473PROMASTIGOTES VIABILITY OF LEISHMANIA MAJOR W.T. AND L. MAJOR KNOCKOUT LMLCB2 AFTER MYRIOCIN TREATMENTSphingolipids (SLs) are major structural constituents of eukaryotes, including the kinetoplastid parasite Leishmania. SLs are important for cellular trafficking and signaling and participate in different cell functions, such as, differentiatio n and cell death (apoptosis). In this study we have investigated the viability of Leishmania major wild type (W.T) and L. major knockout LmLCB2, one of two subunits of serine palmitoyl transferase (SPT) after treatment with myriocin (potent inhibitor of SPT) in order to detect the survival and proliferation of the parasites in vitro. This is to focus on the de novo sphingolipids biosynthesis pathway in both Leishmania wild type which can synthesize SPT and knockout Leishmania which genetically ablated for SPT expression. Different concentrations of myriocin have been used starting from 100 µM to 3.125 µM. Results showed that there were no significance differences in proliferation and viability of both W.T and knockout L. major. These results indicate that Leishmania W.T and knockout promastigotes can survive after myriocin treatment and SLs may be nonessential for Leishmania major promastigotes proliferation in vitroh.z.ali@scbaghdad.edu.iqResearch562014Leishmania,SPT2,MyriocinHayder Zuhair AliAssistant lecturer, Department of Biology, College of Science, University of Baghdad, Baghdad