Encephalitis in immunocompetent patients due to herpes simplex virus type 1 or 2: determination by polymerase chain reaction and detection of intrathecal virus-specific oligoclonal antibodies.

Serum and cerebrospinal fluid (CSF) of 13 patients have been examined to confirm and precise the diagnosis of herpes simplex virus encephalitis (HSVE). By amplifying the DNA with a nested polymerase chain reaction (PCR), we could demonstrate the herpetic origin of these cases of encephalitis. DNA of HSV type 1 or type 2 was directly identified and differentiated, by the use of both type-specific primes in the same reaction. The primer sequences were chosen in the glycoprotein D region for HSV type 1, and in the glycoprotein G region for HSV type 2. Only one case was due to the latter. In all but one cases, an immunoaffinity-mediated capillary blotting study was also performed. This technique showed the occurrence of oligoclonal CSF-specific IgG bands, while the antigen-driven immunoblotting demonstrated intrathecal production of oligoclonal anti HSV antibodies. In most of the cases, repeated CSF analysis allowed us to study the sequential detection of viral DNA and of intrathecal synthesis of virus-specific IgG in relation to the clinical course. All the patients were treated with acyclovir. In one case, a relapse was clinically suspected, but the PCR remained negative.