Japanese encephalitis virus (JEV) is an important cause of encephalitis among children in Cuddalore district, Tamil Nadu, India

Japanese encephalitis virus induces vasodilation and severe lethality in adult and aged AG129 mice lacking alpha, beta and gamma interferon receptors

Japanese encephalitis virus (JEV) is a single-stranded positive-sense RNA virus belonging to the Flaviviridae family. The JEV is the leading cause of viral encephalitis in children and the elderly which is spread by mosquitoes. JEV infection has been established in different animal models such as mouse, hamster, guinea pig, swine, rat, monkey, rabbit by using the different routes of inoculations. Here, we have shown that the alpha/beta and gamma -receptor deficient AG129 mouse induces fatal encephalitis in both young and aged old mice, when challenged with high titer JEV Indian clinical isolate by both intraperitoneal and intradermal route. The JEV infected AG129 mouse have shown neurological symptoms, JEV-induced pathological features and supported high level viral replication. Additionally, administration of JEV in AG129 mice resulted in the induction of severe peripheral vascular permeability, which is a major hall mark of Dengue infection but not shown in JEV. Taken together, our results demonstrate interferon α/β and γ receptors knock out AG129 mouse does not need adaptation of JEV clinical isolates and could be is a promising JEV challenge mouse model by mimicking the natural intradermal route of administration for rapid screening of novel antivirals and vaccines.

Japanese encephalitis in Malaysia: An overview and timeline

Japanese encephalitis (JE) is a vector-borne zoonotic disease caused by the Japanese encephalitis virus (JEV). It causes encephalitis in human and horses, and may lead to reproductive failure in sows. The first human encephalitis case in Malaya (now Malaysia) was reported during World War II in a British prison in 1942. Later, encephalitis was observed among race horses in Singapore. In 1951, the first JEV was isolated from the brain of an encephalitis patient. The true storyline of JE exposure among humans and animals has not been documented in Malaysia. In some places such as Sarawak, JEV has been isolated from mosquitoes before an outbreak in 1992. JE is an epidemic in Malaysia except Sarawak. There are four major outbreaks reported in Pulau Langkawi (1974), Penang (1988), Perak and Negeri Sembilan (1998-1999), and Sarawak (1992). JE is considered endemic only in Sarawak. Initially, both adults and children were victims of JE in Malaysia, however, according to the current reports; JE infection is only lethal to children in Malaysia. This paper describes a timeline of JE cases (background of each case) from first detection to current status, vaccination programs against JE, diagnostic methods used in hospitals and factors which may contribute to the transmission of JE among humans and animals in Malaysia.

Investigation of the genotype III to genotype I shift in Japanese encephalitis virus and the impact on human cases

Japanese encephalitis is a mosquito borne disease and is the leading cause of viral encephalitis in the Asia-Pacific area. The causative agent, Japanese encephalitis virus (JEV) can be phylogenetically classified into five genotypes based on nucleotide sequence. In recent years, genotype I (GI) has displaced genotype III (GIII) as the dominant lineage, but the mechanisms behind this displacement event requires elucidation. In an earlier study, we compared host variation over time between the two genotypes and observed that GI appears to have evolved to achieve more efficient infection in hosts in the replication cycle, with the tradeoff of reduced infectivity in secondary hosts such as humans. To further investigate this phenomenon, we collected JEV surveillance data on human cases and, together with sequence data, and generated genotype/case profiles from seven Asia-Pacific countries and regions to characterize the GI/GIII displacement event. We found that, when comprehensive and consistent vaccination and surveillance data was available, and the GIII to GI shift occurred within a well-defined time period, there was a statistically significant drop in JEV human cases. Our findings provide further support for the argument that GI is less effective in infecting humans, who represent a dead end host. However, experimental investigation is necessary to confirm this hypothesis. The study highlights the value of alternative approaches to investigation of epidemics, as well as the importance of effective data collection for disease surveillance and control.

Epidemiology of Japanese encephalitis: past, present, and future prospects

Japanese encephalitis (JE) is one of severe viral encephalitis that affects individuals in Asia, western Pacific countries, and northern Australia. Although 67,900 JE cases have been estimated among 24 JE epidemic countries annually, only 10,426 have been reported in 2011. With the establishment of JE surveillance and vaccine use in some countries, the JE incidence rate has decreased; however, serious outbreaks still occur. Understanding JE epidemics and identifying the circulating JE virus genotypes will improve JE prevention and control. This review summarizes the current epidemiology data in these countries.

Molecular diagnostics for the detection of human flavivirus infections

Flaviviruses constitute a genus of viruses that are important etiologic agents of human disease, causing clinical disease ranging from fever to severe manifestations, such as encephalitis and hemorrhagic fever. Serology is presently the most frequently used means of diagnosing flavivirus infections. However, other diagnostic tests may be employed, such as molecular detection, virus isolation and antigen-capture procedures. The applicability of the latter three diagnostic procedures can be expected to vary depending upon the infecting flavivirus, as some flaviviruses, such as dengue, display high and long-term viremias, whereas other flaviviruses produce no, or barely detectable, viremias. Molecular diagnostic techniques have been successfully applied to the diagnosis of flavivirus infections and have the advantage of rapidity, sensitivity and specific identification of the infecting virus. However, it is important to ensure that the right detection tools are employed (for example, appropriate primers and probes to detect the specific virus) and that the laboratory maintains a high proficiency in their testing procedures. Some of the studies that have been employed in the diagnosis of flavivirus infections are reviewed in this article. It seems that there is the potential to develop testing algorithms that successfully employ molecular diagnostics alone or in conjunction with other laboratory techniques for the diagnosis of acute human flavivirus infections.

Serological and molecular diagnosis of Japanese encephalitis reveals an increasing public health problem in the state of West Bengal, India

Japanese encephalitis (JE), a neurotrophic disease, was first recorded in the state of West Bengal, India in 1973. Since then JE is being reported every year from different districts. With a view to identify the JE cases accurately, a study was undertaken to detect the Japanese encephalitis virus (JEV) as the etiologic agent from the acute encephalitis syndrome (AES) cases and to identify its distribution in different districts. We report the results of 513 blood or cerebrospinal fluid samples referred/collected from the hospitalized AES cases. The samples were initially subjected to Mac-ELISA test followed by reverse transcriptase (RT)-PCR for the detection of IgM antibodies and the JEV genome, specific to E gene, respectively. Out of 513 samples referred/collected, 139 (27.1%) samples were reactive to JE IgM antibody. The remaining 374 samples were screened to select those which had a history of illness with a duration of ≤3 days. Only 147 samples were selected and tested, out of which 36 (24.5%) isolates were achieved and those were RT-PCR positive against the control JEV strain. Detection of IgM antibody to JE and the RT-PCR result confirms the active circulation of JEV in different districts of West Bengal and needs to be monitored carefully.

Update on imminent vaccines: report of the APPA VU 2010: II

The Asia Pacific Pediatric Association Vaccinology Update 2010 (APPA VU 2010) was held in Mumbai on November 13-14, 2010. This second part of the conference report discusses the interesting information about vaccines which are expected in the near future, namely, live-attenuated Japanese encephalitis virus vaccine, tetravalent dengue virus vaccine, conjugate typhoid vaccine and conjugate meningococcal A vaccine.

Delineation of an epitope on domain I of Japanese encephalitis virus Envelope glycoprotein using monoclonal antibodies

The Envelope glycoprotein (E-protein) of Japanese encephalitis virus (JEV) is the major structural component on the virion surface and is a primary target for the host immune system. Two monoclonal antibodies (MAbs) NHA-I (IgG2b) and NHA-II (IgM) against JEV (Indian strain 733913) were earlier developed in the authors' laboratory and found to be cross-reactive to nuclear histones. However, the epitope specificity of these MAbs has remained unknown. The present study was carried out to delineate the epitopes recognised by these MAbs on the E-protein of JEV strain 733913. The variable regions of the NHA-I and NHA-II were sequenced and the tertiary structures predicted. Molecular docking of the MAbs with the structural model of the JEV E-protein demonstrated that NHA-I binds to a predicted antigenic determinant (residue position 18-33) in domain-I. To understand the epitope specificity and check for possible cross-reactivity of these MAbs, comparative analysis of interactions with the known crystallographic structure of the West Nile virus (WNV) E-protein was also carried out. The studies predicted a differential binding of NHA-I but not of NHA-II between JEV and WNV. Mutagenesis studies could help analyse the specificity of NHA-I. The NHA-II appears to be cross-reactive as it docked in the groove region between domains I and III of both the JEV and WNV E-proteins. In laboratory assays, namely, ELISA and immunofluorescence assay both the MAbs reacted equally with JEV while the NHA-I did not show any reactivity with WNV. In silico results were thus validated by laboratory experiments. The present study would help in better understanding of virus-host interactions at the molecular level, and also be useful for the future design of vaccines as well as peptide based diagnostics.

Evaluation of reverse-transcriptase PCR as a diagnostic tool to confirm Japanese encephalitis virus infection

Japanese encephalitis (JE) is a serious central nervous system infection and major public health problem in several countries of Southeast Asia including India. This study evaluated the use of IgM ELISA and reverse-transcriptase (RT)-PCR in blood and cerebrospinal fluid (CSF) samples from acute encephalitis patients for the detection of Japanese encephalitis virus (JEV). Forty-four children suffering from acute encephalitis were enrolled, and 36 were selected from whom both CSF and serum samples were available. Twenty-two of the 36 CSF samples were positive for JEV by IgM ELISA and all were negative by RT-PCR. Twenty-three of the 36 serum samples were positive by IgM ELISA while 28 were positive by RT-PCR. Total positivity for JEV infection in CSF and serum samples was 66.7% (24/36) and 83.3% (30/36) respectively by one or both tests. The overall positivity for JEV infection was 86.1% (31/36). We suggest that the use of RT-PCR in serum samples during the early days of JEV infection may be helpful in confirming diagnosis in those cases which are negative for JEV-specific IgM antibodies in both serum and CSF samples.

Desiccated vector mosquitoes used for the surveillance of Japanese encephalitis virus activity in endemic southern India

To monitor Japanese encephalitis virus (JEV) activity in endemic areas of Tamil Nadu, southern India, desiccated vector mosquitoes were screened for JEV antigen using ELISA, from 1996. A total of 133 233 specimens from eight index villages comprising 2816 pools (mainly Culex vishnui subgroup) were tested. Of these, 59 pools (2.1%) were positive for JEV antigen. Control measures were undertaken in positive villages accordingly. The average annual minimum infection rate was 0.8 at the beginning of the study and remained lower for nearly 8 years. A declining trend in JE cases was recorded.

Does antiviral therapy have a role in the control of Japanese encephalitis?

Approximately 2 billion people live in countries where Japanese encephalitis (JE) presents a significant risk to humans and animals, particularly in China and India, with at least 700 million potentially susceptible children. The combined effects of climate change, altered bird migratory patterns, increasing movement of humans, animals and goods, increasing deforestation and development of irrigation projects will inevitably lead to further geographic dispersal of the virus and an enhanced threat. Although most human infections are mild or asymptomatic, some 50% of patients who develop encephalitis suffer permanent neurologic defects, and 25% die. Vaccines have reduced the incidence of JE in some countries. No specific antiviral therapy is currently available. Interferon alpha-2a was tested in a double-blind placebo-controlled trial on children with Japanese encephalitis, but with negative results. There is thus a real need for antivirals that can reduce the toll of death and neurological sequelae resulting from infection with JE virus. Here we briefly review the epidemiological problems presented by this virus, the present state of drug development and the contributory role that antiviral therapy might play in developing future control strategies for JE.

Development and evaluation of SYBR Green I-based one-step real-time RT-PCR assay for detection and quantitation of Japanese encephalitis virus

One-step SYBR Green I-based real-time RT-PCR assay for rapid detection as well as quantitation of Japanese encephalitis virus (JEV) in acute-phase patient CSF samples by targeting the NS3 gene was developed. The assay developed in this study was found to be more sensitive as compared to conventional RT-PCR. The specificity of the reported assay system was established through melting curve analysis as well as by cross-reactivity studies with related members of Flavivirus. The applicability of Real-time PCR assay for clinical diagnosis was validated with 32 suspected acute-phase CSF samples of Gorakhpur epidemic, India, 2005. The improved sensitivity of real-time RT-PCR was reflected by picking up 10 additional samples with low copy number of template in comparison to conventional RT-PCR. The quantitation of the viral load in acute-phase CSF samples was done using a standard curve obtained by plotting cycle threshold (C(t)) values versus copy numbers of the RNA template. This is the first report on the application of real-time RT-PCR for detection as well as quantitation of JEV from patient CSF samples. These findings demonstrate the potential clinical application of the reported assay as a sensitive diagnostic test for rapid and real-time detection and quantitation of JEV in acute-phase clinical samples.

Japanese Encephalitis Outbreak, India, 2005

An outbreak of viral encephalitis occurred in Gorakhpur, India, from July through November 2005. The etiologic agent was confirmed to be Japanese encephalitis virus by analyzing 326 acute-phase clinical specimens for virus-specific antibodies and viral RNA and by virus isolation. Phylogenetic analysis showed that these isolates belonged to genogroup 3.

Development and evaluation of reverse transcription-loop-mediated isothermal amplification assay for rapid and real-time detection of Japanese encephalitis virus

The standardization and validation of a one-step, single-tube accelerated quantitative reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay is reported for rapid and real-time detection of Japanese encephalitis virus (JEV). The RT-LAMP assay reported in this study is very simple and rapid; the amplification can be obtained in 30 min under isothermal conditions at 63 degrees C by employing a set of six primers targeting the E gene of JEV. The RT-LAMP assay demonstrated exceptionally higher sensitivity compared to that of RT-PCR, with a detection limit of 0.1 PFU. The specificities of the selected primer sets were established by cross-reactivity studies with other closely related members of the JEV serocomplex as well as by evaluation of healthy human volunteers. The comparative evaluation of the RT-LAMP assay for clinical diagnosis with a limited number of patient cerebrospinal fluid samples revealed 85% concordance with conventional RT-PCR, with a sensitivity and a specificity of 100% and 86%, respectively. The concentration of virus in most of the clinical samples was 10(2) to 10(5) PFU/ml, as determined from the standard curve based on the time of positivity in the samples. In addition, the monitoring of gene amplification can also be visualized with the naked eye by using SYBR green I fluorescent dye. Thus, due to easy operation without a requirement of sophisticated equipment and skilled personnel, the RT-LAMP assay reported here is a valuable tool for the rapid and real-time detection of JEV not only by well-equipped laboratories but also by peripheral diagnostic laboratories with limited financial resources in developing countries.

Japanese encephalitis in India: an overview

Japanese encephalitis (JE)-epidemics have been reported in many parts of the country. The incidence has been reported to be high among pediatric group with high mortality. The incidence of JE in recent times is showing an increasing trend. It appears that JE may become one of the major public health problems in India, considering the quantum of the vulnerable pediatric population, the proportion of JEV infections among the encephalitic children and wide scattering of JE-prone areas. JE burden can be estimated satisfactorily to some extend by strengthening diagnostic facilities for JE confirmation in hospitals and by maintenance of contact with the nearby referral hospitals to collect the particulars on JE cases. Vaccination proves to be the best to protect the individual against any disease. In the case of JE, it is essential to immunize the pigs (amplifying host) also to interrupt the transmission of the disease.