Figure 2.

A model of Marek's disease virus and chicken host genomic, molecular, cellular, and tissue interactions during early infection, pathogenesis, and transformation. Three highly simplified, inter-connected routes are depicted by arrows: green, MDV-host genome status; blue, virus movement internally (host cells and tissues) and externally (dander in the environment); light red, transformation and tumorigenesis. Along these routes, the light gray pentagons with text and diagrams indicate the organs involved in the disease and the hexagons indicate MDV serotype pathways (blue, all MDV serotypes; green, virulent MDV vs. MD vaccine; light red, oncogenic MDV). The overlapping disease stages (cytolytic, latent, reactivated, transformed) and virus-host genome status (see main text for cytogenetic viral phenotype explanations) are indicated by the bold font along the routes: cytolytic, circularized-episomal MDV (cytogenetic chromosome-associated phenotype); cytolytic, episomal and linear telomere-integrated MDV (cytogenetic chromosome-associated and telomere-integrated phenotype); latency, telomere-integrated MDV (cytogenetic telomere-integrated only phenotype); reactivation or return to cytolytic phase; transformed cells, (mostly cytogenetic telomere-integrated only phenotype). In susceptible research chickens, tumors can develop as early as 21 d post-infection. See main text for outline of the overlapping timing of early cytolytic, latency, late cytolytic, and transformation stages. FFE = feather follicle epithelium.