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Project C4 - Development of an improved sero-diagnostic for visceral leishmaniasis

Project description

Background: Visceral leishmaniasis is a tropical infectious disease that occurs in humans and animals and is transmitted by sandflies. In humans, there are three clinical manifestations: cutaneous leishmaniasis (CL, oriental sore), mucocutaneous leishmaniasis (MCL), and visceral leishmaniasis (VL, Kala-Azar). The latter is the most dangerous form as it is 100% lethal if left untreated. Of particular concern is the spread of VL in East Africa, where 90% of all cases of the disease occur worldwide. The armed conflicts in Sudan and Somalia led to an almost complete destruction of the infrastructure and the health system, causing a massive exodus of people and, consequently, an increased spread of the vector (sandfly, phlebotomus). Since 2006, VL has again occurred in areas of Central Sudan that had been considered leishmaniasis-free for decades. A major problem of the control of infection or adequate treatment of VL is the lack of accurate, field-suitable diagnosis, since the clinical picture of VL can be very similar to other infections (see picture). The rapid tests (strip tests) used hitherto are based on the kinesin antigen rK39 from L. infantum (Brazil) or rKE16 from L. donovani (India); unfortunately, both test systems show only slight sensitivity in Africa. The poor diagnostic sensitivity of currently available test systems in Africa can be explained by the antigenic variation of different Leishmania isolates that elicit a different immune response. Therefore, we have cloned and sequenced the homologous kinesin antigen (rKLO8) from an East African L. donovaniisolate and could show that it differs from rK39. As part of the preliminary work, we have cloned, expressed, and purified rKLO8 as a His-tag fusion protein and developed a diagnostic ELISA. In a comparative study, we could demonstrate that the diagnostic potential of the newly developed rKLO8 test in Sudan and India is significantly better than that of the currently used test antigen, rK39.

Scientific goals: Our aim is to improve the diagnostic sensitivity of the rKLO8-based ELISA for VL in Africa and canine VL in Brazil (testing infected dogs) and to make it suitable for the field. We will combine rKLO8 with rK39 and KE16 and test the diagnostic performance of single and combined antigens in the ELISA. With the best antigen combination, a rapid test (strip test) should be developed. Finally, we will perform molecular analyses of L. donovani isolates from different areas of Sudan that show distinct infection behavior, i.e. exclusive infection of children or adults in White Nile State and Gadaref, respectively.

 

References C4: Reinhard K et al. (2011) Eur J Immunol, 41:133-38, Abass E et al. (2013) PloS Negl Trop Dis 18;7:e2322, Abass E et al. (2015) Plos One 3;10:e0116408, Martínez Abad LP et al. (2017) Acta Trop 166: 133-138.