Physiological and proteomic profiles of Trypanosoma brucei rhodesiense parasite isolated from suramin responsive and non-responsive HAT patients in Busoga, Uganda

Abstract

Human African Trypanosomiasis (HAT) is a disease of major economic importance in Sub-Saharan Africa. The HAT is caused by Trypanosoma brucei rhodesiense (Tbr) parasite in eastern and southern Africa, with suramin as drug of choice for treatment of early stage of the disease. Suramin treatment failures has been observed among HAT patients in Tbr foci in Uganda. In this study, we assessed Tbr parasite strains isolated from HAT patients responsive (Tbr EATRO-232) and non-responsive (Tbr EATRO-734) to suramin treatment in Busoga, Uganda for 1) putative role of suramin resistance in the treatment failure 2) correlation of suramin resistance with Tbr pathogenicity and 3) proteomic pathways underpinning the potential suramin resistance phenotype in vivo. We first assessed suramin response in each isolate by infecting male Swiss white mice followed by treatment using a series of suramin doses. We then assessed relative pathogenicity of the two Tbr isolates by assessing changes pathogenicity indices (prepatent period, survival and mortality). We finally isolated proteins from mice infected by the isolates, and assessed their proteomic profiles using mass spectrometry. We established putative resistance to 2.5 mg/kg suramin in the parasite Tbr EATRO-734. We established that Tbr EATRO-734 proliferated slower and has significantly enriched pathways associated with detoxification and metabolism of energy and drugs relative to Tbr EATRO-232. The Tbr EATRO-734 also has more abundantly expressed mitochondrion proteins and enzymes than Tbr EATRO-232. The suramin treatment failure may be linked to the relatively higher resistance to suramin in Tbr EATRO-734 than Tbr EATRO-232, among other host and parasite specific factors. However, the Tbr EATRO-734 appears to be less pathogenic than Tbr EATRO-232, as evidenced by its lower rate of parasitaemia. The Tbr EATRO-734 putatively surmount suramin challenges through induction of energy metabolism pathways. These cellular and molecular processes may be involved in suramin resistance in Tbr.

Keywords: Drug resistance; Drug sensitive, Trypanosoma brucei rhodesience; Suramin.

Graphical abstract

Fig. 1a

Heatmap of differentially expressed proteins between T. brucei rhodesiense EATRO 734 and T. brucei rhodesiense EATRO 232 isolates. R1, R2, R3 and S1, S2, S3 are replicates for the suramin resistant (EATRO-734 and sensitive (EATRO-232) isolates respectively. Red – Highly expressed proteins and Blue – Lowly expressed proteins.

Fig. 1b

A Volcano plot showing differentially expressed proteins between T. brucei rhodesiense EATRO 734 and T. brucei rhodesiense EATRO 232 isolates. Red dots indicate differentially expressed proteins with an FC of ≥1.5 and false detection rate (FDR) corrected P-value of <0.05 between the isolates. The x-axis displays magnitude of fold-changes and y-axis the statistical significance (-log₁₀ of P-value). Points having FC of <1.5 on an FDR corrected P-value of <0.05 are shown in black, and indicate proteins with non-significance change between different developmental states.