Sensitization of Mice with Olive Pollen Allergen Ole e 1 Induces a Th2 Response

Abstract

Background: Olive pollen is one of the main causes of allergy in Mediterranean countries, where it is widely distributed. One inconvenience in studying new immunotherapies for olive pollen allergy is the lack of suitable animal models. The aim of this study was to develop a murine model of IgE sensitization to Ole e 1, the major allergen of olive pollen, which mimics the immunological features of olive pollinosis in humans and to investigate the in vivo antigenicity of the recombinant form of the allergen. Methods: BALB/c mice were sensitized by intraperitoneal administration of natural Ole e 1 (nOle e 1) and recombinant Ole e 1 (rOle e 1) in Al(OH)₃, respectively. Serum levels of specific IgE, IgG1 and IgG2a, cytokine production and the proliferative response of splenocytes after in vitro stimulation with nOle e 1 were analyzed by ELISA and flow cytometry. The binding capacity of rOle e 1-specific IgG1 was examined by ELISA and immunoblotting. Results: Sensitization with nOle e 1 or rOle e 1 induced high levels of specific IgE and IgG1 versus low IgG2a antibody levels. Splenocytes from sensitized mice exhibited a proliferative response to nOle e 1. In vitro stimulated splenic cells from nOle e 1-primed mice produced IL-4 and low or nondetectable levels of IFN-γ. Specific IgE and IgG1 antibodies of immunized mice bound to the same Ole e 1 isoforms and showed a similar degree of cross-reactivity as observed for human IgE. Mouse specific nOle e 1 IgG1 was strongly inhibited by IgE from allergic patients. The IgG1 antibodies elicited by rOle e 1 reacted with both the recombinant and natural forms of the allergen. Conclusions: A murine model of Ole e 1 sensitization has been established. rOle e 1 shows similar allergenicity and antigenicity to its natural form. This model should provide a useful tool for evaluating antigenic molecules and exploring new therapeutic approaches in order to treat IgE-mediated olive pollinosis.