Contents lists available at ScienceDirect Cytokine journal homepage: www.elsevier.com/locate/cytokine Enhanced expression of PD-L1 and IFN-γ on dendritic cells is associated with BCG-induced Th2 inhibition A.C.C. Gouveia, F.G. Braga, M. Mota, F.M.C. Silva, A.S.S. Brugiolo, E.E. Oliveira, M.C. Ayupe, H.C. Teixeira, A.P. Ferreira ⁎ Department of Parasitology, Microbiology, and Immunology, Institute of Biological Sciences, Federal University of Juiz de Fora, Juiz de Fora, MG, Brazil ARTICLE INFO Keywords: Asthma OVA-induced airway inflammation Mycobacterium bovis BCG Dendritic cells Toll-like receptors PD-L1 ABSTRACT Accumulating evidence indicates that the exposure to Mycobacterium bovis bacillus Calmette-Guérin (BCG) prevents the development of allergy and the airway dendritic cells (DCs) may be involved in this protective effect. However, studies to better characterize the specific interactions between BCG and DCs and their role in this mycobacteria-mediated Th2 cell suppression are still ongoing. This study aimed to evaluate the effect of the neonatal BCG vaccination in the innate immune response in a mouse model of ovalbumin (OVA)-induced airway inflammation. BCG treated neonatal BALB/c mice were sensitized and challenged with aerosolized OVA. Twenty-four hours after the last challenge, samples were collected for analysis. The intranasal BCG treatment inhibited the allergic Th2-response by decreasing the allergen-induced eosinophilic inflammation, EPO activity, CCL11, IL-25, TSLP, IL-4 and IL-5 lung levels, and serum levels of IgE. Mycobacteria treatment increased lung levels of IL-10 and TGF-β, and the TLR2 and TLR4 expressions by pulmonary CD11c + CD103 + CD8α + DCs. Additionally an enhanced expression of PD-L1 was observed besides an increased production of IFN-γ by these cells. These results indicated that neonatal BCG vaccination inhibits key features of allergic airway inflamma- tion, probably by promoting T regulatory immune response via an enhanced expression of TLR2, TLR4 and PD- L1 on DCs. 1. Introduction Atopic asthma is a potentially life-threatening chronic respiratory disease characterized by episodes of reversible airway narrowing, bronchial hyperresponsiveness, mucus over-production and airway in- flammation associated with an increase of T helper 2 (Th2)-type cyto- kines and IgE synthesis [1,2]. The asthma incidence is increasing leading to major health and economic consequences [3]. Although conventional pharmacological therapies are highly effective for con- trolling disease in most individuals, many patients have concerns about side-effects and treatment may not be effective in cases of difficult-to- control asthma [4]. In addition, such interventions provide short-term relief from disease symptoms, not altering the underlying immune re- sponse to an allergen. Therefore, there remains a clear need for new strategies that have specific and long-lasting effects for the treatment of asthma [5]. The hygiene hypothesis postulates that reduced exposure to mi- croorganisms should increase immune reactivity, favoring the development of allergic diseases [6]. Even though the original concept has been modified [7], the hypothesis that microbial experience mod- ulates our immune systems has been strengthened by solid epidemio- logical [8,9] and experimental data [10,11]. In keeping with these findings there have been extensive efforts to subvert the Th2 immune response by treatment with microbial products, paving the way for future therapies [12]. In this context, a number of studies have shown that Mycobacterium bovis bacillus Calmette-Guérin (BCG) treatment is capable of ameliorating an established allergen-driven inflammatory response [13], probably resulting from an immune deviation from a pathogenic Th2 towards protective T helper 1 (Th1) and/or T reg- ulatory (Treg) responses [13,14]. Although several models have been used to evaluate this mycobacteria effect, the immunological mechan- isms by which BCG could reprogram effector T cell lineage commitment in allergic inflammation has not been clearly defined. It is now well established that the development of a Th2-response is fundamentally influenced by a fine balance between the functions of innate immune and epithelial cells [15,16]. In this way, as a critical link http://dx.doi.org/10.1016/j.cyto.2017.09.005 Received 16 May 2017; Received in revised form 5 September 2017; Accepted 6 September 2017 ⁎ Corresponding author. E-mail address: ana.paula@ufjf.edu.br (A.P. Ferreira). Abbreviations: BCG, Mycobacterium bovis bacillus Calmette-Guérin; DC, dendritic cells; HE, hematoxylin and eosin; OVA, ovalbumin; PD, programmed death; PD-L, programmed death ligand; SR, sirius red; TLRs, tool-like receptors; TSLP, thymic stromal lymphopoietin; Treg, regulatory T cells Cytokine 99 (2017) 163–172 1043-4666/ © 2017 Elsevier Ltd. All rights reserved. MARK