Treatment with 8-OH-modified adenine (TLR7 ligand)-allergen conjugates decreases T helper type 2-oriented murine airway inflammation

A strategy to improve allergen-specific immunotherapy is to employ new adjuvants stably linked to allergens. The study is addressed to evaluate the in vivo and in vitro effects of allergens [natural Dermatophagoides pteronyssinus 2 (nDer p 2) and ovalbumin (OVA)] chemically bound to an 8-OH-modified adenine. Humoral and cellular responses were analysed in allergen-sensitized and challenged mice by using conjugates (Conj) in a therapeutic setting. The in vitro activity of the conjugates on cytokine production induced by bone marrow dendritic cells and the co-culture system was also investigated. The nDer p 2-Conj treatment in nDer p 2-primed and challenged BALB/c mice reduced the numbers of eosinophils in bronchoalveolar lavage fluid and lung, airway allergen-driven interleukin-13 (IL-13) production in lung mononuclear cells and IgE, in comparison with nDer p 2-treated mice. The increase of IgG2a paralleled that of interferon-γ (IFN-γ) and IL-10 in allergen-stimulated spleen cells. Similar effects were elicited by treatment with OVA-Conj in an OVA-driven BALB/c model. The nDer p 2-Conj or OVA-Conj redirected memory T helper type 2 cells towards the production of IL-10 and IFN-γ also in C57BL/6 mice and when subcutaneously administered. Interleukin-10, IL-12 and IL-27 were produced in vitro by Conj-stimulated bone marrow dendritic cells, whereas IL-10 and IFN-γ were up-regulated in co-cultures of CD11c(+) and CD4(+) T cells from Conj-treated mice stimulated with allergen. Cytofluorometric analysis indicated that the Conj expanded IFN-γ- and IL-10- producing memory T cells. The Conj effects on IL-10(-/-) and IL-12(-/-) mice confirmed the role of IL-10 and IFN-γ in inducing a protective and balanced redirection the T helper type 2-mediated airway inflammation.