Morphologic Observation On The Alzheimer's Disease -like Pathological Change Of Brain Of Aged Mouse With HCMV Congenital Latent Infection

Objective The study was on the base of the aged mouse model with HCMV congenital latent infection. From this model, we observed the pathological changes of the cerebral cortex of mice with HCMV congenital infection. The study aimed at providing a new idea and appropriate model for studing the etiology and mechanism of Alzheimer's diseases.Methods After an aged mouse model was built, 6 mice with congenital HCMV latency and 6 mice from DMEM control group were selected randomly and killed, Then the cerebral cortex were divided into serval portions. Slices of brain were embedded with paraffin. Some were fixed for electron microscope. The other portions were ready for virus isolation and co-culture with HF cell in vitro. The brain slices were used for assays as follows: (1) stained with hematoxylin-eosin (H.E.) for pathology research (2) observed the amyloid plaques by Congo red stain (3) observed the neurofibrillary tangles and amyloid plaques by silver stain (4) detected the expression of p-tau protein by indirect immunofluorescent assay (5) observed the ultrastructural features of neuron and the herpers virus-like particles by electron microscope.(6)Co-culture with HF cells in vitro to test as fopllows: (1)HCMV UL83, IE gene and transcripts were analyzed by polymerase chain reaction (PCR) and RT-PCR (2)cells were fixed with acetone for detection of HCMV IE and pp65 protein by indirect immunofiuorescent assay. (3) The cells were cellected to observe the ultrastructural features of neuron and the herpers virus-like particles by electron microscope. (7) counte the number of neuron, neurofibrillary tangles and the numerical densities of synapse in the cerebral cortex. Results A lot ofl neuron in the cerebral cortex in infected mice were stained slightlyby HE stain, finding neuron lost and quantity decreased. The amyloid plaque exists in the cerebral cortex of infected mice by Congo red stain. The amyloid plaque and abundant neurofibrillary tangles (NFTs) in the cerebral cortex.e of infected mice were found by silver stain. The expression of p-tau protein was detected by indirect immunofluorescent assay in infected group. The ultrastructures of neuron in infected group were severely damaged and Paired helical filaments, two membranous annulation and long nestraight filaments appeared in the neuronal nucleus. But Electron microscope examination didn't show the appearance of herpes-like virus particles in infected group. Typical HCMV CPE wasn't found in infected group by virus isolation and the latent cytomegalovirus in the cerebral cortex in infection group can be reactivated after co-culture in vitro. HCMV UL83 and IE DNA were detected in the cell slice of infection group HCMV UL83 and IE mRNA were detected after co-culture in vitro. HCMV IE antigen and pp65 antigen were detected by immunofluorescent assay. A lot of herpes-like virus particles were found in cell after co-culture. The numerical densities of synapse and the number of neuron of mice in congenital infected group were lower than the control mice (p<0.01) .Compared with control group, the number of neurofibrillary tangles in the cerebral cortex of infected mice was higher. In DMEM control mice, there were no obvious pathological alterations in the cerebral cortex by HE staining, but several neurofibrillary tangles existed in the cerebral cortex and the other results of detection were negative.Conclusion (1) On the basis of these results, we found HCMV congenital latency may be result in the appearance of AD-like pathologic changes and may be a risk factor for Alzheimer's disease. It provides a new idea and a technic flat for us to study AD pathogeny and the occurrence mechanism of AD. (2) HCMV congenital latent infection can result in the appearance of Paired helical filamem^ membranous annulation and long nestraight filaments in the neuronal nucleus.. This provides us a new way to study congenital HCMV latency.