Eukaryotic Pathogenesis; Microbial Pathogenesis; Microbiology; Molecular and Cellular Biology
Human African trypanosomiasis (commonly called Sleeping Sickness) is one of the global great neglected diseases, causing ~10,000 cases annually according to most recent estimates (2009). The related veterinary disease of livestock (Nagana) also has significant impact on human economic well being throughout sub-Saharan Africa wherever the insect vector (tsetse flies) are found. Both diseases are caused parasitic protozoa called trypanosomes (Trypanosoma brucei ssp.) Because trypanosomes are eukaryotic cells, organized similarly to every cell in our bodies, treatment of infection is not unlike cancer treatment in that chemotherapy against the parasite has harsh consequences for the patient. However, infection is invariably fatal without intervention, consequently new more specific drugs are desperately needed. In addition, because trypanosomes are an anciently divergent evolutionary lineage, they provide a unique model system for studying basic eukaryotic biology. My laboratory focuses on the cell biology of these protozoa, specifically on intracellular trafficking of lysosomal and cell surface proteins as key aspects of the host:parasite relationship. The trypanosome lifecycle alternates between the mammalian bloodstream and the tsetse midgut, and each stage has a unique protein surface coat that forms the first line of contact with the host. These coat proteins are anchored in membranes by glycosylphosphatidylinositol (GPI) anchors and are essential for survival in each stage. Consequently, correct protein targeting to the cell surface is critical to the success of the parasite. Also, endocytic and lysosomal functions are greatly up-regulated in the pathogenic bloodstream stage for both nutritional and defensive purposes. Using classic and current cell biological and biochemical approaches we work on four distinct areas: 1) GPI-dependent targeting of surface coat proteins; 2) machinery of secretory trafficking; 3) stage-specific lysosomal biogenesis and proteomics; and 4) role of sphingolipids in secretory transport. Our ultimate goal is to define aspects of trypanosomal secretory processes that may provide novel avenues to chemotherapeutic intervention.
Eukaryotic Pathogenesis; Immunology; Infectious Disease; Microbial Pathogenesis; Microbiology; Molecular Basis of Disease; Signal Transduction; Vision science
Toxoplasma gondii is an obligate intracellular parasite that has the unique ability of infecting most nucleated cells in almost all warm-blooded animals. It is one of the most widespread infections in the world: approximately 50 percent of the world‘s population is infected. Luckily, most infected people are asymptomatic; however, in AIDS patients and other immune-compromised individuals, Toxoplasma causes serious and life-threatening disease. Besides its own medical importance, we study Toxoplasma because it represents an ideal model system to study how other related pathogens cause disease. These include Plasmodium, which is the causative agent of malaria that is responsible for millions of deaths worldwide, and Cryptosporidium, which causes another important secondary infection in AIDS patients. Toxoplasma is a great model system because it can easily be grown in vitro, its genome has been sequenced and it can be genetically manipulated. My research team and I are focused on two different but related questions. First, we want to know how the parasite grows inside of its host cell. One of the important things Toxoplasma must do to grow is hijack host cell pathway and factors. We are using functional genomic assays such as microarrays and genome-wide RNA interference (RNAi) screens to identify these host factors. Identifying them is important because if the parasite cannot use these pathways, the parasite will not grow or cause disease. Thus, these pathways represent novel drug targets. As an example, we discovered that oxygen-regulated transcription factors in the host cell are necessary to support parasite growth. We are currently identifying how these transcription factors function and how the parasite adapts to the various oxygen environments it encounters during its lifecycle. Second, we want to know how Toxoplasma affects the central nervous system and how anti-Toxoplasma immune responses function in the central nervous system. These questions are important because Toxoplasma primarily causes disease in the brain and retina. Our work has revealed that when Toxoplasma actively grows in the brain (a condition known as toxoplasmic encephalitis), it causes a massive reorganization of inhibitory synapses. These changes inhibit GABAergic synaptic transmission and this inhibition is a major factor in the onset of seizures in infected individuals. A second line of research using an ocular infection model has focused on defining how immune responses in the central nervous system are generated by Toxoplasma and then resolved once the infection is under control.
Bacterial Pathogenesis; Infectious Disease; Microbial Pathogenesis; Microbiology
My research interests focus on bacterial pathogenesis, emphasizing bacterial biofilms, antimicrobial therapies and vaccine antigens. One major area of my research lab is otitis media (OM) or middle ear disease. Approximately 80 percent of children experience one episode of OM while others have recurrent infections. Chronic OM infection causes hearing impairment leading to developmental problems as these children reach school age. My laboratory has concentrated on two major causes of OM, Moraxella catarrhalis and Streptococcus pneumoniae. Our recent work suggests that M. catarrhalis colonization predisposes patients to colonization with S. pneumoniae in polymicrobial biofilms. The goals of this work are to define biofilm-associated factors and to identify signals that induce bacteria to transition from asymptomatic colonizers to pathogenic organisms leading to OM. Our second major research focus is the identification of novel antimicrobial therapies. Chronic OM is likely a biofilm-associated disease and biofilms are highly antibiotic resistant. Antibiotic resistance is a major problem worldwide and new drug development is both time consuming and extremely expensive. We have demonstrated that photodynamic therapy (PDT), an FDA-approved cancer treatment, is also bactericidal against the three major otopathogens. Thus, the goal of this research is to adapt PDT into a clinically effective treatment for chronic OM. Our third research area involves novel antimicrobial treatments for orthopedic/prosthetic infections. Infections after orthopedic intervention, including knee/hip replacements and insertion of prosthetic devices, are devastating to the patient and these infections will likely increase over the next 20 years. This is particularly relevant to the military where improvised explosive devices cause severe extremity injuries requiring amputation. Antibiotic-resistant biofilms are the primary source of these infections. In collaboration with colleagues at UB, we are testing a novel electrical stimulation method for prevention/eradication of biofilm infections on implant materials. The goals of this research are to define the optimal antimicrobial parameters that are broadly effective against multiple pathogens, including Staphylococcus aureus, Acinetobacter baumannii, Staphylococcus epidermidis and Klebsiella pneumoniae. The members of my research team typically include a combination of graduate students, lab technicians and a junior faculty member. In the summer, I usually mentor medical students or undergraduates who are interested in the fundamentals of basic science and translational research focused on microbial pathogenesis.
Allergy and Immunology; Medical Microbiology; Infectious Disease; Microbiology; Genomics and proteomics; Immunology; Microbial Pathogenesis; Molecular and Cellular Biology; Molecular Basis of Disease; Molecular genetics; Gene Expression; Signal Transduction; Protein Function and Structure; Bacterial Pathogenesis
Research efforts in my laboratory are focused in the fields of immunology and bacterial pathogenesis, two diverse fields of biomedical research for which I have two separate research groups. Projects in both fields are performed by undergraduates, doctoral and master’s degree students, postdoctoral fellows and senior research associates. One major focus of my laboratory is studying the regulation of mucosal immune responses. We investigate the cellular and molecular events by which Type II heat-labile enterotoxins (HLTs), produced by certain strains of Escherichia coli, modulate immune responses. We have demonstrated that LT-Ilia, LT-IIb and LT-IIc, when co-administered with an antigen, have the capacity to enhance antibody and cellular immune responses to that antigen. Using a variety of immunological and cellular technologies, including flow cytometry, fluorescence resonance energy transfer (FRET) detection, cytokine multiplex analysis, mutagenesis, quantitative Reverse Transcription PCR (qRT-PCR), RNA-sequencing (RNA-Seq) and a variety of transgenic mice, we are investigating the mechanisms by which these immunomodulators productively interact with various immunocompetent cells (T cells, B cells, dendritic cells, macrophages) to induce or suppress cytokine production, costimulatory ligand expression and cellular proliferation. A practical outgrowth of these experiments is the potential to engineer novel recombinant vaccines by genetically fusing antigens from different pathogens to the enterotoxins. Recent experiments have shown that these HLT are lethal for triple-negative breast cancer cells, which has opened a new area of oncological research for the lab. A second focus of my laboratory is to investigate the molecular mechanisms by which adherent-invasive Escherichia coli (AIEC) induce, exacerbate or prolong the symptoms of inflammatory bowel disease (IBD) and Crohn’s disease, two acute and chronic inflammatory diseases of the human gut. In vitro, AIEC strains invade into the cytoplasm of several epithelial cell lines. Using recombinant screening methods and RNA-Seq technologies, we are identifying the genes of AIEC that are required to attach and to invade gut cells.
Infectious Disease; Infectious Disease; Microbial Pathogenesis; Vitamins and Trace Nutrient
I care for patients who are hospitalized at Erie County Medical Center where I also serve as the hospital epidemiologist addressing infection control. I teach medical students, residents, and fellows in both hospital and classroom settings. In UB’s schools of medicine and dentistry, I teach a variety of topics including microbiology, pharmacology and toxicology, oral biology, and gastrointestinal systems, host defenses, and global health. I also conduct laboratory research on diarrhea-producing strains of E. coli bacteria. My lab focuses on enteropathogenic Escherichia coli (EPEC), Shiga-toxigenic E. coli (STEC, aka EHEC) and enterotoxigenic E. coli (ETEC). We are working on the role of intestinal host defenses such as nitric oxide and on the immune modulatory effects of adenosine. We have discovered that zinc can directly inhibit the virulence of pathogenic bacteria, and we are working on turning these laboratory findings into treatments. In our work on zinc we collaborate with Michael Duffey, PhD, in the Department of Physiology and Biophysics. Recently we have discovered that zinc can inhibit the development of resistance to antibiotics in Escherichia coli and other bacteria. Zinc does this by its ability to inhibit the SOS response, a bacterial stress response triggered by damage to the bacterial DNA. We are collaborating with Dr. Mark Sutton of Biochemistry to better determine the mechanism of zinc in this regard. I am interested in international medicine and global health and participate in an annual medical mission trip to Honduras, a trip in which student volunteers are encouraged to participate. Closer to home, I am a volunteer physician at Good Neighbors Health Center, a free clinic for the underserved on Jefferson Avenue in Buffalo. Resident physicians are encouraged to volunteer, and students may also be able to arrange clinical experiences. I am Co-Medical Director, with Dr. Ryosuke Osawa, of the Erie County TB Clinic. Learning experiences in my laboratory, in infection prevention and hospital epidemiology, or in international health, may be available for motivated students, residents, and fellows.
Structural Biology; X-ray Crystallography; Microbial Pathogenesis; Microbiology; Protein Function and Structure; Proteins and metalloenzymes
My research program aims to understand how bacteria produce natural products, small molecules that are secreted from the cell to adapt to diverse environments. These molecules allow the bacteria to compete with other microbes or, in the host-pathogen setting, to establish or exacerbate an infection. Natural product biosynthesis may therefore serve as a target for antimicrobial development. My lab uses a variety of techniques to examine these pathways. A core approach is to use X-ray crystallography to determine the molecular structure of proteins that catalyze important steps in natural product biosynthesis. Structural observations are tested and validated using biochemical techniques to examine the catalytic reactions. Finally, molecular and cellular techniques are used to examine biosynthetic gene cluster activity in the cell. These studies will inform efforts to engineer enzymes to produce novel natural product and identify new products of previously uncharacterized pathways. I have a long-standing interest in the Nonribosomal Peptide Synthetases (NRPSs), a family of large, multidomain enzymes that produce important peptide natural products like the antibiotic vancomycin or the anticancer agent bleomycin. NRPSs operate like an assembly line in which the nascent peptide is attached to a carrier domain that shuttles the synthetic intermediates to neighboring catalytic domains. The carrier and catalytic domains are often joined in a single polypeptide that is thousands of residues in length. By examine the crystal structures of large NRPS proteins, we have determined some of the features that enable this fascinating biosynthetic mechanism. Many NRPS products are siderophores, small molecules that bind iron and are required for growth in the pathogenic environment. My lab also studies aerobactin, an NRPS-independent siderophore pathway that is a virulence factor for hypervirulent Klebsiella pneumoniae. We have biochemically and structurally characterized the aerobactin biosynthetic pathway and have developed an approach to find inhibitors of aerobactin biosynthesis that may be tools to probe the pathway chemically to inhibit growth of this human pathogen.
Infectious Disease; Bioinformatics; Microbial Pathogenesis
My clinical interest work focuses on infectious diseases, particularly those caused by Staphylococcus aureus. I practice medicine at the VA Western New York Healthcare System, where I am Chief of the Infectious Disease Section. The service here treats veterans with a wide variety of infectious diseases, including HIV and hepatitis C. I follow both inpatients and outpatients on this clinical service. Medical students, residents, and fellows evaluate and follow infectious disease consultations with me on the inpatient service. I teach extensively in the Medical School, and serve as Vice Chair for Education in the Department of Medicine. I enjoy working with students throughout the full spectrum of medical education, from first-year medical students to senior fellows in Infectious Disease. My research interests dovetail with my clinical work. I study Staphylococcal infections, particularly complications related to S. aureus bloodstream infections. My laboratory uses advanced molecular biology techniques to identify bacterial virulence factors. In collaboration with Steve Gill at the University of Rochester, we are analyzing three years of clinical data on S. aureus bacteremia in the Buffalo area and sequencing hundreds of bacteremia isolates of S. aureus to identify the genomic architectures associated with more severe complications and those associated with poor clinical outcomes. This work makes use of bioinformatics and database design, techniques that support my ongoing collaborations with other investigators on bioinformatics problems, particularly with Moraxella catarrhalis and Haemophilus influenzae. Prior to my studies in S. aureus, I conducted research on a fascinating pathogen, H. influenzae bio group aegyptius and Brazilian Purpuric Fever. Over that 10-year period my laboratory identified a unique epitope on a surface proteins associated with the disease. We were able to create the only isogenic mutant so far described with this pathogen that is highly refractory to genetic manipulation.
Microbial Pathogenesis; Molecular and Cellular Biology; Gene Expression; Regulation of metabolism
The adaptive success of bacteria depends, in part, on the ability to sense and respond to their environment. Metals such as iron and manganese are important nutrients that can often be limiting, and therefore cellular metabolism must be modified to either scavenge the nutrients or use alternative processes that do not require the metal. Bradyrhizobium japonicum belongs to a group of related organisms that form a close or intracellular relationship with eukaryotes in a pathogenic or symbiotic context. This bacterium serves as a model to study related pathogens that are refractive to genetic and biochemical study. Our lab seeks to understand the mechanisms by which cells maintain iron homeostasis at the level of gene expression. We discovered the global transcriptional regulator Irr that controls iron-dependent processes. Irr is stable only under iron limitation, where it positively and negatively controls target genes. We are interested in understanding the mechanism of this conditional stability, how Irr regulates genes, and the functions of numerous genes under its control. Moreover, Irr integrates iron homeostasis with manganese metabolism, providing a link between the two nutrients. Identifying the Irr regulon and iron stimulon has given us important clues into how bacteria traffic iron into and out of the cell. Recent work suggests that B. japonicum not only adapts at the level of gene expression, but can mutate rapidly to accommodate new nutritional sources in the environment.
Eukaryotic Pathogenesis; Gene Expression; Infectious Disease; Microbial Pathogenesis; Microbiology; RNA; Signal Transduction
There are estimated to be over one million species of fungi on the earth, yet very few of these species are capable of causing deadly systemic infections in humans. One of the major limiting factors for most fungi is their inability to grow at mammalian core body temperature. We utilize the fungal pathogen Cryptococcus neoformans var. grubii as a representative fungal pathogen to understand how these few fungi have adapted to growth at mammalian body temperature. C. neoformans is a worthy pathogen, as it is estimated to cause over 500,000 deaths from meningoencephalitis per year, primarily in Africa and Southeast Asia as an HIV/AIDS comorbidity. We use the temperature-limited Cryptococcus amylolentus as a comparator; it is an environmental strain that produces similar virulence factors to C. neoformans and is fully virulent in surrogate invertebrate hosts at permissive temperatures. We have discovered that host temperature adaptation in C. neoformans is accompanied by a reprogramming of gene expression at the level of messenger RNA (mRNA) stability. In response to temperature stress, C. neoformans rapidly degrades mRNAs that encode energy consuming machinery such as ribosomes. At the same time, it prioritizes the translation of stress-responsive mRNAs on existing ribosomes. Because mRNA synthesis and decay are coupled processes, we seek to identify the protein components of mRNA complexes that mediate the specificity of this decay process and posttranslational modifications, such as arginine methylation and phosphorylation, that modify their function. In addition, we are investigating the signaling pathways that accelerate or slow mRNA decay in response to specific environmental stimuli such as host temperature and nutrient deprivation. Finally, mRNA decay not only alters gene expression at the posttranscriptional level, but the degradation of abundant mRNAs during stress releases nucleotide intermediates that can be utilized by the stressed cell to promote genome stability. We are investigating the process of mRNA degradation as well as nucleotide metabolic pathways as drug targets in C. neoformans and other fungal pathogens. Our goal is to define the unique attributes of C. neoformans that confer pathogenicity and to identify potential targets for novel therapeutics. Each of my students has a project that contributes to the overall goals of my research team. Students in my laboratory work independently, though with frequent interaction with me regarding the direction of investigation and interpretation of data. Regular meetings allow us to provide input on each other’s projects. I expect my students to present their work at least once per year at a national or international meeting, and I expect them to do the bulk of the work in writing papers describing their findings for publication.
Eukaryotic Pathogenesis; Gene Expression; Genomics and proteomics; Infectious Disease; Microbial Pathogenesis; Microbiology; Molecular and Cellular Biology; Molecular genetics; Protein Function and Structure; RNA
Trypanosoma brucei is a eukaryotic pathogen that causes human African trypanosomiasis, a disease that is invariably fatal if not treated. Essential and novel processes in this parasite may serve as starting platforms for new chemotherapeutics, which are urgently needed. Our laboratory combines biochemical, genetic, genomic and proteomic approaches toward understanding gene regulation and protein modification in this pathogenic eukaryote. One focus in my laboratory is RNA editing, a novel mechanism for regulating mitochondrial gene expression in which sequence information is added to mRNAs after transcription by specific insertion and deletion of uridine residues. RNA editing is essential for creating translatable open reading frames (ORFs). We are performing functional and biochemical characterization of the large, dynamic RNA-protein complex termed MRB1, which coordinates multiple aspects of the RNA editing process. A second focus is on regulating RNA stability and translational control in T. brucei, which constitute the major methods of gene regulation in this organism. We identified an RNA binding protein, DRBD18, that impacts the stabilities of hundreds of mRNAs. Our data support a model in which posttranslational modification of DRBD18 by arginine methylation acts as a switch to change DRBD18 from an mRNA destabilizer to an mRNA stabilizer by regulating specific protein-protein and protein-RNA interactions. We are testing this model in vitro and in vivo using reporter assays, in vivo protein-RNA cross-linking and protein-protein interaction assays. A third focus is on understanding the mechanisms by which protein arginine methylation modulates trypanosome biology. We performed a global proteomic analysis of the arginine methylome of T. brucei, identifying >1100 methylproteins spanning most cellular compartments and a wide array of functional classes. We are now analyzing novel mechanisms of protein arginine methyltransferase regulation and defining the physiological and molecular functions of arginine methylmarks on selected proteins. I foster a collaborative and flexible laboratory environment, and I encourage my students to explore the research topics that interest them.
Infectious Disease; Infectious Disease; Microbial Pathogenesis
I am an expert in infectious diseases, and I care for hospitalized patients at the Buffalo VA Medical Center (Buffalo VAMC). I have an active, nationally funded translational research program. My research focuses on Gram-negative bacilli (GNB), including Escherichia coli, Acinetobacter baumannii and a new hypervirulent variant of Klebsiella pneumoniae. These GNB cause infection in nearly every nonintestinal site in the body. The hypervirulent variant of K. pneumoniae is both fascinating and worrisome. Unlike its predecessors, it is capable of causing infection in young, healthy hosts and spreading nearly anywhere in the body from the initial infected site, including the eyes and brain. GNB-caused infections result in the loss of billions of health care dollars, millions of work days and hundreds of thousands of lives each year. GNB are becoming increasingly resistant to antibiotics, including strains that have become resistant to all available antibiotics. Unfortunately, there are virtually no new antimicrobial agents active against highly resistant GNB in the pharmaceutical “pipeline.” To address this formidable clinical challenge, my collaborators and I have increased our understanding of the bacterial factors that are critical for these GNB to cause infection. We use this information to develop vaccines that will prevent infection and antibodies that can be used to treat infection. My UB collaborators include Dr. Campagnari (microbiology), Dr. Gulick (structural biology) and Drs. Elkin and Zola (biomedical informatics). My research also involves identifying potential bacterial drug targets; this information will be used to develop new classes of antibiotics. I intermittently have students in my lab, and I participate in a grant designed to encourage medical students to become physician-scientists. I welcome interested students to contact me about conducting research with me. The Buffalo VAMC is the site of my clinical teaching. I teach first- and second-year medical students in lecture settings and small group sessions, including courses in lung respiration, musculoskeletal, renal and microbiology-immunology. Residents attend my grand rounds; I also teach fellows in all aspects of their training and mentor those who perform their research projects in my lab.