Epicutaneous Exposure to Staphylococcal Superantigen Enterotoxin B Enhances Allergic Lung Inflammation via an IL-17A Dependent Mechanism

<div><p>Atopic dermatitis (AD) is the initial step of the atopic march: the progression from AD to allergic rhinitis and asthma. There is a close association between skin barrier abnormalities and the development of AD and the atopic march. One of cardinal features of AD is that the lesional skin of the majority of AD patients is chronically colonized with <em>Staphylococcus aureus</em> with half isolates producing superantigen enterotoxin B (SEB). Although diverse roles of SEB in the pathogenesis and severity of AD have been recognized, whether SEB contributes to the dermal inflammation that drives lung inflammation and airway hyperresponsiveness (AHR) has not been examined. Here we show a novel role of <em>S. aureus</em> superantigen SEB in augmenting allergen ovalbumin (Ova) induced atopic march through an IL-17A dependent mechanism. When mice epicutaneously (EC) sensitized with allergen Ova, addition of topical SEB led to not only augmented systemic Th2 responses but also a markedly exaggerated systemic Th17/IL-17 immune environment. The ability of SEB in enhancing Th17/IL-17 was mediated through stimulating lymphocytes in spleen and draining lymph nodes to promote IL-6 production. Epicutaneous sensitization of mice with a combination of Ova and SEB significantly enhanced Ova-induced AHR and granulocytic lung inflammation than Ova allergen alone. When IL-17A was deleted genetically, the effects of SEB on augmenting lung inflammation and AHR were markedly diminished. These findings suggest that chronic heavy colonization of enterotoxin producing <em>S. aureus</em> in the skin of patients with atopic dermatitis may have an important role in the development of atopic march via an IL-17A dependent mechanism.</p> </div

SEB enhanced airway resistance and Th17 and Th2 cytokine expression in the lung of EC-sensitized and Ova airway challenged mice.

<p>Airway resistance (<i>R_L</i>) in response to increasing concentrations of methacholine was measured by the invasive PFT method (flexiVent). Cytokines in the BAL and lung tissues were measured by ELISA. (a) Changes in airway resistance (shown are combined data from two separate experiments; n = 4–5 per group; *<i>p</i><0.05). (b, d, e, f) IL-17A, IL-4, IL-13, and IFN-γ in the BAL; (c) IL-17A in lung tissue; and (g, h, i) Lymphocytes of bronchial lymph nodes produced IL-17A, IL-4, and IFN-γ, respectively (n = 7 each group; *p≤0.05, **p≤0.01).</p

SEB stimulated and enhanced Ova induced IL-6 production by immune cells.

<p>(a, b) SEB stimulated IL-6 production by lymphocytes from skin DLNs and spleen for 72 hrs. (c, d) Ova stimulated IL-6 produced by lymphocytes from skin DLNs and spleen for 72 hrs. Data are representative of two experiments with similar results. Columns and error bars represent Mean ± SEM (n = 5–9 mice per group; *p≤0.05, **p≤0.01).</p

SEB synergistically enhanced Ova stimulated IL-17A production by lymphocytes and exaggerated systemic Ova-specific IgE production.

<p>(a–f) Ova stimulated production of IL-17A, IL-4, and IFN-γ by lymphocytes from DLN or spleen of mice sensitized with PBS, SEB, Ova and Ova + SEB (n = 5–7 per group; *p≤0.05, **p≤0.01). (g) SEB-specific IgG1 and (h) Ova-specific IgE in the serum. Data are Mean ± SEM (n = 5–7 per group; *p≤0.05, **p≤0.01).</p

Deletion of IL-17A gene reduced SEB enhanced Ova-induced changes in lung physiology.

<p>(a) Airway resistance in response to methacholine after epicutaneous sensitization and Ova airway challenge. The columns and error bars represent Mean ± SEM (shown are combined data from two separate experiments; n = 4–5 per group; *<i>p</i><0.05, compared to WT mice).</p

SEB stimulated lymphocyte IL-17A production.

<p>IL-17A, IL-4 and IFN-γ produced by lymphocytes from cervical, axillary, inguinal draining lymph nodes (DLNs) or from spleen after SEB stimulation (a-f). Data are representative of two experiments with similar results. Columns and error bars represent Mean ± SEM (n = 5–7 per group; *p≤0.05, **p≤0.01).</p

Systemic (blood) and local (nasal lavage fluid) immune parameters in adults with NAR and AR.

<p>Systemic (blood) and local (nasal lavage fluid) immune parameters in adults with NAR and AR.</p

Correlation analysis of local-systemic interactions in children and adults.

<p>(A) Scatter plots and regression lines show interactions of (A) total IgE between NAL fluids and serum and (B) eosinophilia (%) between NAL fluid and peripheral blood. IgE-mediated eosinophilic inflammation is shown in the peripheral blood (C) and NAL fluids (D).</p

Local immune parameters in children and adults with allergic rhinitis (AR, A-C) and nonallergic rhinitis (NAR, D-F).

<p>(A, D), flow cytometry; (B, E), CAP immunoassay; (C, F), ELISA. *P < 0.05, **P < 0.01.</p

Cut-off value and areas under the receiver operating characteristics for local immune markers in children and adults with AR.

<p>Cut-off value and areas under the receiver operating characteristics for local immune markers in children and adults with AR.</p