Study On The Effect Of Norovirus P Particle-Based Aβ Immunotherapy Of Alzheimer’s Disease

Alzheimer’s disease(AD)is a progressive age-related neurodegenerative disorder that aff ects more than 46 million people worldwide.As the etiology and pathophysiology of AD are multifactorial and complex,only a few symptomatic treatments,such as cholinesterase inhibitors and memantine,are approved for AD therapy;however,no disease-modifying therapies are currently available.There are three pathological hallmarks of AD: accumulation of the amyloid beta(Aβ)protein in senile plaques;intracellular neurofibrillary tangles(NFT)in the brain and loss of neurons.Currently,the deposition of amyloid β(Aβ)in the brain is regarded as the central pathological hallmark of AD.Thus,immunotherapy targeting Aβ clearance may be the most promising therapeutic options for AD.Over the past 15 years,various active and passive Aβ immunotherapies have progressed from preclinical studies in AD mouse models to clinical trials in humans,but unfortunately,until now,no data have been reported regarding the most potent Aβ immunotherapy,which is currently in phase III clinical trials.The first clinical trial of the active AD vaccine AN1792,which used full-length Aβ42 formulated in the adjuvant QS21,was halted at phase II when 6% of the trial subjects developed aseptic meningoencephalitis.Further studies of aff ected patients demonstrated that a strong Aβ-reactive T-cell autoimmune response had occurred due to the use of full-length Aβ42,which contains T-cell epitopes residing in amino acids 15 to 42.Thereafter,many groups developed Aβ-based epitope vaccines composed of diff erent N-terminal regions of Aβ42,ending between amino acids 6 and 15 to avoid strong T-cell responses.Aside from the safety issue of T-cell-mediated autoimmune responses,another problem with the failed Aβ immunotherapies was the modest immunogenicity.In the course of avoiding Aβ42-specifc T-cell activation,the second-generation Aβ active vaccines were all produced with a small B-cell epitope of Aβ,which has low immunogenicity.So,several AD active immunotherapies applied diff erent vaccine carriers to provide T cell epitopes,which can stimulate B cells to produce maximal antibody titers.For instance,CAD106 used phage Qβ as the vaccine platform and the ACC001 vaccine used diphtheria toxin to carry the Aβ1-7 epitope.However,none of the above AD vaccines has produced clinically meaningful results,indicating that a more optimal and potent vaccine platform is required for the future development of Aβ epitope vaccines.Noroviruses(NoVs),are associated with human epidemic acute gastroenteritis.The NoV contains a protein capsid protein(VP1),which has two major domains,the shell(S)domain and the protruding(P)domain.The P particle(PP)is a subviral nanoparticle formed by 24 copies of the P domain,which is easily produced,extremely stable and highly immunogenic.The structural analysis of the P domain revealed three surface loops on its distal surface,which have been shown to be the sites of foreign epitope insertion and presentation.Thus,the PP is considered to be an excellent multipurpose platform for antibody induction and vaccine development against many pathogens,including rotavirus and influenza virus.In this study,we used Aβ1–6,which only contains B-cell epitopes as immunogen,and P particles as the vaccine platform to develop a safe and effective AD vaccine.The Aβ1–6 peptides were designed to be inserted and presented on the outermost surface of the P particles.We successfully constructed and purified five recombinant P particle vaccines containing different copies of Aβ1–6 and distinct loop insertion forms.We test the immunogenicity of five recombinant P particle vaccines in WT mice,and results showed that all five AD protein vaccines could efficiently stimulate Aβ antibody titers without inducing a T-cell-mediated immune response,and PP-3 copy-Aβ1-6-loop123 was the most effective vaccine for inducing Aβ antibodies in vivo.Then we used APP/PS1 transgene mouse of different ages to test the effect of PP-3copy-Aβ1-6-loop123.The result demonstrated that PP-3copy-Aβ1-6-loop123 was able to elicit high antibody titers against Aβ42,without causing T-cell activation,in AD mice regardless of their age.Importantly,PP-3copy-Aβ1-6-loop123 treatment successfully reduced amyloid deposition,rescued memory loss,and repaired hippocampus damage in AD mice.In addition,our results suggested PP-3copy-Aβ1-6-loop123 immunization could restore Aβ42 homeostasis in the serum and brain.Thus,the P particle-based Aβ epitope vaccine is a sufficiently immunogenic and safe immunotherapeutic intervention for Alzheimer’s disease.