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

描述(申请人提供)：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；从良性的局部皮肤感染到危及生命的全身疾病，包括肺炎、败血症和经期或非经期中毒性休克综合征(TSS)。金黄色葡萄球菌的毒力和致病性归因于其几种外毒素。超抗原外毒素(SAG)是其中重要的一种，因为SAG是已知的最有效的T淋巴细胞激活剂。某些SAG也可以用作生物武器。因此，从多个角度来看，SAG都很重要。然而，由于缺乏良好的动物模型，SAG参与该病发病的分子途径尚不完全清楚。由于SAG与小鼠MHC II类分子结合较差，常规小鼠株对TSS具有抗药性。然而，SAG能更有效地与人MHC I类分子结合。因此，转基因表达HLAII类分子的小鼠很容易屈服于SAG通过不同途径传递的致病作用和金黄色葡萄球菌感染。由于SAG在人类白细胞抗原II类(HL A-DR3)转基因小鼠体内引起的疾病也与人类相似，是理想的动物模型。利用这个小鼠模型，我们已经证明了依赖干扰素-γ的小肠病理在与TSS相关的致死性中起着关键作用。然而，干扰素-γ直接或通过其他介导物间接促进TSS致死的分子途径尚不清楚。因此，建议(1)阐明干扰素-γ在葡萄球菌SAG诱导的TSS中起致死作用的机制。这将通过在人类白细胞抗原-DR3、干扰素-γR+/+和人类白细胞抗原-DR3、干扰素-γR-/-小鼠之间产生骨髓嵌合体来实现。骨髓嵌合体将被SEB挑战，并将比较几种分子途径。然而，干扰素-γ对金黄色葡萄球菌的免疫感染也很重要。因此，我们建议(2)确定干扰素-γ在耐甲氧西林金黄色葡萄球菌肺炎和败血症的发病机制和免疫中的作用。这将通过诱导人类白细胞抗原-DR3、干扰素-γ+/+和人类白细胞抗原-DR3、干扰素-γR-/-小鼠的肺炎和败血症来实现。我们将在这两个品系的小鼠之间比较一些细菌学、免疫学、生化和病理学参数，包括死亡率。已知，人类白细胞抗原II类基因的多态可以强烈影响T细胞的活化和干扰素-γ的产生。然而，人类白细胞抗原-DR和人类白细胞抗原-DQ基因多态性对葡萄球菌SAG诱导的免疫应答的影响尚未被研究。因此，有人建议(3)确定葡萄球菌超抗原诱导的干扰素-γ的产生在多大程度上受到HLAII类基因多态性的调节，从而影响MRSA诱导的肺炎和脓毒症的结局。这将通过一系列体内研究来进行，这些转基因小鼠表达了人类白细胞抗原DR2、人类白细胞抗原DR3、人类白细胞抗原DR4、人类白细胞抗原DQ2、人类白细胞抗原DQ6或人类白细胞抗原DQ8分子。

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.