T Cell Immunity in Endemic Burkitt Lymphoma

描述(由申请人提供)：这项提案的长期目标是了解地方性Burkitt淋巴瘤(EBL)的病因，EBL是赤道非洲最常见的儿科癌症。EBL的流行病学研究表明，儿童早期感染恶性疟疾和EB病毒(EBV)有很强的相关性。虽然目前尚不清楚疟疾和EBV的相互作用如何增加EBL的风险，但已有研究表明，疟疾介导了EBV特异性T细胞免疫的抑制。我们的中心假设是，全地方性疟疾损害了EBV特异性效应器和中枢记忆T细胞免疫的发展和维持。我们推测，虽然不是相互排斥的，但两种机制导致了在非洲儿童中观察到的EBV免疫抑制：1)重复/慢性疟疾感染导致高EBV病毒载量，进而诱导“CD45RA+重新表达”的效应记忆CD8+T细胞(TEMRA)，它立即显示出干扰素-3的表达，但比效应记忆T细胞(TEM)更容易发生凋亡；和/或2)重复/慢性疟疾感染降低了EBV特异性T细胞对稳态细胞因子(即IL-15和IL-7)的反应。这一假设将通过对有不同疟疾暴露史的健康肯尼亚儿童和EBL儿童的EBV特异性免疫检查来验证。具体的AIMS将检验以下假设：AIM 1.累积暴露于疟疾和高EBV病毒载量决定了EBV特异性CD8+TEMRA的频率。EBV特异性CD8+T细胞将使用人类白细胞抗原I类四聚体和T细胞亚群进行量化，定义为中央记忆，Tcm(CD45RA-CD62L+CCR7+)；效应记忆，TEM(CD45RA-CD62L-CCR7-)；以及RA重新表达效应记忆，TEMRA(CD45RA+CD62L-CCR7-)。将比较三组儿童EBV特异性T细胞干扰素-3的产生、TCR V2的利用和羧基荧光素琥珀酰亚胺酯(CFSE)稀释法的增殖情况。目的2.慢性疟疾暴露组和EBL组儿童EBV特异性记忆T细胞的IL-15和/或IL-7反应性受损。将比较三组儿童IL-15R1和IL-7R1的表面表达、EBV特异性T细胞对同源抗原加和不加IL-15或IL7后的CFSE增殖，以及STAT5磷酸化检测的反应性。目的3.累积暴露于疟疾和高EBV病毒载量决定了EBNA1特异性记忆T细胞亚群的频率。EBNA1的重叠多肽文库将用于鉴定EBNA1特异性的干扰素-3表达和增殖的记忆T细胞亚群。将比较三组儿童的增殖前体数量和产生EBNA1特异性T细胞的频率。鉴于大多数关于EBV T细胞免疫的知识是基于对无症状成人或传染性单核细胞增多症患者的检查，这里提出的研究将提供关于EBV免疫在健康儿童和EBL患者中的演变的新信息。公共卫生相关性：伯基特淋巴瘤是一种常见的儿科癌症。了解淋巴瘤的病因将有助于预防这种侵袭性的B细胞恶性肿瘤。这项研究的结果将最终改善成功的癌症免疫疗法和EB病毒相关淋巴瘤疫苗开发的前景。

DESCRIPTION (provided by applicant): The long-term goal of this proposal is to understand the etiology of endemic Burkitt's lymphoma (eBL), the most prevalent pediatric cancer in equatorial Africa. Epidemiologic studies of eBL indicate a strong association with Plasmodium falciparum malaria and Epstein-Barr virus (EBV) infections early in childhood. Although it is not known how malaria-EBV interactions increase the risk of eBL, it has been suggested that malaria-mediates suppression of EBV-specific T cell immunity. Our central hypothesis is that holoendemic malaria impairs the development and maintenance of EBV-specific effector and central memory T cell immunity. We hypothesize that two, though not mutually exclusive, mechanisms are responsible for the observed suppression of EBV immunity in African children: 1) Repeat/chronic malaria infections result in high EBV viral load, that in turn induce `CD45RA+ re-expressing' effector memory CD8+ T cell (TEMRA) which display immediate IFN-3 expression but are more susceptible to apoptosis than effector memory T cells (TEM) and/or 2) Repeat/chronic malaria infections diminish EBV-specific T cell responsiveness to homeostatic cytokines (i.e. IL-15 and IL-7). This hypothesis will be tested by examination of EBV-specific immunity in healthy Kenyan children with divergent malaria exposure histories and of eBL children. The specific aims will test the following hypotheses: Aim 1. Cumulative exposure to malaria and high EBV viral load determine the frequencies of EBV- specific CD8+ TEMRA. EBV-specific CD8+ T cells will be quantified using HLA Class I tetramers and T cell subsets defined as central memory, TCM (CD45RA-CD62L+CCR7+); effector memory, TEM (CD45RA-CD62L- CCR7-); and RA re-expressing effector memory, TEMRA (CD45RA+CD62L-CCR7-). EBV-specific T cell IFN-3 production, TCR V2 usage and proliferation by carboxyfluorescein succinimidyl ester (CFSE) dilution will be compared between the three groups of children. Aim 2. IL-15 and/or IL-7 responsiveness of EBV-specific memory T cells is impaired in children with chronic malaria exposure and in children with eBL. IL-15R1 and IL-7R1 surface expression, CFSE proliferation of EBV-specific T cells in response to cognate antigen with and without IL-15 or IL7, and responsiveness measured by STAT5 phosphorylation will be compared between the three groups of children. Aim 3. Cumulative exposure to malaria and high EBV viral load determine the frequencies of EBNA1- specific memory T cell subsets. Overlapping peptide libraries of EBNA1 will be used to identify EBNA1- specific IFN-3 expressing and proliferating memory T cell subsets. The precursor numbers of proliferating and the frequency of IFN-3 producing EBNA1-specific T cells will be compared between the three groups of children. Given that most knowledge regarding EBV T cell immunity is based on examination of asymptomatic adults or those who have had infectious mononucleosis, studies proposed here will provide novel information with respect to the evolution of EBV immunity in healthy children as well as those with eBL. PUBLIC HEALTH RELEVANCE: Burkitt lymphoma (BL) is a prevalent pediatric cancer. Understanding BL etiology will aid in the prevention of this aggressive B cell malignancy. Results from this research will ultimately improve the prospects for successful cancer immunotherapies and vaccine development for EBV-associated lymphomas such as BL.