On the relationship between measles virus and Alzheimer neurofibrillary tangles in subacute sclerosing panencephalitis

We have studied the relationship between measles virus and the accumulation of abnormally phosphorylated tau (PHF-tau) in nine cases of subacute sclerosing panencephalitis (SSPE). By assessing the presence of viral intranuclear inclusions and neurofibrillary tangles (NFT) in each case, we found no correlation between presence and amount of measles virus and the numbers of neurons containing PHF-tau. Immunohistochemical double labeling in a case with long duration of disease and severe histopathologic change revealed no strict colocalization of measles virus antigen and PHF-tau throughout different brain regions. In areas containing both antigens, most neurons carrying measles virus did not have a tangle and vice versa, eventhough some colocalization beyond that expected by chance was observed in specific cortical areas. These results indicate that, although secondary to viral infection, NFT formation in SSPE is not restricted to cells carrying viral antigen. Conversely, measles virus infected cells do not necessarily accumulate PHF-tau. This lack of colocalization at the cellular level, throughout different brain areas and among different cases suggests that the formation of NFT in SSPE is not directly induced by the infectious agent. The formation of NFT in this disease appears to be elicited through a specific type of tissue damage and, thus, to be an epiphenomenon. This pathogenetic detail may be of interest for our understanding of the role of neurofibrillary degeneration in the pathogenesis of other more frequent neurodegenerative diseases with cytoskeletal pathology.