Abstract: A nucleotide sequence encoding the gp82 polypeptide of Marek's disease virus is disclosed. Also disclosed are recombinant viruses which are useful as vaccines for protecting against Marek's Disease, preferably containing two more genes encoding Marek's Disease Virus antigens such as glyprotein B and glycoprotein gp82, under the control of a poxvirus promoter within a region of the DNA of fowlpox virus which is not essential for virus growth. Also provided is a vaccine exhibiting a synergistic immunoprotective effect, comprising a recombinant fowlpox virus expressing Marek's Disease Virus gB protein in combination with turkey herpesvirus. A method of immunizing poultry, comprising administering any of the disclosed vaccines, is also provided.

Abstract: A nucleotide sequence encoding the gp82 polypeptide of Marek's disease virus is disclosed. Also disclosed are recombinant viruses which are useful as vaccines for protecting against Marek's Disease, preferably containing two or more genes encoding Marek's Disease Virus antigens such as glycoprotein B and glycoprotein gp82, under the control of a poxvirus promoter within a region of the DNA of fowlpox virus which is not essential for virus growth. Also provided is a vaccine exhibiting a synergistic immunoprotective effect, comprising a recombinant fowlpox virus expressing Marek's Disease Virus gB protein in combination with turkey herpesvirus. A method of immunizing poultry, comprising administering any of the disclosed vaccines, is also provided.

Abstract: A Marek's disease vaccine comprising an attenuated revertant virus derived as a clone of Md11/75/R2 or an antigenic component of the virus is characterized by a markedly reduced pathogenicity compared to the parent virus, without a comparable loss in immunogenicity. Attenuated revertants of the invention are exemplified by Md11/75/R2/23 and Md11/75/R2/29. These viruses or immunogenic components thereof can be formulated into monovalent and polyvalent vaccines.

Abstract: A vaccine for Marek's disease using mutant strains of a serotype 2 field isolate, designated 471B/1, is disclosed. The mutant viruses, which are produced by serial passage of 471B/1 in cell culture, not only retain effective immunizing ability against Marek's disease virus, but which also exhibit reduced enhancement of lymphoid leukosis in comparison to non-passaged 471B/1 and conventional serotype 2 vaccines. These viruses or immunogenic components thereof can be formulated into monovalent and polyvalent vaccines.

Abstract: A recombinant fowlpox virus is provided which is useful as a vaccine for protection against avian reticuloendo-theliosis virus-associated diseases. In a specific embodiment, the recombinant virus expresses a gene encoding an envelope glycoprotein of spleen necrosis virus under the control of a poxvirus promoter, inserted in a nonessential region of the fowlpox virus genome.

Abstract: The combination of monoclonal antibodies 11A25 and 11E32, which recognize two distinct antigenic sites on the 62-kd glycoprotein of reticuloendotheliosis virus (REV) in ELISA, enables an increase in the sensitivity of an ELISA assay for subtype 2 REV over what was heretofore possible. The combination of MAbs is useful for diagnosing REV antigen and antibody in poultry flocks and for detecting new strains and variants of the viral subtype.

Abstract: 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.

Abstract: A serotype 2 Marek's disease vaccine comprising a cloned strain designated as 301B/1 has been derived from a field isolate. This strain is characterized by superior levels of replicative ability and protectivity in chickens as compared to existing commercial serotype 2 strains, and it is virtually nonpathogenic. 301B/1 is particularly useful in the formulation of highly efficacious bivalent and polyvalent vaccines.