Protective efficacy of a recombinant bacterial artificial chromosome clone of a very virulent Marek's disease virus containing a reticuloendotheliosis virus long terminal repeat.
Marek's disease virus (MDV), an alphaherpesvirus, causes Marek's disease (MD), a lymphoproliferative disease in poultry characterized by T-cell lymphomas, nerve lesions, and mortality. Vaccination is used worldwide to control MD, but increasingly virulent field strains can overcome this protection, driving a need to create new vaccines. Previous studies revealed that insertion of reticuloendotheliosis virus (REV) long terminal repeat (LTR) into a bacterial artificial chromosome (BAC) clone of a very virulent strain of MDV, Md5, rendered the resultant recombinant virus, rMd5 REV-LTR BAC, fully attenuated in maternal antibody positive (Mab+) chickens at passage 40. In the current study, the protective efficacy of rMd5 REV-LTR BAC was evaluated. First, passage 70 was identified as being fully attenuated in maternal antibody negative chickens and chosen as the optimal passage level for use in protective efficacy studies. Second, three protective efficacy trials were conducted comparing the rMd5 REV-LTR p70 BAC to the CVI988/Rispens vaccine. Groups of Mab+ and Mab- 15I5× 71chickens were vaccinated in ovo at 18 days of embryonation or intra-abdominally at day of hatch, and challenged at 5 days post-hatch with the vv+MDV strain 686. Vaccination at day of hatch and in ovo with rMd5 REV-LTR p70 BAC protected chickens against MDV-induced bursa and thymic atrophy, but did not provide the same level of protection against MD tumours as that afforded by the commercial vaccine, CVI988/Rispens.
a Avian Disease and Oncology Laboratory, United States Department of Agriculture , Agricultural Research Service , East Lansing , MI , USA.
Jody K
JK
Mays
a Avian Disease and Oncology Laboratory, United States Department of Agriculture , Agricultural Research Service , East Lansing , MI , USA.
Alexis
A
Black-Pyrkosz
b US National Poultry Research Center, United States Department of Agriculture , Agricultural Research Service , Athens , GA , USA.
Stephen
S
Spatz
a Avian Disease and Oncology Laboratory, United States Department of Agriculture , Agricultural Research Service , East Lansing , MI , USA.
Aly M
AM
Fadly
a Avian Disease and Oncology Laboratory, United States Department of Agriculture , Agricultural Research Service , East Lansing , MI , USA.
John R
JR
Dunn
D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D002478:Cells, Cultured; D002645:Chickens / Q000276:immunology* / Q000821:virology; D022202:Chromosomes, Artificial, Bacterial / Q000235:genetics; D004274:DNA, Recombinant; D004372:Ducks; D005260:Female; D008381:Herpesvirus 2, Gallid / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity; D059014:High-Throughput Nucleotide Sequencing / Q000662:veterinary; D008297:Male; D008380:Marek Disease / Q000517:prevention & control* / Q000821:virology; D022501:Marek Disease Vaccines / Q000276:immunology*; D011201:Poultry Diseases / Q000517:prevention & control* / Q000821:virology; D001356:Reticuloendotheliosis virus / Q000235:genetics*; D017422:Sequence Analysis, DNA / Q000662:veterinary; D020079:Terminal Repeat Sequences / Q000235:genetics; D014611:Vaccination / Q000662:veterinary
D000914:Antibodies, Viral; D004274:DNA, Recombinant; D022501:Marek Disease Vaccines
Marek’s disease virus; bacterial artificial chromosome; long terminal repeat; reticuloendotheliosis virus