Regulation of the Immune Response to Polysaccharides and

对多糖的免疫反应的调节

• 批准号: 6679848
• 负责人: KE E STEIN
• 金额: --
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6679848
• 关键词: antibacterial antibody; antibody formation; antibody specificity; bacterial antigens; bacterial polysaccharides; bacterial vaccines; bactericidal immunity; biological models; chemical conjugate; chemical structure function; developmental immunology; genetic recombination; genetically modified animals; immunogenetics; immunoglobulin genes; immunoregulation; immunotherapy; laboratory mouse; nonhuman therapy evaluation; site directed mutagenesis

Summary: The immune response to polysaccharide (PS) antigens is highly regulated and has several distinguishing features including restricted subclass, variable region gene usage, fine specificity, and avidity. Simple PS not conjugated to protein (such as bacterial Levan, BL and Neisseria meningitidis group C, MCPS) elicit a thymus-independent (TI) response. PS conjugated to proteins (such as MCPS coupled to tetanus toxoid, (MCPS-TT)), on the other hand, elicit a different type of response, termed thymus-dependent (TD). We previously analyzed anti-BL antibodies and showed the importance of aromatic and basic amino acids in the CDRs of anti-PS antibodies. Our analysis of the regulation of diversity in the anti-In response mapped the Sr1 diversity gene to mouse chromosome 14. Recent studies in TCR KO mice have shown that the response to In is not only TI, but is not influenced by T cells when added back, despite a large increase in serum IgG and IgM. Previous analyses of anti-MCPS and anti-MCPS TT mAb reveal that VH gene family usage in both the TI and TD response is dominated by VHJ558. Consistent with anti-BL Abs, modeling studies also suggest a correlation of basic amino acids in the combining with an increase in affinity. BIAcore analysis of mice immunized with commercial conjugate vaccines compared with mice immunized with fixed N. meningitides showed the O-acetylation status of the PS moiety of conjugate vaccines determines the relative specificity of anti-PS Abs. Compared to immunization with fixed bacteria, the conjugate vaccines elicit a greater IgG response including antibodies to both OAc+ and OAc- PS. Furthermore, the conjugates induce higher relative avidity IgG Abs of either equal reactivity on OAc+ or OAc- or higher OAc- reactivity. Our earlier studies showed that neonatal dendritic cells are functionally impaired in their ability to present tetanus toxoid (TT) and meingococcal group C polysaccharide-tetanus toxoid conjugate (MCPS-TT) to specific T cells suggesting it could be one of the mechanisms why neonates failed to make adult-like anti-MCPS antibody responses. Therefore, studies were undertaken further to understand whether or not dendritic cells are capable of regulating the function of B cells directly. Dendritic cells isolated from MCPS-TT primed mice induced significant antigen specific proliferation of B cells in vitro. Culturing antigen primed B cells in the presence of T cells isolated from the same mice also resulted in the proliferation of B cells. The addition of dendritic cells into the immune B and T cell culture caused more robust proliferation of B cells. However, dendritic cells isolated from neonatal mice failed to have such an effect on B cell proliferation either in the presence or absence of adult immune T cells. These results suggest that dendritic cells play an important role in regulating B cell growth and responses apart from their ability to activate naive T cells, and such effect is defective in neonatal dendritic cells. Also unlike adult dendritic cells, dendritic cells from neonatal mice failed to induce IL-2 and IFN-g secretion from TT or MCPS-TT primed T cells in vitro. MCPS was found to induce IL-6 secretion from dendritic cells and the level of IL-6 produced by neonatal dendrtic cells is significantly less. In another study, characterization of T cells clones derived from MCPS-TT immunized mice revealed that polysaccharide-reactive T cell clones require antigen presenting cell contact but are not MHC restricted. One of the goals of the Children's Vaccine Initiative is to reduce the number of contacts required to immunize a child fully. To meet this goal several combined vaccines have been tested for their safety and immunogenicity in infants. We have developed a model in SW outbred mice to examine the effects of combining vaccines on the response to individual components. Groups of mice were given different combinations of Hib-TT, DTaP and IPV, in separate and mixed injections, and compared their antibody responses to different antigens to those of mice who received only a single one of these three vaccines For all Hib-containing vaccines mixed with IPV or given simultaneously in another site, anti-polio titers were reduced compared to IPV alone and the differences were greater for anti-type 1 than types 2 and 3. The differences for anti-type 1 titers were significant. Similar combinations of MCPS-TT and IPV did nor result in a diminished ant-polio response.

总结：对多糖（PS）抗原的免疫应答是高度调节的，并具有几个显著特征，包括限制性亚类、可变区基因使用、良好的特异性和亲合力。未与蛋白质结合的简单PS（如细菌莱万，BL和脑膜炎奈瑟菌C组，MCPS）引起胸腺非依赖性（TI）反应。另一方面，与蛋白质缀合的PS（例如与破伤风类毒素偶联的MCPS（MCPS-TT））引起不同类型的应答，称为胸腺依赖性（TD）。我们先前分析了抗BL抗体，并显示了芳香族和碱性氨基酸在抗PS抗体的CDR中的重要性。我们的分析，在抗-In反应的多样性的调节映射Sr 1多样性基因小鼠染色体14。最近在TCR KO小鼠中的研究表明，对In的反应不仅是TI，而且当加回时不受T细胞的影响，尽管血清IgG和IgM大量增加。抗MCPS和抗MCPS TT mAb的先前分析揭示，在TI和TD应答中VH基因家族的使用由VHJ 558主导。与抗BL Ab一致，建模研究还表明碱性氨基酸在结合中与亲和力增加相关。用商业缀合物疫苗免疫的小鼠与用固定N.脑膜炎球菌显示缀合物疫苗的PS部分的O-乙酰化状态决定抗PS Ab的相对特异性。 与用固定的细菌免疫相比，缀合物疫苗引发更大的IgG应答，包括针对0Ac+和0Ac-PS两者的抗体。此外，缀合物诱导对0Ac+或0Ac-具有相等反应性或更高0Ac-反应性的更高相对亲合力IgG Ab。 我们早期的研究表明，新生儿树突状细胞在功能上受损的能力，目前破伤风类毒素（TT）和脑膜炎球菌C组多糖-破伤风类毒素结合物（MCPS-TT）的特定的T细胞，这可能是新生儿未能作出成人样的抗MCPS抗体反应的机制之一。因此，进一步进行研究以了解树突细胞是否能够直接调节B细胞的功能。从MCPS-TT致敏小鼠分离的树突状细胞在体外诱导显著的抗原特异性B细胞增殖。在存在从相同小鼠分离的T细胞的情况下培养抗原致敏的B细胞也导致B细胞的增殖。将树突状细胞添加到免疫B和T细胞培养物中引起B细胞更稳健的增殖。然而，从新生小鼠中分离的树突状细胞在成人免疫T细胞存在或不存在的情况下对B细胞增殖没有这种作用。这些结果表明，树突状细胞在调节B细胞的生长和反应中发挥重要作用，除了它们的能力，激活幼稚T细胞，这种作用是缺陷的新生儿树突状细胞。也不同于成年树突状细胞，来自新生小鼠的树突状细胞在体外不能诱导TT或MCPS-TT致敏的T细胞分泌IL-2和IFN-g。发现MCPS诱导树突状细胞分泌IL-6，而新生树突状细胞产生的IL-6水平显著降低。在另一项研究中，来自MCPS-TT免疫小鼠的T细胞克隆的表征显示，多糖反应性T细胞克隆需要抗原呈递细胞接触，但不受MHC限制。 儿童疫苗倡议的目标之一是减少为儿童进行全面免疫所需的接触次数。为了实现这一目标，已经测试了几种组合疫苗在婴儿中的安全性和免疫原性。我们已经在SW远交系小鼠中开发了一种模型，以检查组合疫苗对单个组分的反应的影响。 各组小鼠分别和混合注射Hib-TT、DTaP和IPV的不同组合，并将它们对不同抗原的抗体反应与仅接受这三种疫苗中的一种的小鼠进行比较 对于与IPV混合或在另一个地点同时给予的所有含Hib的疫苗，与单独使用IPV相比，抗脊髓灰质炎滴度降低，并且抗1型的差异大于抗2型和3型。抗1型滴度的差异具有显著性。 MCPS-TT和IPV的类似组合也未导致抗脊髓灰质炎反应减弱。