Title : Improved Diagnosis and Treatment of visceral Leishmaniasis
Abstract:
Visceral Leishmaniasis (VL) is the second-largest parasitic killer in the world (after Malaria) caused by parasites of the Leishmania donovani complex, including L. donovani (East-Africa and India) and L. infantum (Europe, North Africa and India). VL, also known as kala-azar, is mostly fatal if left untreated and the disease is characterized by irregular fever, weight loss, enlargement of the spleen. Therefore, reliable diagnosis and subsequent treatment is vital for VL-patients. Kinesins are the dominant antigens in visceral leishmaniasis (VL), targeted by the patient´s immune response. However, their sequence and structure (number of repeats) vary between different Leishmania isolates. This explains why rapid diagnosis of VL is still unreliable as commercially available tests are mainly based on rK39 (L. infantum, Brazil) and rK16 (L. donovani, India). Our goal was to develop an improved, rapid diagnostic test-system suitable for all VL-endemic countries, including Africa, Brazil and India. Further, as VL infected dogs (CVL) are an important reservoir that enhance the spread of VL, we also tested our new candidate antigens for their potential to diagnose and differentiate between VL-infected and VL-vaccinated dogs. To select the kinesin antigen(s) for most specific and efficient VL diagnosis, we sequenced, cloned and expressed the kinesin of VL isolates from East-Africa, Brazil and India and determined the impact of isolate- and repeat-specific variations on their diagnostic capacity. Furthermore, we studied in-silico and in vitro the influence of the number of kinesin repeats on antigenicity and diagnostic performance and could show that the number of Kinesin-repeats has a bigger influence on diagnostic sensitivity and specificity than strain-specific sequence variations.The second part of our work is concerned with the treatment of VL-patients. Currently, VL treatment strategies differ in the endemic countries - but common to all therapeutic approaches are strong side effects and the occurrence of drug resistant Leishmania-species. Currently, it was shown that the group of Kinetoplastida parasites (Leishmania spp., Trypanosoma brucei and Trypanosoma cruzei) express proteasomes that differ from the host organisms with respect to the proteasomal beta 4 and 5 subunit. Accordingly, a new class of proteasome inhibitors (azabenzoxazole) was developed that selectively binds to the beta 4/5 subunit of Kinetoplastida, suggesting the proteasome as ideal drug target molecule for infections caused by the Kinetoplastida parasites. Currently we are testing the suitability of such an inhibitor in the various Leishmania parasites by analyzing the efficiency of proteasome inhibition -, the parasite viability and survival in host cells. Our current data show that this new class of inhibitors is a very promising drug candidate for the treatment of VL.
