Human sleeping sickness parasite sequenced

10 May 2010

Researchers from the Wellcome Trust Sanger Institute have unveiled a high quality draft genome sequence for the parasite strain responsible for almost all reported cases of sleeping sickness.

The chronic disease, also known as African trypanosomiasis, affects the human central nervous system and is caused by the Trypanosoma brucei gambiense strain (above) of T. brucei. Scientists had previously sequenced the T. brucei brucei strain, which infects cattle but is harmless to humans.

In the new study, researchers compared T. b. gambiense and T. b. brucei, looking for factors that might explain the former's ability to infect and thrive in human populations. The comparison revealed a remarkable level of similarity between the two strains: sequences of comparable genes were, on average, 98.2 per cent identical.

This suggests that T. b. gambiense's ability to infect humans cannot be easily explained by the addition or removal of a few genes. "Single-letter changes in the genome; differences in the number of copies of genes; changes in how the activity of genes is regulated - all of these genetic nuances could play that crucial role in determining why T. b. gambiense behaves so differently," said Dr Andrew Jackson, lead author on the study.

Reference

Jackson AP et al. The genome sequence of Trypanosoma brucei gambiense, causative agent of chronic human African trypanosomiasis. PLoS Negl Trop Dis 2010;4(4):e658.