Determinants of antibody-based host resistance against Pneumocystis carinii

基于抗体的宿主对卡氏肺孢子虫耐药性的决定因素

• 批准号: 7221524
• 负责人: REKHA R RAPAKA
• 金额: $ 4.61万
• 依托单位: CHILDREN'S HOSP PITTSBURGH/UPMC HLTH SYS
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-09-01 至 2010-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7221524
• 关键词: B lymphocyte; HIV infections; Pneumocystis carinii; Pneumocystis pneumonia; SCID mouse; antibody; chitin; disease /disorder prevention /control; enzyme linked immunosorbent assay; genetically modified animals; glucans; helper T lymphocyte; host organism interaction; immune response; immunity; immunologic memory; laboratory mouse; leukocyte activation /transformation; mannose; predoctoral investigator; protein structure function; receptor binding

DESCRIPTION (provided by applicant): Pneumocystis carinii (PC) pneumonia is an opportunistic infection found among HIV-infected patients worldwide. Most infants develop PC-specific antibodies by two years of age, underscoring the frequency at which PC is encountered environmentally. Immuno-intact murine hosts mount protective immune responses leading to subclinical infection, while SCID, CD4 T cell deficient, or B cell deficient mice succumb to PC pneumonia. Yet, mice challenged with PC and thereafter depleted of CD4 T cells resist pneumonia, correlating with high titers of PC specific antibody. While CD4+ T cells appear to be critical in the generation of protective antibodies against PC, maintenance of protective antibodies by memory B cells has not been explored. Further, the specific targets of PC-immunoprotective antibodies have not been fully characterized, particularly their affinity for carbohydrate epitopes, which have recently been shown to be critical in vaccine-based resistance against other opportunistic fungal pathogens. The goal of our efforts is to evaluate the mechanisms whereby antibody based immunity may prevent PC infection, and we approach our studies through two aims. Specific Aim I will evaluate the generation of humoral-mediated immunologic memory against PC through characterization of the kinetics of antibody recall responses in the presence or absence of CD4+ T cells. We will also explore the potential of memory B cells to activate in a CD4+ independent environment and reconstitute PC immunity in SCID mice. Specific Aim II will evaluate whether PC infection elicits specific antibodies against the major surface carbohydrates beta-glucan, mannose, and chitin, and whether memory antibody responses are manifested against these epitopes. Given the affinity of the pattern recognition receptor dectin-1 for PC beta-glucan, we will evaluate whether an antibody-like immunotherapeutic consisting of the extracellular domain of dectin-1 fused to the murine lgG1 Fc fragment enhances PC clearance in SCID mice. Greater understanding of the determinants underlying Pneumocystis-specific humoral immunity and its maintenance will inform on resistance mechanisms against this environmental pathogen and will allow us to optimally vaccinate against PC pneumonia in immunodeficient hosts. PC is a commonly encountered environmental fungus causing lethal pneumonia in HIV+ patients, and little is understood as to how antibodies may prevent infection. Our studies will evaluate the molecules that PC antibodies recognize, and the manner whereby antibody-producing cells remember previous PC exposures, providing insight into normal host resistance and the requirements for vaccine design in the setting of HIV.

描述（由申请人提供）：卡氏肺囊虫（PC）肺炎是一种在全世界hiv感染者中发现的机会性感染。大多数婴儿在两岁时产生PC特异性抗体，强调了PC在环境中遇到的频率。免疫完整的小鼠宿主产生保护性免疫反应导致亚临床感染，而SCID、CD4 T细胞缺陷或B细胞缺陷小鼠则死于PC肺炎。然而，感染PC后CD4 T细胞耗尽的小鼠能够抵抗肺炎，这与高滴度的PC特异性抗体有关。虽然CD4+ T细胞似乎在产生针对PC的保护性抗体中起着关键作用，但记忆性B细胞对保护性抗体的维持作用尚未得到探讨。此外，pc免疫保护性抗体的特异性靶点尚未得到充分表征，特别是它们对碳水化合物表位的亲和力，这在最近被证明对其他机会性真菌病原体的基于疫苗的抗性中至关重要。我们努力的目标是评估基于抗体的免疫预防PC感染的机制，我们的研究有两个目的。我将通过表征CD4+ T细胞存在或不存在时抗体回忆反应的动力学来评估针对PC的体液介导的免疫记忆的产生。我们还将探索记忆B细胞在CD4+独立环境中激活的潜力，并在SCID小鼠中重建PC免疫。特异性Aim II将评估PC感染是否引发针对主要表面碳水化合物-葡聚糖、甘露糖和几丁质的特异性抗体，以及是否针对这些表位表现出记忆抗体反应。鉴于模式识别受体dectin-1对PC β -葡聚糖的亲和力，我们将评估由dectin-1细胞外结构域融合到小鼠lgG1 Fc片段的抗体样免疫治疗是否能增强SCID小鼠的PC清除。更好地了解肺囊虫特异性体液免疫的决定因素及其维持，将有助于了解对这种环境病原体的耐药性机制，并使我们能够在免疫缺陷宿主中最佳地接种针对PC肺炎的疫苗。PC是一种常见的环境真菌，可引起HIV+患者的致死性肺炎，对于抗体如何预防感染知之甚少。我们的研究将评估PC抗体识别的分子，以及抗体产生细胞记住先前PC暴露的方式，从而深入了解正常宿主的抵抗力以及在HIV环境下设计疫苗的要求。