Japanese encephalitis: epidemiology, prevention and current status of antiviral drug development

Effects of the Japanese Encephalitis Virus Genotype V-Derived Sub-Viral Particles on the Immunogenicity of the Vaccine Characterized by a Novel Virus-Like Particle-Based Assay

Japanese encephalitis virus (JEV) is classified into five genotypes labelled I through V. Although the genotype V (GV) JEV was originally found and had apparently been limited in Malaysia for more than 50 years, its emergence in Korea and China has recently been reported. Therefore, the GV JEV might be spreading over new geographical regions as a cause of potential public health problems. However, it is unknown whether the currently available JEV vaccines are effective against the emerging GV strains. To investigate this issue, a novel virus-like particle-based neutralizing assay was developed in this study. By using this assay, the inactivated JEV vaccine used in Japan and the recombinant sub-viral particles (SVPs) bearing the E protein of the GV Muar strain were characterized for the immunogenicity against the GV JEV. Although the inactivated vaccine alone failed to elicit a detectable level of neutralizing antibodies against the GV JEV, the vaccine added with the Muar-derived SVPs induced relatively high titers of neutralizing antibodies, associated with the efficient Th1 immune responses, against the GV JEV. The results indicate that addition of the GV JEV-derived antigens may be useful for developing the vaccine that is universally effective against JEV including the emerging GV strains.

Potential chemotherapeutic targets for Japanese encephalitis: current status of antiviral drug development and future challenges

INTRODUCTION

Japanese encephalitis (JE) remains a public health threat in Asia. Although several vaccines have been licensed, ∼ 67,900 cases of the disease are estimated to occur annually, probably because the vaccine coverage is low. Therefore, effective antiviral drugs are required to control JE. However, no licensed anti-JE drugs are available, despite extensive efforts to develop them.

AREAS COVERED

We provide a general overview of JE and JE virus, including its transmission cycle, distribution, structure, replication machinery, immune evasion mechanisms and vaccines. The current situation in antiviral drug development is then reviewed and future perspectives are discussed.

EXPERT OPINION

Although the development of effective anti-JE drugs is an urgent issue, only supportive care is currently available. Recent progress in our understanding of the viral replication machinery and immune evasion strategies has identified new targets for anti-JE drug development. To date, most candidate drugs have only been evaluated in single-drug formulations, and efficient drug delivery to the CNS has virtually not been considered. However, an effective anti-JE treatment is expected to be achieved with multiple-drug formulations and a targeted drug delivery system in the near future.