GENETIC AND BIOLOGICAL DETERMINANTS OF AVIAN TUMOR VIRUS PATHOGENICITY, TRANSMISSION, AND EVOLUTION
Location: Avian Disease and Oncology Laboratory
Title: Pathogenesis and protective efficacy of attenuated Meq null rMd5 virus in maternal antibody negative and commercial chickens.
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 24, 2012
Publication Date: June 24, 2012
Citation: Lee, L.F., Kreager, K.S., Heidari, M., Zhang, H., Lupiani, B., Reddy, S.M., Fadly, A.M. 2012. Pathogenesis and protective efficacy of attenuated Meq null rMd5 virus in maternal antibody negative and commercial chickens [abstract]. 9th International Symposium on Marek's Disease and Avian Herpesviruses, June 24-28, 2012, Freie Universitat Berlin. p. 42.
A serotype 1 Marek’s disease Meq null virus (rMd5'Meq) has been shown to be an excellent vaccine in maternal antibody positive (MAb+) chickens. The only drawback of this non-oncogenic virus is that, like parental rMd5, it retains the ability to induce bursa and thymus atrophy (BTA) in MAb- chickens. We compared early pathogenesis of various passage levels of a cell culture attenuated Meq null virus and in both MAb- and commercial chickens. The attenuated Meq null virus did not induced BTA at 40th passage onward. Its protective ability against challenge with vv+ MDV, strain 686 was similar to the original virus at 19th passage in MAb- chickens. In commercial chickens, the attenuated viruses quickly lost protection with increasing cell culture passages. These data suggest that attenuation of these Meq null viruses eliminated BTA, but had no influence on their protective efficacy only in MAb- chickens. In commercial chickens (MAb+), the best protection was provided by the original l9th passage Meq null virus, suggesting that lower passage level of these Meq null viruses may be recommended for use in commercial chickens, as its protective efficacy is very high and does not induce BTA in MAb+ chickens.