed against CRA was detected in the mouse serum. The CRA-presenting Y. enterocolitica strain also carried a bioluminescence detection marker, which allowed us to monitor colonization of the intestinal lumen of infected mice. No significant differences were observed between the infectivity of the CRA antigen-producing and -nonproducing Y. enterocolitica strains, despite the fact that one of them no longer produced YopE.