Latent infections with Marek's disease virus and turkey herpesvirus

The number of plaque-forming units (PFU) from lymphocytes latently infected with oncogenic (GA-5) or nononcogenic (SB-1) Marek's disease virus (MDV) was decreased after complement lysis with antisera against thymus-derived lymphocytes or bursa-derived lymphocytes; an additive effect with dual treatment was observed. Complement lysis with antisera against Marek's disease tumor-associated surface antigen (putative tumor antigen) had little effect, which suggests an absence of the antigen on latently infected cells. None of the serum complement treatments affected the number of PFU from lymphocytes infected with turkey herpesvirus (HVT). No viral antigens were detected in spleen lymphocytes when removed from infected birds. After 42-72 hours of incubation, many cultured spleen cells from MDV-infected birds (JM-10, GA-5, and SB-1 isolates) contained viral antigen, whereas very few if any cultured cells from HVT-infected birds were positive. These data suggest that the nature of the latent infections with MDV and HVT may differ significantly.