EIAV Control by High Avidity Rev-Specific CTL Clones

描述(申请人提供)：在确定慢病毒感染的免疫控制机制方面取得了重大进展，显然，病毒特异性CTL和CD4+辅助T淋巴细胞在限制慢病毒复制方面至关重要。然而，T淋巴细胞介导的保护作用的相关性仍不清楚。具体的知识空白包括如何在面对CD4+T淋巴细胞缺乏的情况下诱导和支持保护性CTL反应，CTL必须识别的特定表位来控制慢病毒的复制，以及保护性CTL的质量特征(即功能亲和力)。这项拟议研究的总体目标是描述在CD4+T淋巴细胞缺乏的环境中CTL介导的预防慢病毒感染的要求。正在研究的慢病毒系统是马的EIAV。大多数马在一年内控制了EIAV的复制，并仍然持续感染，没有明显的携带者。在感染SCID的阿拉伯马驹中感染EIAV的结果，以及在EIAV攻击之前SCID马驹中病毒特异性T和B淋巴细胞的免疫重建的结果表明，这种对病毒复制的控制是由病毒特异性免疫反应介导的。由于马的SCID缺陷自然发生在EIAV致病的宿主物种中，这种淋巴细胞缺陷模型系统提供了一个机会，以一种在任何其他慢病毒模型系统中都不存在的严格方式来剖析慢病毒免疫的相关性。特别是，CD8+CTL可以被转移到SCID马驹体内，并在没有CD4+T淋巴细胞的情况下进行评估。本提案中概述的实验将通过过继转移外源IL-2支持的EIAV REV特异性CTL克隆来剖析CTL介导的对SCID马驹的EIAV保护的亲和力要求。CTL克隆将针对REV蛋白的一个高度保守的区域。预计针对该非可变REV表位的高亲和力CTL克隆将在不选择逃逸变异体的情况下具有保护性。相反，在通过转移具有相同特异性的低亲和力CTL克隆后，预计不会产生保护。实现这些目标应该有助于确定在CD4+T淋巴细胞缺乏的环境中针对慢病毒挑战的CTL保护的相关性，包括表位特异性、亲和力和病毒逃逸。从拟议的研究中获得的信息应该对HIV-1免疫治疗和疫苗设计产生影响，在这些领域，这种类型的实验可能更困难。

DESCRIPTION (provided by applicant): Significant progress has been made toward defining the mechanisms of immune control of lentiviral infections, and it is evident that viral specific CTL and CD4+ helper T lymphocytes are critically important in limiting lentiviral replication. However, correlates of T lymphocyte-mediated protection are still not known. Specific knowledge gaps include how to induce and support a protective CTL response in the face of CD4+ T lymphocyte deficiency, the specific epitopes that must be recognized by CTL to control lentivirus replication, and the qualitative characteristics (i.e. functional avidity) of protective CTL. The overall goal of the proposed research is to delineate the requirements of CTL-mediated protection against lentiviral infection in a CD4+ T lymphocyte deficient environment. The lentiviral system under study is EIAV in horses. Most horses control EIAV replication within a year and remain persistently infected unapparent carriers. Results of EIAV infection in Arabian foals affected with SCID, as well as immune reconstitution with viral-specific T and B-lymphocytes in a SCID foal prior to EIAV challenge, indicate that this control of viral replication is mediated by a viral-specific immune response. Since the equine SCID defect occurs naturally in the host species in which EIAV causes disease, this lymphocyte deficient model system provides an opportunity to dissect the correlates of lentiviral immunity in a rigorous way that is unavailable in any other lentiviral model system. In particular, CD8+ CTL can be transferred into SCID foals and evaluated in the absence of CD4+ T lymphocytes. The experiments outlined in this proposal will dissect the avidity requirements for CTL-mediated protection against EIAV in SCID foals by adoptive transfer of EIAV Rev-specific CTL clones supported with exogenous IL-2 administration. The CTL clones will target a highly conserved region of the Rev protein. It is anticipated that a high avidity CTL clone specific for this nonvariable Rev epitope will be protective without selecting for escape variants. In contrast, protection is not expected following adoptive transfer of a low avidity CTL clone with the same specificity. Accomplishing these aims should help define the correlates for CTL protection against a lentivirus challenge in a CD4+ T lymphocyte-deficient environment, in terms of epitope specificity, avidity, and viral escape. The information obtained from the proposed studies should have implications for HIV-1 immunotherapy and vaccine design, where experiments of this type may be more difficult.