An adult male African green monkey (Cercopithecus aethiops) with an undifferentiated carcinoma, probably originating from the nasal mucosa, was received from the Akron, Ohio zoo. Cultivation of this tumor in vitro resulted in a mixture of fibroblastic and epithelial cells which was subsequently separated using differential trypsinization. The neoplastic nature of the cultured epithelial cells was verified by their ability to transplant into athymic nude, or antithymocyte serum-treated mice, where poorly differentiated carcinomas were produced, and cultures of the tumors that arose in nude mice were morphologically similar to pretransplantation cultures. Early cultures showed a normal male karyotype characteristic of the species; however, in long-term cultures, a clearly defined, small submetacentric Y chromosome was not observed. Electron microscopic examination of tumor tissue and cultured tumor cells revealed desmosomes and the presence of cytoplasmic (keratin-type) fibrils, which tended to be organized around the nucleus. In addition to the keratin-type fibrils, the cultured tumor cells also contained a large amount of cytoplasmic inclusion material that may represent keratohyalin granules. There was no evidence of a viral association with tumor material or cultured cells. The cultures were susceptible to infection by vesicular stomatitis virus, Herpesvirus hominis type 1, and H. saimiri, but were resistant to the Epstein-Barr virus.

THE inoculation of Herpesvirus saimiri (HVS) heated to 56° C for 30 min into several marmosets (Sanguinus sp.) and an owl monkey (Aotus trivirgatus) has previously been described. No illness was reported following the inoculation1. In our laboratories, two owl monkeys were inoculated with heated HVS shown to be non-cytopathogenic in owl monkey kidney (OMK) and Vero cells. Both monkeys developed malignant lymphoma with lymphogenous leukaemia in a manner identical to animals inoculated with untreated HVS2.

AN oncorna-type virus (M-PMV) was detected in a spontaneous breast tumour of a female rhesus monkey1,2. This virus is morphologically and biochemically similar to oncogenic RNA viruses of other species3–5. Using in vitro tissue culture assays and electron microscopy we have observed proliferation of infectious virus in hyperplastic lymph nodes of M-PMV inoculated infant rhesus monkeys.

Five owl monkeys inoculated with Herpesvirus saimiri (HVS), propagated in owl and African green monkey kidney cell cultures, developed malignant lymphoma with lymphocytic leukemia. The virus was recovered from these monkeys and identified as HVS. The disease lasted from 57–78 days. It was characterized by generalized lymphadenopathy and lymphocytic leukemia with circulating actively motile lymphocytes. The lesions were characterized by the obliteration of normal lymphoid tissue architecture by neoplastic lymphocytes and invasion of most organs by neoplastic lymphocytes. On cultivation of tissues, HVS was recovered, however, virus particles could not be detected by electron microscopy.