Hippocampal neurogenesis occurs within the subgranular zone of the dentate gyrus and is important for learning and memory. Neurogenesis is impaired in many pathological conditions; an observation that may account for learning and memory deficits in patients suffering from these conditions. Studies on immune-deficient mice show reduced hippocampal neurogenesis and associated learning and memory impairments in mice devoid of CD4+ T lymphocytes. Neuropeptides are potential candidates for mediating neuro-immune interactions. Vasoactive Intestinal Peptide (VIP) is a neuropeptide, released by firing interneurons from the stem cell niche, that modulates hippocampal neurogenesis via VPAC1/2 receptors. VIP receptors are also present on T lymphocytes. Microglia are innate immune cells that regulate hippocampal neurogenesis. They are ideally placed to communicate with T lymphocytes that normally reside outwith the brain parenchyma. Given the nescience underlying T lymphocyte regulation of hippocampal neurogenesis, we sought to investigate the hypothesis that VIP modulates T lymphocytes to release cytokines to regulate hippocampal neurogenesis via interaction with microglia. We have shown that T lymphocytes supernatant increases the proliferation of hippocampal nestin-expressing cells. This effect is further enhanced under VIP treatment via VPAC1 receptor subtype. Examining possible cytokine involvement, we found that IL-4 mediates proliferation. Using Mac-1-SAP to deplete resident microglia, we demonstrated that supernatant acts primarily via microglia to increase supernatant effects. T lymphocytes induce microglia to upregulate cytokines and mediators such as IL-10 and BDNF. Phenotyping showed an additional neurogenic effect under VIP treated supernatant. Our results show VPAC1 receptor subtype expressed by CD4+ T lymphocytes mediates VIP proliferative effects on hippocampal precursor cells via IL-4 cytokine release. Microglia are key for mediating this effect via release of mediators. The findings of this study implicate a novel mechanism for VPAC1 CD4+ T lymphocyte receptor as a neuro-immune mediator of hippocampal neurogenesis, and from a therapeutic perspective, shows that the effect can be pharmacologically manipulated.

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Background: There are a large number of viruses spread by mosquitoes, many of which cause debilitating, often fatal, neurological disease such as acute encephalitis. In this study we have used two different neurotropic viruses: Semliki Forest virus (SFV), and West Nile virus (WNV), both of which can cause severe panencephalitis in the mouse. The influx of leukocytes into the infected tissues is mediated by chemokines and is believed to be important for virus clearance. To date, we have only limited insights into the precise nature of chemokine involvement, and an improved understanding of these important axes provides a new target for the development of novel therapies. Hypothesis: Based on previous studies investigating the role of chemokines during neuroinflammation it was hypothesised that chemokines and other cytokines are highly upregulated during viral encephalitis, and the blockade of selected chemokine receptors would lead to altered disease outcome. It was also hypothesised that chemokine receptors would present plausible targets for the treatment of viral encephalitis. Results: To test these hypotheses, the chemokine expression pattern and the kinetics of chemokine mediated leukocyte recruitment during viral encephalitis were analysed in unprecedented detail by TaqMan low density array, and flow cytometry, respectively, and key chemokine receptor were identified as therapeutic targets. Both SFV and WNV exhibited a similar pattern of chemokine upregulation, although WNV induced significantly higher fold expression. The key chemokines upregulated were CCL2, 3, 5, 7, CXCL9 and CXCL10. The upregulation of chemokines coincided with leukocyte influx into the CNS. After identifying the key chemokines upregulated during viral encephalitis, next a selected panel of chemokine receptor antagonists was utilized to evaluate the hierarchy and relative importance of distinct chemokine receptors for CNS leukocyte influx, viral clearance, neuropathogenesis and host survival. We identified the CXCR3 axis as being the key instigator of CNS inflammation in response to alphavirus infection, placing it at the top of a hierarchal cascade that is followed by CCR2 and CCR5. Critically, inhibition of both CXCR3 and CCR2 simultaneously, significantly improved host survival to otherwise lethal encephalitis. Conclusion: These data suggest that chemokine receptors represent plausible therapeutic targets for viral encephalitis.

Gangliosides, complex sialic acid-containing glycolipids, and other glycosphingolipids are active physiological membrane components with an array of functions in development and disease. Altered profiles are found in many disorders including those of neurological and cancerous aetiologies. Glycosphingolipids are also important for lateral membrane organization, cell communication and as binding sites for extra-cellular components. These lipids have long been implicated as targets in autoimmune diseases such as Guillain-Barré Syndrome (GBS) and Multifocal Motor Neuropathy. In GBS, auto-antibodies bind native membrane gangliosides signalling immune-mediated breakdown of nerves causing acute flaccid paralysis. While the fundamental pathology is understood, differences in clinical presentation, and preference for motor over sensory nerves, have yet to be explained. Understanding the precise nature of native gangliosides, including low abundance species and modifications, is an important first step. Meanwhile genetically engineered mouse models are under development that should increase our understanding of disease pathogenesis. To be truly functional it is essential these models contain a full range of complex and simple glycosphingolipids in the neurological tissue. Mass spectrometry has recently been applied with great effect to lipidomics; the comprehensive profiling of all lipids involved in a system. However, heavily glycosylated, low abundance and chemically unusual lipids such as the gangliosides tend to be neglected in otherwise thorough lipidomic studies. It was the aim here to optimise separation and mass spectrometry methodologies for ganglioside analysis. Workflows were developed for high performance thin layer chromatography (HPTLC) combined with direct imaging mass spectrometry (IMS) detection and identification, and for high performance liquid chromatography (HPLC) with online high resolution mass spectrometry detection and identification with dissociation to confirm structures (MSMS). A range of lipid standards were analysed using this second method to build a database of characteristic ionization behaviour, retention times, and product ion spectra to aid the analysis of unknowns in complex mixtures. Methods were then applied to molecular phenotyping in novel mouse models of GBS, and to glycosphingolipidomics in peripheral sensory and motor nerves. Finally the recently developed technique of imaging mass spectrometry, using matrix assisted laser desorption ionisation (MALDI) and secondary ion mass spectrometry (SIMS) ion sources, was investigated for its capability for direct ganglioside analysis in brain and spinal cord tissue sections. Results are presented below demonstrating the significant benefits of the mass spectrometry-based workflows over more conventional profiling methods as well as comparing and contrasting the two techniques developed here. Limitations and potential areas for future development are debated. Findings from profiling knockout and rescue mouse models and from single nerve glycosphingolipidomics are discussed along with further experiments and directions for these studies. The discovery of a full range of complex gangliosides in neurological tissue from rescue mice, albeit at low levels compared to the wild type, confirmed their molecular usefulness for modelling neurological autoimmune diseases. The sensitivity and reproducibility of the mass spectrometry technique enabled relative quantitation, revealing details into the abundance of different ganglioside species and inclusion of ceramide structures in each mouse type. The ability to detect very low abundance lipids with an additional dimension of structural description also suggested that O-acetylation of the second sialic acid on native disialylated lipids is more prevalent than previously thought. Finally imaging mass spectrometry results are presented. Although sensitivity was limited, both simple and complex gangliosides were detected in spinal cord sections; the first known IMS detection of these lipids outside of the brain. Results also demonstrate the abundance of parallel lipidomic information that can be obtained using these methods. Possible solutions to increasing the sensitivity limit are discussed that may increase IMS usefulness to glycosphingolipid studies in future.

Initially, prostaglandins (PGs) were considered to only exist as free acid mediators. Although, formation of PG glycerol esters and PG ethanolamides by cellular cyclooxygenase (COX)-2 has been reported, generation of complex oxidised lipids via COX-1 has not been considered. In this study, formation of sixteen unique PG-containing phospholipids generated by agonist-activated human platelets is demonstrated using lipidomic approaches. Precursor scanning-tandem mass spectrometry identified a group of specific lipids comprising PGE2, PGD2 and two previously undescribed PG-like molecules (named PGb and PGc), attached to four phosphatidylethanolamine (PE) phospholipids (16:0p/, 18:1p/, 18:0p/ and 18:0a/). PGb and PGc were also detected as free eicosanoids and their structures remain to be characterised. These novel lipids formed within 2-5 minutes of platelet activation by thrombin, collagen or ionophore and required activation of several intracellular signalling intermediates, including cytosolic phospholipase A2 (cPLA2), p38 mitogen-activated protein kinase (MAPK), src tyrosine kinases, phospholipase C (PLC) and cytosolic calcium. Unlike free PGs that are secreted, PG-PEs remain cell associated, suggesting an autocrine mode of action. Aspirin supplementation in vivo (75 mg/day) or in vitro (1 mM) blocked their generation, indicating that COX-1 is required. Pharmacological studies using inhibitors of fatty acyl re-esterification significantly reduced formation of PG-PEs. Furthermore, purified COX-1 was unable to directly oxidise PE in vitro. Collectively, these indicate that PG-PEs are initially formed as free PGs via COX-1, and then rapidly esterified into PEs. In summary, this is the first demonstration of acute generation of PG-PEs in agonist-activated human platelets from endogenous substrate via COX-1. These unique lipids may represent additional bioactive molecules from this key platelet enzyme.

Hepatitis C virus (HCV) infects 3% of the global population and HCV-related liver inflammation is a major cause of liver failure and hepatocellular carcinoma. Current treatments are based upon long courses of interferon-α (IFNα) injections, which have significant side effects and are only effective in 40-80% of individuals depending on viral genotype. Natural killer (NK) cells are innate lymphocytes, which can kill virally infected cells and are stimulated by IFNα. To establish a chronic infection HCV must evade immune responses. I hypothesised that NK cells are important for the successful eradication of HCV and that chronic HCV infection impinges upon NK cell function to prevent viral clearance. I found that NK cell function was reduced in chronic HCV and correlated with the proportion of NKp46+ NK cells in vitro. In keeping with these findings NKp46-rich intrahepatic NK cell populations were more activated and the proportion of these cells correlated with liver inflammation. During interferon-α treatment individuals who had the greatest increase in NK cell function in response to increasing stimulation had the fastest rate of viral clearance and were most likely to successfully clear the virus. Using a novel adenovirus vector expressing HCV proteins I have discovered that NS5B protein reduces NK cell cytotoxicity and cytokine production. Therefore, in this thesis I have described novel insights into the mechanisms of HCV immunoevasion, HCV-related disease pathogenesis with implications for viral eradication therapy.

Peptide immunotherapy for Type 1 diabetes aims to restore tolerance to self, whilst leaving the rest of the immune system intact. Once the right peptide isdelivered to the right cell, it is important to closely monitor the effect of such atherapy, both in the regards to the immune and metabolic response. Clinical trials are designed to test the effect of a drug at the end of the trial period, which can be years later. Ex-vivo human models are not subject to extensive regulatory requirements, and can rapidly provide proof of principle on the efficacy of a treatment, which can be then translated to the clinic. I have shown that the skin organ bath culture is a useful system for studying treatment effects of variety of ex-vivo delivered agents. When used to optimise peptides delivery, it indicated a potential role of dry coated microneedles in targeting epidermal DCs, important because of their endogenous tolerogenic potential, which can be further modified by topical treatments and locally injected agents. Whether true tolerogenic potential can be achieved in such a way, is subject to further studies designed to optimise the type, dose and the duration of the treatment by the conditioning agent. My data also suggested that lymph node fine needle aspiration biopsy is a feasible non-invasive method suitable for monitoring the cellular immune responses after antigen skin delivery. Subject to confirmatory study, it has a potential to find immediate application as an efficient and reliable tool for monitoring immune response after antigen-specific immunotherapy in clinical trials. Once recognised as ‘immune responders’ in such a way, participants in clinical trials can be subjected to the monitoring of the metabolic response to the immune intervention, by measuring !-cell function via stimulated UCPCR as a non-invasive and more compliant-prone alternative to the standard MMTT.

The innate immune system has a variety of ways of recognizing infection from pathogens such as viruses and bacteria. One of its first lines of defence is to detect Pattern Associated Molecular Patterns (PAMPs) using Pattern Recognition Receptors (PRRs) such as the Toll-Like Receptors (TLRs), the RIG-Like Helicases (RLHs) and the Nod-Like Receptors (NLRs). These receptors recognize certain molecular structures from the pathogens and lead to first line of defence which includes increased cytokines and IFNs. This study delineate the human body’s innate immune responses to human respiratory viruses such as HRV (Human Rhinovirus), RSV (Respiratory Syncytial Virus) and IAV (Influenza A virus). In Vitro experiments carried out on various kinds of lung tissues suggest that respiratory disease pathogenesis is related to inflammatory mediators including interleukins and cytokines produced by the host’s innate immune system. Virus induced respiratory tract infection are known to trigger bronchiolitis, wheezing and acute asthma exacerbations, as a result of inflammation of lung tissues and excessive release of pro- inflammatory cytokines such as IL-1β. This study identifies that intracellular macromolecular complexes called inflammasomes assemble as a result of viral trigger. Inflammasomes convert the inactive forms of the pro-inflammatory cytokines to their active forms. Although the exact mechanism of activations of these complexes was unknown. This study identified that Virus encoded proteins such as the 2B protein of HRV, the SH protein from RSV and the Influenza M2 which are also termed viroporins can activate the inflammasome by causing ion imbalance (across cells membranes and organelles). Thus providing a trigger for inflammasome assemblage. v Drugs which act as Ion channel blockers have been shown to block viroporin activity and hence reduce IL-1β production. Therefore in the future the use of ion inhibitors could be a possible therapeutic intervention in order to reduce lung inflammation and prevent associated respiratory disease such as COPD and Asthma.