Revertant serotype 1 Marek's disease vaccine

摘要

A Marek's disease vaccine comprising either a revertant virus derived by backpassaging an attenuated serotype 1 Md11 virus or an antigenic component of the virus is characterized by increased levels of replicative ability and protectivity in chickens as compared to the original attenuated strain. Revertants of the invention are exemplified by a clone identified as Md11/75C/R2 and can be formulated into monovalent and polyvalent vaccines.