Transcription profiling of chicken spleen and thymus infected Mareks disease virus (MDV) - a highly contagious oncogenic herpes virus

Marek's disease virus (MDV) is a highly contagious oncogenic herpes virus. Classed as an alpha herpes virus due to its DNA sequence and genome organization, its biological properties are more similar to those of gamma herpes viruses. MDV causes an initial cytolytic infection in B lymphocytes (3-6dpi) followed by infection of CD4+ T cells (at around 7dpi) where the virus becomes latent (for around two weeks) and then goes on to produce lymphoid tumours in the skin, nerves and internal organs. Early symptoms in susceptible birds include lameness, paralysis, loss of appetite, depression, blindness and immuno-suppression. The route of infection is usually respiratory and the disease is highly contagious, being spread by infective feather-follicle dander. Although birds may survive MDV infection, the resultant immuno-suppression leaves the birds highly susceptible to other infections. MDV infection can thus be associated with high mortality rates and, in turn, large economic losses throughout the worldﾒs poultry industry. Three-week-old chicks were inoculated with virus (RB1B) via an intra-gastric route and tissue samples were collected at 2, 3 and 4 days post-inoculation. Spleen and thymus tissue were examined from control and infected birds at 2, 3 and 4 days post-infection in birds known to be either susceptible or resistant to the virus. As well as understanding the host immune response to MDV, we are interested in identifying genes involved in disease resistance and so we have analysed the gene expression profiles at these times, when the innate immune response is active. We assume that genes underlying resistance will be involved at this early stage of the host immune response.

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