A Clinical Study of Protective and Pathogenic Immunity to Dengue during Infancy

描述（由申请人提供）：世界卫生组织将登革热列为高优先级新发病毒性疾病。保护性免疫和导致严重登革出血热（DHF）的致病性免疫反应之间存在一条细微的界限。更好地了解保护性免疫将对登革热流行国家的登革热疫苗试验和实施战略产生直接影响。更好地了解DHF免疫发病机制将有助于改进分诊、治疗和干预策略。本建议的目标是描述在婴幼儿独特的免疫环境中，针对登革热病毒（DENV）感染的保护性和致病性人类免疫反应。婴儿期DENV原发性感染的研究提供了重要的人类免疫学数据，而这些数据无法从年龄较大的儿童或成人的研究中获得。该项目的第一个目的是对婴幼儿DENV感染进行前瞻性临床研究。研究地点位于菲律宾拉古纳的圣巴勃罗。这项前瞻性研究将收集临床和流行病学数据、人体测量数据和婴儿血液样本。监测活动将涵盖整个疾病严重程度的婴幼儿DENV感染，包括临床不明显感染。第一个目标将描述婴儿登革热的广泛临床谱，确定总体和特定年龄的发病率，并描述婴儿年龄、体脂量/人体测量指数和登革热疾病严重程度之间的关联。它还将为其他特定目的提供重要的感染前、感染后和纵向婴儿血液样本。在第二个目标中，将使用感染前婴儿血液样本测量中和抗体滴度和抗denv E蛋白结构域III IgG水平和贪婪度。还将测量DENV感染的抗体依赖性增强（ADE）和抗DENV prM/抗e IgG比率。将进行检测，以反映婴儿感染DENV时的循环抗体水平。将确定血清型特异性抗体水平，这些抗体水平与体内对症状性登革热的保护有关。拟议的ADE检测将提供可靠的临床数据，以支持、反驳或显著修改现有的ADE登革热发病机制范式。第三个目标将描述不同婴儿先天免疫反应随年龄和体脂量/营养状况的变化，并描述它们在形成登革热严重程度方面的潜在作用。先天性免疫细胞对特异性toll样受体/模式识别受体激动剂和DENV感染的激活概况将通过几种方法测量，这些方法使用从2-16个月以上的婴儿纵向收集的外周血单个核细胞。这方面的其他实验将侧重于确定导致低体脂储存（即营养不良/营养不良）婴儿先天免疫反应受损的特定细胞信号传导途径，这些婴儿随后患DHF的风险较低。该项目和创新的临床研究具有独特的优势，可以解决关于登革热的保护性和致病性人类免疫反应的知识方面的重大空白。

DESCRIPTION (provided by applicant): The World Health Organization has categorized dengue as a high priority emerging viral disease. A fine line exists between protective immunity and pathogenic immune responses that lead to severe dengue hemorrhagic fever (DHF). A better understanding of protective immunity will have a direct impact on dengue vaccine trials and implementation strategies in endemic countries. A better understanding of DHF immunopathogenesis will lead to improved triage, therapeutic, and intervention strategies. The goal of this proposal is to delineate protective and pathogenic human immune responses against dengue virus (DENV) infections in the unique immunological setting of infancy. Studies of primary DENV infections during infancy provide important human immunological data that cannot be obtained from studies of older children or adults. The first aim of this project is to conduct a prospective clinical study of DENV infections during infancy. The study site is in San Pablo, Laguna, Philippines. The prospective study will collect clinical and epidemiological data, anthropometric measurements, and blood samples from infants. Surveillance activities will capture infant DENV infections across the entire spectrum of disease severity, including clinically inapparent infections. The first aim will characterize the wide clinical spectrum of infant dengue, define overall and age-specific incidence rates, and delineate associations between infant age, body fat mass/anthropometric indices, and dengue disease severity. It will also provide crucial pre-infection, post-infection, and longitudinal infant blood samples for the other specific aims. In the second aim, neutralizing antibody titers and anti-DENV E protein domain III IgG levels and avidity will be measured using the pre-infection infant blood samples. Antibody-dependent enhancement (ADE) of DENV infection and anti-DENV prM/anti-E IgG ratios will also be measured. The assays will be conducted so as to reflect circulating antibody levels in infants at the time of their DENV infection. Serotype-specific antibody levels that correlate with in vivo protection against symptomatic dengue will be defined. The proposed ADE assays will provide solid clinical data to either support, refute, or significantly modify the existing ADE dengue pathogenesis paradigm. The third aim will characterize changes in distinct infant innate immune responses with age and body fat mass/nutritional status, and delineate their potential role in shaping dengue disease severity. Innate immune cell activation profiles to specific Toll-like receptor/pattern-recognition receptor agonists and DENV infection will be measured by several methods using peripheral blood mononuclear cells collected longitudinally from infants over ages 2-16 months old. Additional experiments in this aim will focus on identifying specific cellular signaling pathways that contribute to impaired innate immune responses in infants with low body fat stores (i.e. undernourished/malnourished), and subsequently at low risk for developing DHF. This project and innovative clinical study are uniquely poised to address critical gaps in knowledge regarding protective and pathogenic human immune responses in dengue.