Comparison of potential protection induced by three vaccination strategies (DNA/DNA, Protein/Protein and DNA/Protein) against Leishmania major infection using Signal Peptidase type I in BALB/c mice

Signal Peptidase (SPase) is an essential enzyme in both prokaryotes and eukaryotes; which removes signal sequence from secretary proteins. Previously, type I SPase from Leishmania major (Lmjsp) has been isolated and characterized. The sera from cutaneous and visceral forms of leishmaniasis are highly reactive to both the recombinant SPase (rSP) and synthetic SPase (Sy-Sp) antigens. Therefore, the Leishmania SPase, albeit localized intracellularly, is a significant target of the Leishmania specific immune response and highlights its use as a candidate vaccine against cutaneous leishmaniasis (CL).In this study as a first report, the potential protection of Lmjsp was evaluated in three different vaccination strategies (DNA/DNA, Protein/Protein and DNA/Protein), against L. major infection. We demonstrated that vaccination with SPase through all three mentioned strategies induced a parasite specific Th1 response and conferred partial protection against parasite challenge. However, our results indicated that DNA/DNA strategy developed more effective protective responses than the other two approaches and induced 81% reduction in L. major parasite load.