Expression of Phlebotomus papatasi Salivary Protein 15 (PpSP15) in COS-7 Cells

Background: Cutaneous leishmaniasis (CL) is a neglected tropical infection and the most prevalent vector-borne dis-ease in Iran. There is no approved human vaccine and current treatments are restricted; some drugs are expensive and have notable side effects. Therefore, the need for the development of a safe and effective vaccine that can be produced at a low cost remains urgent. It has been shown that vaccinating animals with salivary gland homogenate or saliva com¬ponents of sand flies protected against Leishmania infection. In this study, we aimed to prepare a mammalian expres¬sion vector encoding Phlebotomus papatasi salivary protein 15 (PpSP15) intended to be used as a DNA vaccine in our forthcoming studies. Methods: In this study, we designed and constructed pcDNA3. 1, a constitutive mammalian expression vector, to en-code the immunogenic protein PpSP15. The presence of the target gene was confirmed by enzymatic digestion and se-quencing. The mammalian COS-7 cells were transfected with the pcDNA3.1 vector and the expression of PpSP15 pro-tein was then examined in the cell line using Western Blotting analysis. Results: Restriction enzyme digestion and sequencing revealed the correctly constructed pcDNA3.1-PpSP15. After the transfection of the COS-7 cell line with pcDNA3.1-PpSP15 using Linear Polyethylenimine, the PpSP15 protein expres-sion was confirmed by western blot analysis using anti-His antibody. Conclusion: A high expression level of PpSP15 protein in COS-7 cells was achieved after the transfection of COS-7 cells, using cationic Linear Polyethylenimine. In subsequent research, this recombinant plasmid is supposed to be uti-lized as a candidate DNA vaccine to find its immunity induction in susceptible animal models.