Use of Omp16 as a mucosal adjuvant in a sublingual immunotherapy for food allergy

ORSINI DELGADO, M LUCÍA; SMALDINI PAOLA LORENA; PASQUEVICH, KARINA; CASSATARO, JULIANA; DOCENA, GUILLERMO H

Congreso; 11th Congress of the Latin American Association of Immunology; 2015

Asociación Latinoameriacana de inmunologia

Food allergy is an immune mediated adverse reaction characterized by a loss of tolerance to food proteins. Cow´s milk allergy affect 3-5% of pediatric population, being one of the most prevalent food allergies. Nowadays the only accepted therapy for food allergies is an allergen-free diet. However, nutritional complications and eventually allergic reactions due to accidental ingestion of allergens may arise. Sublingual allergen immunotherapy (SLIT) has been proposed as a disease-modifying therapy although further studies are needed to improve its efficacy and reduce adverse effects. In this work, we aimed to induce oral tolerance to cow`s milk protein (CMP) through the sublingual administration of CMP and and the TLR4 agonist Outer Membrane Protein 16 (Omp16) of Brucella abortus, as a potential mucosal adjuvant.BALB/c mice were intragastrically sensitized with CMP plus cholera toxin and orally challenged with CMP. Then sensitized mice underwent SLIT twice a week during 8 weeks with CMP (CMPdes), CMP + Omp16 (Omp16des), or PBS as control (Sens). Finally, mice were orally challenged again and the immune response was evaluated with in vivo (clinical score and cutaneous test) and in vitro [serum specific antibodies for Th2 (IgE, IgG1) and Th1 (IgG2a) isotypes, IL-5, IL-13 and IFN-γ production by splenocytes stimulated with CMP by ELISA] assays. Dendritic cells (in intestinal lamina propria and sublingual mucosa) and T cells (in sublingual lymph nodes, intestinal lamina propria and spleen) were evaluated by flow cytometry. After treatment, clinical signs and cutaneous test were lower in both CMPdes and Omp16des groups compared with Sens group. A decrease in serum specific IgE was also observed in both groups [DO = 2,027 ± 0,2965 vs 1,155 ± 0,2389 Sens vs CMPdes and DO = 2,027 ± 0,2965 vs 1,111 ± 0,1680 Sens vs Omp16des (p<0.01)]. However, Omp16-treated mice had more serum specific IgG2a levels [DO = 0,5140 ± 0,1512 vs 2,343 ± 0,5308 Sens vs Omp16des (p<0.001)], and a lower IgG1/IgG2a ratio [12,50 ± 3,813 vs 1,135 ± 0,05861 Sens vs Omp16des(p<0.01)] compared to Sens controls, indicating a Th1-biased immune response. Decreased levels of IL-5 [240,3 ± 9,517 pg/ml vs 129,9 ± 32,10 pg/ml Sens vs Omp16des (p<0,05)] and IL-13 [1118 ± 121,2 pg/ml vs 240,3 ± 42,98 pg/ml Sens vs Omp16des (p<0,001)] and increased IFN-γ [68,42 ± 39,75 pg/ml vs 378,4 ± 306,0 pg/ml Sens vs Omp16des (p<0,05)] were found. Omp16des group also showed a higher percentage of lamina propria dendritic cells CD11c+ CD11b- CD8α+ [4,552 ± 2,226% vs 11,23 ± 3,370% Sens vs Omp16des (p < 0,05)] and of sublingual lymph nodes CD4+ IFNγ+ α4β7+ T cells [1,326 ± 0,5295 % vs 5,633 ± 1,574 Sens vs Omp16des(p < 0,05)], CD4+ Foxp3+ T cells (9,835 ± 2,297 % vs 12,31 ± 3,094 % Sens vs Omp16des) and CD4+ Foxp3+ IL-10+ T cells [1,584 ± 0,2471 % vs 4,833 ± 1,686 % Sens vs Omp16des (p<0,05)] .In conclusion, our results showed that the sublingual administration of Omp16 induced a Th1 immune response that modulated the allergic response in a food allergy mouse model. These findings suggest that Omp16 may be used as a mucosal adjuvant in a sublingual immunotherapy