Development of new serodiagnostic tests for African trypanosomiasis due to Trypanosoma evansi and Trypanosoma brucei gambiense

Research output: ThesisDoctoral dissertation - Doctoral dissertation

Abstract

African trypanosomiases are neglected parasitic diseases that perpetuate poverty through their burden on public health and agriculture. Gambiense human African trypanosomiasis (HAT) is caused by Trypanosoma brucei (T.b.) gambiense in West and Central Africa. Surra is caused by Trypanosoma evansi, affects wild and domestic animals and leads to economic losses for the farmers.
Serodiagnosis of HAT and surra is performed with agglutination tests based on lyophilised trypanosomes propagated in rats. These parasites carry cell surface proteins, the variant surface glycoproteins (VSGs). VSGs LiTat 1.3 and RoTat 1.2 are used for diagnostic purposes. In this study we aimed to replace native antigens by recombinant ones in new diagnostic tests for African trypanosomiases. Use of recombinants enhances reproducibility, lowers the antigen production cost and precludes the use of laboratory animals and the infection risk for the laboratory staff.
We succeeded to express fragments of VSGs LiTat 1.3, LiTat 1.5 and RoTat 1.2 in Pichia pastoris. Yields up to 20 mg per litre cell culture were attained. The diagnostic capacity of the recombinants was demonstrated on a panel of patient and control sera.
Next, the recombinant RoTat 1.2 was incorporated in rapid diagnostic tests, respectively a rLATEX/T. evansi agglutination test and, in cooperation with Coris BioConcept, a immunochromatographic test, the Surra Sero K-SeT. The accuracy of both tests was evaluated on reference sera and proved comparable or even better than CATT/T. evansi. Hence, the recombinant VSGs constitute a human- and animal-friendly alternative to native antigens in diagnostic tests for African trypanosomiases.
Another highly sensitive and specific laboratory tests, such as immune trypanolysis (TL), exist as reference antibody detection test for African trypanosomiases. TL is used to fight HAT to eliminate the disease by 2030. TL relies on highly virulent parasites grown in rodents. To avoid the inherent infection risk, we modified a non-human infective T.b. brucei to express gambiense specific VSGs on their surface and that can be grown in vitro. However, further research is needed to transiently protect these genetically modified T.b. brucei strains against the trypanolytic factor, apoL1, before it can be used as an alternative human- and animal-friendly TL test.
Original languageEnglish
Place of PublicationAntwerpen
Publisher
Print ISBNs9781339550664
Publication statusPublished - 2015

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