Innate Immunity to Influenza in Caloric Restricted Aged Mice

描述（由申请人提供）：流感及其继发性肺炎是美国65岁及以上人群死亡的第四大原因。与随意喂食（AL）相比，热量限制（CR）延长了健康啮齿动物的中位和最大寿命。老年CR啮齿动物的肿瘤和癌症减少，抗体滴度和T细胞增殖增加，表明CR延缓了与年龄相关的免疫功能下降的发生。我们采用小鼠CR模型来研究流感初级反应的年龄相关性下降。尽管CR延缓了T细胞增殖的年龄相关性下降，但与之形成鲜明对比的是，老年CR小鼠在原发性流感感染后4-6天死亡，表现出肺部病毒滴度增加和肺部NK活性降低。重要的是，CR小鼠在感染时的体重比AL小鼠轻30%，感染后体重急剧下降。由于早期的时间过程，我们假设老龄CR小鼠由于先天免疫改变而无法控制原发性流感感染。这可能反映了NK细胞本身的内在缺陷，也可能继发于巨噬细胞和/或树突状细胞早期产生的信号的外在缺陷。具体而言，我们将：1)确定CR小鼠对原发性流感感染的易感性增强是否与年龄相关。观察幼年AL和CR C57BL/6小鼠感染流感后的存活、体重减轻和恢复情况、肺和纵隔淋巴结细胞类型以及肺病毒滴度。2)研究原发性流感感染期间NK活性降低的机制。我们将通过细胞毒性、穿孔素和颗粒酶的产生、IFN-a/¿体外刺激NK细胞和细胞因子的产生来评估NK细胞的功能。我们将研究NK细胞活性降低是否与NK细胞数量或NK细胞占肺总淋巴细胞的百分比减少有关。我们将进一步确定NK细胞数量或功能的缺陷是否由巨噬细胞/树突状细胞产生的细胞因子对NK细胞的募集和/或激活受损引起。我们将定量测定肺中巨噬细胞和树突状细胞的激活标记物及其细胞因子和趋化因子的产生(IFN-a/¿？白介素IL-15,地震,MIP-1a /害怕,MCP-1,害怕il - 1、il - 6, TNF-a)。3)确定CR小鼠对流感的易感性是否与体重减轻有关，以及感染前再喂养是否能恢复对流感感染的免疫反应。将给感染流感前的CR小鼠喂食AL饲料，使其体重恢复到AL小鼠的50%和100%，并评估特定目标1和2的结果。

DESCRIPTION (provided by applicant): Influenza and its secondary pneumonias are the fourth leading cause of death in persons 65 years and older in the United States. Caloric restriction (CR) extends median and maximal life span in healthy rodents, compared to those fed ad-libitum (AL). Aged CR rodents show decreases in tumors and cancers, and increases in antibody titers and T cell proliferation suggesting CR delays the onset of age-related decreased immune function. We have employed a mouse model of CR to examine the age-related decline in primary response to influenza. Although CR delayed the age-related decline in T cell proliferation, in stark contrast, aged CR mice died 4-6 days after primary influenza infection, exhibiting increased lung virus titers and reduced pulmonary NK activity. Importantly, CR mice weighed 30% less than AL mice at the time of infection and had dramatic weight loss following infection. Due to the early time course, we hypothesize that aged CR mice cannot control primary influenza infection because of altered innate immunity. This may reflect an intrinsic defect in NK cells themselves or may be secondary to an extrinsic defect involving signals produced early on by macrophages and/or dendritic cells. Specifically, we will: 1) Determine if enhanced susceptibility of CR mice to primary influenza infection is age-dependent. Young AL and CR C57BL/6 mice will be infected with influenza and survival, weight loss and recovery, cell types in lung and mediastinal lymph nodes, and lung virus titers will be evaluated. 2) Investigate mechanism(s) for reduced NK activity during primary influenza infection. We will assess NK function by cytotoxicity, perforin and granzyme production, in vitro stimulation of NK cells with IFN-a/¿, and cytokine production. We will investigate whether decreased NK cell activity is related to decreased NK cell number or NK cells as a percentage of total lymphocytes in lung. We will further determine if the defect in NK number or function results from impaired recruitment and/or activation of NK cells by cytokines produced by macrophages/dendritic cells. We will quantitate activation markers on macrophage and dendritic cells in lung and their cytokine and chemokine production (IFN-a/¿?, IL-12, IL-15, IL-18, MIP-1a/¿, MCP-1, IL-1¿, IL-6, TNF-a). 3) Determine if the susceptibility of CR mice to influenza is related to reduced body weight and if refeeding prior to infection restores the immune response to influenza infection. CR mice will be fed AL diets to restore weight to 50% and 100% of AL mice before infection with influenza and outcomes in Specific Aims 1 and 2 will be assessed.