类鼻疽伯克霍尔德菌（Bp）所致的类鼻疽误诊率和病死率极高，肺部感染最为常见，海南是我国发病率最高的地区。作为兼性胞内菌，Bp在胞内存活和繁殖机制仍不清楚。VI型分泌系统（T6SS）为新发现的细菌分泌系统，与细菌的致病力等有关，有趣的是Bp有6套T6SS，远超过其它致病菌,可能与其超强致病力和对多种药物天然耐药有关。我们前期工作发现，T6SS-4结构蛋白基因TssM-4在Bp临床和环境分离株中的携带率分别为100%和15.1%，不携带TssM-4的环境株对巨噬细胞的侵袭力弱于临床株，提示T6SS-4可能与Bp的致病力密切相关。本研究拟构建缺失T6SS-4核心基因的Bp缺失株，观察其对细菌表型和耐药性影响；展开细菌对细胞和宿主的致病机制研究；筛选毒力蛋白作为疫苗免疫小鼠，观察其保护作用。如获预期结果，有望揭示T6SS-4的生物学功能、耐药机制和致病机制，为类鼻疽的防治提供新思路和理论依据。

Burkholderia pseudomallei is the causative agent of melioidosis.The organism can infect any organ system, although the lung is the most common organ affected.Melioidosis is often fatal, as illustrated by the high mortality and misdiagnosis rates among cases.Hainan island is regarded as a main endemic area in China. As a facultative intracellular pathogen,virtually nothing is known about the molecular mechanisms that allow B. pseudomallei to survive intracellularly.Type VI secretion system, a new bacterial secretion system，mediates bacterial virulence on host cells and drug resistance.And there is significant virulence differentiation between the environmental and clinical strains. Interestingly, B. pseudomallei contains six T6SSs,it is more than other bacterial pathogens.PCR identification of TssM-4 (structure gene of T6SS-4) in clinical isolates of Bp and environmental isolates stored in our lab, which has 100% possession in clinical isolates and 15.1% in environmental isolates.Unlike clinical isolates, the environmental isolates were only weakly virulent to RAW 264.7 macrophages 24 h after infection.Our observations suggest that,the T6SS-4 may be involved in the pathogenicity of B. pseudomallei.To investigate the function of T6SS-4, T6SS-4 deletion mutants will be made . Functional analysis targets about bacteria infection, including cell adherence, cytotoxicity, autophagy, apoptosis and hemolysis.These virulence proteins will be selected as candidate vaccine antigens and tested in the BALB/c mouse model of infection.We want to prove the pathogenicity mechanism and function of T6SS-4, and find a new strategy for melioidosis prevention and cure.