Regulatory T cells (Treg) are essential for the induction and maintenance of immunological tolerance to self and foreign antigens. The development of allergic asthma is mediated by T helper cell type-2 (Th2) inflammatory mechanisms and may also involve, based on murine and human studies of allergic asthma, compromised Treg immune regulation. Our overall objective was to more thoroughly elucidate the biology of Treg in allergic asthma, and to better understand their potential as a treatment for the disease. Initially, we characterized three different Treg phenotypes based on frequency and functional capacity. We showed both quantitative and functional heterogeneity in circulating Treg. Quantitative variability was also observed in circulating, but not airway, Treg when comparisons were made between healthy controls and asthmatic subjects. These findings emphasize the need for clear definitions of Treg phenotypes, and that interpretation of their frequency and function in health and disease needs to be phenotype-specific. Next, we assessed the Treg response in mild allergic asthmatic isolated early responders and dual responders after allergen inhalation challenge. We observed a reduced frequency of airway Treg after allergen challenge in DR, but not IER, associated with a smaller ratio of Treg to CD4+ cells. These data suggest that Treg to T effector cell (Teff) balance is important in the regulation of late asthmatic responses. Lastly, we evaluated the effects of two novel monoclonal anti-asthma therapies on circulating Treg after allergen inhalation challenge. We demonstrated that neither anti-OX40L nor anti-TSLP therapy altered circulating Treg frequency, while anti-TSLP, but not anti-OX40L, was effective in attenuating allergen-induced airway responses. These observations demonstrate the need for further investigation into the effects of anti-asthma therapies on Treg as well as the development of novel therapies aimed at manipulating Treg in order to better control immune responses. The findings of this thesis enhance our understanding of Treg in allergic asthma. Treg, utilized as stand-alone or adjunct therapy, may provide a novel therapy in the treatment of allergic asthma. / Thesis / Doctor of Philosophy (PhD)

No description available.

No description available.

<p><strong>Background:</strong> Early infancy is a critical period during which the interplay between host and environmental factors influences susceptibility to allergic sensitization, a process that can also be construed as a failure to induce tolerance. Indeed, allergic asthma emerges, in most instances, in early childhood although the specific intervals of protection or susceptibility remain to be elucidated. We found that exposure to a concentration of allergen, house dust mite (HDM), that normally induces robust airway inflammation in adult mice elicits negligible immune-inflammatory responses in infant mice.</p> <p><strong>Methods:</strong> We investigated immune-inflammatory responses in mice exposed to 25 μg of HDM intranasally for 10 consecutive days at different points in development (3, 4, 5 and 7 weeks of age). We delineated the immune cell profile in the lungs of naïve mice from birth to adulthood, focusing on markers of immune maturation and immunosuppression. Moreover, we studied the impact of T-regulatory cell (Treg) depletion with the use of α-CD25 antibodies administered intraperitoneally one day prior to the start of HDM exposures, and then again on day 6 of the above protocol.</p> <p><strong>Results:</strong> Our data show that there is a progressive acquisition of immune-inflammatory responsiveness to HDM in BALB/c mice as exposures are initiated later in development, evidenced by total cell number and eosinophilia in the BAL and serum HDM-specific IgG₁ levels. Additionally, there is an immunological shift that occurs in the infant lung during development in that the early immunosuppressive environment, defined by T-regulatory cells and immunosuppressive alveolar macrophages, subsides as the capacity to respond to ensuing immune challenges, defined by natural killer (NK) cell, dendritic cell (DC) and alveolar macrophage (AM) maturation, increases. Specifically, in regards to the immunosuppressive lung environment during infancy, we identified higher baseline levels of CD25⁺Foxp3⁺CD101⁺ and CD25⁺Foxp3^highTregs, i.e. those with more potent suppressive ability. These populations also expand following HDM exposure in both adult and infant mice. Interestingly, 2 week-old infant mice depleted of Tregs or exposed to a very high dose of HDM (125 μg) overcome the natural immunosuppressive environment resulting in the acquisition of HDM responsiveness, as manifested by robust Th2 immune-inflammatory responses, comparable to that observed in 8 week-old adult mice.</p> <p><strong>Conclusion/Implications: </strong>Together, our data suggest that the hyporesponsiveness to HDM very early in life may be explained by two connected events: a) the inherent immunosuppressive environment in the lung, and b) the immaturity of the machinery for effective immune responses. Furthermore, we demonstrate that a disruption in the homeostatic immune balance in infancy, Treg depletion in this case, may lead to the imprinting of aberrant immune-inflammatory responses, like allergen sensitization. Thus, the inherent immunosuppressive environment in infancy may have long-term implications on allergen responsiveness.</p> / Master of Science in Medical Sciences (MSMS)

No / Neuroimmune dysregulation characterizes atopic disease, but its nature and clinical impact remain ill-defined. Induced by stress, the neurotrophin nerve growth factor (NGF) may worsen cutaneous inflammation. We therefore studied the role of NGF in the cutaneous stress response in a mouse model for atopic dermatitis–like allergic dermatitis (AlD). Combining several methods, we found that stress increased cutaneous but not serum or hypothalamic NGF in telogen mice. Microarray analysis showed increased mRNAs of inflammatory and growth factors associated with NGF in the skin. In stress-worsened AlD, NGF-neutralizing antibodies markedly reduced epidermal thickening together with NGF, neurotrophin receptor (tyrosine kinase A and p75 neurotrophin receptor), and transforming growth factor-β expression by keratinocytes but did not alter transepidermal water loss. Moreover, NGF expression by mast cells was reduced; this corresponded to reduced cutaneous tumor necrosis factor-α (TNF-α) mRNA levels but not to changes in mast cell degranulation or in the T helper type 1 (Th1)/Th2 cytokine balance. Also, eosinophils expressed TNF receptor type 2, and we observed reduced eosinophil infiltration after treatment with NGF-neutralizing antibodies. We thus conclude that NGF acts as a local stress mediator in perceived stress and allergy and that increased NGF message contributes to worsening of cutaneous inflammation mainly by enhancing epidermal hyperplasia, pro-allergic cytokine induction, and allergy-characteristic cellular infiltration.

Yes / Background:To inform the development of the European Academy of Allergy and Clinical Immunology’s (EAACI) Guidelines on Allergen Immunotherapy (AIT) for allergic asthma, we assessed the evidence on the effectiveness, cost-effectiveness and safety of AIT. Methods:We performed a systematic review, which involved searching nine data-bases. Studies were screened against predefined eligibility criteria and critically appraised using established instruments. Data were synthesized using random-effects meta-analyses.Results:98 studies satisfied the inclusion criteria. Short-term symptom scores were reduced with a standardized mean difference (SMD) of 1.11 (95% CI 1.66, 0.56). This was robust to a prespecified sensitivity analyses, but there was evidence suggestive of publication bias. Short-term medication scores were reduced SMD 1.21 (95% CI 1.87, 0.54), again with evidence of potential publication bias. There was no reduction in short-term combined medication and symptom scores SMD 0.17 (95% CI 0.23, 0.58), but one study showed a beneficial long-term effect. For secondary outcomes, subcutaneous immunotherapy (SCIT) improved quality of life and decreased allergen-specific airway hyperreactivity (AHR), but this was not the case for sublingual immunotherapy (SLIT). There were no consistent effects on asthma control, exacerbations, lung function, and nonspecific AHR. AIT resulted in a modest increased risk of adverse events (AEs). Although relatively uncommon, systemic AEs were more frequent with SCIT; however no fatalities were reported. The limited evidence on cost-effectiveness was mainly available for sublingual immunotherapy (SLIT) and this suggested that SLIT is likely to be cost-effective. Conclusions: AIT can achieve substantial reductions in short-term symptom and medication scores in allergic asthma. It was however associated with a modest increased risk of systemic and local AEs. More data are needed in relation to secondary outcomes, longer-term effectiveness and cost-effectiveness. / EAACI; BM4SIT. Grant Number: 601763; European Union's Seventh Framework Programme FP7

Allergic diseases are chronic inflammatory conditions, characterised by eosinophil inflammation systemically and in target organs, where cytotoxic granule proteins are responsible for tissue injury. Allergic rhinitis is known to be a risk factor for the development of asthma, yet not all with rhinitis develop asthma. The overall aim was to investigate the involvement of eosinophils in allergic rhinitis and allergic asthma in vivo and in experimental settings, with a focus on differences between rhinitis and asthma. Birch pollen allergy was used as a model and patients were studied during pollen season and after nasal and bronchial allergen challenge. During pollen season and at baseline, allergic rhinitis and allergic asthma had the same degree of systemic eosinophil inflammation. Despite this, impairment in lung function during season and increased bronchial responsiveness at baseline were more common in the asthmatics. Systemic inflammation was more pronounced after seasonal exposure than after experimental challenge. Allergic rhinitis and allergic asthma had the same degree of eosinophil airway inflammation after bronchial challenge, but only the asthmatics had increased bronchial responsiveness measured as PD20 for birch allergen. Allergen primed eosinophils were investigated in vitro for C3b-induced degranulation after seasonal and experimental challenge. The released amount of eosinophil granule proteins was within the same range for all three allergen challenge models with just minor differences in propensity for degranulation between rhinitics and asthmatics. Signalling through PI3K for degranulation was studied with the specific inhibitor Wortmannin. PI3K signalling for eosinophil degranulation was clearly involved in allergic rhinitis and allergic asthma irrespective of the model for allergen exposure. Asthmatics demonstrated less inhibition of degranulation through PI3K during pollen season, indicating that other pathways contribute to eosinophil degranulation in allergic asthmatics. Conclusion: Allergic rhinitis and allergic asthma present with the same degree of systemic and local eosinophil inflammation. The eosinophils are primed for degranulation equally and follow the same pathway through PI3K for degranulation. Our data indicates that eosinophil inflammation per se is not sufficient for the development of asthma.

Abstract An excess of atopic allergies has been found in patients with depression, and conversely, increased amounts of depressive symptoms have been reported in patients with atopic disorders. Thus far, however, the findings have mainly been based on clinical samples. In this thesis, the association between atopic disorders and depression was investigated at epidemiological level by using data from the Northern Finland 1966 Birth Cohort. An unselected cohort of 12058 liveborn children was followed prospectively from prenatal stages until 1997. During the 31-year follow-up, 6025 cohort members underwent skin prick tests. Data on lifetime depression diagnoses and atopic conditions were obtained from postal questionnaires and Finnish Hospital Discharge Registers, and the severity of the depressive symptoms was assessed with Hopkins Symptom Checklist-25. Information on the family histories of the atopic disorders was obtained from questionnaires of the 31-year follow-up. Females with positive skin prick test responses and self-reported histories of allergic symptoms exhibited a 2.7-fold probability of developing lifetime depression. The corresponding probability increased in line with the increased severity of depressive symptoms in atopic but not in non-atopic females, ranging from 3.0 to 4.7-fold. Among males, the atopy-depression association was seen only in the highest depression scores, the odds ratio being up to 6.3-fold. While the most severe, hospital-treated manifestations of both disorders were considered, atopic disorders increased the risk of depression 3-fold independently of the subject's gender and sociodemographic characteristics. When investigating the effect of familial atopy on a child's depression, maternal atopy increased the probability of lifetime depression nearly 2-fold in females, and over 4-fold, when a female cohort member's own atopy was also present. At epidemiological level, the presence of atopic conditions seemed to increase the probability of lifetime depression especially in females. Since both atopic disorders and depression are illnesses of major public health importance in Western countries, also the co-morbidity between these disorders should be seriously taken into account in clinical practice. Further investigations are called for in evaluating whether this association is specific to atopic disorders, since increased risks of depression have been noted in connection with many other physical diseases as well.

Twenty publications are submitted. All deal with the issues of control of two ends of the spectrum of immune-mediated respiratory disorders in children, namely atopic (asthma and allergic rhinitis) and HIV-related lung disease. This submission summarises the research by the author into this spectrum of lung diseases of children in South Africa, highlighting the diversity of conditions that are not only clinically important, but also common. Understanding of all conditions is required to improve the health of children in this region. Management of chronic conditions requires two major end points - adequate and timely diagnosis and - management to control the condition. The author has a passion for improving the quality of life of children and firmly believes that the research findings will, and have, led to transformation in management of both these common disorders. This document follows the progression of the authors research work and highlights how interesting and important is the scope of two disorders which could be thought to have a central origin, namely in the T-cell. T-cells form the basis of cellular immunity and an excess of T-helper 2 cell activity promotes atopy, whilst the human immunodeficiency (HI) virus infects T-helper cells and promotes cellular immune deficiency and its attendant clinical disorders. The author’s research work is not based on the immunological basis of these conditions but does deal with the clinical implications and especially aspects relating to control of these two extremes of a clinical spectrum of disorders. To take the clarity of two diseases at the end of a spectrum to its natural conclusion these extremes are defined in aetiology or pathophysiological differences (excess versus suppression of the immune system), occurring in the affluent and poor alike versus just the poor, control being required to improve quality of life versus to save lives and finally that management requires anti-inflammatory therapy versus antibiotic and anti-infective therapy. For the eight publications based on atopic respiratory disease in children the themes are firstly that children with asthma and chronic rhinitis are diagnosed late, that most individuals with these conditions are not well controlled and finally that the reasons for lack of control are becoming obvious. For the first time, the significant lack of asthma and allergic rhinitis control in South Africa is documented. These studies suggest that, like surveys from the rest of the world, asthma control is seriously under-estimated and neglected in all asthmatics in South Africa, in both the privileged and the under-privileged. The research also defines reasons for poor asthma and allergic rhinitis control in this region. As in many studies published from around the world it is now evident that poor asthma and allergic rhinitis control cannot be blamed on any one source. A multitude of reasons underlie this phenomenon and each of the subsequent papers in this section illustrates attempts at defining these principles. The three most important reasons for poor control are probably that most asthmatics are managed in the wrong hands (by doctors who don’t understand adequate control and who aren’t empowered to use the correct therapy), that control may actually be a pipe dream and practically difficult to do or even impossible to achieve and lastly that the allergic basis of asthma is over emphasised and may not in fact determine all asthma. The subsequent papers summarise research work in the field of HV infection in children and exposes the opposite end of a spectrum of Paediatric respiratory disease and highlight research into the conditions common in HIV-infected children. Eleven papers are presented. For the diseases associated with the HI virus the major complications of inadequate diagnosis and prevention in children are acute pneumonia (especially severe pneumonia) and bronchiectasis. Bronchiolitis is not common in HIV infected children, despite epidemics of this condition in non-infected children. Passive smoking does not aggrevate or worsen disease progression in children. The complications of HIV related diseases in children require the same principles of adequate diagnosis and control as would apply to the chronic atopic conditions. Once the author delved into the disorders at the other end of the clinical spectrum, namely those associated with immune deficiency secondary to HIVinfection he faced the question of a possible relationship between the conditions. One submission explores that relationship. This research has a unique perspective, conferred by the fact that these two conditions do not occur to the same extent anywhere else in the world. Atopic respiratory conditions and HIV-related lung diseases occur side by side in abundance in this region. This perspective has created a clarity for research to address the two most important aims in clinical medicine, namely to diagnose correctly and then to manage the condition so that control is achieved. These must be universal principles of the successful practice of medicine. / Thesis (DSc)--University of Pretoria, 2013. / gm2013 / Paediatrics and Child Health / unrestricted

<p>Allergic asthma is a chronic and complex disease of the airways characterized by dysregulated immune-inflammatory responses to aeroallergens and reversible airflow obstruction. The prevalence and economic burden of allergic asthma have increased substantially over the last five decades. Despite remarkable progress in our understanding of the immunobiology and pathophysiology of asthma, the ontogeny of the disease remains elusive. As a result, there is a lack of effective preventative strategies. Here, we used a murine model of allergic asthma to house dust mite (HDM), the most pervasive indoor aeroallergen worldwide to address issues pertaining to the development of allergic asthma. First, we provided a comprehensive computational view of the impact of dose and length of HDM exposure on both local and systemic allergic outcomes (Chapter 2). Parameters, such as thresholds of responsiveness, and non-linear relationships between allergen exposure, allergic sensitization and airway inflammation were identified. We, then, investigated molecular signatures implicated in the onset of allergic responses (Chapter 3). HDM exposure was associated with production of the epithelial-associated cytokines TSLP, IL-25 and IL-33. However, only IL-33 signaling was necessary for intact Th2 immunity to HDM, likely because of its superior ability to induce the critical co-stimulatory molecule OX40L on dendritic cells and expand innate lymphoid cells. Lastly, as individuals are most likely exposed to allergens concomitantly to other environmental immunogenic agents, we studied the impact of an initial immune perturbation on allergic responses to sub-threshold amounts of HDM (Chapter 4). We showed that transient expression of GM-CSF in the airway substantially lowers the threshold of allergen required to generate robust, HDM-specific Th2 immunity, likely through increasing IL-33 production from alveolar type II cells. These studies favor a paradigm whereby distinct molecular pathways can elicit type 2 immunity, intimating the need to classify asthma into distinct clinical subsets.</p> / Doctor of Philosophy (PhD)