Intranasal ovalbumin immunotherapy with mycobacterial adjuvant promotes regulatory T cell accumulation in lung tissues

ABSTRACTAllergen‐specific immunotherapy to induce T regulatory cells in the periphery has been used to treat allergic diseases. Mycobacteria can be used as an adjuvant for inducing T regulatory cells. However, it is unclear whether intranasal immunotherapy in combination with Mycobacteria adjuvant induces regulatory T cell differentiation and attenuates allergic responses in vivo. To investigate the role of intranasal ovalbumin (OVA) treatment alone and in combination with Mycobacteria vaccae, proportions of FoxP3+ regulatory T cells and anti‐inflammatory responses were evaluated in a murine model of asthma that was established in three groups of bicistronic Foxp3EGFP reporter BALB/c mice. Before establishment of the asthma model, two groups of mice received intranasal OVA immunotherapy and one also received simultaneous s.c. M. vaccae. Expression of CD4+CD25+Foxp3+EGFP+ T cells in the lung and spleen was analyzed by flow cytometry and the cytokine profiles of allergen‐stimulated lung and spleen lymphocytes assessed. The intranasal OVA immunotherapy group showed greater expression of CD4+CD25+Foxp3+EGFP+ T cells in the spleen whereas in the group that also received M. vaccae such greater expression was demonstrated in the lung. Additionally, the proportion of IL‐10 and IFN‐γ‐secreting splenocytes was greater in the intranasal OVA + M. vaccae group. CD25 neutralization decreased CD4+Foxp3+ cells more than other groups. In parallel with this finding, production of IL‐10 and IFN‐γ was down‐regulated. Mucosal administration of OVA antigen results in a greater proportion of CD4+Foxp3+ T cells in the spleen. IL‐10 and IFN‐γ induced by intranasal OVA immunotherapy and M. vaccae administration is down‐regulated after CD25 neutralization.