Genetic variation in the sand fly salivary protein, SP‐15, a potential vaccine candidate against Leishmania major

Abstract

SP-15 is a sandfly salivary protein that provides strong protection against cutaneous leishmaniasis, caused by Leishmania major , and has been proposed as a potential vaccine against this disease. To investigate possible antigenic variation in this protein, we examined genetic polymorphism of SP-15 in 100 Phlebotomus papatasi sandflies, from a natural population from Sudan and four laboratory colonies from Egypt, Jordan, Israel and Saudi Arabia. We found that although many variants of SP-15 may be found in nature, differences among them are minimal (mean ± ± ± ± SD pairwise differences = 1.69 ± ± ± ± 0.83% for forty nucleotide sequences and 3.06 ± ± ± ± 1.13% for thirty amino acid sequence variants). Analysis of proportions of synonymous and non-synonymous substitutions indicated that SP-15 is not under diver- sifying selection. Our results suggest that a vaccine based on SP-15 protein should result in a uniform immune response.