Transgenic Animal Models Of Human Immune Defects

Niaid Extramural Activities

Investigators

Linked publications & trials

Abstract

We seek to understand the role of enzyme systems in normal host function and immune defense, specifically the NADPH oxidase. The NADPH oxidase is involved in the generation and control of inflammation, protection from infection, and cell-cell signaling. Understanding these will let us better appreciate how to manipulate the immune system pharmacologically, immunologically, and genetically. We have a complex portfolio involving studying patients, animals, and laboratory specimens. We follow a large number of patients with NADPH oxidase deficiency, chronic granulomatous disease (CGD), and we have been involved in characterizing the infections and complications that they develop. We have also used a mouse created in my laboratory that is deficient in the NADPH oxidase and therefore closely mimics human CGD. Numerous studies in these mice have shown a critical role for this enzyme system in not only protection from infection but also in the magnitude and character of the inflammatory response. This mixed approach to understanding the NADPH oxidase in CGD has been very informative about the role of the innate immune system in both early and late aspects of the inflammatory response. [unreadable] [unreadable] Through the study of patients with CGD we have identified a new bacteria that causes infection in CGD, Granulibacter bethesdensis. Biochemical and genetic studies including full genome sequence show it to be the type strain for a new genus and species. This organism has been injected into animal models of CGD and shown to be a significant pathogen in CGD. We have now identified a total of 4 cases of G. bethesdensis in CGD patients, indicating that this is an important infection in CGD. The frequency of this infection in other populations, including normals, is a topic of active study. We have compared the genome of G. bethesdensis to the recently published genomes of other well-known CGD pathogens, such as Burkholderia and Francisella, and identified genes that appear likely to be associated with virulence in CGD. This conjoined bench and bedside approach to CGD will allow us to identify important aspects of both host and bacterial physiology that will help us treat pateints with CGD better, and to understand inflammation better.[unreadable] [unreadable] Working with neurobiologists we have determined a critical role for the NADPH in the normal neurologic function in mice, specifically in memory. The intact NADPH is critical to normal learning and behavior in mice, and there are subtle differences between the p47 and gp91 deficient animals, suggesting important aspects of genotype and phenotype correlation.[unreadable] [unreadable] We have pursued the genetic and cellular basis of hyper-IgE recurrent infection syndrome (HIES or Job's syndrome), an autosomal dominant disease characterized by extremely elevated IgE, recurrent sino-pulmonary infections, osteopenia, kyphoscoliosis, pulmonary cysts, and dental abnormalities. From clinicla grounds we knew that the gene involved in Job's must be critically important to innate immunity, the early and late host immune responses, skeletal growth and development, and tooth deciduation. Our comprehensive patient evaluation system recruited over 90 candidate families. Through a conjoined transcriptional and in vitro cytokine functional approach we identified the causative gene as STAT3, one of the critical signal transducers in mammalian cells. This discovery lets us now focus on the specific mechanisms of STAT3 immune control and its contribution to immunopathology. We are now creating these mutations in mice to study their permutations and genotype-phenotype correlations.[unreadable] [unreadable] These combined approaches continue to be productive and will lead to better understanding of the pathways of innate immunity and inflammation. We believe that these studies will help us understand several different infections, including fungal infections, at a molecular genetic and functional level.