The bug can't escape now

Vaccine against a disease that plagues the poor countries

Published: Sunday 15 August 2004

researchers from Spain and Peru have developed a vaccine against the Chagas disease, which infects about 12 million people in Latin America each year, and kills thousands of them. If the vaccine proves successful during clinical trials, the scientists will have overcome a major public health challenge -- to date no vaccine exists against protozoans (a group of microscopic parasites that includes Trypanosoma cruzi, the causative agent of the Chagas disease). T cruzi usually enters humans when they are bitten by the assassin bugs. It can also be transmitted through blood transfusions, and from mother to child during pregnancy.

The researchers used one of the parasite's genes as the basis for their 'dna vaccine'. Oflia Magdalena Crdoba of Peru's University of Trujillo identified the protein during her search for ways to block the parasite's normal metabolism.

When injected into mammals, the vaccine causes the recipients' cells to produce a protein that would ordinarily be produced only when exposed to the parasite. This in turn triggers an immune response, even though the parasite is not present. This means that if the individual is later infected by the parasite, the host's immune system will be able to recognise it and quickly act against it. "During laboratory tests, [the vaccine] provided animals with a high degree of protection -- around 90 per cent," says the lead researcher Antonio Osuna of Spain's University of Granada.

The researchers say their work may also help develop new drugs to treat the disease. Currently, drugs are only available for the acute phase but they can cause a number of side effects. The researchers next steps will include studies of 'adjuvants'-- substances that make vaccines more effective at producing an immune response, and therefore result in smaller quantities of vaccine being needed.

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