Morphometrics and protein profiles of the salivary glands of Phlebotomus papatasi and Phlebotomus langeroni sand flies

Sand fly salivary fluid contains numerous proteins that modulate host immune responses to infection and facilitate blood-feeding and establishing Leishmania infection. Salivary proteins are differentially expressed in adaptation to the host, the meal type and ecological factors. We report on the morphometrics and protein composition of salivary glands of colonised Phlebotomus papatasi and P. langeroni sand flies from Egypt. Female glands were dissected at day 1 (D1, unfed), day 2 (D2, sugar-fed), day 3 (D3, blood-fed) and day 7 (D7, blood-digested). The salivary glands are composed of two lobes: heterogeneous in P. papatasi and homogeneous in P. langeroni. Lobe sizes varied considerably with fly age and feeding state; D3 flies had the largest lobe sizes and protein content. The P. papatasi flies had larger lobes and higher protein content than the P. langeroni flies. The P. papatasi D1 flies had 15 protein bands that decreased in the D2, D3 and D7 flies to 10 bands in the Sinai flies and 9 bands in the Alexandria flies. All P. langeroni flies had 12 protein bands but with different intensities. The results reveal inter-specific variation between P. papatasi and P. langeroni, while no intra-specific variation between P. papatasi strains. These results increase our understanding of salivary gland protein composition and blood-feeding behaviour in Old World sand flies with implications for leishmaniasis epidemiology and control.