Analysis of herpesvirus saimiri structural proteins with monoclonal antibodies

Herpesvirus saimiri is a lymphotrophic virus isolated from squirrel monkeys that causes highly malignant lymphomas in owl monkeys, marmosets, and rabbits, but not in its natural host. We have been interested in exploring immunological and biological aspects of this phenomenon and describe in this report the isolation of 27 monoclonal antibodies (MCAs) to herpesvirus saimiri which were grouped into 11 distinct sets based on the proteins they immunoprecipitated. In total, these 11 groups of MCAs identify the majority of the proteins present in the virion. Immunofluorescence was used to study how the viral antigens are compartmentalized in infected cells. One antibody produced intense nuclear staining and immunoprecipitated both the largest protein seen in gels (150,000 daltons) and one of the smallest (13,000 daltons). All of the other groups of MCAs principally stained the cytoplasm of infected cells. One of the unexpected results of this study was the observation that a majority of the MCAs precipitated more than one protein (15 of 27 antibodies, 7 of 11 groups). Whereas one group of MCAs, which normally precipitated four proteins, identified only single polypeptides after dithiothreitol pretreatment, the other sets of antibodies continued to recognize two or more viral antigens under reducing conditions. Immunoprecipitation of viral proteins with polyvalent sera obtained from virus-infected rabbits and monkeys was carried out to verify and extend previously published reports on the proteins of herpesvirus saimiri.