In Vivo Electroporation of a New Gene Vaccine Encoding Ten Repeats of Aβ3-10 Prevents Brain Aβ Deposition and Delays Cognitive Impairment in Young Tg-APPswe/PSEN1dE9 Mice

A Review of Brain-Targeted Nonviral Gene-Based Therapies for the Treatment of Alzheimer's Disease

Diseases of the central nervous system (CNS) are difficult to treat owing to the complexity of the brain and the presence of a natural blood-brain-barrier (BBB). Alzheimer's disease (AD) is one of the major progressive and currently incurable neurodegenerative disorders of the CNS, which accounts for 60-80% of cases of dementia. The pathophysiology of AD involves the accumulation of amyloid beta (Aβ) plaques and neurofibrillary tangles (NFTs) in the brain. Additionally, synaptic loss and imbalance of neuronal signaling molecules are characterized as important markers of AD. Existing treatments of AD help in the management of its symptoms and aim toward the maintenance of cognitive functions, behavior, and attenuation of gradual memory loss. Over the past decade, nonviral gene therapy has attracted increasing interest due to its various advantages over its viral counterparts. Moreover, advancements in nonviral gene technology have led to their increasing contributions in clinical trials. However, brain-targeted nonviral gene delivery vectors come across various extracellular and intracellular barriers, limiting their ability to transfer the therapeutic gene into the target cells. Chief barriers to nonviral gene therapy have been discussed briefly in this review. We have also highlighted the rapid advancement of several nonviral gene therapies for AD, which are broadly categorized into physical and chemical methods. These methods aim to modulate Aβ, beta-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1), apolipoprotein E, or neurotrophic factors' expression in the CNS. Overall, this review discusses challenges and recent advancements of nonviral gene therapy for AD.

Early active immunization with Aβ3-10-KLH vaccine reduces tau phosphorylation in the hippocampus and protects cognition of mice

Active and passive anti-Aβ immunotherapies have successfully been used for the prevention and treatment of Alzheimer’s disease animal models. However, clinical use of these immunotherapies is not effective, because the vaccination is administered too late. At 1 month of age, 100 μL of Aβ_3–10-KLH peptide (vaccine, 2 μg/μL) was subcutaneously injected into the neck of an amyloid precursor protein/presenilin-1/tau transgenic (3×Tg-AD) mouse model. Aβ_3–10-KLH peptide was re-injected at 1.5, 2.5, 3.5, 4.5, 5.5, and 6.5 months of age. Serum levels of Aβ antibody were detected by enzyme-linked immunosorbent assay, while spatial learning and memory ability were evaluated by Morris water maze. Immunohistochemistry was used to detect total tau with HT7 and phosphorylated tau with AT8 (phosphorylation sites Ser202 and Thr205) and AT180 (phosphorylation site Thr231) antibodies in the hippocampus. In addition, western blot analysis was used to quantify AT8 and AT180 expression in the hippocampus. The results showed that after vaccine injection, mice produced high levels of Aβ antibody, cognitive function was significantly improved, and total tau and phosphorylated tau levels were significantly reduced. These findings suggest that early active immunization with Aβ_3–10-KLH vaccine can greatly reduce tau phosphorylation, thereby mitigating the cognitive decline of 3×Tg-AD mice. This study was approved by the Animal Ethics Committee of China Medical University, China (approval No. 103-316) on April 2, 2016.

Active Immunization with DNA Vaccine Reduced Cerebral Inflammation and Improved Cognitive Ability in APP/PS1 Transgenic Mice by In Vivo Electroporation

The aggregation of amyloid β-peptide (Aβ) is thought to play a pivotal role in the disease progression of Alzheimer's disease (AD). Amyloid β directed immunotherapy has been considered an alternative AD treatment. In this study, we constructed a DNA vaccine, p(Aβ3-10)10-mIL-4, encoding ten tandem repeats of Aβ3-10 fused with mouse IL-4. Eight-month-old APP/PS1 transgenic mice were injected intramuscularly with p(Aβ3-10)10-mIL-4 followed by in vivo electroporation. Immunization with the vaccine induced high-titer anti-Aβ antibodies and attenuated the behavior impairment. Immunoglobulin isotyping revealed a predominantly IgG1 response and ex vivo cultured splenocytes exhibited a low IFN-γ and high IL-4 response, indicating a Th2 anti-inflammatory response. Immunohistochemical analysis revealed that p(Aβ3-10)10-mIL-4 immunization decreased Aβ deposition, and the microglial attraction significantly decreased accompanied by the clearance of Aβ. There was no microhemorrhage in the brain of the immunized mice. These results suggest that the immunization potentially reduced the inflammation in brain of transgenic mice and therefore improved their cognitive ability. This novel DNA vaccine p(Aβ3-10)10-mIL-4 may be an effective immunization method as therapy for AD.