Process Characterization and Biophysical Analysis for a Yeast-Expressed Phlebotomus papatasi Salivary Protein (PpSP15) as a Leishmania Vaccine Candidate

J Pharm Sci. 2020 May;109(5):1673-1680. doi: 10.1016/j.xphs.2020.02.004. Epub 2020 Feb 15.


Cutaneous leishmaniasis is a neglected tropical disease caused by the parasite Leishmania and transmitted by sandflies. It has become a major health problem in many tropical and subtropical countries, especially in regions of conflict and political instability. Currently, there are only limited drug treatments and no available licensed vaccine; thus, the need for more therapeutic interventions remains urgent. Previously, a DNA vaccine encoding a 15 kDa sandfly (Phlebotomus papatasi) salivary protein (PpSP15) and recombinant nonpathogenic Leishmania tarentolae secreting PpSP15 have been shown to induce protective immunity against Leishmania major in mice, demonstrating that PpSP15 is a promising vaccine candidate. In this study, we developed a fermentation process in yeast with a yield of ~1g PpSP15/L and a scalable purification process consisting of only 2 chromatographic purification steps with high binding capacity for PpSP15, suggesting that PpSP15 can be produced economically. The biophysical/biochemical analysis of the purified PpSP15 indicated that the protein was of high purity (>97%) and conformationally stable between pH 4.4 and 9.0. More importantly, the recombinant protein had a defined structure similar to that of the related PdSP15 from Phlebotomus duboscqi, implying the suitability of the yeast expression system for producing a correctly folded PpSP15.

Keywords: analytical biochemistry; biopharmaceutical characterization; biotechnology; chromatography; protein(s); vaccine(s).

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Insect Proteins
  • Leishmaniasis Vaccines*
  • Mice
  • Phlebotomus*
  • Saccharomyces cerevisiae / genetics
  • Salivary Proteins and Peptides / genetics


  • Insect Proteins
  • Leishmaniasis Vaccines
  • Salivary Proteins and Peptides