Molecular characterization and pathogenicity of melarsoprol resistant and sensitive Trypanosoma brucei rhodesiense isolates from Uganda

Abstract

Molecular characterization and pathogenicity of two isolates of Trypanosoma brucei rhodesiense, one resistant to melarsoprol and the other sensitive to melarsoprol were investigated in Swiss white mice. The two trypanosome populations had been isolated from sleeping sickness patients in Uganda. The study aimed at investigating whether there are any molecular and pathogenesis differences between the two isolates. Each form of parasite was inoculated into eighteen mice at 104 trypanosomes/ml and treated with melarsoprol at various dosages while six mice were used as un-infected controls. Parasitaemia progression was monitored every two days for sixty days to confirm the status of cure. Molecular characterization was undertaken by extracting and amplifying specific parasite DNA for the brucei subgroup first using TBR1 and TBR2 primers then for determining the presence of SRA gene in the strains. Pre-patent period, parasitaemia progression, packed cell volume, body weight and survival time were monitored for sixty days in infected Swiss white mice as markers of pathogenicity. The sensitivity test revealed that all mice infected with melarsoprol sensitive isolate and treated were cured. However, only one mouse infected with melarsoprol resistant isolate and treated was aparasitaemic for sixty days post infection. No molecular differences were observed since the fragment of DNA was amplified at the same size in both strains using all the primers. Mice infected with melarsoprol sensitive isolate had the shortest pre-patent period and survival time, the parasitaemia levels of this group of mice increased faster than in the group infected with resistant isolate. The rate of decline of packed cell volume and body weight was faster in the drug sensitive group than the drug resistant group of mice, however the differences were not significant (P>0.05). Results from this study demonstrated that the sensitive isolate appeared relatively more pathogenic than the resistant isolate. It is recommended that similar studies using a higher number of isolates from different regions and using also more advanced molecular techniques such as DNA sequencing, RFLP-PCR be carried out, this would shed some light on the genetic basis of pathogenesis.