Ultrastructural and immunofluorescent studies of the replication of herpesvirus saimiri in cultured lymphocytes of infected owl monkeys.

The lymphocytes of five owl monkeys infected with herpesvirus saimiri (HVS) and of three control owl monkeys were studied by electron microscopic (EM) and immunofluorescent (IF) techniques. Buffy coats of whole blood immediately after bleeding were also prepared for study. At the time of the study, two of the five infected monkeys were leukaemic; within 50 days after the study, four of the five had died with malignant lymphoma and lymphocytic leukaemia. HVS virions were demonstrated by EM and HVS antigens by IF in 1-20% of the lymphocytes from infected monkeys in 2/5 cultures at 24 hours AC, 4/5 at 48 hours AC, and 5/5 at 72 hours AC. There was quite good agreement between the EM and IF data. None of the control monkey cultures and none of the buffy coat preparations contained HVS virions or antigens. By EM, the great majority of the virus particles were nucleocapsids within the nuclei of lymphocytes. Enveloped virions were rare. There was some evidence to suggest that the higher the percentage of lymphocytes containing HVS, the poorer the prognosis for the monkey. HVS was isolated from all five infected monkeys by co-cultivation of lymphocytes with Vero cells. Control lymphocyte co-cultivations were negative.