Background Eosinophils are highly related to allergic asthma inflammation.Interleukin(IL)-5 is the major chemokine ofeosinophils,inhibition of the activity of IL-5 thus seems to be a potential approach to asthma therapy.The current studywas performed to determine whether a recombinant human IL-5 protein as a xenogeneic vaccine has the capability ofinducing anti-asthma activities.Methods Recombinant human iL-5 was used as a protein vaccine.Mouse asthma model was established to observethe anti-asthma activities.Lung histology was observed;eosinophils in blood and bronchoalveolar lavage were stainedand counted.Airway hyperresponsiveness was determined by whole body plethysmograph.Antibody characters andcytokines were detected with enzyme linked immunosorbent assay(ELISA)and Western blot assay.Results Vaccination with recombinant human IL-5 protein as vaccine significantly reduced airway inflammation andairway hyperresponsiveness,and shifted the cytokine production from Th2(IL-4)to Thl(INF-γ)in mice allergic-asthmamodel.Immunization with recombinant human IL-5 protein vaccine bypassed the immunological tolerance and inducedproduction of polyclonal antibodies that were cross-reactive with murine IL-5.Conclusions Active immunization with xenogeneic homologous iL-5 may be a possible therapeutic approach to thetreatment of asthma and potentially of other eosinophilic disorders.Chin Med J 2007;120(17):1517-1522 Background Eosinophils are highly related to allergic asthma inflammation. Interleukin (IL) -5 is the major chemokine of eosinophils, inhibition of the activity of IL-5 thus seems to be a potential approach to asthma therapy. Current study was performed to determine whether a recombinant human IL-5 protein as a xenogeneic vaccine has the capability of inducing anti-asthma activities. Methods Recombinant human iL-5 was used as a protein vaccine. Mouse asthma model was established to observe the anti-asthma activities. Lung histology was observed; eosinophils in blood and bronchoalveolar lavage were stainedand counted. Airway hyperresponsiveness was determined by whole body plethysmograph. Antibody characters andcytokines were detected with enzyme linked immunosorbent assay (ELISA) and Western blot assay. Results Vaccination with recombinant human IL-5 protein as vaccine significantly reduced airway inflammation andairway hyperresponsiveness, and shifted the cytokine production from Th2 (IL-4) to Thl (INF -γ) in mice allergic-asthma model. Immunization with recombinant human IL-5 protein vaccine bypassed the immunological tolerance and inducedproduction of polyclonal antibodies that were cross-reactive with murine IL-5.Conclusions Active immunization with xenogeneic homologous iL-5 may be a possible therapeutic approach to the treatment of asthma and potentially other other eosinophilic disorders. Chin Med J 2007; 120 (17): 1517-1522