The Relationship Between the Immune System and the Normal Gut Microflora in Salmonella Typhimurium Infection: A Two Sided Tale

Understanding the role of the microbiota in the development and progression of diseases has received a great deal of attention in recent years. The microbiota is defined as the group of microorganisms, such as bacteria, which normally inhabit the human body. These microorganisms, also known as microflora, are composed of a variety of species of bacteria, each having a different function, and there are some bacteria whose functions remain unknown. Several studies have shown that patients with inflammatory bowel diseases, such as Crohn’s Disease, have a microbiota composition that is different from healthy individuals, suggesting that certain species of bacteria might be important in causing some common gut inflammatory disorders. Dr. Navkiran Gill is investigating how the human immune system regulates the microbiota and how our microbiota may direct our immune responses to various pathogens. Specifically, she is doing a series of experiments involving antibiotic use in specially bred mice infected with Salmonella. The results will provide important information regarding the effect of antibiotics on the microflora, and allow her to correlate changes in our microflora to changes in our ability to mount an immune response against a pathogen such as Salmonella. The results of Dr. Gill’s research will provide information that may be used to design new therapeutics that take into consideration the important role of our microflora.

Elucidating the molecular mechanisms underlying retinoid action in chondrogenesis

Musculoskeletal diseases represent the largest burden to the healthcare system and are major contributors to long-term disability and reduced quality of life. Degenerative joint diseases, such as osteoarthritis, make up the largest proportion of musculoskeletal diseases. Osteoarthritis is characterized by a deficiency of particular cartilage, which results in a loss of joint mobility, pain, deformity and dysfunction. The research being undertaken by Helen Dranse involves characterizing the basic mechanisms that regulate the formation of cartilage, or chondrogenesis, with a particular focus on the role of vitamin A and its metabolites, the retinoids. Retinoic acid (RA) plays an essential role in cartilage formation and related functions by regulating the expression of specific RA receptor (RAR) target genes. However, the mechanisms through which the RA signalling pathway influence chondrogenesis remain poorly understood. Recently, Ms. Dranse and colleagues identified a novel direct RAR target gene. The activation of RAR target genes is controlled to a large extent by RA availability, which is influenced by a number of factors including the CYP26 enzymes. In her current research, Ms. Dranse is examining the distribution of RA in the Cyp26b1-deficient mouse limb, and how this relates to the expression of genes involved in chondrogenesis and the newly identified and other potential RAR target genes. Having gained insight into these processes, Ms. Dranse will attempt to rescue the limb defects observed in Cyp26b1-deficient mice by eliminating the expression of the newly identified RAR target gene in these animals. The information generated from her work will provide much needed insights into the role of RAR-mediated signalling in the regulatory networks that underlie cartilage formation. A better understanding of the molecular processes that regulate chondrogenesis will consequently lead to novel therapeutic targets that enhance cartilage repair and/or regeneration in adults, and assist in the development of treatment strategies for degenerative joint disease.

Mapping phosphorylation pathways to discover host signaling events induced by Salmonella.

Responding and adapting to environmental changes is crucial to the survival of all living organisms, including cells. Cells use signaling cascades to detect stimuli in their environment and respond by altering the expression and turnover of specific genes and proteins. Since many signaling events are regulated by the addition of a phosphate to serine, threonine, or tyrosine residues on proteins within these cascades, identifying and characterizing these modifications is crucial to understanding how signalling pathways function. Until very recently, studying protein phosphorylation has been a slow and laborious process, as existing techniques limited researchers to studying only a few phosphsphorylation sites in isolation. However, the recent emergence of highly sensitive techniques in liquid chromatography-tandem mass spectrometry (LC-MS/MS), has enabled scientists to analyze thousands of phosphorylated proteins simultaneously. Lindsay Roger’s research utilizes LC-MS/MS to analyze thousands of protein phosphorylation events simultaneously in cells infected by Salmonella. Salmonella is an intracellular bacterial pathogen which, in humans, causes gastroenteritis and typhoid fever and is one of the most common and widely distributed food borne illnesses. During infection, Salmonella use a needle like complex to transport bacterial proteins, termed effectors, into host cells where they mimic host proteins and influence signalling. Currently, little is known about the host targets of the majority of Salmonella effectors and how they cause disease. Using these LC-MS/MS experiments, Ms. Rogers’s research is identifying a myriad of novel host targets of these proteins. It is expected that this research will provide a considerable leap in our understanding of how Salmonella infects its host.

Identification of alternative BACE1 and BACE2 substrates and affected pathways in neuroinflammation and Alzheimer's disease

Alzheimer’s disease (AD) is the most common neurodegenerative disease in humans, affecting millions of people worldwide. Currently, there is no cure for AD or treatment that can mitigate the disease process. However, recent research has revealed beta-site amyloid precursor cleaving enzyme 1 (BACE1), as a promising therapeutic target for AD. BACE1 is the protease that cuts Amyloid Precursor Protein (APP) at the beta-site. This cleavage of APP triggers a second cleavage, which releases the Amyloid-beta fragment. Accumulation of Amyloid-beta is believed to initiate the catastrophic cascade of events that lead to the onset of AD. Animal data suggest that BACE1 inhibition prevents Amyloid-beta formation and may be well tolerated, and therefore, BACE1 is considered one of the most promising drug targets for preventing and mitigating AD. However, recent work has revealed that APP is not the only substrate of BACE1. Consequently, drug-targeting strategies will modulate processing of both known and unknown substrates, any one of which may lead to undesirable or deleterious side effects. Therefore, the identification of all BACE1 substrates is necessary to predict and understand side effects of BACE1 inhibitors. Pitter Huesgen is working to identify new substrates and pathways modified by BCAE1 and the related enzyme, BACE2. His results will provide essential information on the complex physiological functions of BACE1 and BACE2 and their roles in the pathogenesis of AD, and help to predict side effects of BACE1 inhibitors, which will ultimately decide if BACE1 inhibition is a viable treatment strategy for AD.

Defining Immune Abnormalities And Their Consequences In The HIV Exposed But Uninfected Child

The primary route of infection for human immunodeficiency virus (HIV), in infants is from mother to child. Following the introduction of ‘Prevention of Mother To Child Transmission’ (PMTCT), programs, HIV infection rates in newborns from mother to child (vertical transmission), have been reduced from 30 percent to less than five percent. As a result, the number of ‘HIV Exposed but Uninfected’ infants (HEU) has steadily risen. In South Africa, where 30 percent of all women of childbearing age are HIV infected, 300,000 HEU births occur per year. Recently, infection and death rates among HEU infants have been determined to be much higher than those in HIV unexposed (UE) infants. Consequently, there is an urgent need to understand why HEU infants are so vulnerable to infections. Briefly, when a person is exposed to an infecting microbe, two major arms of the immune system respond: innate immunity, which keeps the microbe at bay, and adaptive immunity, which eventually clears the infection. While it is now known that alterations in the adaptive immune system of HEU infants do take place, there is little known about how the innate immune system of HEU compared to that of the UE infant. Mr. Brian Reikie, working in collaboration with Stellenbosch University, South Africa, is conducting a pilot study to determine whether exposure to HIV, in the womb or around birth, activates the innate immune system, which then causes damage to the adaptive immune system. As well, he will explore the HIV-innate-adaptive interaction to help explain why HEU infants are so susceptible to infections. Beyond the study of HEU, this will be the first demonstration of how innate immune responsiveness correlates with development of either normal or altered adaptive vaccine immune responses over time. The findings from this project will provide the essential groundwork for urgently needed guidelines for appropriate treatment and clinical follow-up of this vulnerable population.

The role of Apical Junction Complex in airway epithelial repair and differentiation in asthma

Asthma is a serious global health problem, affecting over 300 million people worldwide. The disease is predominantly an inflammatory disorder of the conducting airways, and can be treated or controlled using current therapies. However, un-controlled asthma leads to continual inflammation and damage, resulting in permanent scaring which is termed airway remodeling. Airway remodeling can be defined as changes in the composition, content and organization of cellular and molecular constituents of the conducting airways. One of the structural changes that occurs as a result of airway remodeling is detachment of the cells that line the surface of the airways, called the epithelium. In normal airways, the epithelium forms a barrier against the inhaled external environment which includes aero allergens, viruses and particulate matter, through the formation of apical junction complexes (AJCs). In asthma, part of the abnormal response to inhaled allergens is thought to be due to impaired barrier function caused by damage to the airway epithelium and loss of AJCs. Emerging evidence suggests that AJCs are able to influence other aspects of epithelial function such as release of inflammatory mediators and mechanisms of epithelial repair. Building on earlier work in this area, Dr. Tillie-Louise Hackett’s current research is designed to determine whether AJCs play an important role in normal airway epithelial repair and if the mechanisms involved are altered in asthmatic patients. The results of her research will provide scientists and clinicians with a better understanding of the pathological mechanisms that contribute to multiple respiratory diseases. In addition, Dr. Hackett’s findings will open avenues for the development of new therapeutics to improve the lung health of Canadians living with obstructive lung diseases, such as asthma and Chronic Obstructive Pulmonary Disorder.

Real-time fMRI training of functional connectivity and adaptive self-awareness

Awareness of one’s thoughts and feelings represents one of the highest mental processes in humans. Its dysregulation leads to rumination, which involves repetitively focusing on negative experiences and mental events. Rumination is consistently and strongly related to depression as both a precursor and a symptom, and therefore has important treatment implications. Given the high rates of relapse and treatment dropout in depressed individuals, a need exists for ongoing and immediate feedback in cognitive therapies that could facilitate learning and treatment compliance, and thereby improve clinical outcomes in people with depression. Real-time functional magnetic resonance imaging (fMRI), can add ongoing and immediate feedback to mindfulness-based cognitive therapy to increase its effectiveness. Mindfulness, a relatively successful treatment for depression, is an adaptive moment-to-moment awareness of mental events without controlling or elaborating (i.e. ruminating), and recruits both the anterior prefrontal cortex (PFC), (associated with cognitive and emotional self-awareness and self-regulation), and the anterior insula (associated with awareness of the self in the present moment). Previous studies show that people can successfully use real-time fMRI feedback along with awareness of their thoughts and emotions to modulate activation in the anterior PFC and the anterior insula separately. Melissa Ellamil is using real-time fMRI to examine whether it can help increase a person’s modulation ability over the functional connectivity between their anterior PFC and insular cortex and thereby improve the outcome of the strategies taught in mindfulness-based cognitive therapy. Ms. Ellamil’s research complements ongoing investigations using real-time fMRI to define functions and interactions of various regions of the brain. Her results could fine-tune the real-time fMRI feedback and self-awareness strategies and thereby enhance and prolong the results of cognitive treatments for depression.

Social Attention and Visual Exploration in Children with Autism Spectrum Disorders

Autism is a severe neurological developmental disorder characterized, in part, by social impairment. A key social impairment present early in the development of children with autism is abnormal gaze following. Children with autism often do not follow the eye-gaze of others towards objects or events in the environment, which hampers their development of language and social skills. It may be that the seemingly abnormal gaze following evident in children with autism results from abnormal basic attentional responses to gaze cues. Clinical reports suggest that when in object-rich environments, these children demonstrate a diminished ability to focus on socially meaningful stimuli. Therefore, further research focusing on the ability to orient to gaze cues within complex visual environments such as classrooms, is critical. Adrienne Rombough has developed a computer task that examines orienting responses to gaze cues within complex visual scenes. In her current research she is using this program to examine the ability of children with autism to detect changes in complex visual scenes with or without the presence of gaze cues. Her study is designed to compare the performance of school-aged children with autism to that of mental age-matched, typically developing children. Her short term objective is to address the question of whether (and to what extent), the attention orienting response to gaze cues is abnormal in autism. This is the first known study to use an alternative, indirect measure of attention (i.e. change detection), to investigate gaze cueing within complex visual scenes. Over the longer term, Ms. Rombough’s findings could potentially improve the present understanding of how children with autism use social cues to explore their visual environments and how this skill set is potentially related to social impairment. The project is part of a larger research program designed to characterize the cognitive underpinnings of social impairments in autism.

Defining the Transcription Factors Capable of Forming Pancreatic Beta-Cells from Human Embryonic Stem Cells

In Type 1 diabetes the body’s immune system attacks key cells of the pancreas known as beta-cells. The loss of these cells results in a loss of the protein hormone insulin which is secreted by the beta-cells in response to high blood sugar levels. Recently, advances in the field of pancreatic islet cell transplantation have shown that the replacement of beta-cells represents a possible cure for diabetes. Unfortunately, the poor availability of donor organs to provide the transplantation cell source greatly limits the use of this treatment. One promising possible source of new beta-cells for transplantation is human embryonic stem cells (hESCs,) and a number of researchers have shown that these cells can form pancreatic tissue including beta-cells. Blair Gage is currently exploring how proteins known as transcription factors (TFs), control the formation of beta-cells from hESCs. Specifically, he is investigating whether adding TFs, which help in the formation of beta-cells, and removing the TFs, which block the formation of beta-cells, will help in understanding how to control hESC growth and development. The results of Mr. Gage’s research will enhance ongoing work with industry and the Canadian Stem Cell Network that is focused on stimulating hESCs to form beta-cells for transplantation. The ultimate goals is to apply this technology to the treatment of patients with diabetes in a similar way to that of islet tissue transplantation, using a theoretically limitless supply of beta-cells.

The role of Raf-1 in pancreatic beta cell survival and insulin signaling

While we know that Type 1 diabetes is caused by the destruction of insulin-secreting beta-cells in the pancreatic islets, the processes that regulate beta-cell death remain unclear. This has hindered the development of strategies to halt or prevent the development of diabetes. One possible new treatment, islet transplantation, was initially heralded as a promising therapy for Type 1 diabetes because it removed the need of daily insulin injections. However, the transplanted beta-cells were found to gradually die, which resulted in transplant recipients having to resume the use of insulin injections. In order for islet transplantation to be effective, new approaches to promote islet survival are required. In earlier work, Dr. Gareth Lim’s colleagues identified insulin as a critical pro-survival factor for beta-cells. Their findings suggest that secreted insulin from beta-cells may promote self-survival. However, the mechanisms that lead to the beneficial effects of insulin need to be clarified. Consequently, Gareth Lim is currently investigating the mechanisms by which insulin acts on the beta- cell. Specifically, he is doing a series of experiments to show that the protein Raf-1 kinase, which is activated by insulin and has been shown to have an important role in regulating cell death, is essential for beta-cell survival. The results of his studies will improve our understanding of the mechanisms of beta-cell death. They may also lead to novel therapeutic strategies for preventing beta-cell destruction in Type 1 diabetics and their at-risk relatives. Furthermore, an understanding of the pathways involved in beta-cell survival may also lead to new methods to increase the survival of beta-cells after islet transplantation, thereby increasing the effectiveness of this treatment.