Immunostimulatory sequence DNA linked to the Amb a 1 allergen promotes T(H)1 cytokine expression while downregulating T(H)2 cytokine expression in PBMCs from human patients with ragweed allergy

Background: Recent studies have demonstrated that bacterially derived immun ostimulatory sequences (ISSs) of DNA can activate the mammalian innate immu ne system and promote the development of T(H)1 cells. Promotion of T(H)1 im munity by means of immunotherapy in allergic patients has led to the allevi ation of symptoms that result from allergen-specific T(H)2 responses. Objective: Our purpose was to investigate whether the T(H)1-enhancing prope rties of ISSs could be used to alter the T(H)2-dominated immune response of allergic PBMCs in vitro. Methods: Ragweed protein-Iinked ISS (PLI) was generated from a specific, hi ghly active 22-base ISS and Amb a 1, the immunodominant allergen in ragweed pollen, to combine the T(H)1-enhancing properties of ISSs with allergen se lectivity, and its activity was investigated in PBMC cultures from subjects with ragweed allergy. Results: PLI was markedly successful at reversing the dominant allergen-ind uced T(H)2 profile while greatly enhancing IFN-gamma production. Delivering ISSs in a linked form proved to be much more effective at modulating the r esulting cytokine profile than delivering free ISSs in a mixture with unlin ked Amb a 1. PLI also demonstrated cytokine-modulating properties, even whe n 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 obse rvations that PLI enhances Arab a 1-specific T-cell proliferation. Conclusion: These data indicate that delivery of ISSs within an antigen-spe cific context exhibits potent cytokine-modulating activity and, combined wi th its reduced allergenicity, makes this molecule a strong candidate for us e in improved immunotherapy applications.