Cerebrospinal fluid IgG bands and virus-specific IgG, IgM, and IgA antibodies in herpes simplex virus encephalitis

To characterize the immune response of the central nervous system in herpes simplex virus (HSV) encephalitis, cerebrospinal fluid (CSF) specimens of 7 biopsy proven and 7 presumptive herpes simplex virus (HSV) encephalitis patients were studied, using sodium dodecyl sulfate polyacrylamide gel electrophoresis for the presence of CSF IgG bands, and solid-phase enzyme immunoassays for HSV-specific antibodies. IgG bands were detected in all CSF specimens of the patients, as early as day 6 and up to day 1088. A novel, unidentified, 120 000 dalton polypeptide was found in the CSF of most of the patients, in a total of 25/50 specimens, but not in the controls. This polypeptide was evident by day 6, its intensity fluctuated and it was present in specimens collected as late as day 855. HSV-specific antibodies, of either IgG, IgM, or IgA class, were not detected in the CSF during the first week of illness. IgG antibodies appeared later in all patients and persisted to the end of the follow-up of 3 years. The fact that CSF IgG bands were present in some patients before the appearance of HSV antibodies, and also persisted longer, suggests that the IgG response is not restricted to HSV-specific antigenic determinants.