Mechanisms of Immune Memory Regulation by PD-1

描述（由申请人提供）：了解免疫记忆是如何形成的，对于我们设计针对各种传染病和癌症的有效疫苗的能力至关重要。我们已经表明，免疫记忆的定量和定性性质是在感染或免疫后早期决定的，抗原的持续时间是一个关键的决定因素。我们还发现了新的细胞表面标记物，可以成功地预测T细胞扩增初始阶段的记忆结果。此外，使用这些细胞表面标记物来区分记忆宿命细胞，我们发现效应分化程度与记忆电位呈负相关。我们的研究涉及记忆宿命效应细胞和终末分化效应细胞的全基因组微阵列比较，有趣的是，记忆宿命效应细胞在其表面表达更高水平的抑制受体，程序性死亡-1 （PD-1）。这一观察结果促使我们假设PD-1对记忆宿命的CD8 T细胞施加抑制，以防止过度刺激并促进记忆分化。由于PD-1在CD4 T细胞、CD8 T细胞、B细胞、单核细胞、树突状细胞等细胞上广泛表达，我们产生了CD8 T细胞特异性PD-1敲除小鼠，专门研究PD-1信号传导在CD8 T细胞记忆反应中的作用。在混合嵌合体环境中，野生型（WT）和PD-1敲除（KO） CD8 T细胞存在于同一只WT小鼠中，我们发现PD-1 KO CD8 T细胞在急性病毒感染后扩增并分化为与WT CD8 T细胞相似的效应细胞。然而，它们的生存潜力存在显著差异——PD-1 KO CD8 T细胞在病原体清除后死亡更严重，与WT CD8 T细胞相比，PD-1 KO CD8 T细胞产生的记忆库最小。这个非常专注的R03提案的目标有两个：目标1：确定PD-1信号何时起调节记忆细胞存活的作用。将采用全基因组转录组分析和抗体阻断相结合的方法来确定PD-1信号在急性感染期间调节免疫记忆寿命的时间和来源。目的2：确定PD-1信号如何促进记忆细胞的寿命。在这个特定的目的，PD-1的表达对细胞因子信号转导对T细胞增殖的抑制作用将被评估

DESCRIPTION (provided by applicant): Understanding how immunological memory is formed is central to our ability to design efficacious vaccines against a variety of infectious diseases ad cancer. We have shown that quantitative and qualitative properties of immunologic memory are decided early after infection or immunization, and that the duration of antigen is a key determinant. We also identified novel cell surface markers that can successfully predict memory outcome during initial stages of T cell expansion. Moreover, using these cell surface markers to distinguish memory- fated cells, we found that the extent of effector differentiation correlates negatively with memory potential. Our studies involving genome-wide microarray comparisons of memory-fated and terminally differentiated effector cells intriguingly revealed that memory-fated effectors expressed higher levels of inhibitory receptor, programmed death-1 (PD-1) on their surface. This observation prompted us to hypothesize that PD-1 exerts brakes on memory-fated CD8 T cells to prevent overstimulation and promote memory differentiation. Because PD-1 is expressed widely on CD4 T cells, CD8 T cells, B cells, monocytes, dendritic cells, etc., we generated CD8 T cell-specific PD-1 knockout mice, to specifically address the role of PD-1 signaling in CD8 T cell memory responses. In a mixed chimera setting where wild-type (WT) and PD-1 knockout (KO) CD8 T cells were present in the same WT mouse, we found that PD-1 KO CD8 T cells expanded and differentiated into effector cells similar to WT CD8 T cells following an acute viral infection. However, there was a dramatic difference in their survival potential - PD-1 KO CD8 T cells underwent greater death after pathogen clearance and minimal memory reservoirs were generated from PD-1 KO CD8 T cells compared to WT CD8 T cells. The goal of this very focused R03 proposal is two-fold - Aim 1: To determine when PD-1 signals function to regulate memory cell survival. A combination of genome-wide transcriptome analyses and antibody blockade will be employed to determine the timing and source of PD-1 signals in regulating longevity of immune memory during acute infections. Aim 2: To determine how PD-1 signals promote longevity of memory cells. In this specific aim, inhibitory effects of PD-1 expression on T cell proliferation vis a vis cytokine signal transduction will be evaluated to understand whether inhibitory PD-1 signals exert "brakes" on T cell stimulation and proliferation to promote memory longevity. While the role of PD-1 in regulating immunopathology in chronic infections is well established, its function in acute infections is not known. When completed, these studies will represent a major step forward in our understanding of factors regulating longevity of immunologic memory, and will crack open the field of PD-1 signaling as a novel research area for vaccine design, which we hope to pursue under the auspice of a follow-up R01 proposal. PHS 398/2590 (Rev. 06/09) Page Continuation Format Page