Type IV secretion by Neisseria gonorrhoeae

描述（由申请人提供）：淋病奈瑟菌引起性传播疾病淋病，较严重的感染为盆腔炎（PID）和播散性淋球菌感染（DGI）。我们在淋病奈瑟菌中发现了一个57 kb的遗传岛，显示了一个致病性岛的特征。在疾病分离株中存在几种形式的淋球菌基因岛（GGI），大约80%的淋球菌菌株携带某种形式的GGI。我们鉴定了一种在GGI中编码的肽聚糖水解酶（atlA），并发现它参与了一种来自细菌细胞壁的不寻常的细胞毒素的产生。这种肽聚糖衍生的细胞毒素（pg -细胞毒素）与百日咳博德泰拉的气管细胞毒素相同，是淋球菌感染的重要毒力因子。pg -细胞毒素在器官培养中引起纤毛输卵管细胞死亡，诱导大鼠关节炎，诱导培养细胞中IL-1和IL-6。遗传岛中atlA的存在与引起DOT的菌株显著相关。

DESCRIPTION (provided by applicant): Neisseria gonorrhoeae causes the sexually transmitted disease gonorrhea, the more serious infections pelvic inflammatory disease (PID) and disseminated gonococcal infection (DGI). We identified a 57 kb genetic island present in N. gonorrhoeae that shows the characteristics of a pathogenicity island. Several forms of the gonococcal genetic island (GGI) are present among disease isolates, with approximately 80 percent of gonococcal strains carrying some form of the GGI. We identified a peptidoglycan hydrolase (atlA) encoded in the GGI and found that it is involved in the production of an unusual cytotoxin derived from the bacterial cell wall. This peptidoglycan-derived cytotoxin (PG-cytotoxin) is identical to the tracheal cytotoxin of Bordetella pertussis and is an important virulence factor in gonococcal infections. PG-cytotoxin causes the death of ciliated fallopian tube cells in organ culture, induces arthritis in rats, and induces IL-1 and IL-6 in cultured cells. The presence of atlA in the genetic island is significantly correlated with strains that cause DOT. DNA sequencing revealed that the GGI encodes a putative type IV secretion system. Type IV secretion systems include plasmid conjugation systems and virulence factor export systems and some type IV secretion systems carry out both processes. Mutations in the putative type IV secretion genes in the GGI result in loss of DNA secretion. These mutants also show delayed adherence to primary cervical cells and exhibit an unusual microcolony phenotype upon binding to cells. Mutations in atlA result in the same phenotypes as the other type IV secretion mutations as well as showing decreased PG-cytotoxin production. Thus AtlA is necessary for type IV secretion and is either directly or indirectly involved in PG-cytotoxin production. These results suggest that the GGI encodes an active type IV secretion system important in interaction of N. gonorrhoeae with the host. The goals of this proposal are contained in two specific aims. 1) We will make mutations designed to affect type IV secretion and test these mutants for secretion of proteins, DNA, and PG-cytotoxin. 2) We will test mutants with defects in secretion for phenotypes relevant to virulence, i.e., epithelial cell adherence and invasion, intracellular survival, and microcolony formation. Overall, these studies are designed to reveal the molecular mechanisms of this novel secretion system and identify previously unrecognized virulence factors important in gonococcal infection which may serve as new targets for chemotherapy or immunoprotection.