Replication of Marek's disease virus in cell cultures derived from genetically resistant chickens.

Various parameters of replication of Marek's disease virus (MDV) were studied in cells derived from genetically resistant (line 6) and susceptible (line 7) chickens. Cell-free and cell-associated preparations of three strains of pathogenic MDV (JM, GA, and Id-1) replicated equally well in cells of resistant and susceptible chickens. There were no demonstrable differences between the two genetic sources of cells for the chronological appearance and type of cytopathic effects and for the type of virus-induced antigens detectable by immunofluorescent and agar-gel precipitin tests. MDV propagated for about 4 weeks in cells of resistant line 6 chickens remained nonvirulent for line 6 and fully virulent for line 7 chickens. The lack of expression of genetic resistance to Marek's disease at cellular level contrasts the infection mechanisms of MDV from those of viruses associated with lymphoid leukosis in chickens.