American trypanosomiasis, or
Chagas disease, is caused by Trypanosoma cruzi, and a
vaccine would greatly improve disease control. While some studies in mice suggest that a
vaccine is feasible, limited efficacy has been observed in dogs. We evaluated here the safety and efficacy of
a DNA vaccine encoding
TSA-1 and Tc24
antigens in a dog model of acute T. cruzi
infection. Mongrel dogs were immunized with two doses of 500 μg of
DNA vaccine, two weeks apart, and infected with T. cruzi (SylvioX10/4 strain) two weeks after the second
vaccine dose. Another group of dogs was infected first and treated with the
vaccine.
Disease progression was monitored for up to 70 days post-
infection. The
vaccine did not induce any critical change in blood parameters, nor exacerbation of disease in vaccinated animals. On the contrary, it prevented
anemia and a decrease in lymphocyte counts following T. cruzi
infection in vaccinated dogs. Both preventive and therapeutic vaccination significantly reduced
parasitemia, cardiac
inflammation and cardiac parasite burden, and tended to reduce the development of
cardiac arrhythmias. These results indicate that a preventive or therapeutic
DNA vaccine encoding
TSA-1 and Tc24
antigens is safe and may reduce both parasite transmission and the
clinical progression of
Chagas disease in vaccinated dogs. This
DNA vaccine may thus be an excellent veterinary
vaccine candidate. These data also further strengthen the feasibility of a
Chagas disease vaccine for humans.