Discovery and development of diagnostic biomarkers for human African trypanosomiasis

Abstract

Human African Trypanosomiasis (HAT) or African Sleeping Sickness is a disease prevalent in many parts of Sub-Saharan Africa. HAT is a parasitic infection caused by two species, Trypanosoma brucei gambiense and T. b. rhodesiense. Clinical diagnosis is not sufficient as symptoms from other endemic diseases, such as Malaria, are similar. Currently the diagnosis of T. b. gambiense infection mainly relies on the Card Agglutination Test for Trypanosomiasis (CATT), which has severe limitations. Other diagnostic tests for T. b. gambiense and T. b. rhodesiense infections require lab based equipment, trained personnel and have varying degrees of sensitivity and specificity. New approaches are needed, firstly to identify new diagnostic biomarkers, and secondly to find a more suitable platform for the test.

Our aim was to develop a lateral flow test based on trypanosome antigens. We used sera from T. b. gambiense infected and non-infected patients to identify infection specific diagnostic trypanosome proteins. The trypanosome proteins identified were then cloned into E. coli for recombinant expression and purification. The recombinant proteins were then screened by ELISA against 145 patients’ sera from the WHO HAT specimen bank. Invariant Surface Glycoprotein (ISG) 65 and a soluble Variant Surface Glycoprotein (VSG) were selected for development into a lateral flow format and 80 randomised patients’ sera were used to evaluate these prototypes. Here we describe the results showing that un-optimised proto-type lateral flow tests match the reported CATT sensitivity and specificity scores.