Study 'proves' Chagas drug efficacy
Research shows that the main drug treatment for Chagas disease can completely rid chronically infected hosts of the disease-causing parasite.
The researchers say this provides the first evidence that the drug can be so effective. The study also suggests a new way of assessing the efficacy of drugs for the disease.
Current therapies are limited in their use due to potentially severe side effects and doubts surrounding their effectiveness. Some drug treatments are thought to be effective in less than 50 per cent of patients.
But the new study found that benznidazole — the principle drug used to treat Chagas disease — can completely clear Trypanosoma cruzi parasites in a mouse model.
"I would hope that the proof of efficacy reported in our study will prompt wider use of the available drugs to treat chronically infected individuals," says Rick Tarleton, lead author of the study from the US-based University of Georgia.
The study also measured the population of CD8 T cells — a type of immune cell — specific to the parasite in the blood. The researchers found that successful treatment of the parasite led to the emergence of a stable population of T. cruzi-specific T cells. These were able to mount an effective immune response against re-infection.
The researchers suggest that monitoring CD8 T cells could be a useful marker to evaluate the efficacy of new Chagas drugs in humans — a marker which they say is lacking in current Chagas drug development. If a treatment works, T cells specific to T. cruzi would be detected.
"Our work shows that we have an experimental model and a 'gold standard' treatment [beznidazole] against which to compare other new drugs. If they do not work as well as benznidazole, they probably should not be pursued in human trials," says Tarleton.
The research was published in the online edition of the journal Nature Medicine.
Chagas disease affects 16–18 million people throughout Latin America.
Nature Medicine doi 10.1038/nm1744 (2008)