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<h1>Autoimmune diseases</h1>
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<p>Autoimmune disease are a range of disorders that result from attack of self-tissues by a dysregulated immune system. Examples are multiple sclerosis, Crohn's disease and type I diabetes. There are significant global inequalities in the treatment and prevalence of autoimmune disorders. 80% of diagnoses of autoimmune epilepsy are in the developing world. This is caused by the production of antibodies against proteins in the brain such as GABA receptors. However, it should be noted that prevalence of autoimmune diseases is greater in Europe and the USA. This is explained by the hygiene hypothesis which suggests that a lack of exposure to microorganisms, both pathogenic and symbiotic, prevents normal development of the immune system. <br> <br>
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T helper (Th) cells produce immune responses and T regulatory (Treg) cells control the populations of Th cells. When Treg cell populations are low they are unable to stop excessive growth of helper cell populations. Th cells will produce superfluous inflammatory molecules that spread. This is the cellular basis of autoimmune disease. <br> <br>
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We have focused on autoimmune diseases in developing countries where bacteria, such as segmented filamentous bacteria (SFB) are prevalent and typically found within water sources. SFB are gram positive bacteria that are tightly bound to the lining of the gut epithelia and have recently been implicated in modifying host immune responses by promoting the development of lymphocytes and the growth of Th17 populations. An additional effect of the signals required for Th17 differentiation is the inhibition of the production of Treg cells. Once fully differentiated, Th17 cells produce interleukin 17a (IL-17a) a proinflammatory cytokine. Elevated levels of IL-17a are associated with MS and the development of epilepsy and other autoimmune diseases. <br> <br> </p>
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                    <h1 class="header-text2">Background</h1>
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<h1>Current treatments</h1>
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            <h2>Autoimmune Disease</h2>
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            <p class="lead">Autoimmune diseases encompass a range of disorders that result from the attack of self-tissues by a dysregulated immune system. More than 80 autoimmune diseases have been characterised, each with long-term effects on health, quality of life and cost to healthcare services. These include Crohn’s disease, Coeliac disease, type 1 diabetes, multiple sclerosis, systemic lupus erythematosus and rheumatic disease.</p>
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<p>Current treatments for autoimmune diseases are limited and act only to control the symptoms and do not attempt to cure the individual. Non- steroidal anti- inflammatory drugs (NSAIDs), such as ibuprofen, are the most commonly prescribed and reduce inflammation and accompanying symptoms. NSAIDs work to block the activity of cyclooxygenase enzymes which, in turn, halts the production of pro- inflammatory prostaglandins. However, there are a number of side effects associated with long- term use of NSAIDs, namely, dizziness, drowsiness and an increased risk of developing stomach ulcers. In addition, their use is restricted due to their tendency to react unpredictably with other common drugs.<br> <br>
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            <h2>Global Burden of IBD</h2>
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            <p class="lead">Inflammatory Bowel Disease (IBD) is a heterogeneous group of autoimmune disorders encompassing Crohn’s disease and Ulcerative Colitis. It is estimated to affect 0.3% of the population in industrialised nations, with over 5 million patients worldwide.</p>
  
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Another common treatment is immunosuppressive drugs such as corticosteroids. These act to reduce expression of genes associated with an increase in inflammation, via the recruitment of histone deacetylases. These treatments are either inhaled, applied topically or ingested in tablet form. Prolonged use of this class of drugs and the consequent excessive exposure to cortisol can lead to the development of Cushing’ syndrome, which is characterised by high blood pressure, abdominal obesity and weak bones. In addition, immunosuppressive drugs can lead to excessive downregulation of the immune system.
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<p>The global prevalence of IBD is increasing rapidly as countries become more developed. In addition, instances of IBD in developing countries are thought to be accelerated by the presence of bacteria, such as segmented filamentous bacteria (SFB), in water sources influencing the gut microbiome and host immune response. Gram-positive SFB have recently been implicated in promoting the development of lymphocytes and the growth of Th17 populations.</p>
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Despite the widespread use of the aforementioned drugs in the treatment of autoimmune diseases it is clear that there are a number of undesirable side effects. Also, unlike our treatment, currently available drugs do not respond to the current state of the immune system and this can result in unrestricted dampening of immune response. <br> <br>
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Current treatments for immunodeficiency are varied in their effects and success. One possible cure for immunodeficiency is a stem cell transplant. Stem cells are extracted from the bone marrow of the patient or of an appropriate donor with the same human leukocyte antigens as the patient. However, there are a number of risks associated with a stem cell transplant as any functional immune cells are removed prior to the transplant, via chemotherapy or radiotherapy, which leaves the patient highly susceptible to infection. Also, the transplant process is lengthy, with a total recovery time of around one to two years. This treatment is often unsuccessful, typically due to rejection of the donor cells. <br> <br>
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<p>An additional effect of the signals required for Th17 differentiation is the inhibition of the production of Treg cells. Once fully differentiated, Th17 cells produce interleukin 17a (IL-17a) a proinflammatory cytokine. Elevated levels of IL-17a are associated with MS and the development of epilepsy and other autoimmune diseases.</p>
  
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In cases where a stem cell transplant is not possible, there are treatments directed at improving the function of the immune system. For example, immunoglobulin therapy is used to boost levels of antibodies. Gamma interferon therapy is used to boost interferon levels, which in turn act to stimulate the immune system. In addition, treatments using growth factors can be used to boost the size of the population of white blood cells. There are also a number of preventative measures such as the regular use of antibiotics, non- live vaccines and antivirals, which are used to manage exposure to infection. </p>
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<p>Most diagnoses occur between the ages of 20 and 30; the disease presents a significant burden to patients, societies, and healthcare systems. Current treatment is focused on symptom management, frequently resulting in sub-optimal control despite the burden of long-term treatment. Common therapeutics, such as corticosteroids, require regular administration, have many side-effects and are less accessible in the developing world. The aim of our project is to address these problems and meet the notable, yet currently unmet, need for curative treatments for autoimmune diseases. This will be achieved via regulation of Treg and T helper cell populations to ensure immune responses of the correct magnitude. The specific control mechanism is discussed below.</p>
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<h1>Our solution</h1>
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            <h2>Immune Cell Populations</h2>
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            <p class="lead">T helper cells (Th) are a component of the adaptive immune systems and are characterised by the presence of the CD4 protein on the cell surface. CD4+ cells are able to interact selectively with major histocompatibility complex 2 on the surface of antigen presenting cells such as macrophages and dendritic cells. These interactions facilitate the release of small proteins known as cytokines and so Th cells contribute to varying the activity of other cell types. More specifically, Th cells are required for the maturation of B cells to upregulate production of antibodies and the proliferation of cytotoxic T cells, which degrade cancerous or infected body cells. Our project focuses on the detection of a particular subset of T helper cells namely, Th17 cells. Th17 cells produce interleukin- 17 (IL-17) and have a proinflammatory function, as well as regulating the production of neutrophils. Incorrect functioning of these cells is associated with the development of autoimmune diseases. Overactivation of Th17 populations that are responsive to self-antigens causes the accumulation of antigen-antibody complexes, leading to type III hypersensitivity. This causes an inflammatory response and is associated with autoimmune diseases such as lupus and arthritis.</p>
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<p>Th17 cells are also closely associated with Treg cells as the chemicals required for Th17 differentiation and maturation are inhibitory with regard to this process for Treg cells. At low concentrations TGFβ associates with IL-6 and IL-21 to promotes Th17 differentiation; however, when TGFβ is at high concentrations, Treg differentiation is favoured as the production of IL-23 is repressed.</p>
  
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<p>Bacteria can’t detect the regulatory proteins due to their size and impermeability to the bacterial cell membrane, so we used two small molecules: adenosine and nitric oxide (NO). The concentrations of these are representative of the populations of T-reg cells and Th cells respectively. An imbalance in the levels correlates with the autoimmune response. We aim to restore these to healthy proportions by secreting Interleukin 10 (IL-10) - a signal protein which stimulates cell differentiation into T-reg cells. <br> <br>
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<p>In contrast to T helper cells, natural T regulatory cells (Tregs) are characterised by the presence of both the CD4 receptor and CD25. The role of Tregs is the suppression of the action of helper and cytotoxic T cells, for example, by blocking the production of cytokines. They also suppress B cell and dendritic cell function, for example, via the production of inflammatory cytokines. The immunosuppressive role of Tregs is important in regulating the activity of the Th cells and to prevent excessive inflammation and help to reduce self- reactivity, thereby limiting the development of autoimmune diseases. </p>
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Our bacteria produce personalised and easily administered doses of IL-10. This avoids impracticalities of current, injection based techniques. The gut has greater ease of introduction to the body over other sites of T-cell populations and no biological barriers need to be crossed for the E. coli to reach their target. Our focus is on autoimmune diseases in developing countries triggered by ingested pathogenic bacteria. In these cases the disease starts in the gut making it the obvious place for us to target. We propose the cultures could be ingested using a live yoghurt or tablet, this avoids the training needed for injections and the risk of infection. <br> <br>
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            <h2>Pathogenesis</h2>
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            <p class="lead">Immunodeficiency is a state where the immune system is unable to fight against infection due to a lack of, or suppression of cells of the innate or adaptive immune responses. Immunodeficiency can be either primary or secondary in nature. Primary immunodeficiency is the result of genetic mutations that lead to reduced immune responses. This is further categorised into B cell and T cell immunodeficiencies, severe combined immunodeficiency, complement defects and phagocyte disorders. Secondary cases are caused by environmental factors or diseases that induce weakening of the immune system.</p>
  
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NO is thought to be produced by Th cells as a signal to induce differentiation of cells into Th cells and control the populations of Th and Treg cells. Continuous production of NO makes it a suitable marker of the size of the population and severity of the autoimmune disease. <br> <br>
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<p>A reduction in the population size of Th cells, as a method to counteract autoimmune diseases, increases the risk of development of immunodeficiency as a depleted population of Th cells will be unable to resist infection as successfully. Preventing the development of immunodeficiency is of particular importance in regions with poor sanitation where exposure to infection is more common.</p>
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<p>To prevent the development of immunodeficiency in individuals that use our treatment, we have created a system that responds to two input values. Upon detection of the size of Th17 and Treg cell populations, the system responds to ensure optimum population sizes. If one cell population exceeds optimum levels, there is a response to restrict a further increase, preventing uncontrollable growth. This mechanism prevents both autoimmune disease and immunodeficiency by maintaining optimum population sizes for both cell types.
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A range of purines are used by Treg cells as immune signals. ATP is released from cells during stress or injury and acts on almost all immune cells. To prevent it from causing excessive inflammation, ATP is rapidly metabolised into AMP then into Adenosine (Ado) by Treg cell surface enzymes. Ado is detected by GPCRs of Th cells, this triggers increased cAMP in the cells. Inflammatory signals are inhibited and IL10 production is enhanced in mature dendritic cells. Ado also induces semi-maturation of immature dendritic cells. Adenosine promotes Treg populations, adenosine generation and increases immunoregulatory activity. Production by Treg cells and its role in regulating T cell populations and IL10 production make it a suitable marker of Treg population size and degree of immunodeficiency. <br> <br>
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In our circuit IL-10 is secreted in the presence of NO and absence of elevated adenosine levels. IL-10 expression is stimulated by the endogenous E. coli SoxR transcription factor, activated by free radicals and oxidative stress, while expression is inhibited in response to adenosine by means of a riboswitch controlled sRNA which will selectively prevent ribosome binding to IL-10 mRNA and thus protein synthesis. <br> <br>
 
  
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We decided to use NO partly because of the Stanford 2009 iGEM team. They responded to NO by producing retinoic acid, an immune regulator. We used the same SoxR/SoxS promoter system to detect NO, this is used by E. coli to respond to oxidative stress. A single stimulus can result in false positives and excessive suppression, leading to immunodeficiency. An inhibitor signaling high Treg populations avoids oversuppression. We are using multiple signals to increase the specificity and accuracy. Instead of retinoic acid we are using it to stimulate IL-10 production. <br> <br> </p>
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            <h2>Human Microbiome</h2>
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            <p class="lead">The microbiota refers to the population of symbiotic microorganisms, typically bacteria, that reside in the gut and are known to play a role in human health. It has been estimated that there are approximately ten times more microbial cells than human cells in adults. There are around 100 species of microorganism in the gut in young infants and this number steadily increases to around 1000 in adults. The populations that compose the community of the microbiota are stable within an individual; however, the composition of the microbiota is highly variable between individuals. The composition of the microbiome is determined as early as birth, for example, by the method of delivery. Babies that are born via the birth canal are exposed to vaginal bacteria and so have a different microbiome than those delivered via C-section, which are typically colonised by bacteria located on the skin. Age, gender, diet, exercise also play a role in determining the composition of the bacterial community within the gut.</p>  
  
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<p>Traditionally, the microbiota refers to the microorganisms, for example, bacteria, viruses and fungi that have colonised the human body. In contrast, the microbiome is the total sum of the genes that the species within the microbiota possess.</p>  
  
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<p>The microbiota differs between regions of the body. It should be noted that opportunistic pathogens are present in the microbiota alongside non-pathogenic species. High microbial diversity within the gut is known to be associated with good gut health and lower incidence of Inflammatory Bowel Disease.</p>
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<p>No riboswitches have been characterised which selectively bind to adenosine so instead we have used the adenine-specific riboswitch pbuE. Thus, cleavage of the adenine moiety is necessary for detection of adenosine by E.coli. In order to reduce the impact of unregulated adenosine hydrolase on cellular metabolism, we decided to exclude it from the cytoplasm.</p>
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            <h2>Our Solution</h2>
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            <p class="lead">Our solution is to develop a probiotic strain that restores the Th17/Treg cell balance via secretion of IL-10 in response to nitric oxide in the intestinal lumen. Overshoot is prevented by an adenine riboswitch-sRNA construct which responds to extracellular adenosine, an indicator of Treg cell function. Integration of separate stimuli in a dual feedback loop enables a more dynamic, robust response to the immune state of the body. Various features have been incorporated to maximise biological safety, including an inducible kill switch system. We believe our design offers a non-invasive, self-tuning therapeutic for IBD, with the potential to replace conventional immunosuppressants in the treatment of gastrointestinal autoimmune disorders.</p>  
  
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<h2>Functional RNA</h2>
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<p>A range of purines are used by Treg cells as immune signals. ATP is released from cells during stress or injury. To prevent it from causing excessive inflammation, ATP is rapidly metabolised into AMP then into Adenosine (Ado) by Treg cell surface enzymes. Ado is detected by GPCRs of Th cells, triggering increased cAMP in the cells. Inflammatory signals are inhibited and IL-10 production is enhanced in mature dendritic cells. Ado acts as an anti-inflammatory metabolite by inducing semi-maturation of immature dendritic cells, in order to increase immunoregulatory activity. Production by Treg cells and its role in regulating T cell populations and IL-10 production make it a suitable marker of Treg function and degree of immunodeficiency.</p>
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<p>The adenine riboswitch controls sRNA transcription, absence of adenine prevents RNA synthesis. The riboswitch, which is also transcribed, would hinder the sRNA binding to the target mRNA resulting in a loss of specificity and affinity. To prevent this the hepatitis delta virus ribozyme is between the features, this self-cleaves and liberates the sRNA. Modelling the effect of sRNA length on binding affinity allows us to create a tuneable inhibitory effect. This gives control over specificity and sensitivity to the adenosine stimulus. </p>
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<h2>Hydrolase</h2>
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<p>As well as being a generalised marker of inflammation, NO is thought to be produced by Th cells as a signal to induce differentiation of precursors into Th cells, thereby influencing the relative populations of Th and Treg cells. Continuous production of NO makes it a suitable marker of the size of the population and severity of the autoimmune disease.</p>
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<p>Adenosine is a key metabolite; to prevent unregulated adenosine hydrolase inhibiting cell growth, we decided to exclude it from the cytoplasm. This will minimise the impact on cellular metabolism and refine the signal by excluding cytoplasmic noise.
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We have proposed two mechanisms for this exclusion. The first involves using the type-II TAT pathway to directly translocate the tagged hydrolase dimer into the periplasm while the second involves the targeting to the outer membrane, fused to an E.coli membrane anchor - YiaT. In the second approach, to promote dimer association, a flexible linker was used to join two hydrolase monomers together.</p>
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<h2> References </h2>
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<tr><td>Cicerone C, Nenna R, Pontone S. Th17, intestinal microbiota and the abnormal immune response in the pathogenesis of celiac disease . Gastroenterology and Hepatology From Bed to Bench. 2015;8(2):117-122.</td></tr>
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<tr><td>Granzotto M, dal Bo S, Quaglia S et al. Regulatory T-cell function is impaired in celiac disease. Dig Dis Sci 2009;54:1513.</td></tr>
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<tr><td>Kumawat AK, Strid H, Tysk C, Bohr J, Hörnquist EH. Microscopic colitis patients demonstrate a mixed Th17/Tc17 and Th1/Tc1 mucosal cytokine profile. Molecular Immunology 2013;55(3-4):355-364.</td></tr>
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<tr><td>MD Magazine. (2018). IBD Rates Rising Worldwide in Proportion with Urbanization. [online] Available at: https://www.mdmag.com/medical-news/ibd-rates-rising-worldwide-in-proportion-with-urbanization.</td></tr>
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<tr><td>Gaffen SL. Role of IL-17 in the Pathogenesis of Rheumatoid Arthritis. Current rheumatology reports. 2009;11(5):365-370.</td></tr>
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<tr><td>Cooles, F.A.H., Isaacs, J.D. & Anderson, A.E. Treg Cells in Rheumatoid Arthritis: An Update. Curr Rheumatol Rep. 2013;15:352.</td></tr>
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<tr><td>Asadullah K, Sterry W, Stephanek K, et al. IL-10 is a key cytokine in psoriasis. Proof of principle by IL-10 therapy: a new therapeutic approach. Journal of Clinical Investigation. 1998;101(4):783-794.</td></tr>
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<tr><td>Omenetti S, Pizarro TT. The Treg/Th17 Axis: A Dynamic Balance Regulated by the Gut Microbiome. Frontiers in Immunology. 2015;6:639.</td></tr>
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<tr><td>Cosorich I, Dalla-Costa G, Sorini C, et al. High frequency of intestinal TH17 cells correlates with microbiota alterations and disease activity in multiple sclerosis. Science Advances. 2017;3(7):e1700492.</td></tr>
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<tr><td>Slingerland AE, Schwabkey Z, Wiesnoski DH, Jenq RR. Clinical Evidence for the Microbiome in Inflammatory Diseases. Frontiers in Immunology. 2017;8:400.</td></tr>
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<tr><td>Köhling H, Plummer S, Marchesi J, Davidge K, Ludgate M, The microbiota and autoimmunity: Their role in thyroid autoimmune diseases. Clinical Immunology. 2017;183:63-74.</td></tr>
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Latest revision as of 10:54, 5 December 2018

Full Width Pics - Start Bootstrap Template

Background

Autoimmune Disease

Autoimmune diseases encompass a range of disorders that result from the attack of self-tissues by a dysregulated immune system. More than 80 autoimmune diseases have been characterised, each with long-term effects on health, quality of life and cost to healthcare services. These include Crohn’s disease, Coeliac disease, type 1 diabetes, multiple sclerosis, systemic lupus erythematosus and rheumatic disease.

Global Burden of IBD

Inflammatory Bowel Disease (IBD) is a heterogeneous group of autoimmune disorders encompassing Crohn’s disease and Ulcerative Colitis. It is estimated to affect 0.3% of the population in industrialised nations, with over 5 million patients worldwide.

The global prevalence of IBD is increasing rapidly as countries become more developed. In addition, instances of IBD in developing countries are thought to be accelerated by the presence of bacteria, such as segmented filamentous bacteria (SFB), in water sources influencing the gut microbiome and host immune response. Gram-positive SFB have recently been implicated in promoting the development of lymphocytes and the growth of Th17 populations.

An additional effect of the signals required for Th17 differentiation is the inhibition of the production of Treg cells. Once fully differentiated, Th17 cells produce interleukin 17a (IL-17a) a proinflammatory cytokine. Elevated levels of IL-17a are associated with MS and the development of epilepsy and other autoimmune diseases.

Most diagnoses occur between the ages of 20 and 30; the disease presents a significant burden to patients, societies, and healthcare systems. Current treatment is focused on symptom management, frequently resulting in sub-optimal control despite the burden of long-term treatment. Common therapeutics, such as corticosteroids, require regular administration, have many side-effects and are less accessible in the developing world. The aim of our project is to address these problems and meet the notable, yet currently unmet, need for curative treatments for autoimmune diseases. This will be achieved via regulation of Treg and T helper cell populations to ensure immune responses of the correct magnitude. The specific control mechanism is discussed below.

Immune Cell Populations

T helper cells (Th) are a component of the adaptive immune systems and are characterised by the presence of the CD4 protein on the cell surface. CD4+ cells are able to interact selectively with major histocompatibility complex 2 on the surface of antigen presenting cells such as macrophages and dendritic cells. These interactions facilitate the release of small proteins known as cytokines and so Th cells contribute to varying the activity of other cell types. More specifically, Th cells are required for the maturation of B cells to upregulate production of antibodies and the proliferation of cytotoxic T cells, which degrade cancerous or infected body cells. Our project focuses on the detection of a particular subset of T helper cells namely, Th17 cells. Th17 cells produce interleukin- 17 (IL-17) and have a proinflammatory function, as well as regulating the production of neutrophils. Incorrect functioning of these cells is associated with the development of autoimmune diseases. Overactivation of Th17 populations that are responsive to self-antigens causes the accumulation of antigen-antibody complexes, leading to type III hypersensitivity. This causes an inflammatory response and is associated with autoimmune diseases such as lupus and arthritis.

Th17 cells are also closely associated with Treg cells as the chemicals required for Th17 differentiation and maturation are inhibitory with regard to this process for Treg cells. At low concentrations TGFβ associates with IL-6 and IL-21 to promotes Th17 differentiation; however, when TGFβ is at high concentrations, Treg differentiation is favoured as the production of IL-23 is repressed.

In contrast to T helper cells, natural T regulatory cells (Tregs) are characterised by the presence of both the CD4 receptor and CD25. The role of Tregs is the suppression of the action of helper and cytotoxic T cells, for example, by blocking the production of cytokines. They also suppress B cell and dendritic cell function, for example, via the production of inflammatory cytokines. The immunosuppressive role of Tregs is important in regulating the activity of the Th cells and to prevent excessive inflammation and help to reduce self- reactivity, thereby limiting the development of autoimmune diseases.

Pathogenesis

Immunodeficiency is a state where the immune system is unable to fight against infection due to a lack of, or suppression of cells of the innate or adaptive immune responses. Immunodeficiency can be either primary or secondary in nature. Primary immunodeficiency is the result of genetic mutations that lead to reduced immune responses. This is further categorised into B cell and T cell immunodeficiencies, severe combined immunodeficiency, complement defects and phagocyte disorders. Secondary cases are caused by environmental factors or diseases that induce weakening of the immune system.

A reduction in the population size of Th cells, as a method to counteract autoimmune diseases, increases the risk of development of immunodeficiency as a depleted population of Th cells will be unable to resist infection as successfully. Preventing the development of immunodeficiency is of particular importance in regions with poor sanitation where exposure to infection is more common.

To prevent the development of immunodeficiency in individuals that use our treatment, we have created a system that responds to two input values. Upon detection of the size of Th17 and Treg cell populations, the system responds to ensure optimum population sizes. If one cell population exceeds optimum levels, there is a response to restrict a further increase, preventing uncontrollable growth. This mechanism prevents both autoimmune disease and immunodeficiency by maintaining optimum population sizes for both cell types.



Human Microbiome

The microbiota refers to the population of symbiotic microorganisms, typically bacteria, that reside in the gut and are known to play a role in human health. It has been estimated that there are approximately ten times more microbial cells than human cells in adults. There are around 100 species of microorganism in the gut in young infants and this number steadily increases to around 1000 in adults. The populations that compose the community of the microbiota are stable within an individual; however, the composition of the microbiota is highly variable between individuals. The composition of the microbiome is determined as early as birth, for example, by the method of delivery. Babies that are born via the birth canal are exposed to vaginal bacteria and so have a different microbiome than those delivered via C-section, which are typically colonised by bacteria located on the skin. Age, gender, diet, exercise also play a role in determining the composition of the bacterial community within the gut.

Traditionally, the microbiota refers to the microorganisms, for example, bacteria, viruses and fungi that have colonised the human body. In contrast, the microbiome is the total sum of the genes that the species within the microbiota possess.

The microbiota differs between regions of the body. It should be noted that opportunistic pathogens are present in the microbiota alongside non-pathogenic species. High microbial diversity within the gut is known to be associated with good gut health and lower incidence of Inflammatory Bowel Disease.

Our Solution

Our solution is to develop a probiotic strain that restores the Th17/Treg cell balance via secretion of IL-10 in response to nitric oxide in the intestinal lumen. Overshoot is prevented by an adenine riboswitch-sRNA construct which responds to extracellular adenosine, an indicator of Treg cell function. Integration of separate stimuli in a dual feedback loop enables a more dynamic, robust response to the immune state of the body. Various features have been incorporated to maximise biological safety, including an inducible kill switch system. We believe our design offers a non-invasive, self-tuning therapeutic for IBD, with the potential to replace conventional immunosuppressants in the treatment of gastrointestinal autoimmune disorders.

A range of purines are used by Treg cells as immune signals. ATP is released from cells during stress or injury. To prevent it from causing excessive inflammation, ATP is rapidly metabolised into AMP then into Adenosine (Ado) by Treg cell surface enzymes. Ado is detected by GPCRs of Th cells, triggering increased cAMP in the cells. Inflammatory signals are inhibited and IL-10 production is enhanced in mature dendritic cells. Ado acts as an anti-inflammatory metabolite by inducing semi-maturation of immature dendritic cells, in order to increase immunoregulatory activity. Production by Treg cells and its role in regulating T cell populations and IL-10 production make it a suitable marker of Treg function and degree of immunodeficiency.

As well as being a generalised marker of inflammation, NO is thought to be produced by Th cells as a signal to induce differentiation of precursors into Th cells, thereby influencing the relative populations of Th and Treg cells. Continuous production of NO makes it a suitable marker of the size of the population and severity of the autoimmune disease.



References

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