β-Glucan microparticles are good candidates for mucosal antigen delivery in oral vaccination Rebecca De Smet a, ⁎, Tine Demoor b , Stephanie Verschuere a , Melissa Dullaers c , Gary R. Ostroff d , Georges Leclercq e , Liesbeth Allais a , Charles Pilette f , Marijke Dierendonck g , Bruno G. De Geest g , Claude A. Cuvelier a a Department of Pathology, Ghent University, De Pintelaan 185, 9000 Ghent, Belgium b Department of Pathology, University of Michigan, Zina Pitcher Place 109, 48109 Ann Arbor, USA c Laboratory of Immunoregulation and Mucosal Immunology, Department of Pneumology, Ghent University, De Pintelaan 185, 9000 Ghent, Belgium d Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Suite 113, Biotech 2, Worcester, 01605, USA e Department of Clinical Chemistry, Microbiology and Immunology, Ghent University, De Pintelaan 185, 9000 Ghent, Belgium f Pole Pneumologie, ORL & Dermatologie, Institut de Recherche Expérimentale & Clinique and Department of Pneumology, Cliniques Universitaires St. Luc, Université Catholique de Louvain, Avenue Hippocrate 54, 1200 Brussels, Belgium g Laboratory of Pharmaceutical Technology, Department of Pharmaceutics, Ghent University, Harelbekestraat 72, 9000 Ghent, Belgium abstract article info Article history: Received 25 June 2013 Accepted 5 September 2013 Available online 14 September 2013 Keywords: β-glucan microparticles Antigen delivery Oral vaccination Peyer's patches Vaccines Continuously improving the developmental process and the efficacy of oral vaccines is essential in the fight against intestinal pathogens. A promising strategy for vaccination applying safe, biodegradable and non-replicating antigen delivery systems has gained increased interest for eliciting cellular and humoral immune responses. The current study evaluates the potential of β-glucan particles (GP) as an oral antigen delivery system and their adjuvant char- acteristics. GP are efficiently internalized by human intestinal epithelial cell lines (Caco-2 and HT-29 cells), without exerting negative effects on cell viability. GP triggered the expression of pro-inflammatory cytokines IL-23p19, IL-8 and the β-glucan receptors dectin-1 and TLR2 by activated Caco-2 cells, and CCL20 in HT-29 cells. In contrast, the expression level of TGF-β, an important mediator of oral tolerance, was significantly downregulated in HT-29 cells. Additionally, adoptive transfer experiments showed proliferating ovalbumin (OVA)-specific CD4 + T cells mainly in the spleens of GP-OVA-fed mice. Furthermore, we detected a significantly increased IL-17 and a trend towards increased IFN-γ production in the spleen of GP-OVA-fed mice upon antigen restimulation. Oral administration of GP-OVA induced increased OVA-specific IgA, secretory-IgA (S-IgA) and secretory component (SC) production in in- testinal fluids. Our data show that GP vehicles are able to deliver OVA via an oral route allowing efficient antigen presentation alongside adaptive immune activation, resulting in a Th17-biased response and the production of OVA-specific IgA, secretory-IgA and secretory component antibodies. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Parenteral vaccination strategies fail to generate an adequate local mucosal immune response against still prevailing intestinal infections, such as cholera, dysentery and typhoid fever. A topical–mucosal route of vaccination is crucial to induce protective immune responses (mucosal S-IgA and serum IgG responses) and may even lead to immunity at distant mucosal effector sites via the interconnected ‘common mucosal immune system’ [1]. Particularly in developing countries, oral vaccina- tion may offer a means to deal with safety concerns (eliminates risk of infections associated with needle re-use), poor patient compliance and the need for mass vaccination. However, the development of oral subunit vaccines holds major chal- lenges with regard to safety and efficacy in overcoming oral tolerance [2]. First, the antigen delivery system must be designed to resist enzymatic degradation by gastric and intestinal proteases and to deliver the antigen across biological barriers — in particular the intestinal epithelium. Secondly, upon successful cellular uptake, the vaccine formulation needs to elicit potent and long-lasting humoral and cellular immune re- sponses. Current oral vaccines are based on inactivated or attenuated pathogens. Although both formulations provide a high level of antigen exposure and to some extent also have an intrinsic adjuvanticity, their immunogenicity and stability still remain a problem. In particular atten- uated vaccines maintain the risk of reversion to virulence and may induce disease in immunocompetent and immunocompromised indi- viduals. This could be counteracted by the use of recombinant/subunit vaccines based on specifically defined and purified antigens (peptides Journal of Controlled Release 172 (2013) 671–678 Abbreviations: GP, β-glucan microparticles; PP, Peyer's patches; MLN, mesenteric lymph nodes; S-IgA, secretory-immunoglobulin A; SC, secretory component; PRR, pattern recognition receptor; pIgR, polymeric immunoglobulin receptor. ⁎ Corresponding author at: Department of Pathology, 5 Blok A, Ghent University, De Pintelaan 185, 9000 Ghent, Belgium. Tel.: +32 9 332 36 86; fax: +32 9 332 49 65. E-mail address: rebecca.desmet@ugent.be (R. De Smet). 0168-3659/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jconrel.2013.09.007 Contents lists available at ScienceDirect Journal of Controlled Release journal homepage: www.elsevier.com/locate/jconrel