A novel vaccine candidate for Chagas disease has been shown to be safe and effective in studies on mice. The research, carried out at the Sealy Center for Vaccine Development at the University of Texas Medical Branch and published in PLoS ONE, may pave the way for the development of a vaccine that protects humans against the potentially life-threatening disease.
Chagas disease, which is endemic in Latin America and is becoming more common in the U.S., is caused by the parasite Trypanosoma cruzi transmitted by triatomine bugs. The World Health Organization (WHO) estimates that about 7 to 8 million people worldwide are infected with T. cruzi, with, in 2008, approximately 11,000 deaths (see 10 most important infectious diseases with no licensed vaccine). The spread of distribution of the disease is thought to mainly be due to population mobility between Latin America and other countries around the world. Chronic infection with the T. cruzi parasite can lead to cardiac gastrointestinal, and neurological complications.
The researchers at UTMB identified and tested potential T. cruzi antigen candidates using computational/bioinformatics analysis and screening of the parasite's genome. The researchers found that a simplified vaccine consisting of two antigens, TcG2 and TcG4, delivered by a DNA-prime/Modified Vaccinia Ankara (MVA)-boost vaccine delivery method, was capable of inducing a 92-96% protection against chronic infection in mice.
“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, in a press release. “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 vaccine, TcVac3, was a simplified version of an earlier vaccine developed by the researchers that incorporated three antigens co-delivered by IL-12 and GM-CSF cytokine adjuvants. The researchers found that the DNA/MVA delivery method was effective enough to omit one antigen and both adjuvants. “Because Chagas is most prevalent in developing countries, it is essential that a potential vaccine be inexpensive to develop and easy to deliver,” said Garg, in a press release. “TcVac3 accomplishes this goal, making it not just an effective candidate, but an ideal one.”
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Article reference: Shivali Gupta, Nisha Jain Garg. TcVac3 Induced Control of Trypanosoma cruzi Infection and Chronic Myocarditis in Mice. PLoS ONE, 2013; 8 (3): e59434 DOI: 10.1371/journal.pone.0059434