Scientists from The University of Texas Medical Branch (UTMB) at Galveston have successfully tested a vaccine to address Chagas disease. This malignancy is widespread in Latin America and is now beginning to emerge among people in the United States – the Houston area included.
Researchers from the UTMB recently published a report in PLOS Pathogens on their vaccine against the parasite that causes Chagas disease, T. cruzi; evidence showed that in animal models this vaccine can provide long-lasting immunity.
Chagas disease is the third most preoccupying tropical disease in the world; it affects several countries in Latin American and is now being recognized as a growing disease within the United States. Between 11 to 18 million people in the world are currently infected and about 50,000 people die per year due to complications and consequences of the infection: intestinal and cardiac complications are the most common reasons.
In 2013, 19 cases of Chagas disease were registered in the Texas Health and Human Services Commission and 17 occurred within the Houston area. Currently, there are no treatments or vaccines to control such infection.
The parasite T. cruzi is spread by triatomine also known as “kissing bugs.” The bugs become infected if they bite an animal or a person infected with the parasite. The infection is then spread if one of these animals leaves feces on the victim’s skin which are rubbed into the bite wound or mucus membranes such as the eyes or mouth.
“Prior to this study, we systematically screened the T. cruzi genome database and identified three proteins with strong potential for vaccine development. The proteins become antigens once the body mounts an immune response that creates antibodies. We found that vaccinating mice with these antigens just prior to infecting them with T. cruzi kept the parasite levels down and staved off the signs of Chagas disease seen in the unvaccinated mice,” explained the UTMB researcher Shivali Gupta.
In this study, the capacity of the 2 strongest T. cruzi antigens against Chagas disease was assessed. Mice were injected with DNA codifying for two selected proteins and three weeks later they were injected with the proteins themselves. A group of mice received an extra injection of the proteins 3 months after treatment initiation. All animals were then exposed to T. cruzi for 4 or 6 months after the immunization series were completed.
The level of parasites was 2 to 3 times lower in immunized mice when compared to unvaccinated mice, even in those that did not received the boost. Those that had the boost evidenced parasite levels 5 times lower when compared to unimmunized animals.
“The vaccine-induced immunity waned slightly six months after the booster immunization, but still provided 2-fold control over the parasites. This should be sufficient to prevent spread of the infection and prevent chronic Chagas disease symptoms in the vaccinated host,” said Nisha Garg, professor at the UTMB.
Scientists concluded that the vaccine could provide long-term immunity against T. cruzi and that boosting immunization could be an effective protection strategy against Chagas disease.