ABSTRACT

Neoplasia resembling human malignant lymphoma, reticulum cell Epstein-Barr virus (EBV) is regularly associated with lymphoproliferative disease. In infectious mononucleosis, a wide range of evidence suggests that the association is causal (1). In Burkitt lymphoma and nasopharyngeal carcinoma, EBV is associated with the tumor, and most patients with these diseases exhibit high titers of specific antibodies (2-4). EBV genome can be detected by nucleic acid hybridization in tumor-cell lines and in tumor biopsies in which viral particles are not found (5-6). Induction of experimental lymphoproliferative disease by EBV is essential, if the classical KochHenle postulates are to be fulfilled in identification of the agent responsible for these conditions. The investigations here described were undertaken with this requirement in mind.A significant biologic property of EBV is its capacity to cause human and certain other primate leukocytes to change into lymphoblastoid cell lines, which proliferate continuously in vitro (7-10). Immunosuppression. Half the animals in each experiment were given azathioprine (1 mg/day) and prednisilone (0.05 mg/day) intramuscularly. Inoculations were begun 3 days before administration of EBV and continued daily, except Sunday, for 3 weeks afterwards. The animals remained well during immunosuppressive therapy, and their leukocyte and platelet counts were stable.Virus Inoculations. Autologous EBV-transformed cells were washed and resuspended in Puck's saline A at a concentration of 1.2 to 3.0 X 108 cells per ml. The total inoculum for each animal was 1 ml, divided into 3 aliquots given intravenously, intraperitoneally, and subcutaneously. 1 ml of cellfree virus was inoculated similarly in other animals.Serology. The animals were bled weekly for 2 months and then biweekly. Sera were tested for EBV "viral capsid antibodies" by the indirect immunofluorescence method (18), with the B95-8 cell line as antigen and Raji cells, which do 2487

No abstract

6 of 20 cotton-top tamarins (Saguinus oedipus) inoculated with Epstein-Barr virus (EBV) developed diffuse malignant lymphoma resembling reticulum cell or immunoblastic sarcoma of man. Hyperplastic lymphoreticular lesions were induced in three additional animals; in two instances the hyperplastic lesions regressed. Inapparent infection with development of antibody occured in eight animals. In two animals there was no evidence of EBV infection. One animal died in the first week after inoculation of parasitic infection. 10 animals uninoculated or mock-inoculated developed neither lymphoproliferative disease nor antibody. The malignant lymphoma appeared to arise from a cell with an uncleaved vesicular nucleus found in the center of the germinal follicle. The prominent cytologic features of this cell were extensive formation or rough endoplasmic reticulum and elaboration of the cytoplasmic membrane with microvilli. Cell lines derived from these tumors did not have receptors for complement. IgFc, or sheep erythrocytes, and the cell lines adhered to glass and plastic. EB nuclear antigen was found in imprints of two lymph nodes, one with lymphoma and one with hyperplasia. EB virus DNA was detected directly in the tumors of three animals and in cell lines from two lymphomas. Typical herpes virus particles were found in supernatant fluids from cell lines obtained from lymph nodes with tumors and hyperplasia, as well as in lines derived from blood leukocytes of marmosets with inapparent infection. These virus preparations had the biologic property characteristic of EBV, namely, stimulation of cellular DNA synthesis and immortalization of human lymphocytes. The virus derived from two cell lines was neutralized by reference human sera with EBV antibody and not by antibody-negative human sera. The virus derived from the experimental lesions is thus indistinghishable from human EBV. The marmoset has enhanced susceptibility to oncogenesis by EB virus. Among identified factors which may play a role in the heightened tumorigenicity of EB virus in this species are the increased production of virus by transformed cells and the absence of membrane receptors for complement or IgFc on transformed cells.