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

描述（由申请人提供）：金黄色葡萄球菌是一种普遍存在的革兰氏阳性菌，与一系列疾病有关；从良性的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，因为SAg是已知的T淋巴细胞最有效的激活剂。某些SAg也可以用作生物武器。因此，从许多角度来看，SAg都很重要。然而，由于缺乏良好的动物模型，SAg参与疾病发病的分子途径尚未完全了解。由于SAg与小鼠MHCⅱ类结合较差，传统小鼠品系对TSS具有抗性。然而，SAg更有效地与人类MHC（称为HLA） I类分子结合。因此，转基因表达HLAⅱ类分子的小鼠容易屈服于通过不同途径传递的SAg的致病作用和金黄色葡萄球菌感染。由于HLAⅱ类（HLA- dr3）转基因小鼠的SAg引起的疾病与人类的综合征非常相似，因此它们是理想的模型。通过该小鼠模型，我们已经证明干扰素- γ (IFN-?)依赖性小肠病理在TSS相关的致死率中起关键作用。然而，INF-¿直接或间接通过其他介质导致TSS致死性的分子途径尚不清楚。因此，我们提出(1)明确IFN-¿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-DR3.IFN-？R+/+和HLA-DR3.IFN-？R - / -小鼠。骨髓嵌合体将受到SEB的挑战，并将比较几种分子途径。然而,干扰素- ?对免疫金黄色葡萄球菌感染也很重要。因此，我们提出(2)确定IFN-？mrsa引起的肺炎和败血症的发病机制和免疫。这将通过在hla - dr3中诱导肺炎和败血症来实现。+/+和HLA-DR3.IFN-？携带MRSA分离物USA300的R-/-小鼠。将比较这两系小鼠的细菌学、免疫学、生化和病理参数，包括死亡率。已知HLA II类多态性可以强烈影响T细胞活化和IFN-？对链球菌SAg的反应。然而，HLA-DR和HLA-DQ多态性对葡萄球菌sag驱动的免疫反应的影响尚未被研究。因此，我们提出(3)确定葡萄球菌超抗原诱导IFN-？HLAⅱ类多态性调节其产生，从而影响mrsa引起的肺炎和败血症的结果。这将通过使用表达HLA-DR2、HLA-DR3、HLA-DR4、HLA-DQ2、HLA-DQ6或HLA-DQ8分子的转基因小鼠进行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-?) dependent small intestinal pathology plays a critical role in lethality associated with TSS. However, the molecular pathways by which INF-¿ 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-¿ plays a lethal role in staphylococcal SAg-induced TSS. This will be achieved by generating bone marrow chimeras between HLA-DR3.IFN-?R+/+ and HLA-DR3.IFN-?R-/- mice. Bone marrow chimeras will be challenged with SEB and several molecular pathways will be compared. However, IFN-? is also important for immunity S. aureus infections. Therefore, it is proposed to (2) Determine the role of IFN-? in the pathogenesis and immunity to MRSA-induced pneumonia and sepsis. This wil be accomplished by inducing pneumonia and sepsis in HLA-DR3.IFN-?+/+ and HLA-DR3.IFN-?R-/- 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-? 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-? 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. PUBLIC HEALTH RELEVANCE: Staphylococcus aureus is a common, yet potentially dangerous bacterium. The occurrence of serious infections caused by the antibiotic resistant strains is increasing worldwide, which could be partly attributed to the ability of these strains t produce several harmful toxins. This study investigates the mechanisms of action of one such family of toxins called "superantigens". Also, the reasons as to why and how certain individuals might have different outcomes following an S. aureus infection will be studied using our humanized mice.