Innate immune responses to malaria liver stage infection

描述（由申请人提供）：疟原虫是疟疾的病原体，每年导致近100万人死亡。它们最初作为子孢子感染肝脏，然后它们在肝细胞内作为肝脏阶段复制以产生引起症状性血液阶段感染的红细胞外裂殖子。这些红细胞前阶段的感染在临床上是沉默的，并被认为不会引起显着的先天免疫应答。然而，我们小组和合作者最近的研究结果表明，红细胞前期阶段在肝脏中诱导明显的先天免疫反应。这些复杂的寄生虫诱导先天免疫应答的机制以及这些应答对寄生虫感染的下游影响仍然不清楚。了解这种真核细胞内病原体的先天免疫反应本身就很重要，但也是理解整个寄生虫免疫产生的杀菌适应性免疫发展的关键缺失部分。因此，我们建议确定哪些先天性免疫反应激活野生型和减毒疟原虫preerythrocytic寄生虫，并确定这些先天性免疫反应如何影响保护性适应性免疫反应。使用基因表达分析和功能测定，我们已经表明，肝脏阶段感染诱导的先天性免疫反应介导的I型和II型干扰素（IFN）信号通路。我们还发现，淋巴细胞在感染后几天内浸润肝脏， 浸润强烈依赖于I型IFN（IFN-1）信号传导。此外，这种先天反应减少了初始感染。这些结果表明IFN-1，淋巴细胞募集，随后的先天性寄生虫消除之间的联系。我们的初步数据还表明，这种IFN-1驱动的先天性应答形成了由整个寄生虫免疫产生的适应性免疫应答。我们用缺乏关键IFN-1信号分子的小鼠证明了这一点，令人惊讶的是，完整寄生虫免疫更好地保护了小鼠。在这个提议中，我们打算进一步描述IFN介导的先天性免疫应答疟原虫肝脏感染的产生和后果。在目标1中，我们将确定宿主-寄生虫的相互作用，启动这种干扰素介导的先天性免疫反应，并确定在肝脏中的细胞类型，响应干扰素。在目标2中，我们将描述感染后肝脏内的细胞特异性反应，并鉴定先天性淋巴细胞浸润所必需的细胞因子和趋化因子受体。此外，我们将评估这些先天细胞消除肝脏阶段寄生虫的细胞机制。最后，在目标3中，我们将研究IFN-1介导的信号传导如何影响整个寄生虫免疫所产生的适应性免疫应答的发展。了解早期先天免疫反应的性质将揭示复杂的真核寄生虫如何参与早期宿主免疫防御。同样重要的是，它还将确定先天分子途径，以靶向改善疫苗接种后的适应性免疫反应，旨在预防疟疾感染。

DESCRIPTION (provided by applicant): Plasmodium species, the etiologic agents of malaria, kill nearly 1 million people annually. They initially infect the liver as sporozoites, then they replicate as liver stages within hepatocytes to generate exoerythrocytic merozoites that initiate symptomatic blood stage infection. These preerythrocytic stages of infection are clinically silent and were thought to not provoke a significant innate immune response. Yet, recent findings from our group and collaborators have shown that preerythrocytic stages induce a pronounced innate immune response in the liver. The mechanisms by which these complex parasites induce an innate immune response and the downstream effects of these responses on parasite infection remain poorly defined. Understanding the innate immune response to this eukaryotic, intracellular pathogen is important in its own right but also a critical missing piece in the puzzl to understand the development of sterilizing adaptive immunity engendered by whole parasite immunizations. Therefore, we propose to identify which innate immune responses are activated by wild-type and attenuated Plasmodium preerythrocytic parasites and to determine how these innate immune responses influence protective adaptive immune responses. Using gene expression analysis and functional assays, we have shown that liver stage infection induces an innate immune response mediated by type I and type II interferon (IFN) signaling pathways. We have also shown that lymphocytes infiltrate the liver within days following infection and that this infiltration is strongly dependent on type I IFN (IFN-1) signaling. Furthermore, this innate response reduces the initial infection. These results indicate a link between IFN-1, lymphocyte recruitment, and subsequent innate parasite elimination. Our preliminary data also shows that this IFN-1 driven innate response shapes the adaptive immune response that is engendered by whole parasite immunizations. This we demonstrate with mice deficient in key IFN-1 signaling molecules, which surprisingly, are better protected by whole parasite immunizations. In this proposal, we intend to further delineate the generation and consequences of an IFN-mediated innate immune response to Plasmodium liver infection. In Aim 1 we will identify the host-parasite interactions that initiate this IFN-mediated innate immune response and identify the cell types in the liver that respond to IFN. In Aim 2 we will characterize cell-specific responses withi the liver following infection and identify cytokine and chemokine receptors that are necessary for innate lymphocyte infiltration. Additionally, we will evaluate the cellular mechanisms by which these innate cells eliminate liver stage parasites. Finally, in Aim 3, we will investigate how IFN-1-mediated signaling influences the development of adaptive immune responses engendered by whole parasite immunizations. Understanding the nature of the early innate immune response will reveal how a complex eukaryotic parasite engages early host immune defenses. Equally important, it will also identify innate molecular pathways to target for improvement of adaptive immune responses after vaccination that aims to protect against malaria infection.