Immunobiology of Japanese Encephalitis Virus

Japanese encephalitis (JE) is an acute central nervous system inflammatory disease cause by infection with Japanese encephalitis virus (JEV), a small, enveloped, plus-strand RNA virus belonging to the family Flaviviridae. It is the leading cause of viral encephalitis in South-East Asia, India and China, where 3 billion people are at risk of contracting the disease (Erlanger et al., 2009). Annually, about 35,000 cases of JE are reported, resulting in about 10,000 deaths and a high incidence of neuropsychiatric deficits among survivors. Treatment of JE patients is supportive and in the absence of availability of antiviral compounds the mainstay of protection against JE is vaccination (Halstead & Thomas, 2011). In the past decades there has been an expansion of the geographic distribution of the virus in Asia and the Asia-Pacific region (van den Hurk et al., 2009) and there is an urgent requirement for improved human and veterinary JE vaccines. An understanding of the immunological responses that lead to recovery from infection with JEV and account for vaccine-mediated protection is important in the design of rational approaches to new treatments and vaccines against the disease, and will be the focus of this review.