Effect Ultraviolet Radiation on Latent M. tuberculosis Infection in Guinea Pigs

描述（由申请人提供）：结核病由结核分枝杆菌引起，在包括美国在内的许多国家仍然是一个公共卫生问题，因为它在艾滋病毒感染患者中流行，也因为结核分枝杆菌的多重耐药（MDR）和广泛耐药（XDR）菌株的出现。据估计，世界上三分之一的人口感染了结核分枝杆菌。牛分枝杆菌卡介苗是目前唯一可用于预防结核病的疫苗；然而，卡介苗的疗效在临床试验中变化很大。大多数受感染的个体由于对细菌产生了强大的免疫反应而控制了感染，然而，许多人在其一生中都有残留的杆菌，没有疾病的临床表现。由于某些人的免疫系统受到艾滋病毒感染、营养不良或使用免疫抑制剂的损害，可能在数年后发展为再活动性结核病。流行病学研究清楚地表明，潜伏感染的重新激活是导致结核病高发病率的因素之一。有令人信服的证据表明，紫外线辐射（UVR）会导致人类和实验动物的免疫抑制。我们假设紫外线辐射可能有助于潜伏结核分枝杆菌感染的重新激活。我们之前的研究表明，暴露于UVR会引起免疫抑制，并增加实验性感染的发病机制。这些研究的目的是研究紫外线照射是否会改变低剂量豚鼠肺结核模型中持续感染结核分枝杆菌期间宿主-寄生虫的相互作用。在第一个具体目标中，我们将通过激光捕获显微解剖和实时RT-PCR检测感染豚鼠器官中活菌的数量，肺肉芽肿中细胞因子和趋化因子的反应，以及抗原刺激后的整个脾脏和肺消化细胞，来确定UVR对持续感染的影响。第二个特定目的是通过检测uvr诱导的表皮细胞产生免疫抑制因子mRNA (real-time RT-PCR)，以及从紫外线照射的表皮细胞中获得的培养上清对T细胞和巨噬细胞功能的影响，来阐明紫外线诱导效应的机制。这些研究对于在高度相关的动物模型中理解UVR、免疫抑制和结核分枝杆菌感染再激活之间的相互作用至关重要。此外，该结果将为分枝杆菌在持续和再激活过程中调节生长的宿主因子提供见解，并为设计未来UVR对结核病影响的流行病学研究奠定基础。公共卫生相关性：结核病在许多国家仍然是一个公共卫生问题，因为它在艾滋病毒感染患者中流行，也因为出现了多重耐药（MDR）和广泛耐药（XDR）结核分枝杆菌菌株。潜伏结核的再激活是人类结核病高发病率的因素之一。这些研究的目的是确定一种环境毒素，如每天接触到的来自阳光的紫外线辐射，是否会通过重新激活潜伏感染而导致结核病的高发病率。这些研究将在肺结核的低剂量豚鼠模型中进行，因为这些动物的疾病与人类疾病非常相似。

DESCRIPTION (provided by applicant): Tuberculosis, caused by Mycobacterium tuberculosis, continues to be a public health problem in many countries including the United States because of its prevalence in HIV-infected patients and also due to the emergence of multi-drug resistant (MDR) and extensively drug-resistant (XDR) strains of Mycobacterium tuberculosis. It is estimated that one third of the world's population is infected with M. tuberculosis. M. bovis BCG is the only vaccine currently available for the prevention of tuberculosis; however, the efficacy of BCG vaccine has been highly variable in clinical trials. The majority of the infected individuals control the infection as they develop a robust immune response to the organism, however, many harbor residual bacilli throughout their life with no clinical manifestations of disease. Reactivation tuberculosis may develop years later in some individuals as their immune system is compromised by HIV infection, malnutrition or the use of immunosuppressive agents. It is clear from epidemiological studies that reactivation of latent infection is one of the contributing factors for the high incidence of tuberculosis. There is compelling evidence that ultraviolet radiation (UVR) causes immune suppression in both humans and experimental animals. We hypothesize that UVR might contribute to the reactivation of latent M. tuberculosis infection. Our previous studies indicated that exposure to UVR caused immune suppression and increased pathogenesis in experimental infections. The purpose of these studies is to investigate whether UVR alters the host-parasite interactions during persistent M. tuberculosis infection in the low-dose guinea pig model of pulmonary tuberculosis. In the first specific aim, we will determine the effect of UVR on persistent infection by examining the number of viable bacteria in the organs of infected guinea pigs and the cytokine and chemokine responses in lung granulomas by laser capture microdissection and real-time RT-PCR as well as whole spleen and lung digest cells following antigen stimulation by real time RT-PCR. The second specific aim will elucidate the mechanism of UV-induced effects by examining UVR-induced production of mRNA for immunosuppressive cytokines by epidermal cells (by real-time RT-PCR) and the effect of culture supernatants obtained from UV-irradiated epidermal cells on T cell and macrophage functions. These studies are crucial in understanding the interaction between UVR, immune suppression and reactivation of M. tuberculosis infection in a highly relevant animal model. Moreover, the results will provide insight into the host-factors that regulate mycobacterial growth during persistence and reactivation as well as serve as a basis for designing future epidemiological studies on the effect of UVR on tuberculosis. PUBLIC HEALTH RELEVANCE: Tuberculosis continues to be a public health problem in many countries because of its prevalence in HIV-infected patients and also due to the emergence of multi-drug resistant (MDR) and extensively drug- resistant (XDR) strains of Mycobacterium tuberculosis. Reactivation of latent tuberculosis is one of the contributing factors for the high incidence of tuberculosis in humans. The purpose of these studies is to determine whether an environmental toxin such as ultraviolet radiation from sunlight that is encountered on a daily basis contributes to the high incidence of tuberculosis by reactivating a latent infection. These studies will be addressed in the low-dose guinea pig model of pulmonary tuberculosis as the disease in these animals closely resembles the human disease.