Leishmania-sandfly interactions

There is a specific association between insect vector species and parasites [1]. The susceptibility or resistance of a species of sandfly to the development of a particular parasite depends on its ability to overcome certain barriers such as the proteolytic enzymes of the midgut, the peritrophic membrane surrounding the blood meal, and excretion of the midgut contents during digestion [2].As for digestive enzymes, proteophosphoglycans (PPGs) and acid phosphatases form a matrix that decreases the amount of digestive enzymes in the intestine and their negative charges protect the parasite from the hydrolysing effect of nearby proteolytic enzymes [2]. To survive, Leishmania must be able to escape quickly from the peritrophic membrane. This membrane is, among others, composed of chitin and it seems that the parasite could lyse it through the production of a chitinase [3]. Finally, the parasite must be able to attach to the epithelial cells of the intestine in order to escape its elimination during the excretion of the blood meal. This attachment is achieved through interaction between LPG (lipophosphoglycan) and intestinal epithelial cells [4].