Distribution of Ia antigen positive cells in chicken embryos infected with oncogenic Marek's Disease Virus (MDV) and MD vaccine viruses of serotypes 1, 2 and 3

Abstract

Chick embryos infected at Day 13 of embryonic development (ED) with the oncogenic serotype 1 Marek's Disease Virus, isolate B (MDV-B) and three MDV vaccines (CVI988, SB1 and HVT, serotypes 1, 2 and 3, respectively) and uninfected chick embryos were studied for the distribution of Ia antigen positive dendritic cells (DC), B cells and MDV antigen positive (Ag+) cells in the lymphoid organs and chorioallantoic membrane (CAM). The immunofluorescence study was conducted on acetone-fixed organ touch impressions using monoclonal antibodies to Ia antigen, and MDV serotypes 1, 2 and 3 and polyclonal antibodies to bursal Ig-bearing (Ig+) B cells. DC were found mainly in the thymus and spleen and Ig+ cells in the bursa, thymus and spleen of normal embryos. All virus-infected embryos had MDV Ag+ cells in the spleen. MDV-B and SB1 infected embryos also had MDV Ag+ cells in the bursa, MDV-B Ag+ cells in the CAM and SB1-Ag+ cells in the thymus. Infection with MDV altered the distribution pattern of DC in a serotype-specific manner: to a lesser extent, infection with MDV-B and SB1 induced their appearance in the CAM, while HVT and CVI988 depleted the DC population from all organs except the bursa and the thymus, respectively. Infection with MDV-B depleted the Ig+ cells from all organs. These results suggest that virus-specific patterns of change in the distribution of DC and B cells occur in various tissues and organs of the chick embryo as a result of infection with oncogenic and apathogenic strains of MDV.