Herpes simplex virus encephalitis. Prolonged intrathecal IgG synthesis and cellular activity in the cerebrospinal fluid with transient impairment of blood-brain barrier.

Alterations of cerebrospinal fluid (CFS) proteins and cells and blood-brain barrier impairment were determined in 4 patients with proven and 2 patients with presumptive herpes simplex virus encephalitis ( HSVE ) using simultaneous nephelometric measurements of CSF and serum albumin and immunoglobulins and combined MilliporeR filtration-cytocentrifuge cytologic techniques. The follow-up period ranged from 17 to 855 days. All patients showed intrathecal IgG synthesis which in 1 case continued for 28.5 months (855 days). The daily production of IgG in the central nervous system ranged up to 1157 mg. CSF-IgA and -IgM were also elevated in the early phase of the disease. The impairment of the blood-brain barrier was variable being apt to develop during the first 2 months of the disease and diminishing thereafter. Pleocytosis, mainly due to lymphoid cells, varied from slight to severe (325 X 10(3) cells/ml) and was observed in the CSF of all cases during the first 2 months. Lymphoid reaction (increase of enlarged stimulated lymphoid cells) was persistent and was the most pronounced cellular alteration. The lymphoid reaction and intrathecal IgG synthesis indicated continuous immunoactivation of the CNS, which was most intensive during the first 2 months and appeared to persist for at least 16-28.5 months.