Persistence, latency and reactivation of Japanese encephalitis virus infection in mice

Persistent and latent Japanese ncephalitis virus (JEV) infection was studied in pregnant and non-pregnant mice. Following intraperitoneal inoculation into pregnant mice JEV persisted for 16 weeks in contrast to 4 weeks in non-pregnant mice. This was followed by a higher frequency of latent infection in pregnant mice. The virus could be reactivated during pregnancy or by cyclophosphamide tr atment, the latter being more effective. Following widespread epidemics, Japanese ncephalitis virus (JEV) has become ndemic in different parts of India, with a sporadic occurrence of cases throughout the year (Indian Council of Medical Research, 1980). Despite extensive studies on non-human amplifiers and reservoirs, the mechanism of overwintering of JEV is still not clear. JEV usually causes acute illness but at times it may run a protracted course with acute exacerbations, In such cases the brain tissue shows chronic as well as acute lesions (Shiraki, 1970). It is not known if these are due to re-infection, or to reactivation of a persistent virus. Evidence of persistent infection with JEV has been described in mammalian and mosquito cell lines (Schmaljohn & Blair, 1979; Rehacek, 1968) and from studies in bats (Ito & Saito, 1952). Defective interfering particles have bee