Demonstration of herpes simplex virus DNA in CSF cells by in situ hybridization for early diagnosis of herpes encephalitis.

Herpes simplex virus (HSV) was studied by in situ DNA hybridization with a biotinylated cDNA probe in 56 air-dried methanol-fixed cerebrospinal fluid (CSF) cell preparations which had been collected from 12 patients with herpes simplex encephalitis (HSE) during the previous 5 years. In three additional HSE cases, freshly prepared acetone-fixed CSF cell preparations were available. In all cases, CSF cell preparations were obtained by cytocentrifugation. Herpes simplex virus DNA could be demonstrated in 8 of the 12 HSE cases with methanol-fixed cells (66%) and in all 3 cases with fresh acetone-fixed CSF cells. The earliest CSF sample was available at the onset of symptoms and showed positive DNA hybridization. In three cases hybridization was positive after a clinical course of more than 5 weeks but was usually found in the 1st week of illness before the beginning of specific inthrathecal IgG synthesis. In 54 control cases with other acute inflammatory diseases of the CNS, including 14 cases of varicella-zoster meningitis, no positive hybridization was detected. These findings strongly suggest that in situ hybridization in CSF cells is a reliable tool for the early and rapid diagnosis of HSE, especially at the onset of the disease, when no antibodies can be detected.