Augmentation of Innate Anti-Microbial Immunity by TLR4 Agonists

描述(申请人提供)：大面积烧伤导致保护性皮肤屏障的丧失和抗菌防御机制的失调，从而为烧伤创面的定植和细菌向血液、肺和其他组织的传播创造了理想的条件。虽然局部和全身抗生素是常规使用，但脓毒症是烧伤患者延长住院时间和死亡的最常见原因，这些患者在最初的侮辱中幸存下来。抗药性细菌的流行加剧了败血症的频率和严重程度。因此，需要新的治疗方法来提高严重烧伤患者对感染的抵抗力。我们的研究表明，用Toll样受体4(TLR4)激动剂单磷酰脂A(Mpla)治疗可以有效地提高小鼠对铜绿假单胞菌烧伤创面败血症的天然宿主抵抗力。Mpla毒性低，目前在临床上被广泛用作疫苗佐剂。然而，MLA增强宿主对全身细菌感染的反应的机制尚不清楚，需要进一步的工作将MLA在高危患者中的使用转化为临床环境。该项目的目标是确定TLR4靶向免疫调节剂，如MPLA，提高高危受试者对感染的先天宿主抵抗力的细胞和分子机制。临床前研究将在烧伤创面感染和烧伤后肺炎的大型动物模型中确定MPLA的安全性和有效性。具体目标1：确定Mpla增强天然抗菌功能的细胞机制。这一目标将检验这样一种假设，即Mpla治疗将通过诱导G-CSF介导的骨髓中性粒细胞池扩张和中性粒细胞趋化增强来改善烧伤后对感染的反应。具体目标2：确定MLA增强对感染的抵抗力的细胞内信号变化。这一目标将检验这样的假设，即Mpla处理将导致感染诱导的信号改变，从而导致保护性PI3K和Trif/IRF-3/干扰素途径的优势。具体目标3：在烧伤创面感染和烧伤后肺炎的绵羊模型上，确定MPLA的安全性和有效性。这一目标将检验这样一种假设，即烧伤绵羊对MLA的耐受性良好，并将改善它们对伤口感染和肺炎的反应。这些研究的结果将有助于将TLR4靶向免疫调节剂转化为临床应用，并将通过促进我们对基于TLR的免疫调节剂提高宿主对感染的抵抗力的细胞和分子机制的理解，填补知识的重要空白。

DESCRIPTION (provided by applicant): Large surface area burns cause loss of the protective skin barrier and dysregulation of antimicrobial defense mechanisms resulting in ideal conditions for colonization of burn wounds and dissemination of bacteria into blood, lung and other tissues. Although topical and systemic antibiotics are routinely used, sepsis is the most common cause of prolonged hospitalization and death in burn patients that survive the initial insult. The frequency and severity of sepsis is exacerbated by the increasing prevalence of antibiotic resistant bacteria. Therefore, there is a need for new treatments to improve resistance to infection in severely burned patients. Our studies show that treatment with the toll-like receptor 4 (TLR4) agonist monophosphoryl lipid A (MPLA) is effective in improving innate host resistance to Pseudomonas aeruginosa burn wound sepsis in mice. MPLA has low toxicity and is currently used widely as a vaccine adjuvant in the clinical setting. However, the mechanisms by which MPLA augments the host response to systemic bacterial infections are not well understood and further work is needed to translate the use of MPLA in high risk patients to the clinical setting. The goal of this project is to identify the cellular and molecular mechanisms by which TLR4-targeted immunomodulators, such as MPLA, improve innate host resistance to infection in high risk subjects. Pre-clinical studies will establish the safety and efficacy of MPLA in large animal models of burn wound infection and post-burn pneumonia. Specific Aim 1: To define the cellular mechanisms by which MPLA augments innate antimicrobial functions. This aim will test the hypothesis that treatment with MPLA will improve the response to infection after burn injury by inducing G-CSF-mediated expansion of the bone marrow neutrophil pool and causing augmentation of neutrophil chemotaxis. Specific aim 2: To define intracellular signaling alterations by which MPLA augments resistance to infection. This aim will test the hypothesis that MPLA treatment will cause alterations in infection-induced signaling resulting in predominance of the protective PI3K and Trif/IRF-3/IFN¿ pathways. Specific Aim 3: To determine the safety and efficacy of MPLA in an ovine model of burn wound infection and post-burn pneumonia. This aim will test the hypothesis that MPLA will be well tolerated in burned sheep and will improve their response to wound infection and pneumonia. The results gained in the proposed studies will facilitate the translation of TLR4-targeted immunomodulators into the clinical setting and will fill important gaps in knowledge by advancing our understanding of the cellular and molecular mechanisms by which TLR-based immunomodulators improve host resistance to infections.