Mechanisms of maternal Immunoglobulin A control over the neonatal microbiota and the development of Necrotizing Enterocolitis.

摘要 新生儿特别容易受到定植细菌的入侵，因此哺乳动物的母亲保护 他们的孩子通过抗体，特别是免疫球蛋白A(IgA)分泌到母乳中。坏死性 小肠结肠炎(NEC)是早产儿的一种疾病，其特征是新生儿的肠道受到 微生物区系。研究表明，用母乳喂养的婴儿患NEC的几率显著降低， 尽管其机制尚不清楚。我们的初步研究表明，母体免疫球蛋白A(MIGA)是一个重要因素 以保护自己免受NEC的伤害。早产儿粪便标本的IgA结合分析表明，乳房 在分娩后的第一个月，牛奶是IgA的主要来源，而 与IgA结合的细菌与NEC的发生有关。免疫球蛋白A结合和未结合的序列测定 细菌显示，NEC与IgA阴性肠杆菌科细菌的独特增加有关。此外， 我们在小鼠模型中证实了IgA在预防NEC方面起着关键作用，在那里我们证明了饲养的幼鼠 由于MIGA缺乏，母亲易患疾病，这表明母乳中的IgA对于 保护。综上所述，这些数据表明，MIGA结合在阻止NEC的发展中起着关键作用 塑造新生儿的微生物区系。为了介导对细菌群落的影响，IgA作用于细菌亚群 人口。因此，我们的中心假设是母乳中的IgA直接修饰肠道细菌， 防止新生儿肠道的入侵和炎性免疫反应的诱导。我们会 从三个方面来检验这一假设。在第一个目标中，我们将调查个体亚群如何 肠杆菌科的种群发生了变化，从而避开了MIGA。此外，我们将调查多边投资担保机构的曲目 不同的母乳捐献者来测试这个曲目中的变异在结合不同的 肠道细菌。在目标2中，我们将研究IgA与新生儿微生物区系结合的机制。 群落水平，通过16S rRNA基因测序和对一个模式生物的转录分析 灵知生菌小鼠。我们希望将这些数据与分析IgA在上皮细胞关联中的作用联系起来。 肠道细菌和诱导的下游免疫反应。在第三个目标中，我们将调查 抵抗NEC的乳腺抗体的产生是否依赖于母体T细胞 细胞。这些目标将有助于更好地理解MIGA如何塑造新生的微生物群和 新生儿免疫反应。此外，我们的建议可能会改进提供战略，以防止通过 有针对性地向高危儿童提供含有保护性抗体的母乳。

Abstract Neonates are particularly susceptible to invasion by colonizing bacteria and thus mammalian mothers protect their children via antibodies and in particular, Immunoglobulin A (IgA), secreted into maternal milk. Necrotizing Enterocolitis (NEC) is a disease of premature infants characterized by invasion of the neonatal intestine by the microbiota. Studies have shown that the incidence of NEC is significantly reduced in infants fed with breast milk, though the mechanism is unclear. Our preliminary studies show that maternal IgA (mIgA) is an important factor in protection against NEC. Analysis of IgA-binding on fecal samples from premature infants indicated that breast milk was the predominant source of IgA in the first month post-delivery and that a relative drop in the fraction of bacteria bound by IgA is associated with the development of NEC. Sequencing of IgA-bound and unbound bacteria indicated that NEC was associated with a unique increase in IgA negative Enterobacteriaceae. Further, we confirmed that IgA is critical in preventing NEC in the murine model, where we demonstrate that pups reared by mIgA deficient mothers are susceptible to disease, indicating that IgA in breast milk is necessary for protection. Together these data indicate that mIgA binding is critical in preventing the development of NEC by shaping the neonatal microbiota. In order to mediate effects on bacterial communities IgA acts on bacterial sub- populations. Therefore, our central hypothesis is that IgA in maternal milk modifies intestinal bacteria directly, preventing their invasion of the neonatal intestine and the induction of inflammatory immune responses. We will test this hypothesis in three aims. In the first aim we will investigate the mechanisms of how individual sub- populations of Enterobacteriaceae change to elude mIgA. Further we will investigate the mIgA repertoire of different breast milk donors to test the hypothesis that variation in this repertoire is important in binding different intestinal bacteria. In aim 2 we will investigate the mechanism of IgA binding on the neonatal microbiota at the community level, via 16S rRNA gene sequencing and by transcriptional analysis of a model organism in gnotobiotic mice. Our hope is to associate these data with analysis of the role of IgA on epithelial association of intestinal bacteria and the downstream immune responses that are induced. In the third aim we will investigate whether the production of mammary gland antibodies that protect against NEC are dependent upon maternal T cells. These aims will lead to a better understanding of how mIgA shapes the nascent microbiome and the neonatal immune response. In addition, our proposal may improve provide strategies to prevent NEC via the targeted provision of breast milk containing protective antibodies to the most at-risk children.