Therapeutic potential of vaccines for Alzheimer's disease

Boosting tendon repair: interplay of cells, growth factors and scaffold-free and gel-based carriers

Background

Tendons are dense connective tissues and critical components for the integrity and function of the musculoskeletal system. Tendons connect bone to muscle and transmit forces on which locomotion entirely depends. Due to trauma, overuse and age-related degeneration, many people suffer from acute or chronic tendon injuries. Owing to their hypovascularity and hypocellularity, tendinopathies remain a substantial challenge for both clinicians and researchers. Surgical treatment includes suture or transplantation of autograft, allograft or xenograft, and these serve as the most common technique for rescuing tendon injuries. However, the therapeutic efficacies are limited by drawbacks including inevitable donor site morbidity, poor graft integration, adhesion formations and high rates of recurrent tearing. This review summarizes the literature of the past 10 y concerning scaffold-free and gel-based approaches for treating tendon injuries, with emphasis on specific advantages of such modes of application, as well as the obtained results regarding in vitro and in vivo tenogenesis.

Results

The search was focused on publications released after 2006 and 83 articles have been analysed. The main results are summarizing and discussing the clear advantages of scaffold-free and hydrogels carriers that can be functionalized with cells alone or in combination with growth factors.

Conclusion

The improved understanding of tissue resident adult stem cells has made a significant progress in recent years as well as strategies to steer their fate toward tendon lineage, with the help of growth factors, have been identified. The field of tendon tissue engineering is exploring diverse models spanning from hard scaffolds to gel-based and scaffold-free approaches seeking easier cell delivery and integration in the site of injury. Still, the field needs to consider a multifactorial approach that is based on the combination and fine-tuning of chemical and biomechanical stimuli. Taken together, tendon tissue engineering has now excellent foundations and enters the period of precision and translation to models with clinical relevance on which better treatment options of tendon injuries can be shaped up.

Doubly Phosphorylated Peptide Vaccines to Protect Transgenic P301S Mice against Alzheimer's Disease Like Tau Aggregation

Intracellular neurofibrillary tangles and extracellular senile plaques are potential targets for active and passive immunotherapies. In this study we used the transgenic mouse model P301S for active immunizations with peptide vaccines composed of a double phosphorylated tau neoepitope (pSer202/pThr205, pThr212/pSer214, pThr231/pSer235) and an immunomodulatory T cell epitope from the tetanus toxin or tuberculosis antigen Ag85B. Importantly, the designed vaccine combining Alzheimer’s disease (AD) specific B cell epitopes with foreign (bacterial) T cell epitopes induced fast immune responses with high IgG₁ titers after prophylactic immunization that subsequently decreased over the observation period. The effectiveness of the immunization was surveyed by evaluating the animal behavior, as well as the pathology in the brain by biochemical and histochemical techniques. Immunized mice clearly lived longer with reduced paralysis than placebo-treated mice. Additionally, they performed significantly better in rotarod and beam walk tests at the age of 20 weeks, indicating that the disease development was slowed down. Forty-eight weeks old vaccinated mice passed the beam walk test significantly better than control animals, which together with the increased survival rates undoubtedly prove the treatment effect. In conclusion, the data provide strong evidence that active immune therapies can reduce toxic effects of deposits formed in AD.

T-cell epitope-dependent immune response in inbred (C57BL/6J, SJL/J, and C3H/HeN) and transgenic P301S and Tg2576 mice

Alzheimer's disease is characterized by two pathological hallmarks, the intracellular deposition of hyperphosphorylated Tau protein and the extracellular deposition of Aβ1-40/42 , both being targets for immunotherapy. This study evaluates the immunogenic properties of three AD-specific B-cell epitopes (Tau229-237 [pT231/pS235], pyroGluAβ3-8 , and Aβ37/38-42/43 ) linked to five foreign T-cell epitopes (MVFP, TT, TBC Ag85B, PvT19, and PvT53) by immunizing inbred C57BL/6J (H-2(b) ), SJL/J (H-2(s2) ), and C3H/HeN (H-2(k) ) mice. Two promising candidates with respect to MHC II restriction were selected, and two transgenic mouse models of AD, P301S (H-2(b/) (k) ) and Tg2576 (H-2(b/) (s) ) animals, were immunized with one B-cell epitope in combination with two T-cell epitopes. Responders displayed an enhanced immune response compared with wild-type animals, which supports the vaccine design and the vaccination strategy. The immune response was also characterized by specific IgG subtype titers, which revealed a strong polarization toward the humoral pathway for immunization of phospho-Tau, whereas for both Aβ vaccines, a mixed cellular/humoral pathway response was observed. Despite the diversity and unpredictability of the immunogenicity of the peptide vaccines, all three peptide vaccine formulations appear to be promising constructs for future evaluation of their therapeutic properties.

Structural characterization by NMR of a double phosphorylated chimeric peptide vaccine for treatment of Alzheimer's disease

Rational design of peptide vaccines becomes important for the treatment of some diseases such as Alzheimer's disease (AD) and related disorders. In this study, as part of a larger effort to explore correlations of structure and activity, we attempt to characterize the doubly phosphorylated chimeric peptide vaccine targeting a hyperphosphorylated epitope of the Tau protein. The 28-mer linear chimeric peptide consists of the double phosphorylated B cell epitope Tau₂₂₉₋₂₃₇[pThr231/pSer235] and the immunomodulatory T cell epitope Ag85B₂₄₁₋₂₅₅ originating from the well-known antigen Ag85B of the Mycobacterium tuberculosis, linked by a four amino acid sequence -GPSL-. NMR chemical shift analysis of our construct demonstrated that the synthesized peptide is essentially unfolded with a tendency to form a β-turn due to the linker. In conclusion, the -GPSL- unit presumably connects the two parts of the vaccine without transferring any structural information from one part to the other. Therefore, the double phosphorylated epitope of the Tau peptide is flexible and accessible.

Immunotherapy for Alzheimer's disease

Alzheimer's disease (AD) is characterized by β-amyloid (Aβ) plaques consisted primarily of aggregated Aβ proteins and neurofibrillary tangles formed by hyperphosphorylated tau protein. Both Aβ and hyperphosphorylated tau are toxic both in vivo and in vitro. Immunotherapy targeting Aβ seems to provide a promising approach to reduce the toxic species in the brain. However, there is little evidence from clinical trials so far indicating the efficacy of Aβ immunotherapy in cognitive improvement. Immunization with tau peptides or anti-tau antibodies could remove the tau aggregates and improve the cognitive function in preclinical study, which provides a novel strategy of AD therapy. In this article, we will summarize the immunotherapeutic strategies targeting either Aβ or tau.

Vaccine Development to Treat Alzheimer's Disease Neuropathology in APP/PS1 Transgenic Mice

A novel vaccine addressing the major hallmarks of Alzheimer's disease (AD), senile plaque-like deposits of amyloid beta-protein (Aβ), neurofibrillary tangle-like structures, and glial proinflammatory cytokines, has been developed. The present vaccine takes a new approach to circumvent failures of previous ones tested in mice and humans, including the Elan-Wyeth vaccine (AN1792), which caused massive T-cell activation, resulting in a meningoencephalitis-like reaction. The EB101 vaccine consists of Aβ_1-42 delivered in a novel immunogen-adjuvant composed of liposomes-containing sphingosine-1-phosphate (S1P). EB101 was administered to APPswe/PS1dE9 transgenic mice before and after AD-like pathological symptoms were detectable. Treatment with EB101 results in a marked reduction of Aβ plaque burden, decrease of neurofibrillary tangle-like structure density, and attenuation of astrocytosis. In this transgenic mouse model, EB101 reduces the basal immunological interaction between the T cells and immune activation markers in the affected hippocampal/cortical areas, consistent with decreased amyloidosis-induced inflammation. Therefore, immunization with EB101 prevents and reverses AD-like neuropathology in a significant manner by halting disease progression without developing behavioral spatial deficits in transgenic mice.

Gene expression profiling and therapeutic interventions in neurodegenerative diseases: a comprehensive study on potentiality and limits

INTRODUCTION

Neurodegenerative diseases are incurable debilitating disorders of the nervous system that affect approximately 30 million people worldwide. Despite profuse efforts attempting to define the molecular mechanisms underlying neurodegeneration, many aspects of these pathologies remain elusive. The novelty of their mechanisms represents a challenge to biology, to their related biomarkers identification and drug discovery. Because of their multifactorial aspects and complexity, gene expression analysis platforms have been extensively used to investigate altered pathways during degeneration and to identify potential biomarkers and drug targets.

AREAS COVERED

This work offers an overview of the gene expression profiling studies carried out on Alzheimer's disease, Huntington's disease, Parkinson's disease and prion disease specimens. Therapeutic approaches are also discussed.

EXPERT OPINION

Although many therapeutic approaches have been tested, some of them acting on several altered cellular pathways, no effective cures for these neurodegenerative diseases have been identified. Microarray technology must be associated with functional proteomics and physiology in an effort to identify specific and selective biomarkers and druggable targets, thus allowing the successful discovery of disease-modifying therapeutic treatments.