Response to primary infection with Herpesvirus saimiri in immunosuppressed juvenile and newborn squirrel monkeys.

Immunosuppression of juvenile squirrel monkeys with combined azathioprine, prednisolone, and antilymphocyte globulin resulted in decreased antibody responses to viral antigens after primary infection with Herpesvirus saimiri (HVS). The virus was repeatedly isolated from the oropharynx of immunosuppressed monkeys but not from untreated infected controls. Thus immune factors are important in inhibiting shedding of HVS from the oropharynx. HVS could be isolated from the peripheral blood lymphocytes of infected control monkeys but not from the lymphocytes of immunosuppressed monkeys. Immunosuppressed monkeys also had decreased percentages of lymphocytes capable of forming rosettes with sheep erythrocytes. These results indicate that the immunosuppressive agents had inhibitory effects on lymphocytes (presumably thymus derived) capable of being latently infected with HVS. Antibody responses in newborn monkeys infected with HVS were delayed compared with juvenile monkeys. Treatment of newborn monkeys with antilymphocyte globulin had no suppressive effect on antibody responses to HVS.