Marek’s disease virus (MDV), the causative agent of Marek’sdisease
(MD) in chickens, is an alpha-herpesvirus. The natural route of
infection is via the respiratory tract after inhalation of cell-free
virus particles by chickens, followed by transportation of MDV to
lymphoid organs where the virus remains cell-associated. MDV
pathogenesis constitutes an early cytolytic phase in B cells followed
by a latency and neoplastic phase in T cells resulting in clinical
signs such as paralysis and immune suppression.
MDV research has been a very fertile field over the last 4–5 decades.
We have gained a great deal of knowledge about the virus itself
and how it interacts with its host. Moreover, research in this
area has contributed immensely to other fields. For instance, given
the strong associations between background genes, especially variants
of the major histocompatibility (MHC) genes, and susceptibility/
resistance to MD, successful breeding schemes have been
implemented to reduce the frequency of genetic variants associated
with susceptibility to this disease. Moreover, the field of vaccinology
is indebted to Marek’s disease research. The first
commercial vaccines against an oncogenic virus were developed
over four decades ago against MD (Churchill et al., 1969; Okazaki
et al., 1970). Also, MD vaccines were the first to be delivered
embryonically in commercial settings.
The aim of the current review article is to provide an overview
of what is known about various aspects of immunity against MD
and also to highlight areas that are still lacking in this field and require
further investigations.