Immunostimulatory sequence DNA linked to the Amb a 1 allergen promotes T_H1 cytokine expression while downregulating T_H2 cytokine expression in PBMCs from human patients with ragweed allergy

Background: Recent studies have demonstrated that bacterially derived immunostimulatory sequences (ISSs) of DNA can activate the mammalian innate immune system and promote the development of T_H1 cells. Promotion of T_H1 immunity by means of immunotherapy in allergic patients has led to the alleviation of symptoms that result from allergen-specific T_H2 responses. Objective: Our purpose was to investigate whether the T_H1-enhancing properties of ISSs could be used to alter the T_H2-dominated immune response of allergic PBMCs in vitro. Methods: Ragweed protein-linked ISS (PLI) was generated from a specific, highly active 22-base ISS and Amb a 1, the immunodominant allergen in ragweed pollen, to combine the T_H1-enhancing properties of ISSs with allergen selectivity, and its activity was investigated in PBMC cultures from subjects with ragweed allergy. Results: PLI was markedly successful at reversing the dominant allergen-induced T_H2 profile while greatly enhancing IFN-γ production. Delivering ISSs in a linked form proved to be much more effective at modulating the resulting cytokine profile than delivering free ISSs in a mixture with unlinked Amb a 1. PLI also demonstrated cytokine-modulating properties, even when used to stimulate cells that had already been primed for 6 days with Amb a 1. The antigen specificity of the action of PLI was confirmed by the observations that PLI enhances Amb a 1-specific T-cell proliferation. Conclusion: These data indicate that delivery of ISSs within an antigen-specific context exhibits potent cytokine-modulating activity and, combined with its reduced allergenicity, makes this molecule a strong candidate for use in improved immunotherapy applications.