Postnatal ontogeny of HCMV-specific CD4 T cell immunity

人巨细胞病毒（HCMV）是美国先天性出生缺陷的主要感染原因，也是免疫功能低下人群发病率和死亡率的重要来源。由于相当大比例的HCMV传播发生在围产期和婴儿早期，因此理想的HCMV疫苗在该年龄组中是有效的。在这个年龄接种疫苗的潜在限制是效应分子，特别是分泌的细胞因子，例如，干扰素-γ（IFN-γ）和肿瘤坏死因子（TNF），表面分子，如CD 40-配体（CD 40-L）。出生后获得性HCMV感染尚未显示出这种局限性。本项目的第一个目的是确定效应分子，特别是分泌的细胞因子，例如，干扰素-γ（IFN-γ）和肿瘤坏死因子（TNF），表面分子，如CD 40-配体（CD 40-L）。出生后获得性HCMV感染尚未显示出这种局限性。本项目的第一个目的是确定婴儿和成人原发性HCMV感染后HCMV特异性CD 4 T细胞记忆/效应功能，及其与其他HCMV特异性免疫应答、病毒清除和病毒潜伏期建立的关系。据推测，与成人相比，年幼的婴儿将具有减少的HCMV抗原特异性记忆/效应CD 4 T细胞的积累，所述细胞可以分泌细胞因子或表达CD 40-L。我们进一步预测，婴儿HCMV特异性CD 4 T细胞将优先产生缺乏抗病毒活性或许多抑制这种活性的Th 2细胞因子。将检查对HCMV的总体应答和对pp 65基质蛋白的应答，pp 65基质蛋白似乎是CD 4 T细胞应答的主要靶点。将确定婴儿CD 4 T细胞应答的降低和/或改变是否伴随着中和HCMV抗体血清水平降低、病毒血症延长、尿液病毒脱落延长（均由临床研究中心确定）、HCMV特异性CD 8 T细胞功能降低（项目2）和抗原呈递功能（APC）降低（项目3）。第二个目标是开发含有ppo 65肽的荧光染料标记的HLA-DR四聚体分子，以鉴定婴儿和成人中对pp 65具有特异性的CD 4 T细胞。这将检验婴儿而不是成人具有相当大部分的对pp 65具有特异性的CD 4 T细胞但对pp 65抗原的反应性降低或不存在的假设。这些研究将为了解正常婴儿和成人原发性HCMV感染后的人CD 4记忆/效应T细胞应答，APC功能提供依据。由于HCMV疫苗的新试验即将到来，这些研究也可能为疫苗效力提供有用的不成熟反应预测因子，例如预防HCMV感染和/或改善潜伏期的维持。他们还可能指出免疫疗法可能增强保护性反应的策略，特别是在婴儿期。

Human cytomegalovirus (HCMV) is the leading infectious cause of congenital birth defects in the United States, and is an important source of morbidity and mortality for those who are immunocompromised. Since a substantial proportion of HCMV transmission occurs perinatally and in early infancy, an ideal HCMV vaccine would be effective in this age group. A potential limitation of vaccination at this age is the apparent immaturity of CD4 T cell expression of effector molecular, particularly secreted cytokines, e.g., interferon-gamma (IFN-gamma) and tumor necrosis factor (TNF), surface molecules, such as CD40-ligand (CD40-L). Such limitations have not been shown for postnatally acquired HCMV infection. The first aim of this project is to determine HCMV-specific CD4 T cell expression of effector molecules, particularly secreted cytokines, e.g., interferon-gamma (IFN-gamma) and tumor necrosis factor (TNF), surface molecules, such as CD40-ligand (CD40-L). Such limitations have not been shown for postnatally acquired HCMV infection. The first aim of this project is to determine HCMV-specific CD4 T cell memory/effector function following primary HCMV infection of infants and adults, and its relationship with other HCMV-specific immune responses, viral clearance, and the establishment of viral latency. It is hypothesized that young infants will have a decreased accumulation of HCMV antigen-specific memory/effector CD4 T cells that can secrete cytokines or express CD40-L compared to adults. We further predict that infant HCMV-specific CD4 T cells will preferentially produce Th2 cytokines that lack anti-viral activity or many inhibit this activity. Responses to HCMV overall, and to the pp65 matrix protein, which appears to be a major target of the CD4 T cell response, will be examined. It will be determined if decreased and/or altered infant CD4 T cell responses are paralleled by decreased serum levels of neutralizing HCMV antibody, prolonged viremia, prolonged urinary viral shedding (all determined by the Clinical Research Core), decreased HCMV-specific CD8 T cell function (Project 2), and decreased antigen-presenting function (APC) (Project 3). The second aim is to develop fluorochrome- labeled HLA-DR tetramer molecules containing ppo65 peptides to identify CD4 T cells in infants and adults with specificity for pp65. This will test the hypothesis that infants but not adults have a substantial fraction of CD4 T cells with specificity for pp65 but reduced or absent responsiveness to pp65 antigen. These studies will provide insight into the human CD4 memory/effector T cell response following primary HCMV infection in normal infants and adults, APC function. Since new trials of HCMV vaccines are imminent, these studies may also provide useful immature response predictors for vaccine efficacy, such as prevention of HCMV infection and/or improved maintenance of latency. They may also point out strategies by which protective responses might be augmented by immunotherapy, particularly during infancy.