VIRULENCE AND GENOTYPE/PHENOTYPE OF MYCOBACTERIUM AVIUM

鸟分枝杆菌在健康个体中通常是非致病性的 但在艾滋病患者中引起侵入性、传播性感染。我们有 发现三个关键变量影响相互作用的结果 分枝（i）M.鸟; (ii)存在巨噬细胞的并发HIV-I感染;和 (iii)宿主对M. avium和M. 结核来定义这些变量在相互作用中的作用 分枝avium与主机我们提出以下工作： 我们将使用RNA消减杂交程序来鉴定M。 在宿主细胞中生长期间特异性表达的鸟基因 而不是在常规培养基中生长期间。这些实验将 使用流行病学相关的临床和环境M. 基因型上无法区分的禽流感分离株。的基因 将鉴定的克隆，在M.包皮垢，并检查 使用PBMC和巨噬细胞中毒力测定的表型效应。 我们将描述M。禽分离株的基因型和表型 将基因型（特别是基因的存在） 在体外对PBMC和巨噬细胞具有毒力， 以确定M.鸟类仅限于 有限的遗传谱系。 我们将研究不同白细胞群的功能， 不同的细胞因子介导人巨噬细胞对 用强毒和无毒M.鸟株我们将 还确定了细胞因子的产生如何随着HIV-1合并感染而变化， 巨噬细胞与分枝杆菌存在宿主免疫力。 我们将确定M.在体外， 暴露于宿主细胞因子和在巨噬细胞中传代菌株。我们将 也培养环境来源，以确定分布 M.环境中的鸟类和水库- 致病菌株 这些研究将使我们（i）鉴定和克隆M.鸟类基因 与毒力相关;（ii）确定细胞因子的作用， 白细胞群体在宿主防御分枝杆菌中的作用;和（iii） 以确定是否有特定的宿主因子诱导M.鸟 菌株这些研究的累积信息将有助于 分枝杆菌感染合理治疗模式的发展 免疫受损宿主的感染。

Mycobacterium avium is generally nonpathogenic in healthy individuals but causes invasive, disseminated infection in AIDS patients. We have found that three critical variables affect the outcome of the interaction of M. avium with the host's immune system: (i) the strain of M. avium; (ii) the presence of concurrent HIV-I infection of the macrophage; and (iii) the immune status of the host with regard to M. avium and M. tuberculosis. To define the role of these variables in the interaction of M. avium with the host we propose the following work: We will use an RNA subtractive hybridization procedure to identify M. avium gene(s) that are specifically expressed during growth in host cells and not during growth in routine media. These experiments will be performed using epidemiologically related clinical and environmental M. avium isolates that are genotypically indistinguishable. The genes identified will be cloned, expressed in M. smegmatis, and examined for phenotypic effects using assays for virulence in PBMCs and Macrophage. We will characterize M. avium isolates genotypically and phenotypically to correlate genotypes (particularly the presence of the gene(s) identified above) with virulence for PBMCs and Macrophage in vitro and to determine if the virulent strains of M. avium are restricted to a limited set of genetic lineages. We will examine the function of different leukocyte populations and of different cytokines in mediating resistance of human Macrophage to infection in vitro with virulent and avirulent M. avium strains. We will also determine how cytokine production varies with HIV-1 coinfection of Macrophage and with the presence of host immunity to mycobacteria. We will determine if the virulence of M. avium is altered in vitro by exposure to host cytokines and passage of strains in Macrophage. We will also culture environmental sources to determine the distribution of virulent strains of M. avium within the environment and the reservoir of- pathogenic strains. These studies will allow us (i) to identify and clone M. avium genes associated with virulence; (ii) to define the role of cytokines and leukocyte populations in the host defense against mycobacteria; and (iii) to determine if specific host factors induce virulence in M. avium strains. Cumulatively, information from these studies will contribute to the development of rational therapeutic modalities for mycobacterial infections in the immunocompromised host.