CD4-mediated regulatory T-cell activation inhibits the development of disease in a humanized mouse model of allergic airway disease.

BACKGROUND: Based on their potency to control allergic diseases, regulatory T (Treg) cells represent a promising target for novel strategies to interfere with allergic airway inflammation. We have previously demonstrated that stimulation of the CD4 molecule on human Treg cells activates their suppressive activity in vitro and in vivo. OBJECTIVE: We sought to determine the effect of CD4-mediated Treg-cell activation on pulmonary inflammation in a humanized mouse model of allergic airway inflammation. METHODS: PBMCs obtained from donors allergic to birch pollen or from healthy donors were injected into NOD-severe combined immunodeficiency γc(-/-) mice, followed by allergen airway challenges and analysis of airway responsiveness and inflammation. For Treg-cell activation, mice were treated with the CD4-binding, lck-activating recombinant HIV-1 surface protein gp120 after sensitization prior to allergen challenge. Control experiments with CD25-depleted PBMCs were performed to evaluate the role of Treg cells. RESULTS: PBMCs from allergic donors but not from healthy donors induced airway inflammation and airway hyperresponsiveness. Treatment with gp120 prior to allergen challenge abrogated airway hyperresponsiveness and reduced the inflammatory immune response. In contrast, treatment had no effect on inflammation and airway hyperresponsiveness in mice that received CD25-depleted PBMCs, demonstrating Treg-cell dependency of disease prevention. CONCLUSION: Allergic airway inflammation can be prevented by stimulation of human Treg cells by CD4. These results suggest a clinical potential of Treg-cell activation by high-affinity CD4 ligands in allergic diseases.