Current dogma on chronic infections is that constant stimulation of the immune system eventually wears it out, which is one of the problems in treating such disorders as HIV/AIDS, said Tarleton. This study shows that one can have an infection for more than a year, but, when cured, the immune system develops a stable, protective memory.
This idea of memory is at the heart of the study, and it involves T-cells, specifically one kind called cytotoxic or killer T-cells, which are blood-borne white blood cells that destroy T. cruzi-infected cells in the case of Chagas disease and virally infected and tumor cells in other cases. Tarleton and his colleagues documented the development of stable killer T-cell memory following drug-induced cure of a chronic infection. In other words, when the body is cleared of parasites, the killer T-cells, which may have been exhausted by battling the persistent infection, bounce back and recall how to do their job.
The implications of the study could be considerable, Tarleton said. The T. cruzi parasite is passed to humans from the bite of blood-sucking assassin bugs, which go by many names, including kissing bugs. The infection can also be acquired through contaminated blood transfusions and by eating food contaminated with parasites.
In its first stages, the disease often causes no more than a local swelling at the point of the bite. This acute phase often passes, but the malady, if untreated, can then enter a chronic phase that can last for decades and cause heart disease and intestinal disorders. In many cases, Chagas, named for the Brazilian scientist who first described it nearly a century ago, is fatal.
While several hundred thousand people in the United States may have the disease, these are largely immigrants from Latin American countries. The disease, however, is a major public health issue in all of South America and kills as many as 50,000 people each year, a
|Contact: Kim Osborne|
University of Georgia