Inducible suicide vector systems for Trypanosoma cruzi.

Chagas disease caused by Trypanosoma cruzi is a major neglected tropical parasitic disease. The pathogenesis of this infection remains disputable. There is no suitable vaccine for the prevention. Attenuated live vaccines can provide strong protection against infection; however, there are the concerns about latent infection or reversion to virulence in such attenuated strains. A method to induce T. cruzi death would provide a critical tool for research into the pathophysiological mechanisms and provide a novel design of safe live attenuated vaccines. We established effective inducible systems for T. cruzi employing the degradation domain based on the Escherichia coli dihydrofolate reductase (ecDHFR). The DHFR degradation domain (DDD) can be stabilized by trimethoprim-lactate and can be used to express detrimental or toxic proteins. T. cruzi lines with Alpha-toxin, Cecropin A and GFP under the control of DDD with a hemagglutinin tag (HA) were developed. Interestingly, amastigotes bearing GFP-DDDHA, Alpha-toxin-DDDHA, Cecropin A-DDDHA and DDDHA all resulted in inducible cell death with these fusions, indicating that DDDHA protein is also detrimental to amastigotes. Furthermore, these strains were attenuated in mouse experiments producing no pathological changes and inoculation with these DDDHA strains in mice provided strong protection against lethal wild type infection.