Potential Chagas Vaccine Candidate Shows Efficacy
- By BSTQ Staff
Researchers at the Sealy Center for Vaccine Development at the University of Texas Medical Branch (UTMB) at Galveston have developed a safe vaccine candidate for Chagas disease that is simple to produce and shows a greater than 90 percent protection rate against chronic infection in mice.
In the study, the researchers identified and tested potential Trypanosoma cruzi (also known as T. cruzi or Chagas disease) antigen candidates and delivery models to establish the safety and efficacy of a vaccine formulation known as TcVac3. Early experiments proved that delivery of the candidate antigens by a DNA-prime/protein boost approach, along with co-delivery of IL-12 and GM-CSF cytokine adjuvants meant to enhance the immune response, was effective in generating antibody and T cell responses. With two doses of the vaccine, the mice with TcVac3-induced antibodies exhibited 92 percent to 96 percent protection against chronic infection. The DNA/MVA approach increased the vaccine efficacy enough to omit one of the antigens and the adjuvants, making it a much simpler but still highly effective vaccine.
The study provides further evidence that a human Chagas vaccine is possible, a topic of debate among some who still believe that Chagas heart disease is the result of an autoimmune disorder. “This signals a scientific breakthrough — unprecedented vaccine efficacy for a common parasitic disease with no cure for chronic sufferers,” said lead author Nisha Garg, PhD, professor of microbiology, immunology and pathology at UTMB. “If this vaccine proves practical, it could be approved in as few as five years for use in canines, which are reservoir hosts of the disease. As many as 20 percent of dogs may be infected in Texas alone, developing the same heart conditions as humans but mistaken by vets for heartworm.”
The study was reported on in the March 26 edition of PLOS ONE. Future research will determine if the vaccine composition can be simplified even further. The researchers already are conducting related trials in canines, and are working on preclinical trials of human patient samples, testing for immune response in patients who are already infected but not showing signs of the chronic disease. Results of both studies are anticipated in late 2013.
