PGRP-LD参与按蚊传播疟原虫机制的研究

Mosquito control has been considered as the key Malaria prevention strategy due to lack of vaccine and increasing drug resistance in Plasmodium. Tsetse Peptidoglycan recognition protein PGRP-LB has been shown to play important roles in denfending trypanosome infection and protecting beneficial symbionts which increase tsetse vector compentence. The function of Anopheles PGRP-LD, an important receptor of insect immune system is unknown. Our data showed that PGRP-LD was significantly induced in mosquitoes infected with Plasmodium berghei, indicating its role in regulating host immune defense against parasites. We also found that total amount of culturable microbiota in PGRP-LD knocked down Anopheles (dsLD) was dramatically increased, suggesting that PGRP-LD may also function in microbiota regulation. Based on experience from Tsetse-symbionts-trypansome system and data accumulated from Anopheles, we plan to 1) investigate the function of PGRP-LD in regulating Plasmodium berghei infection in Anopheles sinensis; 2) study its role in regulating microbiota and characterize culturable bacteria that are controlled by PGRP-LD; 3) Determine the influence of culturable microbiota on mosquito vector competence. By understanding the function of PGRP-LD, we aim to understand mosquito-microbiota-parasites tripartite interaction, which could help to strengthen current mosquito control strategy and develop novel control methods.

按蚊是疟疾传播的媒介,研究表明免疫系统和体内共生菌是影响其传播疟原虫能力的两大因素。申请人前期在采采蝇-锥虫模式系统中发现肽聚糖识别蛋白PGRP-LB具有抑制锥虫生长和通过保护有益共生菌增强宿主抗性的双重功能（PNAS，2009,2012）。申请人近期的探索性研究显示按蚊PGRP-LD在感染疟原虫后表达水平显著增高；PGRP-LD敲低（dsLD）后共生菌数量显著增加，说明其同时参与对疟原虫和共生菌的调控（未发表）。本申请拟1）通过检测dsLD中免疫抗疟分子表达水平的变化，研究PGRP-LD是否直接通过调控免疫系统影响疟原虫感染；2）检测dsLD中共生菌数量和分布的变化，鉴定受PGRP-LD调控的共生菌；3）将此类共生菌回殖入无共生菌按蚊中，检测抗疟能力变化，研究PGRP-LD是否可通过调控共生菌影响按蚊传疟能力，明确PGRP-LD的功能，为疟疾等虫媒传染病控制手段创新提供理论基础。

昆虫肽聚糖识别蛋白家族（PGRP）在识别病原体、调控免疫反应过程中起到重要作用。PGRP-LD虽然存在于果蝇、蚊虫等多种昆虫中，但是它的功能还不清楚。本课题研究发现斯氏按蚊PGRP-LD可以通过负调控免疫系统，抑制抗菌肽的过度激活，从而保护体内肠道菌群；健康的肠道菌群可以调控围食膜形成代谢相关基因的表达，从而保证围食膜结构的完整性，完整围食膜有效阻碍疟原虫感染。本研究阐明了按蚊PGRP-LD的功能，发现PGRP-LD参与调控先天免疫反应、肠道菌群和围食膜三者之间的相互作用关系。当三者之间平衡破坏后，将显著增加按蚊对疟原虫的易感性。本研究的发现将为发展利用调控围食膜结构防控蚊虫传播疟原虫提供理论基础，也为其他媒介免疫系统、微生物组和病原体之间相互作用的研究提供借鉴。本项目开展期间共发表通讯作者论文3篇，分别是Appl Environ Microbiol. 2018；PLoS Pathog. 2018和Dev Comp Immunol. 2018。