Midgut and stomodeal valve attachment of Leishmania in sand flies

Leishmania development in sand flies involves critical attachment steps to the midgut epithelium and the stomodeal valve, mediated by parasite- and vector-derived molecules. Initial midgut attachment prevents parasite loss during defecation and determines vector competence. In specific vectors like Phlebotomus papatasi, attachment involves galectins and Leishmania lipophosphoglycan, while in permissive species like Lutzomyia longipalpis, mucin adhesion dominates. Later, promastigotes adhere to the stomodeal valve, forming adhesion plaques, which in combination with the promastigote secretory gel (PSG) blocks the gut and promotes transmission. Recent studies identified three flagellar proteins (KIAP1-3) crucial for plaque formation. Knockouts of KIAPs prevented stomodeal valve colonization and PSG production, likely impacting parasite transmission. Thus, KIAPs are essential for late-stage Leishmania development in sand flies.