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

Cutaneous leishmaniasis (CL) is a neglected tropical infection and the most prevalent vector-borne disease 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 components of sand flies protected against Leishmania infection. In this study, we aimed to prepare a mammalian expression vector encoding Phlebotomus papatasi salivary protein 15 (PpSP15) intended to be used as a DNA vaccine in our forthcoming studies.

In this study, we designed and constructed pcDNA3. 1, a constitutive mammalian expression vector, to encode the immunogenic protein PpSP15. The presence of the target gene was confirmed by enzymatic digestion and sequencing. The mammalian COS-7 cells were transfected with the pcDNA3.1 vector and the expression of PpSP15 protein was then examined in the cell line using Western Blotting analysis.

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 expression was confirmed by western blot analysis using anti-His antibody.

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 utilized as a candidate DNA vaccine to find its immunity induction in susceptible animal models.