Study On Vaccines Fused To Fragment C Of Tetanus Toxin Of Alzheimer's Disease

Alzheimer's disease (AD), a progressive neurodegenerative disorder, is the main type of dementia in elderly people. The amyloid cascade hypothesis has dominated the field of Alzheimer's disease research and has provided the intellectual framework for therapeutic intervention. The hypothesis indicates that the amyloid-βpeptides, derived from amyloid precursor protein (APP), are the main cause of AD. In 1999, the first study on active immunization was proved successful to immune therapy of AD. The striking biological effect of vaccination in this testing in transgenic mice encouraged the launch of clinical trials with AN- 1792, a vaccine contained preaggregated Aβ1-42 and QS21. Unfortunately, this clinical trial was paused early when 6% of vaccinated patients had symptoms of meningitis because Th1 immune response. Therefore, recent research on vaccines of AD trends to use B cell epitopes of Aβ42(Aβ1-15) and cancel T cell epitopes of Aβ42(Aβ17-21, Aβ29-42). According to previous studies and safety, vaccine of AD should induce organism produced the specific antibody IgG against Aβand avoid Th1 immune response at the same time. In this study, we attempted to develop recombinant sub-unit vaccines and DNA vaccines fused to fragment C of tetanus toxin against Alzheimer's disease.Firstly, we developed three recombinant sub-unit vaccines of Alzheimer's disease. All of fusion genes encoding containing the immunodominant B cell epitope fromβ-amyloid and pan-DR helper T cell epitopes and fragment C of tetanus toxin are artificially synthesized. All of the recombinant protein products were expressed at high level in E. coli. Then, the immunogenicities of the purified recombination protein with Aluminum adjuvants were evaluated in Balb/C mouse model. Antibody levels in serum were determined by both enzyme-linked immunosorbent assays. Compared to the PBS control, all groups produced the specific antibody IgG against Aβ42, and the vaccine antigen fusion to fragment C of tetanus toxin were better to generate immune response than vaccine without fragment C of tetanus toxin. In addition, Aβ-specific antibody isotopes assays and lymphocyte proliferative responses show Th2 immune response in the immunized mice. The results of dot blotting showed that the sera antibodies could bind to the oligomer of Aβbetter than the monomer form. But the antibodies have less binding reaction to the fiber form. Subsequently, the immunogenicity of the recombination protein 6Aβ15-PADRE-TTC-C with Aluminum adjuvant was evaluated in APP-transgenic mouse models. The results show a similar immunogenicity with Blac/b. High antibody levels in serum and Th2 immune response were induced in the immunized mice. The reduction latency in the Morris water maze during the treated mouse indicated recombination protein can improve mouse's cognition. Immunohistochemisty results in the regions of hippocampus and cortical regions showed that recombination protein 6Aβi5-PADRE-TTC-C could reduce Aβplaques in transgenic mouse models. These results showed these recombinant proteins were very efficacious in produced the specific antibody IgG against Aβand could be good candidate vaccines for immune therapy of human AD.Subsequently, we developed two DNA vaccines of Alzheimer's disease. All of fusion genes encoding containing the immunodominant B cell epitope fromβ-amyloid and pan-DR helper T cell epitopes and fragment C of tetanus toxin are artificially synthesized. All groups produced the specific antibody IgG against Aβ. Antibody levels show that all groups were better to generate immune response than not fusion fragment C of tetanus toxin group. Aβspecific antibody isotopes assays and lymphocyte proliferative responses showed that Th2 immune responses were induced in immunized mice. The results of dot blotting still showed that the sera antibodies could best bind to the oligomer of Aβ. The immunogenicity of the DNA vaccine pVAXI-S-6Aβ15-PADRE-TTC was evaluated in transgenic mouse models. Immunohistochemisty results in the regions of hippocampus and cortical regions exhibited that DNA could reduce Aβplaques in transgenic mouse models.Together, these results in our study showed that recombinant sub-unit vaccines and DNA vaccines could be good candidate vaccines for immune therapy of human AD.