Innate immune responses to malaria liver stage infection

描述(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。它们最初以子孢子的形式感染肝脏，然后在肝细胞内以肝期的形式复制，产生红外型裂殖子，从而引发有症状的血液期感染。这些红细胞前阶段的感染在临床上是沉默的，被认为不会引起显著的先天免疫反应。然而，我们团队和合作者最近的发现表明，红细胞前阶段在肝脏中诱导了明显的先天免疫反应。这些复杂的寄生虫诱导先天免疫反应的机制以及这些反应对寄生虫感染的下游影响尚不清楚。了解这种真核细胞内病原体的先天免疫反应本身很重要，但也是理解整个寄生虫免疫所产生的绝育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免疫反应是由野生型和减毒的红细胞前疟原虫激活的，并确定这些先天免疫反应如何影响保护性适应性免疫反应。通过基因表达分析和功能分析，我们发现肝期感染通过I型和II型干扰素信号通路诱导先天免疫反应。我们还表明，淋巴细胞在感染后的几天内渗入肝脏，这 细胞的浸润强烈依赖于I型干扰素信号。此外，这种与生俱来的反应可以减少最初的感染。这些结果表明，干扰素-1、淋巴细胞募集和随后的先天寄生虫清除之间存在联系。我们的初步数据还表明，这种由干扰素-1驱动的先天反应形成了由整个寄生虫免疫产生的适应性免疫反应。我们在缺乏关键的干扰素-1信号分子的小鼠身上证明了这一点，令人惊讶的是，整个寄生虫免疫可以更好地保护这些分子。在这项建议中，我们打算进一步描述干扰素介导的先天性免疫反应对疟原虫肝脏感染的产生和后果。在目标1中，我们将确定启动这种干扰素介导的先天性免疫反应的宿主和寄生虫的相互作用，并确定肝脏中对干扰素做出反应的细胞类型。在目标2中，我们将描述感染后肝脏的细胞特异性反应，并确定天然淋巴细胞渗透所必需的细胞因子和趋化因子受体。此外，我们还将评估这些天然细胞清除肝期寄生虫的细胞机制。最后，在目标3中，我们将研究干扰素-1介导的信号如何影响整个寄生虫免疫所产生的适应性免疫反应的发展。了解早期先天免疫反应的本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，以期在接种疫苗后改善旨在预防疟疾感染的适应性免疫反应。

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.