|Gimeno, I M - MICHIGAN STATE UNIVERSITY|
|Lupiani, B - MICHIGAN STATE UNIVERSITY|
|Reed, W M - MICHIGAN STATE UNIVERSITY|
Submitted to: North Central Avian Disease Conference
Publication Type: Abstract Only
Publication Acceptance Date: October 2, 2001
Publication Date: N/A
Technical Abstract: Vaccines against Marek's disease virus (MDV) have been efficiently used worldwide for more than 40 years. Together with the polyvalent vaccines, including serotype 2 and 3 MDV strains, attenuated serotype 1 MDV strains have been shown to provide high levels of protection against MD. Nonetheless, important differences have been detected in the levels of protection conferred by different serotype 1 MDV strains. Identification of properties of MDV which are related to the level of protection might be useful for selection of new vaccines in the future. The aim of this study was to evaluate if any biological characteristics might be related with high level of protection. A chronological study of in vivo replication of three highly protective serotype 1 MDV strains was conducted. Samples of a variety of tissues were taken at different time points for evaluation of viral DNA load by real time PCR and viral antigen expression by immunohistochemistry. The results of this work showed some similarities among the three vaccines studied, as all the three vaccines had a peak of replication in lymphoid organs (spleen, bursa, thymus and Harderian Gland) at 6 days post inoculation (dpi) and viral antigens were detected at every time point of the study, starting at 1 dpi and persisting through the length of the study (26 dpi). Also, non-lymphoid cells of lymphoid organs and blood supported cytolytic infection for all three vaccines studied, especially on 1, 3 and 6 dpi. In contrast, marked differences in the level of replication (viral DNA load and viral antigen expression), was found among the three vaccines.