A study of viral genomes and antigens in brains of patients with Alzheimer's disease.

The presence of viral nucleic acid sequences and antigens from a variety of conventional viruses in selected brain regions of cases of Alzheimer's disease (AD), diagnosed pathologically, was investigated using molecular hybridization and immunocytochemical techniques. Seven DNA and 4 RNA viruses were used as probes in 18 AD and 5 control brains. With Southern blot hybridization, no viral DNA sequences could be detected in the cerebral cortex. With dot blot hybridization, results were also negative, except for 2 cases, 1 a control brain, the other an AD brain, which gave a positive signal in the RNA extracted from the substantia innominata when c-DNA from measles virus was used as a probe. Four specific brain areas from each of 8 AD brains and 5 controls tested with viral probes (3 DNA and 5 RNA viruses), using immunocytochemical techniques for viral antigens, showed no positive reproducible specific reactions. These results, although negative, do not totally exclude the possibility that conventional viruses may play a role in the aetiology and pathogenesis of AD.