Intestinal Epithelium - The intestinal epithelium is one of humans major interfaces with the outside world. This interface is very heavily colonized with gram negative bacteria and yet permits absorption of life-sustaining nutrients while protecting the tissues below from microbial onslaught. In addition to serving as a highly selective barrier, the intestinal epithelium regulates immune cells, especially in response to pathogens. Specifically, we have shown that upon detection of ingested pathogens, the intestinal epithelium signals to both innate and adaptive immune cells to provide short and long term protection against the perturbing microbe. My research seeks to understand, at the molecular level, the bacterial-epithelial interactions that regulate such signaling to immune cells. Such bacterial-epithelial interactions are likely germane to both mucosal immunity and inflammatory bowel disease.

TRAIL-induced apoptotic and non-apoptotic signal in cancer cells - The goal of my research is to understand TRAIL-induced apoptotic signal pathways in cancer cells for the development of TRAIL as a cancer therapeutic agent. TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) is normally expressed by natural killer cells and plays a role in immunosurveillance against tumorigenesis. TRAIL is therefore a natural cancer killer and recombinant TRAIL is currently under clinical trials for cancer therapies. The majority of human cancers, however, develop resistant mechanisms through activation of cell survival pathways such as NF-kappaB. TRAIL-induced signaling occurs through its interaction with its death receptors on the cancer cell surface. Recently we have identified the receptor-associated proteins complex and demonstrated that the proteins complex determines TRAIL-induced apoptotic and NF-kappaB signaling. Taking a proteomic approach, we have isolated and identified the proteins in the complex. The proteins identified in the complex include E3 ligases and substrate proteins modified by ubiquitin and SUMO (small ubiquitin-like modifier). Our current efforts therefore focus on (i) the characterization of the E3 ligases-mediated ubiquitination and SUMOylation of the substrate proteins in the complex, (ii) the investigation of how the ubiquitin and SUMO modifications modulate the interaction of the substrate proteins with their binding partners and thus control TRAIL-induced apoptotic and NF-kappaB signaling, and (iii) the development of small molecule inhibitors targeting of the ubiquitin/SUMO modification process. The study will t Read more...

Division of Research and Division of Biotechnology, Center for Transfusion and Cellular Therapies - The primary focus of my laboratories, and indeed the Division of Research within the Center for Transfusion and Cellular Therapies (CTCT) which I direct, is the advancement of safe and effective blood transfusion and related biological therpies worldwide. Within this Division, we have 2 sections - the Section of Basic and Translational Research and the Section of Clincal Research. Within the Section of Basic and Transplational Research, we have 5 major program units each investigating a specific topic via a team approach (see also Roback, Zimring, Logdberg, Waller, Mocarski); each of these has several components. Some of these include: 1) transfusion-transmitted CMV (TT-CMV) including basic and translational research investigations to understand the specific molecular and cellular events required to infect a naive recipient via transfusion or transplantation using novel murine models, 2) adoptive immunotherapy and novel vaccine strategies tested in murine models with a focus on mitigating CMV infection and GVHD in immunocompromised recipients, 3) investigations into the cellular and molecular mechanisms of alloimmunization to RBC antigens and immune mediated RBC destruction using novel murine models, 4) understanding the pathogenetic mechanisms of transfusion-related acute lung injury (TRALI), again via a novel animal model, and 5) stem cell "plasticity" and regenerative medicine, with particular reference to hematopoietic and pancreatic stem cells. Within the Section of Clincal Research, we have 4 main human projects/trials (see also Roback, Josephson, Shaz) including: Read more...

Inflammation/ Hematopathology - Our primary focus is a C-type lectin-family receptor (CD303) expressed uniquely on the surface of human plasmacytoid dendritic cells. Limited data suggest that this receptor may impact function of these cells in innate and adaptive immunity. Specific roles in antigen uptake and antagonism of TLR-mediated stimulation have been proposed. Nonetheless, receptor activities are poorly characterized and natural ligands have not been described. Thus, we have developed unique biochemical tools to better understand structure and fucntion of CD303. We have demonstrated lectin activity and identified interesting binding targets including an important pathogen (non-self) and normal leukocyte subset (self). Specific efforts focus on identifying the specific counter-receptors on these targets and better characterizing the functional impact of counter-receptor engagement. A second project involves deciphering the role of the Bcl-6 interacting transcriptional co-repressor MTA3 in B cell lymphomas, studies done in a collaboration with Dr. P. Wade at the NIEHS.

Immunology - In mammals, T cells mature in the thymus. Stem cells with the potential to develop into multiple cell lineages migrate to the thymus from the bone marrow. In the thymus, these precursors diverge into ab and gd T cell lineages, and those in the ab lineage eventually become cells that express both the CD4 and CD8 coreceptors, as well as the ab T cell receptor (TCR). Cells at this stage are called "double positive" thymocytes because of the dual expression of the CD4 and CD8 coreceptors. It is at the double positive stage that cells audition for the right to become part of the mature T cell repertoire. Cells that bear a TCR that confers high reactivity to self peptide/MHC complexes will die by apoptosis, and cells that do not react at all with self peptide/MHC will also die after a few days. Only those cells that have a low reactivity to self peptide/MHC complexes will mature into CD4 or CD8 T cells and leave the thymus to seed the peripheral lymphoid organs.

Research in our lab seeks to understand the molecular mechanisms of these developmental processes and can be divided into three main areas. 1) We are examining how the early growth response (Egr) family of zinc finger transcription factors regulates thymocyte development. These factors can be induced by low-level TCR signals at the double positive stage, as well as other signals earlier in thymocyte development. These factors regulate the growth, lifespan, and differentiation of thymocytes at different stages of development. 2) We are interested in how molecular signals from the TCR can inform a double posit Read more...

Reactive Oxygen Species (ROS) - Studies focus on reactive oxygen species (ROS) such as superoxide and hydrogen peroxide, and their biological roles, for example, in innate immunity, mitogenic growth, apoptosis, angiogenesis, and biosynthesis/ remodelling of extracellualr matrix. Starting in 1999, we described a new family of ROS-generating enzymes, the Nox/Duox family. This group of enzymes catalyzes the regulated generation of superoxide in response to signals including hormones, growth factors and immune mediators. The enzymology and regulation of ROS generation by the Nox enzymes and their regulatory proteins is an active area of investigation in our group. The biological function of these enzymes is being investigate in various model systems including cell culture, Drosophila melanogaster, C. elegans and mouse. In addition, the function of these enzymes in pathological conditions including cancer and atherosclerosis, and in normal aging is under active investigation. These enzymes now provide novel targets for development of anti-cancer and anti-arteriosclerotic drugs, which are currently under development by our group. These are predicted to be useful in the treatment and prevention of hypertension, atherosclerosis, and certain forms of cancer. The laboratory uses multi-disciplinary approaches ranging from enzymology and biochemistry to cell biology to animal models.

Mitochondrial DNA replication in disease: AIDS, congestive heart failure, hepatitis, renal failure - One classic biological teaching is that mitochondria are the "powerhouses of the cell", particularly in tissues that require significant energy, like heart, liver and muscle. The focus of the Lewis lab is the diverse effects of toxins on mitochondria structure and function. The primary focus is the untoward mitochondrial effects of a class of drugs called nucleoside reverse transcriptase inhibitors (NRTI) used to treat HIV infection, that are known to inhibit mitochondrial (mt-) DNA replication in vitro. These drugs are toxic to various tissues including heart, skeletal muscle, liver and kidney. Our overall goals are to (1) define the molecular mechanisms of how NRTIs change the abundance of precursors for mtDNA replication in vivo (2) define the effects of active NRTI triphosphates on the mitochondrial replicon in vivo (3) define the effects of specific polymerase mutants on the replication of mtDNA in vivo and (4) define the effects of the mtDNA template itself on its replication in vivo. The approach taken employs tissue specific targeting of genes involved in the processes and evaluation of structural and functional defects that result using state of the art biochemical, molecular, physiological, and pathological approaches. Conditional, tissue specific targeting also is addressed. The direct clinical benefits of these studies are twofold (1) the toxicity of important compounds is defined so that better therapeutics can be designed and administered and (2) mechanisms of organ specific changes in HIV disease and related illnesses are elucidated.

Replication and Pathogenesis of influenza A virus and arenaviruses - My lab is interested in studying the replication and pathogenesis of human viral pathogens, mainly influenza A virus and arenaviruses. (1) Influenza virus (flu) is a major global human pathogen that causes annual epidemic infection and the occasional more widespread and deadly pandemics. Influenza viral genomes are composed of eight different viral RNAs, each encoding one or two viral genes in a negative sense orientation. How these viral RNAs are incorporated into a single viral particle is not fully understood. We are currently characterizing the RNA elements required for efficient packaging of each viral RNA molecule, and the potential roles of RNA-RNA and RNA-protein interactions in viral packaging. In addition, we are interested in studying the virus-host interactions and the roles of host factors and signaling pathways in viral replication. (2) Arenaviruses such as Lassa fever virus (LASV) can cause hemorrhagic fevers in humans and can potentially be employed as biological agents. The necessity of high-level containment restriction to work with this virus (in BSL-4 laboratory) and the costly expenses of using non-human primates for LASV studies significantly hinder progress in understanding the disease pathogenesis. Guinea pig infected by a related arenavirus Pichinde (PICV) represents a safe, convenient, and economical small animal model for Lassa fever. A spleen-passaged PICV causes Lassa fever-like symptoms that are limited to guinea pigs. We are currently studying the replication and pathogenesis of PICV in cell culture and in guinea pigs, which will shed l Read more...

Lipocalins: Probing the Mechanisms of Allergy - This project aims to identify molecular properties of allergens responsible for their intrinsic allergenicity by focusing on the set of structurally and functionally homologous proteins of the lipocalin family that comprise the major mammalian respiratory allergens. We hypothesized that conserved molecular motifs in these lipocalins, via non-IgE interactions with the innate immune system, promote IgE-dependent allergy. In support, we recently demonstrated the presence of inducible lipocalin receptors on mast cells. This suggests roles for direct mast cell-lipocalin interactions (a) in the development and maintenance of the hypersensitive phenotype of allergy patients (xenogeneic lipocalins) and (b) in normal mast cell physiology (endogenous lipocalins), to be delineated by our ongoing investigations.