Innate and adaptive immune response to Francisella tularensis

土拉热弗朗西丝菌（Ft）是一种革兰氏阴性细胞内细菌，是土拉菌病的病原体， 被归类为A类病原体，因为它可以通过呼吸道途径在低接种量下感染， 如果不治疗，会导致快速发病和死亡。虽然对人类来说是减毒的，但小鼠通过注射感染或i. p. Ft活疫苗株（LVS）是一种B型毒株，感染兔热病样疾病。在这个周期，我们 报道了Ft LVS在小鼠体内和体外诱导有效的炎症反应。使用Ft LVS 不能从吞噬体中逃脱或不能在鼠巨噬细胞中细胞内复制的突变体，我们 确定了宿主先天免疫系统激活的信号通路。Ft LVS诱导TLR 2- 介导的信号传导;然而，一旦Ft从吞噬体逃逸到胞质溶胶中，就产生IFN-J3， 再利用，炎性小体被激活。尽管有这种强烈的炎症反应， 感染我们的数据表明，Ft LVS启动了强烈的炎症反应，导致发展 的“经典活化”巨噬细胞（CA-M0）;然而，一旦IL-4和IL-13被感染的 巨噬细胞，它们分化成“交替激活”（AA-M0），从而促进细胞内 复制的Ft LVS感染的IL-4 Ra巨噬细胞和STAT 6巨噬细胞不能分化成AA-MO和对照 细胞内复制，而用rIFN-β处理的Ft LV感染的巨噬细胞限制细菌生长。Ft LVS脂多糖（LPS）是一种不良的TLR 4激动剂，不能诱导炎症反应。然而，在这方面， 当小鼠在致死性腹膜内攻击前2天用Ft LVS LPS接种时， 抗体应答由脾B-1a细胞诱导。我们现在将寻求新的方法来控制呼吸道疾病 感染Ft LVS和Schu S4，一种强毒株A型，通过测试的假设，（1）Schu S4，像 Ft LVS，驱动AA-M0逃避宿主反应;（2）干扰AA-M0发育的药物将 增加体内抗微生物应答;和（3）增加Ft LVS LPS疫苗的免疫原性 将保护小鼠免受Ft LVS和Schu S4的呼吸和全身攻击。的主要目标 该建议是基于干扰AA-M0的发展来开发用于兔热症的新疗法， 以及改进对A型和B型毒株都具有保护作用的安全疫苗的开发。

Francisella tularensis (Ft), a Gram negative intracellular bacterium, the etiologic agent of tularemia, and is classified as a Category A agent because it can contracted with low inocula by the respiratory route and causes rapid morbidity and mortality if untreated. While attenuated for humans, mice infected i.n. or i.p. with Ft Live Vaccine Strain (LVS), a type B strain, contract a tularemia-like disease. In this grant cycle, we reported that Ft LVS induces in mice a potent inflammatory response in vivo and in vitro. Using Ft LVS mutants that fail to escape from the phagosome or fail to replicate intracellularly in murine macrophages, we identified the signaling pathways by the host innate immune system is activated. Ft LVS induces TLR2- mediated signaling; however, once Ft escapes from the phagosome into the cytosol, IFN-J3 is produced and reutilized, and the inflammasome activated. Despite this robust inflammatory response, the host succumbs to infection. Our data indicate that Ft LVS initiates a strong inflammatory response leading to development of "classically activated" macrophages (CA-M0); however, once IL-4 and IL-13 are induced by infected macrophages, they differentiate into "alternatively activated" (AA-M0), thereby facilitating intracellular replication. Ft LVS-infected IL-4Ra~'~ and STAT6"'" macrophages fail to differentiate into AA-M0 and control intracellular replication, while Ft LVS-infected macrophages treated with rIFN-p restrict bacterial growth. Ft LVS lipopolysaccharide (LPS), a poor TLR4 agonist, fails to induce an inflammatory response. However, when mice are vaccinated with Ft LVS LPS 2 days prior to lethal i.p. challenge, a protective anti-LPS antibody response is induced by splenic B-1a cells. We will now seek novel ways to control respiratory infection with Ft LVS and Schu S4, a virulent type A strain, by testing the hypotheses that (1) Schu S4, like Ft LVS, drives AA-M0 to evade host responses; (2) agents that interfere with development ofAA-M0 will increase the anti-microbial response in vivo; and, (3) increasing the immunogenicity of a Ft LVS LPS vaccine will protect mice against respiratory and systemic challenge with Ft LVS and Schu S4. The main objective of this proposal is to develop novel therapies for tularemia based on interfering with development of AA-M0, as well as improve development of a safe vaccine(s) that protects against both type A and B strains.