Sacks D L, Saraiva E M, Rowton E, Turco S J, Pimenta P F
Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892.
Parasitology. 1994;108 Suppl:S55-62. doi: 10.1017/s0031182000075727.
The surface lipophosphoglycans (LPG) of Leishmania promastigotes express stage- and species-specific polymorphisms that are defined by variations in the type and number of phosphorylated oligosaccharide repeats. We have studied how these polymorphic structures control the development of transmissible infections in the sandfly vector as well as the species-specificity of vectorial competence. Procyclic promastigotes displayed an inherent capacity to bind to midgut epithelial cells of a competent vector. This capacity was lost during their transformation of metacyclic promastigotes, permitting the selective release and anterior migration of infective-stage parasites for subsequent transmission by bite. Midgut attachment and release were found to be controlled by developmental modifications in terminally exposed saccharides on LPG, which, depending on the species of Leishmania, involved either substitution or capping of terminal side-chain sugars, loss of terminal side-chain sugars, substitution or loss of neutral capping sugars. The stage-specific terminal sugars involved in midgut adhesion are, in some cases, also species-specific, and the extent to which these differences affect midgut attachment, forcefully predicted vectorial competence.
利什曼原虫前鞭毛体的表面脂磷壁酸聚糖（LPG）表现出阶段和物种特异性多态性，这些多态性由磷酸化寡糖重复序列的类型和数量变化所定义。我们研究了这些多态性结构如何控制在白蛉媒介中可传播感染的发展以及媒介能力的物种特异性。前循环前鞭毛体表现出与易感媒介中肠上皮细胞结合的内在能力。在它们转变为后循环前鞭毛体的过程中，这种能力丧失，使得感染阶段的寄生虫能够选择性释放并向前迁移，以便随后通过叮咬进行传播。发现中肠附着和释放受LPG上末端暴露糖类的发育修饰控制，根据利什曼原虫的种类，这涉及末端侧链糖的取代或封端、末端侧链糖的丢失、中性封端糖的取代或丢失。在某些情况下，参与中肠黏附的阶段特异性末端糖也是物种特异性的，这些差异影响中肠附着的程度有力地预测了媒介能力。
