T Cell Immunity in Endemic Burkitt Lymphoma

描述（由申请人提供）：本提案的长期目标是了解地方性伯基特淋巴瘤（eBL）的病因，这是赤道非洲最流行的儿科癌症。流行病学研究表明，eBL与恶性疟原虫、疟疾和EB病毒（EBV）感染在儿童早期有很强的关联。虽然目前尚不清楚疟疾-EBV相互作用如何增加eBL的风险，但已表明疟疾介导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EBV特异性效应和中枢记忆T细胞免疫的发展和维持。我们假设有两种机制（虽然不是相互排斥的）导致了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，其依次诱导“CD 45 RA+再表达”效应记忆CD 8 + T细胞（TEMRA），其显示立即IFN-3表达，但比效应记忆T细胞（TEM）更易发生细胞凋亡，和/或2）重复/慢性疟疾感染降低EBV特异性T细胞对稳态细胞因子（即IL-15和IL-7）的反应性。这一假设将通过检查不同疟疾暴露史的健康肯尼亚儿童和eBL儿童的EB病毒特异性免疫力进行检验。具体目标将检验以下假设：目标1。累积暴露于疟疾和高EBV病毒载量决定EBV特异性CD 8 + TEMRA的频率。将使用HLA I类四聚体和T细胞亚群定量EBV特异性CD 8 + T细胞，T细胞亚群定义为中央记忆，TCM（CD 45 RA-CD 62 L + CCR 7+）;效应记忆，TEM（CD 45 RA-CD 62 L-CCR 7-）;和RA再表达效应记忆，TEMRA（CD 45 RA + CD 62 L-CCR 7-）。通过羧基荧光素琥珀酰亚胺酯（CFSE）稀释法比较三组儿童的EBV特异性T细胞IFN-3产生、TCR V2使用和增殖。目标二。EB病毒特异性记忆T细胞的IL-15和/或IL-7反应性在慢性疟疾暴露儿童和eBL儿童中受损将在三组儿童之间比较IL-15 R1和IL-7 R1表面表达、EBV特异性T细胞在有和没有IL-15或IL 7的情况下响应于同源抗原的CFSE增殖以及通过STAT 5磷酸化测量的响应性。目标3.疟疾的累积暴露和高EBV病毒载量决定了EBNA 1特异性记忆T细胞亚群的频率。EBNA 1的重叠肽文库将用于鉴定EBNA 1特异性IFN-3表达和增殖记忆T细胞亚群。将在三组儿童之间比较增殖的前体数量和产生IFN-3的EBNA 1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患有传染性单核细胞增多症的人的检查，本文提出的研究将提供关于健康儿童以及eBL儿童EBV免疫进化的新信息。公共卫生相关性：伯基特淋巴瘤（BL）是一种常见的儿科癌症。了解BL病因将有助于预防这种侵袭性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EBV相关淋巴瘤（如BL）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.