The outer-membrane-derived proteoliposome (PL) of Neisseria meningitidis has been reported as a potent vaccine adjuvant, inducing a Th1-skewed response. This work aimed to assess the immunogenicity of a novel anti-allergic vaccine candidate based on allergens from Dermatophagoides siboney house dust mite and a combination adjuvant containing PL and Alum. In a preventative experimental setting, BALB/c mice were administered with three doses containing 2 µg of Der s1 and 0.4 µg Der s2 allergen, PL and Alum, at 7 days intervals, by subcutaneous route. Furthermore, mice were subjected to an allergen aerosol challenge for 6 consecutive days. Serum IgE, IgG1, and IgG2a allergen-specific antibodies were assessed by ELISA. Cytokine levels in supernatants of D. siboney stimulated lymphocyte cultures and in bronchoalveolar lavage (BAL) were measured by ELISA. Lung tissues were subjected to histological examination. The vaccine prevented the development of both, systemic (IgE) and local allergic responses (featuring lower IL-4, and IL-5 levels in BAL) upon allergen exposure by the inhalant route. Histological examination showed also a diminished allergic inflammatory response in the lungs. After the allergen challenge, cytokine levels in stimulated lymphocyte cultures showed lower values of IL-13 and augmented IFN-γ and IL-10. The vaccine induced a mixed IgG2a/IgG1 antibody response; although only IgG2a was PL-dependent. Both, IgG1/IgE and IgG2a/IgE ratios, showed significantly greater values in vaccinated mice. The findings support a preventative anti-allergic effect associated with the induction of a Th1-like IFN-γ/IL-10 response. IgG1/IgE and IgG2a/IgE ratios could be useful biomarkers for translation into clinical trials.

BackgroundIn recent years one important trend of Allergen-specific immunotherapy is to investigate new adjuvants with immunomodulatory properties. The outer membrane vesicle or proteoliposome (PL) from Neisseria meningitidis serogroup B has been reported as a potent adjuvant inducing a Th1-skewed response. The aim of this work was to assess the immunogenicity of a novel anti-allergic vaccine candidate based on purified allergens from Dermatophagoides siboney mite and PL as adjuvant, both components adsorbed onto Aluminum hydroxide.MethodsIn a preventative experimental setting BALB/c mice were administered with 3 doses containing 5 μg of Der s 1 allergen at one week intervals by subcutaneous route. Further, mice were subjected to allergen challenge by aerosol inhalation. In another experiment, mice were administered first with 2 doses of PL + Alum and later with the whole vaccines formulation, including the allergen. The allergen-specific antibody response was assessed determining serum levels of IgE, IgG1, and IgG2a by ELISA. The local allergic inflammatory response was evaluated by measuring cytokine levels (IL-4, IL-5, IFNg and IL-10) in broncho-alveolar lavage (BAL) by ELISA.ResultsThe formulation consistently induced IgG2a, as well as IgG1 antibodies with a potential anti-IgE blocking effect. The induction of IgG2a was clearly PL dependent while IgG1 was dependent mostly of Alum. Prior administration of the proteoliposome with alum without allergen showed to enhance this allergen-specific immunogenic effect. The vaccine prevented the development of systemic (IgE) and local allergic response in mice subjected to allergen exposure by inhalant route. Vaccinated mice showed lower levels of serum IgE, Th2 cytokines (IL-4, IL-5) in BAL and lower eosinophil counting in blood as compared to controls. Histological examination of lungs showed also a diminished allergic inflammatory response in vaccinated mice in contrast with mice which were administered with the conventional formulation of Alum-adsorbed allergen.ConclusionsThe antiallergic protective effect was proven in a preventative setting, showing to decrease the inflammatory response in the lungs of mice exposed to allergen aerosol, as well as, a Th2-antagonistic immune response with few injections.

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