Early Diagnosis Of Alzheimer's Disease Biomarkers And Recombinant Vaccines

Alzheimer's disease (AD) is a progressive degenerative disease, which is characterized clinically by a progressive loss of memory function and cognition impairment associated with the presence of degenerative well known pathological lesions. There are no specific biomarkers for assisting the early diagnosis of AD and no efficient approaches for preventing or treating AD. The present study included two principal issues as follows. 1. The study of biomarkers for assisting early diagnosis of ADMany biomrkers have been found to be associated with the development of AD. However, most of them seem to be lack of specificity or sensitivity. The pathogenesis of AD is unclear so far. The involvement of the immune system in the pathogenesis of AD has been studied for years. Recent reports demonstrated that there was impairment of immune function in patients with AD, and the perturbation of immune system was involved in the pathogenesis of AD. In the present study, we analyzed several immunological biomarkers of AD patients in order to search certain specific or sensitive biomarkers for early diagnosis of AD, and primarily investigated the possible mechanism of the impairment of immune function in AD patients.First, we analyzed the levels of IL-1, IL-6, TNF-αand M-CSF in sera from 32 cases of AD patients and 32 cases of age- and sex-matched healthy controls. The results demonstrated that levels of M-CSF in sera in AD patients significantly increased when compared with healthy controls (P<0.05). To further analyze the specificity of overexpression of M-CSF in patients with AD and the correlation between the levels of M-CSF and the degree of dementia of AD patients, we analyzed the levels of M-CSF in sera from 180 patients with AD, 53 patients with Vascular dementia (VD), and 92 age- and sex-matched healthy controls, respectively. The results showed that the levels of M-CSF in sera from AD patients were significantly increased when compared with VD patients and healthy controls, respectively, and there was significantly statistical correlation between the levels of M-CSF in sera from patients with AD and the degree of dementia of patients with AD. In contrast, no significantly statistical difference was found between the levels of serum M-CSF of VD patients and that of healthy controls. These data indicate that M-CSF might be involved in the pathologic process.Second, we explored the mechanism of the perturbation of immune function in patients with AD. We analyzed telomerase activities of PHA-activated peripheral blood mononuclear cells (PBMC) from 187 cases of patients with AD, 53 cases of patients with VD, and 80 cases of age-matched healthy controls, respectively. The results showed that telomerase activities of PHA-activated PBMC in AD patients were significantly much higher than those in healthy controls or VD patients, respectively, whereas no significant difference was found between the telomerase activities of PHA-activated PBMC in AD patients and those of healthy controls. We also found that there was significantly statistical correlation between the telomerase activities of PHA-activated PBMC and the degree of dementia in AD patients. Since the changes of telomerase activity reflect the instability of telomere, these data indicate that telomere instability of PBMC occurs in patients with AD, and the dysfunction of telomere contributes to the increase of telomerase activities of PBMC.In summary, our findings indicated that M-CSF might be involved in the pathogenesis of AD, and play an important role in the development of neuropathological changes of patients with AD, while the dysfunction of telomere of PBMC, especially T lymphocytes, could contribute to the impairment of immune function in AD patients. Telomerase activities of PBMC and M-CSF might be useful biomarkers for early diagnosis of AD and monitoring the perturbation of immune function of AD.2. The study of gene recombinant vaccine against ADAlzheimer's disease (AD) is a neurodegenerative disorder characterized by a progressive decline of cognitive abilities and by neuropathological features' including diffuse loss of neurons in the hippocampus and neocortex, accumulation of intracellular protein deposits (neurofibrillary tangles), and accumulation of extracellular protein deposits (amyloid or senile plaques) characteristically seen in the associative cortices and limbic system. A main constituent of these amyloid plaques is the amyloid-β-peptide (Aβ), a 39-43-amino-acid protein derived from the processing of a large transmembrane protein, theβ-amyloid precursor protein (APP). It has been postulated that accumulation of Aβin the brain, resulting from abnormal processing of APP to Aβor reduced clearance of Aβfrom brain, is the primary cause of AD pathogenesis. The rest of the disease process, including formation of neurofibrillary tangles containing tau protein, is thought to result from an imbalance between Aβproduction and Aβclearance. As a result, there is a widespread interest in developing therapeutic approaches to improve the balance between Aβproduction and Aβclearance.In the present study, we developed a cholera toxin B subunit (CB) and Aβ42 gene-recombinant adeno-associated virus (AAV-CB-Aβ42) vaccine and detected the efficacy of it on PDAPP^V7171 transgenic mice with different routes of administration. The results showed that the AAV vaccine expressed a fusion protein of CB and Aβ42 in vivo. A single administration of the AAV-CB-Aβ42 vaccine induced a prolonged, strong production of Aβspecific serum IgG in PDAPP^V7171 transgenic mice, and resulted in improved ability of memory and cognition, decreased Aβdeposition in the brain and a resultant decrease in plaque-associated astrocytosis. Our results extended the immunological approaches for the treatment and prevention of AD to an oral, intranasal or intramuscular route that might be better tolerated in human patients than repetitive immunizations in the presence of adjuvant. Our data raised the possibility that AAV-CB-Aβ42 vaccine immunization may provide the basis of a novel and promising Alzheimer's disease vaccination strategy.