Herpes simplex type 1 DNA in human brain tissue.

Herpes simplex virus type 1 (HSV-1) is known to reside latently in the trigeminal ganglia of man. Reactivation of this virus causes skin lesions and may occasionally infect other tissues, including the brain. To determine whether the brain tissue of humans free of clinical signs of HSV-1 infection contains any trace of HSV-1, we examined the DNA from brain tissue by endonuclease digestion, separation of the fragments by gel electrophoresis, and hybridization with labeled HSV-1 DNA probes. Hybrid bands were detected autoradiographically in experiments using cloned and virion-purified fragments of the HSV-1 genome. HSV-1 DNA sequences were found in 6 of 11 human brain DNA samples tested. In some cases, these bands corresponded to the bands expected for the complete viral genome, whereas others contained bands representing only a part of the genome. In some cases, the terminal fragments could be found, suggesting that the DNA was in a linear, nonintegrated form.