The contribution of epidermal apoptosis to the clinical outcome of Leishmania aethiopica induced cutaneous Leishmaniasis, and its laboratory diagnosis using low cost culture media

Abstract: Background: Cutaneous Leishmaniasis (CL) induced by Leishmania aethiopica has two clinical manifestations: ulcerating, self-healing CL and non-ulcerating, non-healing CL. The grossly disfiguring multiple nodules on the face and exterior surface of limbs during non-ulcerative CL are sometimes misdiagnosed as other skin infections. Thus the need for definitive and prompt laboratory diagnosis will be required. Identifying Leishmania parasite by culture method is considered as a definitive method for initiation of treatment and as an effective component of leishmaniasis control methods. Recently the involvement of Fas (CD95) and Tumor Necrosis Factor (TNF) Related Apoptosis Inducing Ligand (TRAIL) induced apoptotic pathways were proposed to be involved in tissue destruction and ulceration during L. major induced CL. Aims: 1) to develop an alternative culture media that could minimize the cost for culturing Leishmania from patient lesions. 2) to investigate if the expression of FasL and TRAIL differs in ulcerating and non- ulcerative CL. Methods: GALF-1 media was formulated in our lab and compared to RPMI 1640 medium and conventional Locke s semi solid media (LSSM) which is one of the modifications of Novy-MacNeal-Nicolle (NNN) culture media. Amastigotes transformation, cryopreservation, recovery of parasites, cost and mass cultivation were analysed. Expression of Fas ligand (FasL), TRAIL and apoptosis were assessed by immunohistology in human skin biopsies from L. aethiopica induced ulcerative or non-ulcerative CL. FasL and TRAIL blocking experiments were performed in a murine model of CL. Results and discussion: GALF-1 is cheap and its ingredients available in a low income country such as Ethiopia. GALF-1 was able to transform amastigotes from Ethiopian patients samples and could be used to cultivate promastigotes in large quantities. Cost analysis showed 80% to 95 % decreased costs as compared to conventional media. Promastigotes cultured with GALF-1 could be cryopreserved in liquid nitrogen with comparable re-culture potential to conventional media. Affordability of diagnostic assays is a key issue for resource poor countries and the possibility to cut the cost of the efficient culture method for diagnosis through the use of inexpensive local formulated reagents could improve the diagnosis of leishmaniasis in low income endemic countries. More FasL expressing cells were detected in dermis of ulcerative CL as compared to non-ulcerative CL and controls. TRAIL expression was higher in ulcerative CL as compared to non-ulcerative CL and controls in both epidermis and dermis. Increased dermal expression of FasL and TRAIL was associated with ulcer formation during CL. This correlated with an inhibition of the ulcerative process in a murine CL model during FasL and TRAIL neutralisation.The mechanisms of the involvement of FasL and TRAIL in ulceration was not elucidated and putative reason(s) for the difference in dysregulation of apoptosis are discussed.