The invention discloses a recombined chicken Marek's
disease virus vaccine strain for expressing Gag and Env genes of an
avian leukosis virus subgroup J (ALV-J) and a construction method and application of the recombined chicken Marek's
disease virus vaccine strain, and belongs to the technical field of
medicine or
veterinary medicine. By means of the recombination and clone technology, a
gene segment CAG-ALVGE containing the ALV-J Gag and Env genes and a CAG
promoter sequence is inserted in a US2
gene of the strain 814 of the chicken Marek's
disease virus, a recombined
cosmid with a CAG-ALVGE expression frame inserted in a US2
gene is constructed, and the recombined chicken Marek's disease
virus vaccine strain for expressing the Gag and Env genes is obtained through salvation of the recombined
cosmid. Research shows that the obtained
vaccine strain has the same in-vitro replication ability as a parent virulent vaccine strain 814 and good hereditary stability, and can
resist attacks of a very virulent MDV strain and a very virulent ALV-J strain at the same time. It can be seen that the obtained recombined MDV vaccine strain can be used for preparing
medicine for preventing or treating
avian leukosis and the chicken Marek's disease.