Browsing by Author "Khumalo, Jermaine"

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    Open Access
    The temporal requirement of IL-4Rα signalling in allergic asthma and the role of IL-4Rα-responsive Regulatory T cells in restraining allergic airway inflammation
    (2019) Khumalo, Jermaine; Brombacher, Frank; Kirstein, Frank
    Allergic asthma is a chronic inflammatory airway disease driven predominantly by a TH2 immune response to environmental allergens. The asthma pathology is predominantly elicited by IL-4 and IL-13 signalling via IL-4Rα-signalling which is essential for driving TH2-type immunity to allergens. Interestingly, the failure by regulatory T cells to maintain tolerance during allergic asthma, suggested to be driven by TH2 inflammatory signals, still remains elusive and anti-TH2 therapies with the potential to effectively reduce airway obstruction and inflammation in allergic asthma, have had limited success. Therefore, we aimed to investigate the function of IL-4/IL-13 responsive regulatory T cells in a TH2 rich environment and the temporal requirement of IL-4Rα-signalling in asymptomatic and acute airway disease. Objective 1: We investigated potential therapeutic effects of selective inhibition of this pathway in mice with established allergic airway disease and systemically sensitised mice to prevent the onset of the disease. We used RosacreERT2IL-4Rα-/lox mice, a novel, tamoxifen inducible IL-4Rα knockdown model to investigate the role of IL-4/IL-13 signalling during the effector phase of ovalbumin induced allergic airway disease (AAD) and for the onset of the disease. The deletion of the IL-4Rα had a therapeutic effect on established AAD and prevented the development of ovalbumin induced airway hyperreactivity, goblet cell metaplasia and eosinophilia in allergensensitised mice. We concluded that the abrogation of IL-4Rα signalling after allergic sensitisation would have significant therapeutic benefit for TH2 type allergic asthma. Objective 2: The canonical IL-4Rα-signalling, was investigated on its role on Foxp3+ Tregs in allergic asthma with aims to re-establish tolerance during allergic asthma. We used transgenic Foxp3cre IL-4Rα-/lox mice IL-4Rα-/lox mice to investigate the role of IL-4/IL-13 signalling during the induction or maintenance of tolerance in house dust mite-induced ADD. The depletion of IL-4Ra on Foxp3+ Tregs exacerbated airway hyperreactivity and airway inflammation in allergen- sensitised mice. Interestingly, a reduced induction of Foxp3+ Tregs in peripheral tissue and an accompanying increased IL-33 induced ILC2 driven inflammation in the lung responsible for the exacerbation of TH2 acute disease. Conclusively, the IL-4Rα responsive Foxp3+ T regulatory cells are key in maintaining tolerance in type 2 innate immune driven allergic asthma, therefore the TH2 environment has both an innate immune specific regulative role in local lung tissue and induction of Foxp3+ Tregs in peripheral tissue during AAD. A combined targeting of the pathogenic TH2 environment in anti-TH2 therapy and the augmentation of regulatory T cell function in the local lung tissue is necessary to inhibit both adaptive and innate drivers of TH2 inflammation in allergic disease.
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    The use of molecular diagnostic methods to improve the detection of the common bacterial and viral causes of community acquired meningitis in children in South Africa
    (2015) Khumalo, Jermaine; Bamford, Colleen; Du Toit, Elloise
    With conventional methods of diagnosis, substantial overlaps are common due to an absence of the expected CSF findings clearly aligning to bacterial or viral infection. Reduced sensitivity is commonly observed chiefly due to empiric antibiotic treatment leading to bacterial culture negative results. This leads to costly hospital admissions and unnecessarily prolonged treatment for the unexplained aetiology, further compounded by routine viral diagnostics not being commonly implemented for meningitis diagnosis. We developed and validated in-house quantitative real-time (qPCR) multiplex assays to test for bacterial causes namely: Neisseria meningitidis (ctrA gene), Haemophilus influenzae (hpd gene) and Streptococcus pneumoniae (lytA gene) and viral causes namely: enterovirus (5' UTR), herpes simplex (UL30 gene) and mumps virus (Fusion protein gene). The qPCR assays were carried out on the Biorad CFX 96 real-time instrument. These validated assays were used to screen a cohort of suspected meningitis cases. The retrospective study included 300 paediatric patients aged from 60 days-12 years, over a 1-year period (November1, 2012 to November 30, 2013) with suspected meningitis presented to the outpatient departments of the Red Cross War Memorial Children‟s Hospital (RCCH) in Cape Town. Cerebrospinal fluid with abnormal chemistry and cell counts was selected and total nucleic acid was extracted with the QIAsymphony virus/bacterial DSP kit (QIAGEN, Valencia, CA). The median age of children was 19 months (IQR: 6-65 months). Among the screened 291 CSF samples, 7 (2.4%) cases Gram stain results were obtained along with relatively few cases with positive bacterial culture growth 4/291 (1.4%). Based on bacterial qPCR results, 8 (2.7%), 3 (1%) and 1 (0.3%) were positive for S. pneumoniae, N. meningitidis and H. influenzae respectively. A majority of cases were viral positives with enteroviruses being the dominant at 91/291 (31.3%) and mumps virus 3/291 (1%). No herpes simplex DNA was detected. The bacterial qPCR showed a sensitivity and specificity of 85.7% and 97.7% respectively when compared against a composite reference standard (CRS). We report an improvement with additional detected causes of bacterial meningitis and highlight the burden of the common viral causes. However, a large proportion of cases (63.6 %) have aetiology still unknown. PCR shows valuable in concluding viral aetiology in routine diagnosis.