HLA class II transgenic mouse models for S. aureus infections and superantigens

描述（由申请方提供）：金黄色葡萄球菌是一种普遍存在的革兰氏阳性微生物，涉及一系列疾病;从良性局部皮肤感染到危及生命的全身性疾病，包括肺炎、败血症和月经或非月经中毒性休克综合征（TSS）。结果表明，该菌的毒力和致病性均较强。金黄色葡萄球菌是由于它的几种外毒素。超抗原外毒素（SAg）是其中重要的，因为SAg是已知的最有效的T淋巴细胞活化剂。某些SAg也可以用作生物武器。因此，SAg从许多角度来看都很重要。然而，由于缺乏良好的动物模型，SAg参与疾病发病机制的分子途径尚未完全了解。常规小鼠品系由于SAg与小鼠II类MHC的结合差而对TSS具有抗性。然而，SAg更有效地结合人类MHC（称为HLA）I类分子。因此，转基因表达HLA II类分子的小鼠容易屈服于通过不同途径递送的SAg的致病作用和S.金黄色葡萄球菌感染。由于SAg在HLA-DR 3转基因小鼠中引起的疾病也与人类的综合征非常相似，因此它们是理想的模型。使用该小鼠模型，我们已经证明干扰素-γ（IFN-γ）依赖性小肠病理在与TSS相关的致死性中起关键作用。然而，INF-γ直接或间接通过其他介质导致TSS致死的分子途径尚不清楚。因此，我们建议：（1）阐明IFN-γ在葡萄球菌SAg诱导的TSS中发挥致死作用的机制。这将通过在HLA-DR 3.IFN-γR+/+和HLA-DR 3.IFN-γR-/-小鼠之间产生骨髓嵌合体来实现。将用SEB挑战骨髓嵌合体，并将比较几种分子途径。然而，IFN-γ对于免疫S也是重要的。金黄色葡萄球菌感染因此，建议（2）确定IFN-γ在MRSA诱导的肺炎和脓毒症的发病机制和免疫中的作用。这将通过用MRSA分离株USA 300在HLA-DR 3.IFN-γ+/+和HLA-DR 3.IFN-γR-/-小鼠中诱导肺炎和脓毒症来实现。将比较这两系小鼠之间的几个细菌学、免疫学、生化和病理学参数，包括死亡率。已知HLA II类多态性可强烈影响响应于链球菌SAg的T细胞活化和IFN-γ产生的幅度。然而，HLA-DR和HLA-DQ多态性对葡萄球菌SAg驱动的免疫应答的影响尚未研究。因此，建议（3）确定葡萄球菌超抗原诱导的IFN-γ产生受HLA II类多态性调节的程度，从而影响MRSA诱导的肺炎和脓毒症的结局。这将通过使用表达HLA-DR 2、HLA-DR 3、HLA-DR 4、HLA-DQ 2、HLA-DQ 6或HLA-DQ 8分子的转基因小鼠的一系列体内研究来研究。

DESCRIPTION (provided by applicant): Staphylococcus aureus is a ubiquitous Gram-positive organism implicated in a spectrum of diseases; from benign, localized skin infections to life-threatening, systemic illnesses including pneumonia, sepsis and menstrual or non-menstrual toxic shock syndromes (TSS). The virulence and pathogenicity of S. aureus is attributed to its several exotoxins. The superantigen exotoxins (SAg) are important amongst them because SAg are the most potent activators of T lymphocytes known. Certain SAg could also be used as biological weapons. Thus, SAg are important from many perspectives. Nonetheless, the molecular pathways by which SAg participate in the disease pathogenesis have not been completely understood due to lack of good animal models. The conventional mouse strains are resistant to TSS due to poor binding of SAg to mouse MHC class II. However, SAg binds more efficiently to human MHC (called HLA) class I molecules. Therefore, mice transgenically expressing HLA class II molecules readily succumb to the pathogenic effects of SAg delivered through different routes and to S. aureus infection. As the disease caused by SAg in HLA class II (HLA-DR3) transgenic mice also closely mimics the syndrome in humans, they are ideal models. Using this mouse model we have demonstrated that interferon-gamma (IFN-γ) dependent small intestinal pathology plays a critical role in lethality associated with TSS. However, the molecular pathways by which INF-γ contributes to lethality in TSS, either directly or indirectly through other mediators, are not clear. Therefore, it is proposed to (1) Delineate th mechanisms by which IFN-γ plays a lethal role in staphylococcal SAg-induced TSS. This will be achieved by generating bone marrow chimeras between HLA-DR3.IFN-γR+/+ and HLA-DR3.IFN-γR-/- mice. Bone marrow chimeras will be challenged with SEB and several molecular pathways will be compared. However, IFN-γ is also important for immunity S. aureus infections. Therefore, it is proposed to (2) Determine the role of IFN-γ in the pathogenesis and immunity to MRSA-induced pneumonia and sepsis. This wil be accomplished by inducing pneumonia and sepsis in HLA-DR3.IFN-γ+/+ and HLA-DR3.IFN-γR-/- mice with the MRSA isolate, USA300. Several bacteriological, immunological, biochemical and pathological parameters including mortality will be compared between these two lines of mice. It is known that HLA class II polymorphisms could strongly influence the magnitude of T cell activation and IFN-γ production in response to streptococcal SAg. However, the impact of HLA-DR and HLA-DQ polymorphisms on staphylococcal SAg-driven immuneresponses has not been investigated. Therefore, it is proposed to (3) Determine the extent to which staphylococcal superantigen-induced IFN-γ production is modulated by HLA class II polymorphisms thereby influencing the outcome of MRSA-induced pneumonia and sepsis. This will be investigated by a series of in vivo studies using transgenic mice expressing HLA-DR2, HLA-DR3, HLA-DR4, HLA-DQ2, HLA-DQ6 or HLA-DQ8 molecules.