Development and diagnostic accuracy field testing in Sudan of a novel serodiagnostic POC for Visceral Veishmaniasis

Introduction

Visceral leishmaniasis (VL) is the most severe form of leishmaniasis leading to death if not properly diagnosed and treated. Reliable diagnosis of infected patients and reservoir animals (dogs) is vital for controlling the spread of leishmaniasis. East-African countries suffer from a very high incidence of VL and although several diagnostic tests are available, point of care diagnosis (POC) continues to be a big challenge in these countries due to low sensitivity and specificity in these countries.

Goal

The aim was to develop a reliable, stable and easy to handle POC test that significantly improves the VL-diagnostic efficiency in East-Africa and other VL-endemic countries in both, humans and dogs.

Material & Methods

Bioinformatic and biochemical analysis of B-cell epitopes of kinesins from different East African VL-strains lead to the identification of a new diagnostic kinesin antigen (rKLi8.3) with high B-cell affinity. A novel cloning and expression strategy was developed to express rKLi8.3 for the production of a new and improved lateral flow test (LFT) POC.

Results

Prospective comparative field-testing of the rKLi8.3 LFT with the standard rK39 LFT in Sudan (Gedaref) on 107 VL suspects revealed 98.7% sensitivity and 100% specificity. No cross-reactivity was observed in patients with malaria, typhoid, brucellosis and tuberculosis and trypanosomiasis. Retrospective and comparative testing of the rK39 and rKLi8.3 ELISAs on 300 sera from Sudanese patients and controls revealed a sensitivity of 93.2% to 97.2% and a specificity of 93.6% to 99.2%, respectively. Similar results were observed in VL-patients from Brazil. In contrast to rK39, the rKLi8.3 based ELlSA and LFT showed no cross-reactivity with African and American Trypanosomiasis. Similar results were also obtained in VL-infected dogs (CanL) in Brazil and Croatia.

Summary

rKLi8.3 based LFTs offer substantially improved diagnostic efficiency for VL in East Africa and other endemic areas, compared to currently available sero-diagnostic tests. Further, rKLi8.3 LFT are easy to handle and very heat stable, thus excellent for the use in tropical and remote endemic areas.