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A rat model of herpes encephalitis using intraocular inoculation of herpes simplex virus strain SC16 was investigated. Virus distribution in the brain was examined by virus isolation and immunocytochemical staining using immuno-gold silver and peroxidase-anti-peroxidase. At 5 days post-infection virus was found in the thalamus, hypothalamus, septum, colliculus, geniculate bodies, the pons, trapezoidium and medulla oblongata, but less frequently, in the cerebellum and occipital lobes. Possible routes of spread of virus and the potential of this model in neuro-radiological scanning procedures are discussed.

The potential of utilizing a radio-labelled derivative of the antiviral drug (E)-5-(2-iodovinyl)-2'-deoxyuridine (IVDU) for the specific, non-invasive, in vivo diagnosis of Herpes simplex virus encephalitis (HSVE) was investigated in a rat model of the disease. Following pharmacological disruption of the blood brain barrier radiolabelled IVDU was administered by intra-carotid injection. Brain radioactivity was compared between control and infected animals via gamma camera scintigraphy. After clearance of non-metabolized drug, markedly higher levels of activity were found in infected brain. Post-mortem studies of cryostat sections of brain examined by autoradiography and immunochemical staining showed the radioactivity selectively accumulated in areas of virus infection. These results indicate that radio-labelled derivatives of antiviral drugs may allow the specific neuro-radiological diagnosis of HSVE.

A prospective study of 84 renal graft recipients demonstrated cytomegalovirus (CMV) disease after transplantation in 37% of patients. Reactivation infection was found in 20 of 44 patients (46%) who were seropositive for CMV prior to transplant and primary CMV disease occurred in 11 of 40 (28%) initially seronegative patients. Nearly all cases of primary disease (91%) were associated with symptoms and in these cases CMV was probably acquired via the donated kidneys. Only 35% of the reactivation infections were associated with clinical symptoms. Actuarial life tables indicated that CMV disease did not reduce the length of graft survival. Herpes simplex virus (HSV) infections were diagnosed in 44 (52%) of the patients and included a fatal case of disseminated disease associated with hepatitis.

The advent of acyclovir has accentuated the problem of diagnosis and particularly the need for brain biopsy in patients with suspected herpes simplex encephalitis. U.S.A. and U.K. practices are contrasted and the current U.K. study of acyclovir in herpes simplex encephalitis is mentioned in which retrospective and relatively non-invasive methods of diagnosis are employed.

Diseases of man caused by the virus of herpes simplex fall into two broad categories. The primary disease occurs only once in any individual's life and is caused by transmission of virus from an already infected human. Thereafter, the individual may be subject to recurrent herpetic disease, the manifestations of which are different from the primary disease. Recurrent disease varies in severity from trivial, to incapacitating and frankly lethal (as in diseases resulting from the virus's neurotropic and oncogenic properties). The source of the virus in recurrent herpetic disease has never been conclusively resolved, but is almost certainly endogenous to the patient. Theories, case reports and experiments exist to show that endogenous virus may, in periods of clinical quiescence, be latent (or persistent) at the site of the recurrent lesions itself, or more remotely in nerve tissues related to the site of recurrence.

Three cases of herpes encephalitis are described. A definite diagnosis was established and all patients made a good recovery without specific antiviral chemotherapy. These reports are representative of those forms of herpes encephalitis with a good prognosis. It is suggested that the introduction of rapid non-invasive procedures will indicate a higher incidence of herpes encephalitis than is presently accepted. The relevance of repeated episodes of herpes encephalitis with respect to the aetiology of some psychiatric disorders and in the evaluation of antiviral agents is also discussed.

A rare occurrence of disseminated herpes simplex virus infection with hepatitis in an adult renal transplant recipient is described.

The blood-brain barrier penetration of a radiohalogenated (125I) derivative of the antiviral drug (E)-5-(2-iodovinyl)-2'-deoxyuridine (IVDU) was investigated in a rat model of herpes encephalitis. CNS delivery was assessed by external gamma camera scintigraphic imaging in vivo, a technique which may have general application in evaluating brain specific delivery of drugs, and by autoradiography of cryostat sections of rat brain. Radiohalogenated IVDU was found to be almost totally excluded from the CNS. These findings may be explained in terms of the poor lipid solubility of IVDU (in vitro oil/aqueous salt solution partition coefficient 0.012). Since IVDU appears in CSF after carotid artery administration, our results stress the necessity, in the design of compounds for the treatment of CNS infections, of distinguishing blood-brain, blood-CSF, and CSF-brain drug barriers. The significance of our data both in relation to the development of neuro-radiological diagnosis and antiviral chemotherapy of CNS infection is discussed.

A sensitive and specific radioimmunosorbent assay for serum and cerebrospinal fluid (CSF) IgG antibodies against Herpesvirus simplex has been evaluated as an early diagnostic test for herpes encephalitis. When combined with the measurement of albumin in serum and CSF as accurate diagnostic index was obtained in twenty-four out of twenty-six patients. Out of ten patients tested before day 10 of neurological illness, five had positive diagnostic indices. Three patients with negative indices before day 10 had positive indices when re-tested later.

One hundred and seventy nine children with atopic eczema were studied prospectively for two and three quarter years; the mean period of observation being 18 months. Ten children had initial infections with herpes simplex. Four children, very ill with a persistently high fever despite intravenous antibiotics and rectal aspirin, continued to produce vesicles and were given intravenous acyclovir. There were 11 recurrences among five patients. In two patients the recurrences were as severe as the initial lesions, and one of these children had IgG2 deficiency. Use of topical corticosteroids preceded the episode of herpes in only three of the 21 episodes. Symptomatic herpes simplex infections are common in children with atopic eczema, and are suggested by the presence of vesicles or by infected eczema which does not respond to antibiotic treatment. Virological investigations are simple and rapid: electron microscopy takes minutes, and cultures are often positive within 24 hours.