Yamasaki-Yashiki Shino, Miyoshi Yuki, Nakayama Tomoya, Kunisawa Jun, Katakura Yoshio
Faculty of Chemistry, Materials and Bioengineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680, Japan.
Laboratory of Vaccine Materials, Center for Vaccine and Adjuvant Research and Laboratory of Gut Environmental System, National Institutes of Biomedical Innovation, Health and Nutrition, 7-6-8 Asagi, Saito, Ibaraki, Osaka 567-0085, Japan.
Biosci Microbiota Food Health. 2019;38(1):23-29. doi: 10.12938/bmfh.18-015. Epub 2018 Nov 1.
Immunoglobulin (Ig) A in the mucus of the intestinal tract plays an important role in preventing the invasion of pathogenic microorganisms and regulating the composition of the gut microbiota. Several strains of probiotic lactic acid bacteria (LAB) are known to promote intestinal IgA production. Bacteria are also known to naturally release spherical membrane vesicles (MVs) that are involved in various biological functions such as quorum sensing, pathogenesis, and host immunomodulation. However, the production of MVs by LAB and their effects on host immunity remain poorly understood. In this study, we investigated the MV production by subsp. NBRC15893 isolated from , the traditional seed mash used for brewing sake. MVs were separated from the culture broth of NBRC15893 through filtration and density gradient ultracentrifugation and were observed by transmission electron microscopy. The MVs showed a spherical morphology, with a diameter of 30-400 nm, and contained proteins and nucleic acids. In addition, both the LAB cells and purified MVs promoted IgA production by murine Peyer's patch cells. This MV- and cell-induced IgA production was suppressed by neutralization of Toll-like receptor (TLR) 2, which recognizes cell wall components of gram-positive bacteria, using an anti-TLR2 antibody. Collectively, our results indicate that MVs released from NBRC15893 enhance IgA production by activating host TLR2 signaling through its cell wall components. Thus, it is important to consider novel interactions between gut microbiota and hosts via MVs, and MVs derived from probiotic bacteria could have promising applications as safe adjuvants.
肠道黏液中的免疫球蛋白A（IgA）在预防病原微生物入侵和调节肠道微生物群组成方面发挥着重要作用。已知几种益生菌乳酸菌（LAB）菌株可促进肠道IgA的产生。细菌还会自然释放球形膜泡（MVs），这些膜泡参与群体感应、发病机制和宿主免疫调节等多种生物学功能。然而，LAB产生MVs及其对宿主免疫的影响仍知之甚少。在本研究中，我们调查了从用于酿造清酒的传统酒曲中分离出的NBRC15893亚种产生MVs的情况。通过过滤和密度梯度超速离心从NBRC15893的培养液中分离出MVs，并通过透射电子显微镜进行观察。MVs呈球形，直径为30 - 400nm，含有蛋白质和核酸。此外，LAB细胞和纯化的MVs均能促进小鼠派尔集合淋巴结细胞产生IgA。使用抗Toll样受体（TLR）2抗体中和识别革兰氏阳性细菌细胞壁成分的TLR2，可抑制这种由MVs和细胞诱导的IgA产生。总体而言，我们的结果表明，NBRC15893释放的MVs通过其细胞壁成分激活宿主TLR2信号通路来增强IgA的产生。因此，考虑肠道微生物群与宿主之间通过MVs产生的新型相互作用非常重要，并且源自益生菌的MVs作为安全佐剂可能具有广阔的应用前景。
