Proteomic Identification of Immunodiagnostic Antigens for Trypanosoma vivax Infections in Cattle and Generation of a Proof-of-Concept Lateral Flow Test Diagnostic Device

Abstract

Trypanosoma vivax is one of the causative agents of Animal African Trypanosomosis in cattle, which is endemic in sub-Saharan Africa and transmitted primarily by the bite of the tsetse fly vector. The parasite can also be mechanically transmitted, and this has allowed its spread to South America. Diagnostics are limited for this parasite and in farm settings diagnosis is mainly symptom-based. We set out to identify, using a proteomic approach, candidate diagnostic antigens to develop into an easy to use pen-side lateral flow test device. Two related members the invariant surface glycoprotein family, TvY486_0045500 and TvY486_0019690, were selected. Segments of these antigens, lacking N-terminal signal peptides and C-terminal transmembrane domains, were expressed in E. coli. Both were developed into ELISA tests and one of them, TvY486_0045500, was developed into a lateral flow test prototype. The tests were all evaluated blind with 113 randomised serum samples, taken from 37 calves before and after infection with T. vivax or T. congolense. The TvY486_0045500 and TvY486_0019690 ELISA tests gave identical sensitivity and specificity values for T. vivax infection of 94.5% (95% CI, 86.5% to 98.5%) and 88.0% (95% CI, 75.7% to 95.5%), respectively, and the TvY486_0045500 lateral flow test prototype a sensitivity and specificity of 92.0% (95% CI, 83.4% to 97.0%) and 89.8% (95% CI, 77.8% to 96.6%), respectively. These data suggest that recombinant TvY486_0045500 shows promise for the development of a pen-side lateral flow test for the diagnosis of T. vivax animal African trypanosomosis.

Structural basis for the high specificity of a Trypanosoma congolense immunoassay targeting glycosomal aldolase

“…congolense and T . vivax infections (the two important causative agents of AAT in livestock) are under development [ 4 – 7 , 9 ]. Recently, we described the generation of a highly specific Nb-based homologous sandwich ELISA targeting Tco ALD to detect active T .…”

Product Development Partnerships: Delivering Innovation for the Elimination of African Trypanosomiasis?

“…Currently, the only way to confirm a diagnosis in infected animals is to demonstrate and identify the parasites in blood and other bodily fluids (which is in itself difficult as parasite numbers are generally low). Most treatment of AAT is therefore presumptive, which has costs for farmers and their perception of the efficacy of treatment [54,55]. The lack of a simple diagnostic test similarly makes it difficult to identity and deal with parasitic reservoirs within livestock populations.…”

“…This portfolio approach preserved the diversity of promising antigen candidates that were discovered and could then be tested. One of the partners included the University of Dundee where promising T. vivax proteins were identified and developed into prototype lateral flow and ELISA tests [54]. A further collaboration with BBI Solutions, who specialise in immunoassay development, led to the development of a simple lateral flow test that could be used in situ as the favoured approach (hence 'pen-side').…”

Trypanosoma vivax infection in sheep: Different patterns of virulence and pathogenicity associated with differentially expressed proteomes

“…A further challenge is that knowledge about trypanosome antigenic variation comes primarily from the T. brucei model where variant surface glycoprotein (VSG) is highly immunogenic. T. vivax expression of the VSG repertoire differs from that of T. brucei , and this protein family is not the most immunodominant antigen in this species ( Fleming et al, 2016 , Greif et al, 2013 , Jackson et al, 2012 , Ramirez-Barrios et al, 2015 ). The identification of invariant trypanosome components rather than variant surface proteins as potential targets for limiting infection or infection-mediated disease has been the focus of some previous studies ( Black and Mansfield, 2016 , Grébaut et al, 2009 ); thus, characterization of pathogenic or virulent biomarkers is highly relevant.…”