Syngeneic Marek's disease virus (MDV)-specific cell-mediated immune responses against immediate early, late, and unique MDV proteins.

Marek's disease (MD) infection has been controlled effectively by vaccination using nononcogenic and/or attenuated oncogenic Marek's disease virus (MDV) vaccines. Thus far, there is little knowledge on the role of cell-mediated immune (CMI) responses during MDV infection or vaccination. To elucidate the importance of MDV proteins in CMI responses, the pp38, Meq, ICP4, or ICP22 genes of an oncogenic strain, GA and the gB, ORF A, A41, or L1 genes of a highly oncogenic strain, RB1B were stably transfected into reticuloendotheliosis virus (REV)-transformed lymphoblastoid cells, CU-91 (MHC: B19B19) and CU-205 (MHC: B21B21). Cell lines positive for MDV gene transcription and/or protein expression were used in a standard 4-hr chromium release assay. Effector cells for this assay were obtained from splenocytes of chickens infected with the oncogenic strain, JM-16/13 or the nononcogenic vaccine strain, SB-1/12. Cell lines expressing MDV pp38, Meq, or gB were lysed by syngeneic but not allogeneic MDV-sensitized splenocytes obtained from chickens of B19B19 and B21B21 haplotypes. However, syngeneic CMI responses against ICP4 were detected only in B21B21 chickens. CMI responses were not detected against B19B19 and B21B21 cell lines expressing A41, L1, ORF A, or ICP22. This report suggests that syngeneic CMI responses against pp38, Meq, ICP4, and gB of GA and RB1B strains, respectively, can be induced in chickens inoculated with JM16/13 or SB-1/12. The difference in CMI response to ICP4 in genetically susceptible (B19B19) and genetically resistant (B21B21) chickens may be an important factor in genetic resistance.