BALB/c mice were infected with the lymphotropic mouse gammaherpesvirus (MHV-72). At late (7-12 months) post-infection intervals the latent virus was detected in the cells of lymphatic system (peripheral blood, lymphocytes and macrophages, thymocytes, lymph nodes, bone marrow, and peritoneal macrophages,) and in the spleen, lungs, liver, and kidney by cocultivation as well as by explantation. The MHV-72 infected mice, in which latency had been established, were treated with the immunosuppressive (IS) drug FK-506 (2 mg/kg/mouse for 30 days). This treatment increased the probability of virus reactivation by over two-fold. During the post-treatment observation period of 19 months, the incidence of lymphomas and the development of MHV-related lymphoproliferative and hemoblastic disorders raised to nearly five-fold in the drug treated mice as compared to untreated animals.

A panel of six monoclonal antibodies (mAbs) specific for murine gammaherpesvirus (MHV) was used for analysis of the antigenic relationship between five MHV-isolates (MHV 68, MHV 72, MHV 76, MHV 78, MHV S). Two mAbs raised against MHV 72 and four raised against MHV S were used in the study. Antibody-virus interactions were tested using immunochemical (ELISA, Western blot, immunofluorescence) and biological (virus-neutralization) assays. Immunoanalysis by ELISA showed a close antigenic relationship between the five viruses, nevertheless, some antigenic individuality of the isolate MHV S was observed. This isolate originated from a geographically distinct area in Czechia relative to the other four isolates from Slovakia. In Western blot analysis, antibodies to MHV 72 recognized viral antigens with the relative molecular mass about 116,000. Of four mAbs against MHV S, only two reacted with denatured viral antigen in Western blot and showed specificity for the 50-55,000 protein. These findings suggested that both isolates, besides of minor antigenic variability, could differ also in immunodominant proteins. Mabs to MHV S exhibited much stronger virus-neutralizing potency than mAbs to MHV 72, indicating thus that the 50-55,000 antigen might be more relevant for the infectivity of MHV-virus. Immunofluorescence with mAbs allowed specific localization of antigens in virus-infected VERO cells.