title: A MEQ-deleted Marek's disease virus cloned as a bacterial artificial chromosome is a highly efficacious vaccine.
abstract: The Marek's disease virus (MDV) induces T-cell tumors in susceptible chickens. Of the 80 to 100 known MDV genes, only the MDV MEQ gene was shown to have transforming properties. Further evidence that MEQ is probably the principal oncogene in MDV came when researchers used overlapping cosmid clones of MDV and demonstrated that deleting MEQ resulted in a highly protective Marek's disease (MD) vaccine. We deleted both copies of MEQ from a bacterial artificial chromosome clone (BAC) of MDV. The virus, BACdelMEQ, was completely attenuated and did not appear to have any adverse effect on chicken body weight in MDV maternal-antibody-positive chickens, as measured at 8 wk of age. In two protection studies, BACdelMEQ efficiently protected susceptible chickens from a challenge by MDV strain 686, one of the most virulent MDV strains. In both protection studies, the BACdelMEQ protected chickens significantly better than the commercial MD vaccine, CVI988/Rispens. Only the protein-coding sequences of MEQ were deleted and all upstream and downstream regulatory sequences were left intact. Thus, BACdelMEQ has the potential to be a superior MD vaccine as well as a vector to deliver various foreign genes to poultry.
authors.affiliation: USDA, Agricultural Research Service, Avian Disease and Oncology Laboratory, East Lansing, MI 48823, USA. Bob.Silva@ars.usda.gov
authors.forename: Robert F
authors.initials: RF
authors.lastname: Silva
authors.forename: John R
authors.initials: JR
authors.lastname: Dunn
authors.forename: Hans H
authors.initials: HH
authors.lastname: Cheng
authors.forename: Masahiro
authors.initials: M
authors.lastname: Niikura
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002645:Chickens; D022202:Chromosomes, Artificial, Bacterial / Q000235:genetics* / Q000276:immunology*; D003001:Cloning, Molecular; D017353:Gene Deletion; D016679:Genome, Viral; D025922:Mardivirus / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity; D008380:Marek Disease / Q000517:prevention & control* / Q000821:virology; D008969:Molecular Sequence Data; D009856:Oncogene Proteins, Viral / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014765:Viral Vaccines / Q000276:immunology*; D014774:Virulence
chemical_list: C100369:Eco-Q protein, Gallid herpesvirus 2; D009856:Oncogene Proteins, Viral; D014765:Viral Vaccines