Molecular diagnosis of herpes simplex encephalitis

Herpes simplex virus encephalitis (HSE) is associated with significant morbidity and mortality both in neonates and adults. An early diagnosis can greatly help to reduce mortality in both groups; however, since none of the presenting symptoms is pathognomonic for HSE, a clinical diagnosis is unreliable. On the other hand, the technique of isolating herpes simplex virus (HSV) from brain biopsies, although providing an early and specific diagnosis, has never been widely accepted because of the risk of neurological complications connected with the invasiveness of the method. In addition, several studies reported that the two HSV types appear to be differently associated with specific neurological complications, indicating that it would be important to gain a differential-type diagnosis to guide both prevention strategies and antiviral therapy. Therefore, the need for noninvasive specific and sensitive techniques has given impulse to the development of assays based on the search of either specific anti-HSV antibodies or viral DNA footprints in patient serum or cerebrospinal fluid. While enzyme-linked immunosorbent assays and immunoblot assays, using HSV type-1- and 2-specific viral glycoproteins, are useful for serological typing, the polymerase chain reaction technique has proved highly effective in giving early, precise and specific HSE diagnosis, thus providing a helpful tool for the identification and treatment of this disease.