GSK, Siena, Italy.
GSK, Wavre, Belgium.
PLoS One. 2019 Aug 1;14(8):e0203234. doi: 10.1371/journal.pone.0203234. eCollection 2019.
Neisserial Heparin Binding Antigen (NHBA) is a surface-exposed lipoprotein of Neisseria meningitidis and a component of the Bexsero vaccine. NHBA is characterized by the presence of a highly conserved Arg-rich region involved in binding to heparin and heparan sulphate proteoglycans present on the surface of host epithelial cells, suggesting a possible role of NHBA during N. meningitidis colonization. NHBA has been shown to be cleaved by the meningococcal protease NalP and by human lactoferrin (hLF), a host protease presents in different body fluids (saliva, breast milk and serum). Cleavage occurs upstream or downstream the Arg-rich region. Since the human nasopharynx is the only known reservoir of infection, we further investigated the susceptibility of NHBA to human proteases present in the saliva to assess whether proteolytic cleavage could happen during the initial steps of colonization. Here we show that human saliva proteolytically cleaves NHBA, and identified human kallikrein 1 (hK1), a serine protease, as responsible for this cleavage. Kallikrein-related peptidases (KLKs) have a distinct domain structure and exist as a family of 15 genes which are differentially expressed in many tissues and in the central nervous system. They are present in plasma, lymph, urine, saliva, pancreatic juices, and other body fluids where they catalyze the proteolysis of several human proteins. Here we report the characterization of NHBA cleavage by the tissue kallikrein, expressed in saliva and the identification of the cleavage site on NHBA both, as recombinant protein or as native protein, when expressed on live bacteria. Overall, these findings provide new insights on NHBA as target of host proteases, highlights thepotential role of NHBA in the Neisseria meningitidis nasopharyngeal colonization, and of kallikrein as a defensive agent against meningococcal infection.
奈瑟氏肝素结合抗原 (NHBA) 是脑膜炎奈瑟氏球菌表面暴露的脂蛋白，也是 Bexsero 疫苗的成分。NHBA 的特征是存在一个高度保守的富含精氨酸的区域，该区域参与与宿主上皮细胞表面的肝素和硫酸乙酰肝素蛋白聚糖结合，表明 NHBA 在脑膜炎奈瑟氏球菌定植过程中可能发挥作用。已证明 NHBA 可被脑膜炎球菌蛋白酶 NalP 和宿主蛋白酶人乳铁蛋白 (hLF) 切割，后者存在于不同的体液（唾液、母乳和血清）中。切割发生在富含精氨酸的区域的上游或下游。由于人类鼻咽部是唯一已知的感染储库，我们进一步研究了 NHBA 对唾液中存在的人类蛋白酶的易感性，以评估在定植的初始步骤中是否会发生蛋白水解切割。在这里，我们表明人类唾液蛋白水解切割 NHBA，并鉴定出人类激肽释放酶 1 (hK1)，一种丝氨酸蛋白酶，是导致这种切割的原因。激肽释放酶相关肽酶 (KLKs) 具有独特的结构域结构，作为一个家族存在，由 15 个基因组成，这些基因在许多组织和中枢神经系统中差异表达。它们存在于血浆、淋巴液、尿液、唾液、胰液和其他体液中，在那里它们催化几种人类蛋白质的蛋白水解。在这里，我们报告了组织激肽对 NHBA 的切割特性，该激肽在唾液中表达，并鉴定了当在活细菌上表达时，NHBA 的切割位点，无论是重组蛋白还是天然蛋白。总的来说，这些发现为 NHBA 作为宿主蛋白酶的靶标提供了新的见解，强调了 NHBA 在脑膜炎奈瑟氏球菌鼻咽部定植中的潜在作用，以及激肽作为针对脑膜炎奈瑟氏球菌感染的防御剂的作用。
