Abstract:

We have analysed the Trypanosoma brucei gene TbATl, which codes for the P2 adenosine transporter, to
investigate a possible link between the presence of mutations in this gene and trypanocidal drug resistence.
About 70% of T. b. gam bi ease isolates from a focus in North Western Uganda with high treatment failure
rates following mclarsoprol therapy had a mutations within TbATl. Unexpectedly, all individual isolates
contained the same set of nine mutations in their TbATl genes. Identical sets of mutations were also found
in a multi-drug resistant T.h.rhodesiense isolate from South Eastern Uganda and in a T.b.ganibiense isolate
from a relapsing patient from Northern Angola. Quantitative analysis of isolates from North western Uganda
revealed that mclarsoprol relapse patients have significantly more infections with mutant TbATl (c2 = 6.70;
d.f = 1; p = 0.0097, two tailed). Genetic knock out of TbATl of bloodstream trypanosomes did no affect in
vitro cell proliferation, as well as mouse infectivity. However, the cells were rendered up to four times less
susceptible to mclarsoprol, melarsene oxide, and diniinazene aceturatc. In vivo experiments revealed that
mouse infections of TbATl knock out clones could not be treated with four injections of2mg/kg melarsoprol,
while the same dose cured all the animals infected with the wild type clone. We conclude that loss of P2
transport activity significantly contributes to the increased drug resistence in African trypanosomes