response to phenotypic switch variants to C. neoformans

描述(由申请人提供)：越来越多的证据表明，在慢性新生葡萄球菌感染过程中，微生物微进化作为一种机制发挥了关键作用，使新生葡萄球菌能够逃避宿主的反应，并在慢性感染期间持续存在。我们最近证明，在慢性感染过程中，新生葡萄球菌可以从光滑(SM)菌落变种转换为粘液(MC)菌落变种，并表明这种转换与致死结果有关。同时，我们发现新产生的MC Switch变异体产生一种粘性的囊膜多糖，导致巨噬细胞吞噬功能障碍。MC感染小鼠的肺部炎症反应以巨噬细胞的大量浸润和肺组织的破坏为特征，而SM感染的小鼠肺部则表现为以淋巴细胞为主的有效炎症反应。对开关变异体之间差异表达基因的分析表明，在MC开关变异体中，免疫原性表位下调。与这些发现一致，我们发现缺乏有效的T细胞反应，以及吞噬功能不足和肺泡巨噬细胞过度刺激的证据。在这里，我们将研究表型转换对炎性免疫反应和生存的影响。我们提出了三个具体目标来检验我们的中心假设：1)探讨表型转换影响肺泡巨噬细胞与新生葡萄球菌相互作用的机制。目标2。)以确定病原体中免疫原性表位的下调是否会影响T细胞反应和目标3。)目的：探讨宿主巨噬细胞功能和病原体表位表达对小鼠新生弧菌感染结局的影响。如果我们的假设是正确的，从长远来看，这里提出的工作将具有广泛的意义，因为它将建立对慢性隐球菌病宿主-病原体相互作用动力学的洞察。从长远来看，这应该使我们能够开发新的、选择性的肺保护疗法。

DESCRIPTION (provided by applicant): Increasing evidence points to a critical role of microbial microevolution during chronic C. neoformans infection as a mechanism, which allows C. neoformans to escape host response and persist during chronic infection. We recently demonstrated that C. neoformans can switch from a smooth (SM) to a mucoid (MC) colony variant during chronic infection and showed that this switch is associated with lethal outcome. Simultaneously we showed that the newly generated MC switch variant produces a viscous capsular polysaccharide, which leads to dysfunctional phagocytosis by macrophages. The inflammatory response in the lung of MC infected mice is characterized by intense macrophage infiltration and lung destruction, whereas lungs of SM infected mice exhibit an effective lymphocyte dominated inflammatory response. Analysis of differentially expressed genes between the switch variants demonstrated that an immunogenic epitope is downregulated in the MC switch variant. Consistent with these findings we find a lack of effective T-cell response and evidence for inadequate phagocytosis and overstimulation of alveolar macrophages. Here we will examine the effects of phenotypic switching on the inflammatory immune response and survival. We propose three specific Aims to test our central hypothesis: 1.) To explore mechanisms by which phenotypic switching affects interactions of alveolar macrophages with C. neoformans. Aim 2.) To determine if down regulation of an immunogenic epitope in the pathogen affects T-cell response and Aim 3.) To examine the effects of macrophage function in the host and epitope expression in the pathogen on outcome of C. neoformans infection in mice. If our hypothesis is correct, the work proposed here will have broad significance in the long-term, because it will establish insight into the dynamics of host-pathogen interaction in chronic cryptococcosis. This should in the long-term enable us to develop novel, selective lung-protective therapies.