Marek's disease virus: Biology and life cycle

Publisher Summary This chapter describes the biology and life cycle of Marek's disease virus (MDV). Marek's disease virus spreads by indirect contact and can remain infectious for several months in environments contaminated by infected birds. The source of infectious cell-free virus is the feather-follicle epithelium, which is the only site where fully productive infection and release of cell-free MDV occurs. The lung is the portal for virus entry, although the actual site(s) of uptake along the airways and the cellular mechanisms involved in the virus are yet to be identified. MDV has a complex life cycle and uses two means of replication—productive and nonproductive—to exist and propagate. The method of reproduction changes according to a defined pattern that depends on the changes in virus–cell interactions at different stages of the disease and in different tissues. Productive (lytic) interactions involve active invasion and takeover of the host cell, thereby resulting in the production of infectious progeny virions. The pathogenesis of Marek's disease can be described in four phases: (1) the early cytolytic phase, (2) the latent phase, (3) the late cytolytic and immunosuppressive phase, and (4) the proliferative phase.