title: Morphology of immune organs after very virulent plus strain of Marek's disease virus infection in vaccinated hens.
abstract: Marek's disease (MD) outbreaks in poultry flocks may be associated with overriding of vaccine immune protection by very virulent (vvMDV) or very virulent plus (vv+MDV) strains. This paper presents the study on lymphoid organ morphology in the latent phase of MD caused by vv+MDV which break post-vaccinal protection in hens. We also immunohistochemically examined B and T populations as well as B/T and CD4+/CD8+ ratio of lymphocytes in lymphatic organs and, as a background, in MD lymphomas from non-lymphatic organs. The number of antigen expressed cells was evaluated as a percentage of positive cells in the one power field. Organ samples were collected from 24 dead reproductive hens (Ross 308 line) in age between 35-56 weeks, infected with vv+MDV. The hens originated from farms with MD outbreaks, despite earlier routine vaccination with CVI988/Rispens + HVT. The control organ samples originated from 15 clinically healthy hens at the same age and line, subjected to the same vaccination schedule. The number of CD3+, CD8+ and TCRγδ+ cells was significantly lower in MDV infected thymus, spleen and cecal tonsils in comparison to that found in the control organs. The proportion of CD4+ was also distinctly reduced in the thymus and limited in the spleen of MDV infected hens. This study revealed that infection with field vv+MDV isolates might break post-vaccinal protection and influence the central and peripheral immune system. The decrease in CD8+ and TCRγδ+ cell number in the thymus, spleen and cecal tonsils suggests that primarily these cells are involved in cell-mediated cytotoxicity against MDV transformed cells during latency.
authors.forename: J P
authors.initials: JP
authors.lastname: Madej
authors.forename: G
authors.initials: G
authors.lastname: Woźniakowski
authors.forename: A
authors.initials: A
authors.lastname: Gaweł
mesh_terms: D000818:Animals; D002645:Chickens; D005260:Female; D025922:Mardivirus / Q000472:pathogenicity*; D008380:Marek Disease / Q000473:pathology / Q000517:prevention & control / Q000821:virology*; D022501:Marek Disease Vaccines / Q000276:immunology*; D014774:Virulence
chemical_list: D022501:Marek Disease Vaccines