IMPACT OF RNA VIRUSES ON THE REGULATION OF IL-23 IN MOUSE AND HUMAN MODELS OF INFECTION.

Interluekin-23 (IL-23) is a pro-inflammatory cytokine critical to the regulation of innate and adaptive immune responses. The main role for this cytokine is in the proliferation and differentiation of the IL-17 producing CD4 T helper cell, Th17. Virus infection deregulates IL-23 expression and function, but little is known about the mechanism behind this phenomena. Here, I demonstrate a reduction of Toll like receptor (TLR) ligand-induced IL-23 expression in lymphocytic choriomeningitis virus (LCMV)-infected bone marrow-derived dendritic cells (BMDCs), indicating that a function of these cells is disrupted during virus infection. I propose a mechanism of TLR ligand-induced IL-23 expression inhibition upon LCMV infection via the deactivation of p38, AP-1, and NF-κB. Further analysis revealed a direct relationship between LCMV infection with the IL-10 and SOCS3 expression. To understand IL-23 function, I characterized IL-23-induced JAK/STAT signalling pathway and IL-23 receptor expression on human CD4 T cells. My results demonstrate that IL-23 induces activation of p-JAK2, p-Tyk2, p-STAT1, p-STAT3, and p-STAT4 in CD4 T cells. For the first time I show that IL-23 alone induces the expression of its own receptor components, IL-12Rβ1 and IL-23Rα, in CD4 T cells. Blocking JAK2, STAT1, and STAT3 activation with specific inhibitors detrimentally effected expression of IL-23 receptor demonstrating that activation of JAK/STAT signalling is important for IL-23 receptor expression. I also addressed the effect of viral infection on IL-23 function and receptor expression in CD4 T cells using cells isolated from HIV positive individuals. These studies were based on earlier reports that the expression of IL-23 and the IL-23 receptor are impaired during HIV infection. I demonstrate that the phosphorylation of JAK2, STAT1, and STAT3 induced by IL-23, as well as IL-23 receptor expression are deregulated in CD4 T cells isolated from HIV positive individuals. This study has furthered the understanding of how the expression and function of IL-23 is regulated during viral infections.

The Influence of 1,25-Dihydroxyvitamin D3 on the Cross-Priming of Lymphocytic Choriomeningitis Virus Nucleoprotein

Biologically active 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) binds the vitamin D receptor (VDR) to exert its effect on target cells. VDR expression is found in a number of immune cells including professional antigen-presenting cells such as dendritic cells. It has been found that the actions of 1,25-(OH)2D3 on the immune system are mainly immunosuppressive. The cross-presentation pathway allows for exogenously derived antigens to be presented by pAPCs on MHC-I molecules to CD8+ T cells. CD8+ T cell activation results in the expansion of epitope-specific T cell populations that confer host protection. These epitopes can be organized into an immunodominance hierarchy. Previous work demonstrated that introducing LCMV-NP via the cross-priming pathway significantly alters the immunodominance hierarchy of a subsequent LCMV infection. Building upon these observations, our study assessed the effects of LCMV-NP cross priming in the presence of a single dose of 1,25-(OH)2D3. Treatment with 1,25-(OH)2D3 was found to have biological effects in our model system. In vitro pAPCs were demonstrated to up-regulate IL-10 and CYP24A1 mRNA, in addition to the transactivation of cellular VDR, as demonstrated by a relocalization to the nuclear region. Mice treated with 1,25-(OH)2D3 were found to produce up-regulated IL-10 and CYP24A1 transcripts. Expression of VDR was increased at both the transcript and protein level. Our results demonstrate that a single dose of 1,25-(OH)2D3 does not affect the cross-priming pathway in this system. Treatment with 1,25-(OH)2D3 did not influence the ability of differentiated pAPCs to phagocytose or cross-present exogenous antigen to epitope-specific CD8+ T cells. Furthermore, 1,25-(OH)2D3 did not alter cross-priming or the establishment of the LCMV immunodominance hierarchy in vivo. By confirming that 1,25-(OH)2D3 does not suppress cross-priming in our model, our study helps to expand the understanding of the immunomodulatory role of exogenous 1,25-(OH)2D3 on the outcome of virus infection. Collectively, our data supports the observation that the role of 1,25-(OH)2D3 in the immune system is not always associated with suppressive effects.

Optimizing The Nasal Allergen Challenge Model For The Study Of Allergic Rhinitis

Background The Allergic Rhinitis Clinical Investigator Collaborative (AR-CIC) uses a Nasal Allergen Challenge (NAC) model to study the pathophysiology of AR and provides proof of concept for novel therapeutics. The NAC model needs to ensure optimal participant qualification, allergen challenge, clinical symptoms capture and biological samples collection. Repeatability of the protocol is key to ensuring unbiased efficacy analysis of novel therapeutics. The effect of allergen challenge on IL-33 gene expression and its relation to IL1RL1 receptor and cytokine secretion was investigated. Methods Several iterations of the NAC protocol was tested, comparing variations of qualifying criteria based on the Total Nasal Symptom Score (TNSS) and Peak Nasal Inspiratory Flow (PNIF). The lowest allergen concentration was delivered and TNSS and PNIF recorded 15 minutes later. Participants qualified if the particular criteria for the protocol were met, otherwise the next higher allergen concentration (4-fold increase), was administered until the targets were reached. Participants returned for a NAC visit and received varying allergen challenge concentrations depending on the protocol, TNSS/PNIF were recorded at 15 minutes, 30 minutes, 1 hour, and hourly up to 12 hours, a 24 hour time point was added in later iterations. Repeatability was evaluated using a 3-4week interval between screening, NAC1, and NAC2 visits. Various biomarker samples were collected. Results A combined TNSS and PNIF criterion was more successful in qualifying participants. The cumulative allergen challenge (CAC) protocol proved more reliable in producing a robust clinical and biomarker response. Repeatability of the CAC protocol was achieved with a 3-week interval between visits, on a clinical and biological basis. IL-33 cytokine is an important biomarker in initiating the inflammatory response in AR in humans. IL-33 and IL1RL1 expression might employ a negative feedback mechanism in human nasal epithelial cells. Comparing the clinical and biological response to ragweed vs cat allergen challenge, proved the CAC protocol’s suitability for use employing different allergens. Conclusion The AR-CIC’s CAC protocol is an effective method of studying AR, capable of generating measurable and repeatable clinical and biomarker responses, enabling better understanding of AR pathophysiology and ensuring that any change would be purely due to medication under investigation in a clinical trial setting.