Kinetics of IgM and IgG responses to Japanese encephalitis virus in human serum and cerebrospinal fluid

Persistence of West Nile virus in the central nervous system and periphery of mice

Most acute infections with RNA viruses are transient and subsequently cleared from the host. Recent evidence, however, suggests that the RNA virus, West Nile virus (WNV), not only causes acute disease, but can persist long term in humans and animal models. Our goal in this study was to develop a mouse model of WNV persistence. We inoculated immunocompetent mice subcutaneously (s.c.) with WNV and examined their tissues for infectious virus and WNV RNA for 16 months (mo) post-inoculation (p.i.). Infectious WNV persisted for 1 mo p.i. in all mice and for 4 mo p.i. in 12% of mice, and WNV RNA persisted for up to 6 mo p.i. in 12% of mice. The frequency of persistence was tissue dependent and was in the following order: skin, spinal cord, brain, lymphoid tissues, kidney, and heart. Viral persistence occurred in the face of a robust antibody response and in the presence of inflammation in the brain. Furthermore, persistence in the central nervous system (CNS) and encephalitis were observed even in mice with subclinical infections. Mice were treated at 1 mo p.i. with cyclophosphamide, and active viral replication resulted, suggesting that lymphocytes are functional during viral persistence. In summary, WNV persisted in the CNS and periphery of mice for up to 6 mo p.i. in mice with subclinical infections. These results have implications for WNV-infected humans. In particular, immunosuppressed patients, organ transplantation, and long term sequelae may be impacted by WNV persistence.

Evaluation of two commercially available ELISAs for the diagnosis of Japanese encephalitis applied to field samples

OBJECTIVE

To compare two commercially available kits, Japanese Encephalitis-Dengue IgM Combo ELISA (Panbio Diagnostics) and JEV-CheX IgM capture ELISA (XCyton Diagnostics Limited), to a reference standard (Universiti Malaysia Sarawak - Venture Technologies VT ELISA).

METHODS

Samples were obtained from 172/192 children presenting to a site in rural India with acute encephalitis syndrome.

RESULTS

Using the reference VT ELISA, infection with Japanese encephalitis virus (JEV) was confirmed in 44 (26%) patients, with central nervous system infection confirmed in 27 of these; seven patients were dengue seropositive. Of the 121 remaining patients, 37 (31%) were JEV negative and 84 (69%) were JEV unknown because timing of the last sample tested was <10 day of illness or unknown. For patient classification with XCyton, using cerebrospinal fluid alone (the recommended sample), sensitivity was 77.8% (59.2-89.4) with specificity of 97.3% (90.6-99.2). For Panbio ELISA, using serum alone (the recommended sample), sensitivity was 72.5% (57.2-83.9) with specificity of 97.5% (92.8-99.1). Using all available samples for patient classification, sensitivity and specificity were 63.6% (95% CI: 48.9-76.2) and 98.4% (94.5-99.6), respectively, for XCyton ELISA and 75.0% (59.3-85.4) and 97.7% (93.3-99.2) for Panbio ELISA.

CONCLUSION

The two commercially available ELISAs had reasonable sensitivities and excellent specificities for diagnosing JEV.

Viral meningoencephalitis: a review of diagnostic methods and guidelines for management

BACKGROUND

Viral encephalitis is a medical emergency. The prognosis depends mainly on the pathogen and host immunologic state. Correct immediate diagnosis and introduction of symptomatic and specific therapy has a dramatic influence upon survival and reduces the extent of permanent brain injury.

METHODS

We searched the literature from 1966 to 2009. Recommendations were reached by consensus. Where there was lack of evidence but consensus was clear, we have stated our opinion as good practice points.

RECOMMENDATIONS

Diagnosis should be based on medical history and examination followed by CSF analysis for protein and glucose levels, cellular analysis, and identification of the pathogen by polymerase chain reaction amplification (recommendation level A) and serology (level B). Neuroimaging, preferably by MRI, is essential (level B). Lumbar puncture can follow neuroimaging when immediately available, but if this cannot be performed immediately, LP should be delayed only under unusual circumstances. Brain biopsy should be reserved only for unusual and diagnostically difficult cases. Patients must be hospitalized with easy access to intensive care units. Specific, evidence-based, antiviral therapy, acyclovir, is available for herpes encephalitis (level A) and may also be effective for varicella-zoster virus encephalitis. Ganciclovir and foscarnet can be given to treat cytomegalovirus encephalitis, and pleconaril for enterovirus encephalitis (IV class evidence). Corticosteroids as an adjunct treatment for acute viral encephalitis are not generally considered to be effective, and their use is controversial, but this important issue is currently being evaluated in a large clinical trial. Surgical decompression is indicated for impending uncal herniation or increased intracranial pressure refractory to medical management.

Risk factors for Japanese encephalitis: a case-control study

Japanese encephalitis (JE) has been found to be endemic in Bali, Indonesia. A case-control study was conducted to identify factors associated with JE infection. All 94 serologically confirmed JE cases (cases) and 163 cases of encephalitis or aseptic meningitis without JE (controls) identified in Bali during 2001-2004 were included in the study. Potential risk factors were surveyed at hospital admission. Univariate analyses revealed the following factors to be associated with JE: older age, referral from sub-district health centre or private hospital, playing outdoors after dinner, use of mosquito repellent or spraying, proximity of the residence to rice fields, and pig ownership by the family or next-door neighbours. Multivariate analysis identified proximity to rice fields (OR 2.93, 95% CI 1.57-5.45), pig ownership (OR 2.24, 95% CI 1.17-4.26), and older age (OR 1.21, 95% CI 1.09-1.33) as being independently associated with the risk of JE. Because rice cultivation and pig rearing are essential to the economy of Bali, JE immunization is the best intervention for prevention of JE in Bali.

Evidence and rationale for the World Health Organization recommended standards for Japanese encephalitis surveillance

BACKGROUND

Japanese encephalitis (JE) is the most important form of viral encephalitis in Asia. Surveillance for the disease in many countries has been limited. To improve collection of accurate surveillance data in order to increase understanding of the full impact of JE and monitor control programs, World Health Organization (WHO) Recommended Standards for JE Surveillance have been developed. To aid acceptance of the Standards, we describe the process of development, provide the supporting evidence, and explain the rationale for the recommendations made in the document.

METHODS

A JE Core Working Group was formed in 2002 and worked on development of JE surveillance standards. A series of questions on specific topics was initially developed. A literature review was undertaken and the findings were discussed and documented. The group then prepared a draft document, with emphasis placed on the feasibility of implementation in Asian countries. A field test version of the Standards was published by WHO in January 2006. Feedback was then sought from countries that piloted the Standards and from public health professionals in forums and individual meetings to modify the Standards accordingly.

RESULTS

After revisions, a final version of the JE surveillance standards was published in August 2008. The supporting information is presented here together with explanations of the rationale and levels of evidence for specific recommendations.

CONCLUSION

Provision of the supporting evidence and rationale should help to facilitate successful implementation of the JE surveillance standards in JE-endemic countries which will in turn enable better understanding of disease burden and the impact of control programs.

Epidemiology and burden of disease from Japanese encephalitis in Cambodia: results from two years of sentinel surveillance

OBJECTIVES

To describe the results from two years of Japanese encephalitis (JE) sentinel surveillance in Cambodia.

METHODS

Sentinel site surveillance for JE in children aged 15 years and under was implemented in Cambodia in mid-2006. It was integrated into the routine meningoencephalitis surveillance system. Six hospitals were selected as sentinel sites. Epidemiological information and diagnostic specimens were collected from each patient presenting with meningoencephalitis. Cerebrospinal fluid and sera were tested for presence of immunoglobulin M antibodies against JE and dengue viruses by an ELISA. Surveillance data from 2006 to 2008 were analysed.

RESULTS

Of 586 patients presenting with meningoencephalitis, 110 (19%) were confirmed to have JE. The percentage of confirmed JE cases at individual sentinel sites ranged from 13% to 35% of all meningoencephalitis cases. Mean age was 6.2 years, with 95% of JE cases in children aged 12 years and under. Cases occurred year-round in both 12-month reporting periods.

CONCLUSIONS

JE is an important cause of meningoencephalitis in Cambodian children. As JE is a vaccine-preventable disease, an immunization programme could result in a considerable reduction in morbidity and mortality from JE among children in Cambodia.

Involvement of nigrostriatal pathway in Japanese encephalitis with movement disorders: evidence from 99mTc-TRODAT-1 and 123I-IBZM SPECT imagings

PURPOSE

The purpose of this study was to evaluate molecular evidence of nigrostriatal pathway involvement in Japanese encephalitis (JE) survivors with movement complications.

METHODS

Three JE patients were recruited. All had cranial magnetic resonance imaging (MRI) and single-photon emission computed tomography (SPECT) studies with (99m)Tc-TRODAT-1 and (123)I-IBZM.

RESULTS

Cranial MRI revealed involvement of bilateral thalami, substantia nigra, and medial temporal lobes in all three patients, but only case 1 had additional bilateral basal ganglia involvement. The (99m)Tc-TRODAT-1 SPECT for presynaptic dopamine transporter imaging disclosed asymmetrical decreases in bilateral striatal uptake in all three patients. However, the (123)I-IBZM SPECT imaging for postsynaptic D2 dopamine receptors (D2Rs) revealed inconsistent abnormalities including asymmetrical bilateral decreases (case 1), unilateral decrease (case 2), and bilateral increases (case 3) in striatal uptakes.

CONCLUSION

Data have suggested that presynaptic dopaminergic neurons in JE patients are more susceptible to JE virus than postsynaptic striatal neurons. The degree of movement impairment was more closely correlated to the degree of D2Rs disruption seen in (123)I-IBZM SPECT imaging.

Japanese encephalitis virus produces a CD4+ Th2 response and associated immunoprotection in an adoptive-transfer murine model

Japanese encephalitis is an acute infection of the central nervous system caused by Japanese encephalitis virus (JEV). The importance of an effective humoral response in preventing JEV infection has already been established, although the contribution of cellular immunity remains unclear. This study used an experimental murine model to understand the protective effects of cell-mediated immunity in JEV infection. Fourteen-day-old mice adoptively transferred with JEV-immune splenocytes were found to be protected from peripheral JEV challenge. The survival rate was reduced when transferred cells were depleted of their CD4+ T-cell population. Correspondingly, increased protection was observed when JEV-primed isolated CD4+ T cells were transferred compared with isolated CD8+ T cells. Mice protected from JEV infection by the adoptive transfer of JEV-immune splenocytes had higher levels of immunomodulatory cytokines and decreased expression of pro-inflammatory cytokines. Concurrent with the increase in Th2 cytokines, JEV-specific IgM and IgG1 antibody titres were found to be elevated in protected mice. Taken together, these data indicate a definite role for CD4+ T cells in protection from lethal JEV infection in naïve 14-day-old mice. Induction of a Th2 cytokine response and IgG1 antibody probably achieves an immunomodulatory effect that results in the enhanced survival of these animals.

Virus-specific cytolytic antibodies to nonstructural protein 1 of Japanese encephalitis virus effect reduction of virus output from infected cells

We demonstrate the presence of nonstructural protein 1 (NS1)-specific antibodies in a significant proportion of convalescent-phase human serum samples obtained from a cohort in an area where Japanese encephalitis virus (JEV) is endemic. Sera containing antibodies to NS1 but not those with antibodies to other JEV proteins, such as envelope, brought about complement-mediated lysis of JEV-infected BHK-21 cells. Target cells infected with a recombinant poxvirus expressing JEV NS1 on the cell surface confirmed the NS1 specificity of cytolytic antibodies. Mouse anti-NS1 cytolytic sera caused a complement-dependent reduction in virus output from infected human cells, demonstrating their important role in viral control. Antibodies elicited by JEV NS1 did not cross lyse West Nile virus- or dengue virus-infected cells despite immunoprecipitating the NS1 proteins of these related flaviviruses. Additionally, JEV NS1 failed to bind complement factor H, in contrast to NS1 of West Nile virus, suggesting that the NS1 proteins of different flaviviruses have distinctly different mechanisms for interacting with the host. Our results also point to an important role for JEV NS1-specific human immune responses in protection against JE and provide a strong case for inclusion of the NS1 protein in next generation of JEV vaccines.

A cohort study to assess the new WHO Japanese encephalitis surveillance standards

OBJECTIVE

To assess the field-test version of the new WHO Japanese encephalitis (JE) surveillance standards.

METHODS

We applied the clinical case definition of acute encephalitis syndrome (AES), laboratory diagnostic criteria and case classifications to patients with suspected central nervous system (CNS) infections in southern Viet Nam.

FINDINGS

Of the 380 patients (149 children) recruited with suspected CNS infections, 296 (96 children) met the AES case definition. 54 children were infected with JE virus (JEV), of whom 35 (65%) had AES, giving a sensitivity of 65% (95% CI: 56-73) and specificity of 39% (95% CI: 30-48). Nine adults with JEV presented with AES. 19 JEV-infected children missed by surveillance included 10 with acute flaccid paralysis, two with flaccid hemiparesis and six with meningism only. Altering the case definition to include limb paralysis and meningism improved sensitivity to 89% (95% CI: 83-95), while reducing specificity to 23% (95% CI: 15-30). Six children that did not have AES on admission had reduced consciousness after admission. Cerebrospinal fluid (CSF) analysis diagnosed seven patients negative on serum analysis. Five patients with neurological manifestations of dengue infection had JEV antibodies in serum and would have been misdiagnosed had we not tested for dengue antibodies in parallel.

CONCLUSION

Children infected with JEV that presented with acute limb paralysis or neck stiffness only were missed by the surveillance standards, although some of them subsequently became encephalopathic. A footnote in the surveillance standards drawing attention to these presentations would be helpful. An acute CSF sample is more sensitive and specific than an acute serum sample.

Coinfection of Japanese encephalitis with neurocysticercosis: an imaging study

BACKGROUND AND PURPOSE

Coinfection of neurocysticercosis (NCC) and Japanese encephalitis (JE) has been advocated as more than a chance occurrence resulting in poor outcome. We undertook this study to determine whether the association of the 2 infections is more than a chance occurrence, to define the imaging characteristics of coinfections, and to explore the synergistic effect of NCC in JE.

MATERIALS AND METHODS

Sixty-two patients with JE were studied by MR imaging and CT. CT was done in 53 and MR imaging in 53 patients. The diagnosis of JE was established by CSF JE virus immunoglobulin M capture (MAC) enzyme-linked immunosorbent assay (ELISA). NCC was diagnosed from imaging. A control group of 385 patients was evaluated by imaging for prevalence of NCC in the general population.

RESULTS

A significantly high association of NCC with JE (19.3%) was observed in comparison with prevalence of NCC in control subjects (1.04%; P = .0003). JE lesions in coinfection were significantly asymmetric with lateralization to the side of the brain having the maximum NCC or a cyst with edema. The JE lesions in coinfections were more florid, with a significantly higher proportion of abnormal CT scans and more abnormal MR imaging. Coinfections were significantly more common in children. Significantly lower CSF MAC-ELISA units in patients with coinfection reflected low CSF IgM levels, suggesting altered immune status.

CONCLUSION

In our series, there was a strong association between JE and NCC, and, thus, this coinfection was more than a chance occurrence.

Study of Japanese encephalitis and other viral encephalitis in Nepali children

BACKGROUND

A hospital-based prospective cross-sectional study was conducted in children aged 1 month-14 years to identify the proportion of viral encephalitis due to Japanese encephalitis (JE) and compare the clinico-laboratory profile and outcome of JE with that of other viral encephalitis (non-JE).

METHODS

All probable cases of viral encephalitis on clinical and laboratory evaluation were confirmed as JE on anti-JE IgM in cerebrospinal fluid (CSF) and/or serum. Patients not having anti-JE IgM in CSF and/or serum were diagnosed as having non-JE.

RESULTS

Of 94 cases, 58 were JE and 36 non-JE. Although practice of rearing pigs at home was associated with JE (P = 0.0001), significantly higher serum creatinine, protein, aspartate aminotransferase and CSF protein levels were observed in non-JE. Longer duration of fever was associated with complete recovery in JE whereas shorter duration of fever was associated with recovery in non-JE. Risk of neurological sequelae (P = 0.01), especially hemiparesis (P = 0.03) was significantly more in JE. Sequelae were observed at 6 weeks follow up in 18.8% of JE and 13.9% of non-JE.

CONCLUSION

JE was the most common cause of viral encephalitis in eastern Nepal and should be suspected in encephalitic patients having pig rearing at home and neurological sequelae. Although duration of hospitalization and complication were higher in JE, final outcome was similar to non-JE. Longer duration of fever in JE and shorter duration of fever in non-JE correlated with recovery, while altered sensorium and focal neurological deficit were independent predictors of sequelae at 6 weeks only in JE and not in non-JE.

Clinico-laboratory profile and outcome of Japanese encephalitis in Nepali children

BACKGROUND

Japanese encephalitis (JE) is associated with high mortality and neurological sequelae. The unpredictable course and lack of specific treatment pose major challenges in management. The tropical climate and paddy ecosystem in Nepal provide a suitable setting.

AIMS

To determine the aetiology of febrile encephalopathy and describe the clinico-laboratory profile and outcome of JE in Nepali children.

METHODS

A hospital-based prospective and observational study was conducted over a 1-year period (2000-2001). Children aged from >1 month to 14 years with fever >38 degrees C for <2 weeks and altered sensorium were recruited. JE was confirmed by anti-JE IgM in cerebrospinal fluid and/or serum.

RESULTS

Of 117 consecutively enrolled patients, 58 had JE. Ten patients had concomitant infections, four with malaria and six with bacterial meningitis, and were excluded from analysis. Clinical findings were as follows: boys, 69%; age 4-14 years, 71%; presentation during summer and autumn, 83%; fever >3 days, 69%; altered sensorium <2 days, 50%; Glasgow coma score 8-12, 63%; seizures, 58%. Four (8.3%) died. At discharge, neurological sequelae were detected in 24 (50%) and hemiparesis was the most common form. Longer duration of vomiting, altered sensorium and focal neurological deficit on admission were independently associated with sequelae at discharge. Sequelae persisted in nine (18.8%) at 6 weeks follow-up. Long duration of altered sensorium (beta co-efficient 0.35, odds ratio 1.4, p=0.042) and presence of focal neurological deficit on admission (beta co-efficient 1.6, odds ratio 5.2, p=0.049) were independent predictors of sequelae at 6 weeks.

CONCLUSION

JE was the commonest cause of febrile encephalopathy. Neurological sequelae were common but resolved in two-thirds of cases.

Neurologic disease associated with 17D-204 yellow fever vaccination: a report of 15 cases

Yellow fever (YF), can be prevented by an attenuated vaccine (YEL). We reviewed neurologic adverse events (AE) following YEL that were reported to the national Vaccine Adverse Events Reporting System (VAERS). VAERS is a passive reporting system with inherent limitations for causality assessment. Based on defined criteria, five cases of encephalitis were classified as 'definitely' and one of acute disseminated encephalomyelitis (ADEM) as 'probably' caused by YEL. Six cases of Guillain-Barre Syndrome (GBS), one of encephalitis, and two of ADEM, were classified as 'suspect' vaccine-associated disease. Laboratory and epidemiological evidence suggests that YEL caused encephalitis. Additional studies will be required to confirm whether YEL can rarely result in GBS and/or ADEM.

A hospital-based surveillance for Japanese encephalitis in Bali, Indonesia

BACKGROUND

Japanese encephalitis (JE) is presumed to be endemic throughout Asia, yet only a few cases have been reported in tropical Asian countries such as Indonesia, Malaysia and the Philippines. To estimate the true disease burden due to JE in this region, we conducted a prospective, hospital-based surveillance with a catchment population of 599,120 children less than 12 years of age in Bali, Indonesia, from July 2001 through December 2003.

METHODS

Balinese children presenting to any health care facility with acute viral encephalitis or aseptic meningitis were enrolled. A "confirmed" diagnosis of JE required the detection of JE virus (JEV)-specific IgM in cerebrospinal fluid, whereas a diagnosis of "probable JE" was assigned to those cases in which JEV-specific IgM was detected only in serum.

RESULTS

In all, 86 confirmed and 4 probable JE cases were identified. The annualized JE incidence rate was 7.1 and adjusted to 8.2 per 100,000 for children less than 10 years of age over the 2.5 consecutive years of study. Only one JE case was found among 96,920 children 10-11 years old (0.4 per 100,000). Nine children (10%) died and 33 (37%) of the survivors had neurological sequelae at discharge. JEV was transmitted in Bali year-round with 70% of cases in the rainy season.

CONCLUSION

JE incidence and case-fatality rates in Bali were comparable to those of other JE-endemic countries of Asia. Our findings contradict the common wisdom that JE is rare in tropical Asia. Hence, the geographical range of endemic JE is broader than previously described. The results of the study support the need to introduce JE vaccination into Bali.

Viral encephalitis: a review of diagnostic methods and guidelines for management

Viral encephalitis is a medical emergency. The spectrum of brain involvement and the prognosis are dependent mainly on the specific pathogen and the immunological state of the host. Although specific therapy is limited to only several viral agents, correct immediate diagnosis and introduction of symptomatic and specific therapy has a dramatic influence upon survival and reduces the extent of permanent brain injury in survivors. We searched MEDLINE (National Library of Medicine) for relevant literature from 1966 to May 2004. Review articles and book chapters were also included. Recommendations are based on this literature based on our judgment of the relevance of the references to the subject. Recommendations were reached by consensus. Where there was lack of evidence but consensus was clear we have stated our opinion as good practice points. Diagnosis should be based on medical history, examination followed by analysis of cerebrospinal fluid for protein and glucose contents, cellular analysis and identification of the pathogen by polymerase chain reaction (PCR) amplification (recommendation level A) and serology (recommendation level B). Neuroimaging, preferably by magnetic resonance imaging, is an essential aspect of evaluation (recommendation level B). Lumbar puncture can follow neuroimaging when immediately available, but if this cannot be obtained at the shortest span of time it should be delayed only in the presence of strict contraindications. Brain biopsy should be reserved only for unusual and diagnostically difficult cases. All encephalitis cases must be hospitalized with an access to intensive care units. Supportive therapy is an important basis of management. Specific, evidence-based, anti-viral therapy, acyclovir, is available for herpes encephalitis (recommendation level A). Acyclovir might also be effective for varicella-zoster virus encephalitis, gancyclovir and foscarnet for cytomegalovirus encephalitis and pleconaril for enterovirus encephalitis (IV class of evidence). Corticosteroids as an adjunct treatment for acute viral encephalitis are not generally considered to be effective and their use is controversial. Surgical decompression is indicated for impending uncal herniation or increased intracranial pressure refractory to medical management.

Detection of Japanese encephalitis virus antigens in the CSF using monoclonal antibodies

BACKGROUND

Antigen detection in the CSF is an invaluable tool in the diagnosis of viral infections of the nervous system, especially in the early phase of the illness. Very little information is available on the use of antigen detection in the diagnosis of Japanese encephalitis (JE).

OBJECTIVES

Evaluation of two monoclonal antibody-based antigen detection methods in the diagnosis of JE in comparison with the detection of virus-specific IgM antibodies in the CSF.

STUDY DESIGN

In this study 115 patients with a clinical diagnosis of JE were investigated. A reverse passive haemagglutination test for the detection of soluble JEV antigens, an immunofluorescent assay for the detection of cell-associated antigen and an IgM capture ELISA for the detection of virus specific IgM antibodies in the CSF were used.

RESULTS

Laboratory confirmation of JE was possible in 92/115 patients. Virus-specific IgM was detected in 75/92 and JEV antigen was detected in 52/92 patients. Soluble antigen was detected in 37/52, cell-associated antigen in 30/52. There was no significant difference in the sensitivity of the two antigen detection systems used.

CONCLUSIONS

Diagnosis by antigen detection could be done less frequently than by demonstration of virus-specific IgM antibodies in the spinal fluid. However, antigen detection proved useful during the first week of illness when IgM antibodies were not detected in the CSF.

Infectious meningitis: prospective evaluation with magnetization transfer MRI

The study was performed with the aim of prospectively characterizing infectious meningitis of different aetiology using magnetization transfer (MT) MRI. Spin-echo (SE) T(1), T(2) and pre- and post-contrast T(1) weighted MT images in 100 patients with aetiologically proven meningitis were evaluated for the visibility and enhancement of the meninges on pre- and post-contrast T(1) weighted MT images, respectively. The MT ratio (MTR) was calculated from the thickened meninges in tuberculous meningitis. In addition, the percentage difference in the mean signal intensity (SI) of the meninges and adjacent brain parenchyma was calculated and compared between different groups using 2-tailed student's t-test. T(1) weighted MT images were highly sensitive (96%) in the detection of abnormal meningeal enhancement. Meninges were visible on pre-contrast T(1) weighted MT images only in patients with tuberculous meningitis. The MTR from meninges in tuberculous infection was 19.10+/-1.02, and the percentage difference in the mean SI of the meninges and the adjacent T(2) normal brain parenchyma was significantly higher (p<0.05) in the tuberculous group compared with that in the non-tuberculous group. MT MRI is an important technique for the detection and characterization of infectious meningitis of different aetiology. Visibility of the meninges on pre-contrast T(1) weighted MT images may be considered highly suggestive of tuberculous meningitis.

Neurovirulence and host factors in flavivirus encephalitis--evidence from clinical epidemiology

Japanese encephalitis virus (JEV) and West Nile virus (WNV) provide some of the most important examples of emerging zoonotic viral encephalitides. For these flaviviruses, only a small proportion of those infected develop clinical features, and these may range from a non-specific flu-like illness to a severe fatal meningoencephalitis, often with Parkinsonian features, or a poliomyelitis-like flaccid paralysis. The factors governing the clinical presentations, and outcome of flavivirus infections are poorly understood, but studies have looked at viral virulence determinants and the host immune response. Previous studies on JEV have suggested that the distribution of the four genotypes across Asia may relate to the differing clinical epidemiology (epidemic disease in the north, endemic disease in the south). However, new data based on the complete nucleotide sequence of a virus representing one of the oldest lineages, and phylogenetic analyses of all JEV strains for which genetic data are available, suggest that the distribution is best explained in terms of the virus' origin in the Indonesia-Malaysia region (where all genotypes have been found), and the spread of the more recent genotypes to new geographical areas. Clinical studies have shown that innate immunity, as manifested by interferon alpha levels, is important in JEV and other flaviviruses, but treatment with interferon alpha did not improve the outcome. A failure of the humoral immune response, is associated with death from encephalitis caused by JEV and WNV. Cellular immunity has been less well characterized, but CD8+ and CD4+ T cells are thought to be important.

Persistence of virus-reactive serum immunoglobulin m antibody in confirmed west nile virus encephalitis cases

Twenty-nine laboratory-confirmed West Nile virus (WNV encephalitis patients were bled serially so that WNV-reactive immunoglobulin (Ig) M activity could be determined. Of those patients bled, 7 (60%) of 12 had anti-WNV IgM at approximately 500 days after onset. Clinicians should be cautious when interpreting serologic results from early season WNV IgM-positive patients.

Pathogenesis of flavivirus encephalitis

Within the flavivirus family, viruses that cause natural infections of the central nervous system (CNS) principally include members of the Japanese encephalitis virus (JEV) serogroup and the tick-borne encephalitis virus (TBEV) serocomplex. The pathogenesis of diseases involves complex interactions of viruses, which differ in neurovirulence potential, and a number of host factors, which govern susceptibility to infection and the capacity to mount effective antiviral immune responses both in the periphery and within the CNS. This chapter summarizes progress in the field of flavivirus neuropathogenesis. Mosquito-borne and tickborne viruses are considered together. Flavivirus neuropathogenesis involves both neuroinvasiveness (capacity to enter the CNS) and neurovirulence (replication within the CNS), both of which can be manipulated experimentally. Neuronal injury as a result of bystander effects may be a factor during flavivirus neuropathogenesis given that microglial activation and elaboration of inflammatory mediators, including IL-1β and TNF-α, occur in the CNS during these infections and may accompany the production of nitric oxide and peroxynitrite, which can cause neurotoxicity.

Diagnosis and genetic analysis of Japanese encephalitis virus infected in horses

Nervous disorders were found in two horses and verified as aseptic encephalitis by necropsy in the summer of 2000. To investigate agents that affected the horses, diagnostic procedures involving virus isolation, neutralization test and reverse transcription-polymerase chain reaction (RT-PCR) were performed. We intracranially inoculated litters of suckling mice with tissues suspected of containing aseptic encephalitis, including cerebrum, cerebellum, brain stem, thalamus, and cerebrospinal fluids; the mice were then observed for 14 days. Neutralizing antibodies against Japanese encephalitis (JE) viruses were present in the cerebrospinal fluid of the horses in titers of 10. Sequences of 500 nucleotides of the premembrane gene of JE virus, synthesized by RT-PCR, from both the cerebrum and cerebellum were determined. The phylogenetic analysis based on sequences of the premembrane gene revealed a relationship with the JE virus. The divergences at the nucleotide level of 1.2-5.7% and at the amino acid level of 0-4.3% were conserved with other JE strains. The results demonstrated that the pathogens causing equine encephalitis were JE viruses. The strains were closely related to Taiwanese isolates.

Japanese viral encephalitis

One of the leading causes of acute encephalopathy in children in the tropics is Japanese encephalitis (JE). Transmitted by the culex mosquito, this neurotropic virus predominately affects the thalamus, anterior horns of the spinal cord, cerebral cortex, and cerebellum. It mainly affects children <15 years and is mostly asymptomatic. The occasional symptomatic child typically presents with a neurological syndrome characterised by altered sensorium, seizures, and features of intracranial hypertension. Aetiological diagnosis is based on virus isolation or demonstration of virus specific antigen or antibodies in the cerebrospinal fluid/blood. Though no antiviral drug is available against JE, effective supportive management can improve the outcome. Control of JE involves efficient vector control and appropriate use of vaccines.

Update on viral encephalitis

Over 100 viruses have been associated with acute central nervous system infections. The present review focuses on some of the most common agents of viral encephalitis, as well as important emerging viral encephalitides. In this context, the initial detection of West Nile virus in the Western Hemisphere during the 1999 New York City outbreak, the first description of Nipah virus in Malaysia, and the appearance in Asia of a new neurovirulent enterovirus 71 strain that causes severe neurologic disease are highlighted. In addition, advances regarding diagnosis, neuroimaging and treatment of Japanese and herpes simplex encephalitis are presented.

Persistence of arboviruses and antiviral antibodies in vertebrate hosts: its occurrence and impacts

The recent isolation of West Nile virus from a bird in mid-winter in New York immediately raised, as one of a few explanations, the possibility of long-term persistence of arboviruses in vertebrate hosts. Although it was a highly popular topic for research many years ago, generally it has since been neglected and its meaning under appreciated. This comprehensive survey of literature worldwide uncovered, contrary to the general perception that it is a rather infrequent phenomenon, a large number of important observations involving all groups of arboviruses that have been accumulating over the years without drawing much attention. In this review, the data and observations were analysed in terms of the occurrence, role in natural transmission, mechanisms and genesis of persistence, source of problems in research and impact. The outcome of the analyses clearly demonstrates that asymptomatic, long-term infection in the absence of viraemia with or without the induction of neutralising antibody, the most frequent characteristics of arboviral persistence, presents a serious question about the validity of some of the past animal experiments that were conducted without the consideration of such a possibility. Likewise, significant impacts are felt on diverse fields ranging from epidemiology to diagnostic virology and from veterinary medicine to agricultural commerce. Published in 2001 by John Wiley & Sons, Ltd.

Biphasic illness pattern due to early relapse in Japanese-B virus encephalitis

Japanese-B virus encephalitis (JE) is considered a uniphasic illness with a variable outcome. Biphasic illness patterns have never been reported previously. From an endemic zone in India we observed six patients of JE (from 62 patients treated in 7 years) who had an early relapse resulting in the biphasic clinical course. Five had poor socio-economic status and three had laboratory evidence of nutritional deficiency. Two patients were adults and the other four were children. Fever, rigors, headaches, body aches, altered consciousness, rigidity and tremors predominated the first phase of illness. During the second phase, behavioural changes, dystonia, pen-oral dyskinesia, drooling, mutism and muscle wasting due to anterior horn cell involvement were the important features. Though the serial antibody titres against the JE virus showed a four-fold rise in the initial or late convalescent phases, there was no increase during the second phase of the illness as compared to the first phase. On MRI, fresh lesions appeared during the second phase at the sites known for their involvement in JE, suggesting recrudescence of the virus. One patient survived with major sequelae, two with minor sequelae and the other three had complete recovery. We conclude that some patients with JE may have an early relapse after partial recovery, giving rise to the biphasic illness pattern. A locally prevalent genetic variant of the virus or host factors may be responsible for the altered clinical course of the disease. Biphasic illness does not necessarily mean a bad prognosis.

Central nervous system infections in the tropics: diagnosis, treatment and prevention

The present review is a brief discussion of some of the important new developments that have been reported relating to bacterial and viral infections of the central nervous system. For many of these conditions, certain issues remain unresolved, including what is the best diagnostic approach, what is the optimum treatment and how best to prevent such conditions. The development of improved surveillance, more effective vaccines and a greater understanding of the pathophysiology of these diseases all offer great potential benefits. The hope is that these advances, when they come, will be affordable to those who need them most.

Evaluation of immunoglobulin M (IgM) and IgG enzyme immunoassays in serologic diagnosis of West Nile Virus infection

A unique urban encephalitis epidemic in Romania signaled the emergence of neurological infection due to West Nile (WN) virus as a novel public health threat in Eastern Europe and provided an opportunity to evaluate patterns of immunoglobulin G (IgG) and IgM reactivity in IgM capture and IgG enzyme-linked immunosorbent assays (ELISAs). WN virus infection was diagnosed serologically in 236 of 290 patients from whom acute serum or cerebrospinal fluid (CSF) samples were available. In 37% of serum samples and in 25% of CSF samples collected in the first week of illness, anti-WN virus IgM antibody was detected in the absence of virus-specific IgG. The switch to an IgG antibody response occurred after 4 to 5 days of illness and earlier in CSF than in serum. A specific humoral immune response was detected in the CSF before the serum in some patients for whom paired CSF and serum samples from the same day were available. IgM antibody in convalescent serum samples persisted beyond 2 months after the onset of illness in more than 50% of patients. ELISA optical density values and antibody concentrations were well correlated for both IgM and IgG immunoassays. Anti-WN virus IgM antibody in acute-phase samples did not cross-react significantly with flaviviruses in other antigenic groups.

Primary and booster immune responses to SA14-14-2 Japanese encephalitis vaccine in Korean infants

Attenuated SA14-14-2 Japanese encephalitis (JE) vaccine has been administered safely and effectively to more than 100 million children in China since 1988 and recently, licensure of the vaccine in Korea has been sought. In the first clinical evaluation of the vaccine outside of China, we monitored side effects in 84 children and evaluated antibody responses to a single dose given as primary JE vaccination in 68 children, 1-3 years old (mean age 27 months). No significant adverse events were noted. Neutralizing antibodies (geometric mean titer [GMT] of 188) were produced in 96% of the 68 subjects. In 10 other children who previously had been immunized with two or three doses of inactivated JE vaccine, the booster administration of SA14-14-2 vaccine produced an anamnestic response in all, with a GMT of 3378. In a comparison group of 25 children previously immunized with two doses of inactivated vaccine, neutralizing antibody titers were detected in 16 (64%). Viral specific IgM was detected in nine primary vaccinees (13%) but in others, IgM may have declined to undetectable levels in the four week postimmunization sample. Live attenuated SA14-14-2 JE vaccine is a promising alternative to the only commercially available JE vaccine for national childhood immunization programs in Asia.

Rapid diagnosis of Japanese encephalitis by using an immunoglobulin M dot enzyme immunoassay

Japanese encephalitis (JE) occurs in rural settings in southern and eastern Asia, where diagnostic facilities are limited. For the diagnosis of JE virus (JEV) infection, we developed a nitrocellulose membrane-based immunoglobulin M (IgM) capture dot enzyme immunoassay (MAC DOT) that is rapid, simple to use, requires no specialized equipment, and can distinguish JEV from dengue infection. In a prospective field study in southern Vietnam, 155 cerebrospinal fluid (CSF) and 341 serum samples were collected from 111 children and 83 adults with suspected encephalitis. The JEV MAC DOT, performed on site, was scored visually from negative to strongly positive by two observers, and the results were compared subsequently with those of the standard IgM capture enzyme-linked immunosorbent assay. For the 179 patients with adequate specimens, the MAC DOT correctly identified 59 of 60 JEV-positive patients and 118 of 119 JEV-negative patients (sensitivity [95% confidence intervals], 98.3% [92.1 to 99.91%]; specificity, 99.2% [95.9 to 100.0%]; positive predictive value, 0.98; negative predictive value, 0.99). The MAC DOT also correctly identified three patients with dengue encephalopathy. Admission specimens were positive for 73% of JE patients. Interobserver agreement for MAC DOT diagnosis was excellent (kappa = 0.94). The JEV MAC DOT is a simple and reliable rapid diagnostic test for JE in rural hospitals.

Intrathecal IgM, IgA and IgG antibody response in tick-borne encephalitis. Long-term follow-up related to clinical course and outcome

BACKGROUND

Tick-borne encephalitis (TBE) of western subtype causes long-term morbidity and is considered a health problem in Scandinavia, eastern and central parts of Europe and Russia. The pathophysiology is not fully elucidated. As TBE RNA is rarely demonstrable in cerebrospinal fluid (CSF) the kinetics of the CSF antibody response to the disease has attracted attention.

OBJECTIVES

To investigate the intrathecal TBE-specific antibody response and to correlate its intensity and persistence to the clinical course. To compare indirect, commercially-based ELISA methods indexed against albumin ratio or IgG ratio with the capture ELISA method for the establishment of CSF response.

STUDY DESIGN

The specific IgM, IgG and IgA antibody responses in serum and CSF were analysed in 69 Swedish patients included in a prospective study of TBE from the acute phase up to 11-13 months after onset.

RESULTS

Antibody response by all three classes was demonstrable in serum and CSF. All methods were useful, but capture technique was the most sensitive and results were easiest to interpret. Peak IgM activity was seen early during the disease and persisted after 6 weeks. Maximum IgG levels were encountered in late convalescent samples (median 6 weeks). Intrathecal antibody production was demonstrable in nearly all patients: in 41% days 0-6, in 97% days 7-19, in 98% days 21-61 and-at lower levels-in 84% of the patients after 1 year (50/52 of CSF-serum sampled in the interval 11-61 days). Day 9 after onset, patients with dominating encephalitic symptoms showed significantly lower intrathecal IgM activity. The persistence of serum and CSF antibodies did not correlate to severity of disease.

CONCLUSIONS

Capture IgM and IgG assays were superior to indirect ELISA. Low early CSF IgM response correlated to encephalitic symptoms, otherwise the intensity and duration of intrathecal antibody response were of limited value for the prediction of clinical course and long-term outcome.

Viral etiology of acute childhood encephalitis in Beijing diagnosed by analysis of single samples

OBJECTIVE

To understand the viral etiology of acute childhood encephalitis in Beijing.

METHODS

Ninety-seven Chinese children (between 7 months and 13 years of age) with acute encephalitis were retrospectively investigated. They were treated in Beijing Children's Hospital between June, 1991, and October, 1994. Different serologic methods (immunofluorescence assay, enzyme-linked immunosorbent assay, solid phase reverse immunosorbent test) were used for detection of IgM antibody to enteroviruses, herpesviruses, mumps, measles, rubella and Japanese encephalitis virus. The viral DNA of six herpesviruses was detected by polymerase chain reaction.

RESULTS

Viral etiology was identified in 35 of 97 (36.0%) cases. The most frequently identified pathogens were enteroviruses (15; 15.4%), followed by mumps (7; 7.2%), rubella (6; 6.1%), Japanese encephalitis virus (5; 5.1%), human herpesvirus 6 (2; 2.0%), herpes simplex virus (2; 2.0%) and Epstein-Barr virus (1; 1.0%). IgM antibody in cerebrospinal fluid was detected for enterovirus, mumps and rubella viruses.

CONCLUSIONS

Enteroviruses were the most frequent viral pathogens of acute childhood encephalitis in Beijing. Detection of IgM in cerebrospinal fluid may be useful for diagnosis in certain cases of viral encephalitis.

Enzyme-linked immunosorbent assay using recombinant antigens for serodiagnosis of Japanese encephalitis

Recombinant Japanese encephalitis (JE) virus proteins were evaluated as antigens for serodiagnosis of JE using an enzyme-linked immunosorbent assay (ELISA). The premembrane/membrane (prM/M) and envelope (E) proteins of JE virus were expressed in HeLa cells infected with a recombinant vaccinia virus that encodes the JE virus prM and E genes and were released from cells in a particulate form. The particulate antigens were partially purified from culture fluid from the infected cells by precipitation of particles with polyethylene glycol and then dissociated from the particles with 0.1% Triton X-100. This antigen preparation was used to evaluate one preimmune and two postvaccination sera from 20 volunteers given three inoculations of the commercial JE vaccine (Biken vaccine) by a conventional ELISA. The results from this assay correlated with neutralization data. The results of an IgM capture ELISA carried out with the recombinant antigen also correlated with the results of an existing IgM capture ELISA performed with JE virus-infected mouse brain, when tested with 29 serum and 13 cerebrospinal fluid samples from JE patients. These results indicated that recombinant JE virus antigens are useful for ELISA as an antigenically equivalent, highly productive, and safe alternative to authentic JE virus antigens.

Japanese encephalitis virus antigen in the human brain and its topographic distribution

This study reports the pathological findings and the distribution of viral antigen in the brains of 13 confirmed and autopsied cases of Japanese encephalitis (JE) in correlation with other virus-specific immunological parameters measured in the cerebrospinal fluid (CSF) antemortem. Japanese encephalitis virus (JEV)-specific antibodies were detected in the CSF of 10 of 13 patients, JEV antigen was detected in the CSF of 7 of 13 and JEV-specific immune complexes were detected in the CSF of 3 of 11 patients. Viral antigen was localised immunocytochemically in the brain tissue of 11 of 13 cases, indicating, that viral antigen could not be cleared from the tissues by the antibody. The topographic distribution of the tissue-associated antigen in the thalamus, hippocampus, substantia nigra and medulla oblongata explain the evolution of post JE sequelae.

Proliferative response of human peripheral blood mononuclear cells to Japanese encephalitis virus

Cell-mediated immune response to Japanese encephalitis virus (JEV) and its purified envelope (E) protein was measured in 45 laboratory confirmed JE patients using a proliferation assay of peripheral blood mononuclear cells (PBMC). In parallel, JEV-specific IgM antibodies were measured by ELISA. No correlation was observed between the antibody response and results of the lymphocyte proliferation assay. Only 11 of the 42 patients positive in the antibody test were positive in the proliferation assay, and PBMC from 14/45 (31%) patients did not respond to either phytohemagglutinin and to JEV and/or its purified E protein antigen. No correlation was observed between the cell-mediated immune response and the final clinical outcome (fatality vs. recovery).

Association of Japanese encephalitis virus infection with Guillain-Barré syndrome in endemic areas of south India

This study is a report of 34 cases of Guillain-Barré syndrome (GBS) observed in Bangalore (South India), an endemic area for Japanese encephalitis virus (JEV) infection. Virological and immunological findings suggested an antecedent and recent JEV infection in 21/34 patients. Nineteen patients among them showed high levels of JEV-specific IgM antibodies in serum and/or CSF, while the viral antigen could be demonstrated in one case and virus isolation from the CSF was successful in one patient. EMG studies revealed features of predominantly demyelinating neuropathy in 18/25 cases. Comparison of clinical findings, duration of illness and outcome in GBS patients with evidence of JEV infection and those without did not reveal any differences. Pathological findings in one patient corroborated the association of JEV with GBS. We conclude that, JEV infection may predispose to Guillain-Barré syndrome in endemic areas.