The Study Of Vaccine On IgE-mediated Disease

Objective: IgE-mediated disease is a hypersensitive syndrome caused by too much IgE when exposed to allergens and often accompanied by some other allergic diseases. Once an antigen enters the host, it is subject to the immune system of the host. The immunoglobulins are used when the antigen encounters one of the host's B-cells. Synthesis of IgE after exposure to allergen is the instigator of the allergic process. IgE is just one player in a highly complex immune response by Th2 cells, it is undoubtedly of central importance in both immediate hypersensitivity and the late-phase responses characteristic of allergy and asthma. IgE bound to mast cells via FcεRI triggers degranulation and release of mediators that produce symptoms associated with allergy vital to disease. IgE-mediated diseases include atopic dermatitis, allergic rhinitis and asthma with some severe cases like allergic shock and even death. The IgE/FceRI interaction is a target for clinical intervention in allergic disease. Using chimeric proteins, the Cε3 was indicated as the principal region in mouse IgE involved in the interaction with FcεRI. The small domain (within Fcε3 ) of the IgE constant region binds to high-affinity (FcεRI) surface receptors on mast cells or basophils or to low-affinity receptors on B lymphocytes and eosinophils. Antibodies, which block IgE binding to FcεRI, have the therapeutic potential for treating allergic diseases. Although anti-IgE mAb has showed promising effect in treatment of IgE-mediated diseases, the cost and inconvenience have restricted the widely application of mAb. So, compared to the passive vaccination with antibodies, active vaccination is more easily to be accepted and applied in therapy. To construct the therapeutic vaccine targeted on IgE receptor binding site and induce the antibody thus block the route of IgE and to provide a new way against IgE-mediated diseases, the experiment is designed.Methods: The binding site of IgE and its receptor (CH3 gene) was obtained by genomic PCR and protein vaccine and gene vaccine of IgE receptor binding site are constructed. An epitope was screened out with computer assistant software to construct polypeptide vaccine. To enhance the immunogecity of vaccines, a universal Th helper cell epitope TT830-844 was linked in N-terminal of CH3 and multiple antigenic peptide (MAP) is synthesized. Healthy female BALB/c mice were randomly divided into six groups, namely the healthy group (H), the asthma group (A), the empty vector group (pVAC-cms), DNA vaccine group (pVAC-CH3-TT), protein vaccine group (pQE30-CH3-TT) and multiple antigen peptide group (MAP).After immunized with different vaccines, BALB/c mice were primed asthmatic model to evaluate the effect of vaccines.Results: The fusion genes were cloned and expressed successfully in E.Coli and the forms of CH3-TT protein expression were inclusion body which was used as antigen to immunize animal. The recombinant plasmid pVAC-CH3-TT was constructed and expressed in CHO cells. The purified plasmid pVAC-CH3-TT was measured up as DNA vaccine antigen. An epitope was screened out with computer assistant software, synthesized in the form of MAP which could be used as peptide antigen. Mice were immunized with three candidate vaccines. The results showed that three candidate vaccines could induce special neutralizing antibody and the titer of gene vaccine group, protein vaccine group and MAP group were1:3200, 1:3200 and 1:6400 respectively. In asthmatic model, eosinophils (Eos) infiltrated around airways and blood vessels, and partial alveolar sacs histologically, but healthy mice group showed none of these changes. In vaccine-treated asthmatic models, histologic evaluation revealed marked suppression of eosinophils peribronchial and perivascular infiltration; the recoverable Eos in BALF were statistically decreased, compared with the asthmatic control group. Compared with group A, the IL-4 content in BALF and IgE level in serum were reduced significantly. Degranulation percentage of mast cells on the mesenterium from vaccinal groups were decreased compared with group A but still have significant difference with group H. Vaccinal groups have no obvious influence on ear swelling, lung index and weight of mice. Conclusion: Three candidate therapeutic vaccines were constructed and systemically compared with each other. These three vaccines have an inhibitory effect on inflammation in a murine model of allergic asthma. Among them, gene vaccine showed a better effect than protein and MAP vaccine which indicates a new strategy against allergic asthma.