Japanese Encephalitis Virus Generated Neurovirulence, Antigenicity, and Host Immune Responses

In response to a JE virus attack, infected body cells start secretion of different cytokines and activate innate immune response. Virus starts neuronal invasion by entering into nerve cells and inflecting the central nervous system. It avoids exposure of body’s natural immunity and generates neurotrophic effects. Virus causes acute susceptibility to CNS and establishes encephalitis syndrome that results in very high fatality in children. In survivors, JEV inhibits the growth and proliferation of NCPs and imposes permanent neuronal disorders like cognitive, motor, and behavioral impairments. However, body cells start TCR mediated interactions, to recognize viral antigens with class I MHC complex on specific target cells, and operate mass killing of virus infected cells by increased CTL activity. Thus, both cell mediated and antibody interactions plays a central role in protection against JEV. In the present review article virus generated neurovirulence, antigenicity, and host immune responses are described in detail. More emphasis is given on diagnosis, clinical care, and active immunization with well-designed potential antiflavivirus vaccines. Further, for achieving an elite success against JEV, global eradication strategies are to be needed for making vaccination program more responsible and effective in endemic areas. 1. Introduction 1.1. Japanese Encephalitis Virus Japanese encephalitis virus (JEV) is an enveloped positive single stranded RNA virus that belongs to genus Flavivirus in the family Flaviviridae. JE is one of the most important endemic diseases that exists in Eastern Asia and Southeastern Asia including India, Nepal, Japan, China, Korea, Thailand, Indonesia, Malaysia, Vietnam, Taiwan, and the Philippines. Recently disease has shown its presence in Continental Australia and New Zealand. JE is a major public health problem, which causes high morbidity and mortality in pediatric groups. It is caused by a dreadful mosquito-borne virus (arbovirus) which is transmitted to human by mosquito, that is, Culex tritaeniorhynchus and Culex vishnui throughout rural areas of Asia. The natural cycle of Japanese encephalitis (JE) virus in endemic areas involves presence of water birds and Culex mosquitoes, particularly Culex tritaeniorhynchus, with pigs being also involved as an amplifying host and providing a link to humans through their proximity to housing. These play important role in amplification, dispersal, and epidemiology of JEV [1]. Transmission of JEV is seasonal, which increases with the increase in number of culicine mosquitoes after more