Visceral Leishmaniasis (VL) is a fatal disease if it is not correctly diagnosed and treated The endemic areas for VL are mostly low- and middle- income countries. However, the existing diagnostic tests for VL are either not adapted for use in resource poor settings or their diagnostic performance in East Africa is variable.
This thesis aims to contribute to the development of an alternative diagnostic test for VL in East Africa based on antibody detection. The goal is to identify novel antigens, that can be incorporated into an immunochromatographic or rapid diagnostic test.
We started by an attempt to replace an existing antibody detection test for VL: the direct agglutination test (DAT). From an analysis of the existing literature we concluded that the DAT Ag is composed of a mixture of Leishmania specific antigens. We first aimed to select so-called mimotopes - peptides that mimic the epitopes of the DAT Ag using a phage display approach. We found peptides that have a diagnostic potential but their reactivity with VL positive compared to VL negative sera was not sufficient. We then analysed hypotheses found in the literature analysis experimentally. We reached the conclusion that lipophosphoglycan is part of the DAT Ag while carbohydrates alone are not.
In Part 3 of this thesis, we analysed the pipeline of serodiagnostic tests for VL. We performed a systematic literature review, which showed that most tests are not tested on sufficient specimens, especially from East Africa. Moreover, we did not find one non-native antigen (recombinant or synthetic) with a carbohydrate or lipid moiety. Based on this analysis we chose the most prominent glycoprotein of Leishmania – gp63 – and expressed it in a L. tarentolae expression system as a proof-of-concept for the use of glycoproteins in the serodiagnosis of VL.
To develop alternative diagnostic tests for VL in East Africa, we propose to focus on the evaluation of mixtures of existing antigens as well as LPG and gp63.