Herpes encephalitis

Encephalitis and poor neuronal death-mediated control of herpes simplex virus in human inherited RIPK3 deficiency

Inborn errors of TLR3-dependent type I IFN immunity in cortical neurons underlie forebrain herpes simplex virus-1 (HSV-1) encephalitis (HSE) due to uncontrolled viral growth and subsequent cell death. We report an otherwise healthy patient with HSE who was compound heterozygous for nonsense (R422*) and frameshift (P493fs9*) RIPK3 variants. Receptor-interacting protein kinase 3 (RIPK3) is a ubiquitous cytoplasmic kinase regulating cell death outcomes, including apoptosis and necroptosis. In vitro, the R422* and P493fs9* RIPK3 proteins impaired cellular apoptosis and necroptosis upon TLR3, TLR4, or TNFR1 stimulation and ZBP1/DAI-mediated necroptotic cell death after HSV-1 infection. The patient's fibroblasts displayed no detectable RIPK3 expression. After TNFR1 or TLR3 stimulation, the patient's cells did not undergo apoptosis or necroptosis. After HSV-1 infection, the cells supported excessive viral growth despite normal induction of antiviral IFN-β and IFN-stimulated genes (ISGs). This phenotype was, nevertheless, rescued by application of exogenous type I IFN. The patient's human pluripotent stem cell (hPSC)-derived cortical neurons displayed impaired cell death and enhanced viral growth after HSV-1 infection, as did isogenic RIPK3-knockout hPSC-derived cortical neurons. Inherited RIPK3 deficiency therefore confers a predisposition to HSE by impairing the cell death-dependent control of HSV-1 in cortical neurons but not their production of or response to type I IFNs.

Polymerase chain reaction-proved herpes simplex encephalitis in children

OBJECTIVE

To investigate the clinical features in PCR-proved herpes simplex encephalitis (HSE) in children, excluding neonates.

METHODS

We studied the clinical manifestations and laboratory findings of 24 children in whom the diagnosis of herpes infection was confirmed by the PCR assay and compared them with those of 38 children with central nervous system infections other than HSE.

RESULTS

There were no significant differences between groups in the percentage with fever or convulsions, the initial neurologic symptoms or the level of consciousness. Analysis of cerebrospinal fluid showed no significant differences in the cell count or concentration of protein and glucose. Computerized tomography of the brain identified localized abnormalities in 18 (75%) of the 24 HSE patients and in 10 (31%) of the 32 non-HSE patients (P = 0.001). Periodic lateralized epileptiform discharges, abnormal findings on electroencephalography, were detected in 8 (36%) of 22 HSE patients and in none of the non-HSE patients (P = 0.0001). The rates of moderate to severe morbidity and death were significantly higher in the HSE patients than in the non-HSE patients. Of the 9 HSE patients with a Glasgow Coma Scale score > or = 11, all patients recovered completely. HSE patients younger than 3 years of age were more likely to develop severe sequelae or to die of the disorder than older patients (P = 0.02).

CONCLUSIONS

There were no specific clinical characteristics of HSE patients. The results of electroencephalography and computerized tomography were helpful, but not confirmatory, in diagnosing HSE. The Glasgow Coma Scale score and age significantly influenced the mortality and morbidity in the HSE patients.

Herpes simplex encephalitis treated with acyclovir: diagnosis and long term outcome

OBJECTIVES

The frequency and characteristics of the long term sequelae of herpes simplex encephalitis were assessed after treatment with acyclovir.

METHODS

Patients were included if they were treated with acyclovir and the diagnosis of herpes simplex encephalitis was confirmed by culture of herpes simplex virus (HSV) from the brain, an increase in the CSF HSV antibody titre, or detection of HSV deoxyribonucleic acid in the CSF. Each patient's medical records were reviewed and surviving patients were interviewed and examined.

RESULTS

A diagnosis of herpes simplex encephalitis was confirmed in 42 patients. Five patients (12%) died in the first month. Three patients (7%) had severe neurological sequelae and died after a longer interval. All but one of the 34 surviving patients had neurological symptoms, an abnormal neurological examination, or both. Twenty patients (48%) performed everyday activities as well as before herpes simplex encephalitis; nine patients (21%) were living independently, but were functioning at a lower level than before the illness; and five patients (12%) had a severe neurological deficit. Twenty nine of the 34 survivors were assessed six months to 11 years after herpes simplex encephalitis. The most common long term symptoms were memory impairment (69%), personality and behavioural abnormalities (45%), and epilepsy (24%). Short term memory impairment (70%), anosmia (65%), and dysphasia (41%) were the most common signs.

CONCLUSIONS

Although acyclovir has reduced the mortality of herpes simplex encephalitis, 30% of this group of patients either died or had a severe neurological deficit. The other 70% of the patients regained independence in activities of daily living, but most of these people had persistent neurological symptoms, signs, or both.

Herpes simplex virus encephalitis in children

Herpes simplex encephalitis (HSE) is an uncommon disease, yet 25 to 30 per cent of cases involve children. The initial clinical findings are nonspecific (fever, altered mental status), but most cases evolve to demonstrate focal neurologic signs and symptoms. The CSF is abnormal in over 90 per cent of cases. The EEG, CT, and MRI will further help in detecting focal encephalitis. The clinician caring for a child with focal encephalitis should institute broad-spectrum antimicrobial therapy plus acyclovir, pending definitive diagnosis by ancillary tests or brain biopsy, which is positive for HSE 33 to 55 per cent of the time and is diagnostic for other treatable conditions 10 to 20 per cent of the time. Acyclovir is the drug of choice for HSE and substantially reduces mortality and morbidity. The management of HSE in a child requires an experienced team of specialists and laboratory support in a tertiary intensive care setting.

Mild forms of herpes encephalitis

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.

Acute encephalitis of viral origin

75 patients with acute encephalitis of confirmed or suggestive viral or virus-like etiology showed a predominance of herpes simplex virus (HSV) as an etiological agent (13.3-32.0%) in all age groups without seasonal variation and increasing in number during years. Mumps, occurring mainly in female patients, was next in order and thereafter coxsackievirus B, varicella-zoster, and adenoviruses, followed by multiple coincident infections, and a large number of occasional agents. HSV seems to have displaced tick-borne encephalitis virus as the major cause of acute encephalitis in Finland. Pregnancy appeared to increase susceptibility to HSV encephalitis. The outcome was associated with the etiological agent in the first hand, HSV and nonviral microbes appeared unfavourable, but also with the clinical symptomatology, particularly altered consciousness, mental symptoms and focal neurological signs. The need for exact and rapid diagnosis in all cases of acute encephalitis is underlined in view of the possibility of specific therapy.