Assessment of <i>In Vitro</i> Models of the Human Buccal Mucosa for Vaccine and Adjuvant Development

To understand requirements for immunization via the oral mucosa, an <i>in vitro</i> model that recapitulates the physical barrier of the mouth, allows for quantification of antigen uptake and permeability and mounts an inflammatory response to antigen and adjuvant is needed. The physical structure of 4 models of the human oral mucosa was determined by histochemical staining and transepithelial electrical resistance (TEER) measurements. A TR146 based air-liquid interface (ALI) model most closely mimicked <i>in vivo</i> conditions. This was confirmed by validation studies using dextran and caffeine as diffusant molecules. Apparent permeability coefficients (<i>P</i>_app) of adenovirus (Ad) and adeno-associated virus (AAV) in this model were 4.3 × 10^-13 and 2.2 × 10^-10 respectively, while 100% of the total dose of H1N1 influenza remained in the epithelial layer. Sodium glycocholate and a hyperosmotic formulation improved the amount of Ad (<i>p</i> = 0.02) and AAV (<i>p</i> = 0.003) that entered the epithelium, respectively. Significant amounts of IL-6 (45.1 pg/mL), GM-CSF (94.7 pg/mL) and IFN-γ (4.3 pg/mL) were produced in response to influenza infection. Treatment with an AS03-like adjuvant induced production of IL-6 (34.9 pg/mL), TNF-∝ (43 pg/mL), GM-CSF (121.2 pg/mL) and IFN-γ (14.1 pg/mL). This highlights the contribution of differentiated epithelial cells to the immune response to vaccines and adjuvants.