Rapid diagnosis of viral infections in the central nervous system

Viral diagnosis of neurological infection by RT multiplex PCR: a search for entero- and herpesviruses in a prospective study

The diagnosis of a wide range of different neurological syndromes was established by a reverse transcription multiplex PCR assay. The presence of enterovirus and herpesviruses was studied in cerebrospinal fluid samples collected prospectively from 200 patients hospitalized with neurological diseases suspected of viral infection. Positive PCR results for enterovirus and neurotropic herpesvirus (herpes simplex, HSV, and varicella zoster, VZV) were obtained among the immunocompetent patients (55/156, 35%) who presented aseptic meningitis or encephalitis. Among immunocompromised patients the yield of positive PCR results was 41% (18/44), predominantly lymphotropic herpesviruses (15/44, 34%). Cytomegalovirus (CMV) DNA was detected in patients with several clinical syndromes, including encephalitis, chronic meningitis, retinitis, ventriculitis, polyradiculomyelitis, and myeloradiculitis. Epstein-Barr (EBV) and VZV-specific DNA sequences were detected in patients with either encephalitis, aseptic meningitis, and chronic meningitis. Dual infections of CMV and HSV or CMV and EBV were established in two AIDS patients with encephalitis and polyradiculomyelitis, respectively. The applications of this RT multiplex PCR assay are extensive and may prove to be particularly valuable for the rapid and sensitive diagnosis of neurological diseases in both immunocompetent and immunocompromised patients.

Detection of enteroviral RNA and specific DNA of herpesviruses by multiplex genome amplification

A reverse transcription (RT) multiplex polymerase chain reaction (PCR) assay was developed to allow rapid, sensitive and simultaneous detection of enteroviral RNA and herpesviral DNA specific sequences in a single tube. The method involves a reverse transcription step followed by a multiplex nested PCR in which the combination of primers amplifies cDNA from enteroviruses and specific herpesviruses DNA. Nested amplification utilises primers designed to anneal into the amplification product from the first reaction. Individual viruses were then detected and differentiated by the size of their PCR products determined using ethidium bromide stained agarose gels. To exclude false negatives due to sample inhibitors an internal amplification control, a cloned fragment of DNA from Pseudorabies virus (PRV DNA) was included in the reaction mixture. Detection levels between 0.01 and 0.001 TCID50 of prototype strains of Polio and Coxsackie type B viruses and between 1 and 100 molecules of cloned-DNA of herpesviruses prototype strains were achieved. The RT multiplex PCR method proved capable of detecting enteroviral RNA or herpesviral DNA in cerebro spinal fluid (CSF) samples from patients with aetiologically well characterized encephalitis or aseptic meningitis.

Detection of both herpes simplex and varicella-zoster viruses in cerebrospinal fluid from patients with encephalitis

Cerebrospinal fluid (CSF) samples from 46 patients with encephalitis were studied for the presence of herpes simplex virus (HSV) types 1 and 2 and/or varicella zoster virus (VZV)-specific DNA sequences by the polymerase chain reaction (PCR) assay. Patients were studied because of detection of intrathecal production of IgG antibody to HSV alone (10 patients, Group A) or to both HSV and VZV (11 patients, Group B) or because of the presence of specific anti-HSV IgG in CSF without evidence of intrathecal antibody production (25 patients, Group C). CSF samples taken between days 1 and 10 from onset of encephalitis were available from all patients, and follow-up samples (taken after 10 days from onset) were obtained from some of them. Positive PCR results were obtained in a total of 13 patients. Four patients (three from Group A and one from Group B) gave amplification of HSV type 1 DNA alone, two patients (both from Group B) showed amplification of VZV DNA alone, and seven patients (all from Group B) gave dual amplification of both HSV type 1 and VZV DNA sequences in CSF. All CSF samples from patients in Group C were negative by PCR. Ten patients with CSF samples positive by PCR lacked a prior history of herpetic cutaneous lesions. In seven patients, serum antibody tests (specific IgM detection and specific IgG avidity assays) identified both primary and recurrent infections. The results suggest that the dual presence of IgG antibody to both HSV and VZV in CSF from patients with encephalitis may reflect in some cases a dual infection of the central nervous system caused by both agents.

Role of the virology laboratory in diagnosis and management of patients with central nervous system disease

A number of viruses cause acute central nervous system disease. The two major clinical presentations are aseptic meningitis and the less common meningoencephalitis. Clinical virology laboratories are now more widely available than a decade ago; they can be operated on a modest scale and can be tailored to the needs of the patients they serve. Most laboratories can provide diagnostic information on diseases caused by enteroviruses, herpesviruses, and human immunodeficiency virus. Antiviral therapy for herpes simplex virus is now available. By providing a rapid diagnostic test or isolation of the virus or both, the virology laboratory plays a direct role in guiding antiviral therapy for patients with herpes simplex encephalitis. Although there is no specific drug available for enteroviruses, attention needs to be paid to these viruses since they are the most common cause of nonbacterial meningitis and the most common pathogens causing hospitalization for suspected sepsis in young infants in the United States during the warm months of the year. When the virology laboratory maximizes the speed of viral detection or isolation, it can make a significant impact on management of these patients. Early viral diagnosis benefits patients with enteroviral meningitis, most of whom are hospitalized and treated for bacterial sepsis or meningitis or both; these patients have the advantage of early withdrawal of antibiotics and intravenous therapy, early hospital discharge, and avoidance of the risks and costs of unnecessary tests and treatment. Enteroviral infection in young infants also is a risk factor for possible long-term sequelae. For compromised patients, the diagnostic information helps in selecting specific immunoglobulin therapy. Good communication between the physician and the laboratory will result in the most benefit to patients with central nervous system viral infection.

Rapid diagnosis of herpes encephalitis by enzyme immuno-assay

Five cases of encephalitis caused by herpes simplex virus (HSV) are described. HSV-specific IgM and IgM antibodies were detected in cerebrospinal fluid and serum by use of antibody-capture noncompetitive enzyme-linked immunosorbent assay. The tests seem suitable for rapid diagnosis in the second week after onset of neurological symptoms. The clinical importance of early diagnosis and therapy in patients of HSV encephalitis has been discussed.

Anti-herpes simplex type 1 activity in IgG subclasses produced systemically and intrathecally in patients with herpes encephalitis

The role of the humoral immune response in herpes simplex encephalitis (HSE) is largely unknown. The finding that herpes simplex virus type 1 (HSV 1) induced IgG Fc receptor binds to all IgG subclasses except IgG 3 prompted an investigation of anti-HSV activity in IgG subclasses from serum and cerebrospinal fluid (CSF) in ten patients with proven or highly probable HSE by means of a monoclonal antibody IgG subclass-specific solid-phase radioimmunoassay (SPRIA). In contrast to serum, CSF contained no or low anti-HSV IgG titres during the first 2 weeks of disease in five of seven patients tested. The IgG titres rose thereafter for at least 4 weeks after the start of illness and remained high in both serum and CSF up to 393 days. The anti-HSV IgG subclass distribution in serum was IgG 1 (ten of ten), IgG 2 (two of ten), IgG 3 (six of ten), and IgG 4 (six of ten). Two patients had a simultaneous anti-HSV IgG 3 and IgG 4 response. With the exception of one patient lacking anti-HSV IgG 4 and two patients lacking anti-HSV IgG 2, the subclass distribution in CSF was the same as in serum. The anti-HSV subclass distribution in sera from ten seropositive patients without evidence of recent herpes infection did not differ from that of the HSE patients, except that five of ten patients had simultaneous anti-HSV IgG 3 and IgG 4 responses. Thus we could not correlate the anti-HSV subclass response in patients with HSE with the subclass preference of the HSV-induced Fc receptor.

Intrathecal synthesis of IgG antibodies to varicella-zoster virus in two cases of acute aseptic meningitis syndrome with no cutaneous lesions

IgG antibodies to varicella-zoster virus (VZV) were detected by indirect enzyme-immunoassay (EIA) in CSF of two patients with acute aseptic meningitis syndrome (AAMS) not associated with evident cutaneous lesion or recent history of zoster infection. Their characteristic features and serological data are compared with those observed in two patients with AAMS and zoster cutaneous lesions, and in 13 patients with AAMS of unknown or other etiology. According to several indexes applied to assess the origin of the detected antibodies, it is concluded that VZV IgG antibodies are of intrathecal production. The possible etiologic relationship between the neurological syndrome and the detection of VZV antibodies in CSF is discussed. Routine serological procedures are proposed for the diagnosis of CNS acute infections of probable viral etiology that should provide additional data on these rarely described cases.