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 g 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.