A continuous cell culture designated SS5 was established from a lymph node biopsy specimen taken from a male with Hodgkin's disease. The cells grew in suspension as aggregates, in pairs, and singly. During their logarithmic growth the cell doubling time was approximately 24 hours. Chromosome studies were carried out on cells from the patient's bone marrow, the lymph node biopsy before culture, and again after 4 months' culture. On direct examination, the bone marrow and lymph node showed no abnormalities. After 4 months in culture, 89% of the cells examined had 46 chromosomes and were pseudodiploid. There were a low incidence of polyploidy (0.4%) and a low incidence of cells with aberrations (4%). Electron microscope examination showed that the cells carried two kinds of virus-like particles: the herpes-type virus which has been described for cultured Burkitt's tumor cells, and other particles of about the same size with morphology suggestive of a different type of virus. Since the herpes-type virus will not replicate in monolayer cultures, we could separate the two types by inoculating WI38 monolayer cultures with a cell-free concentrate from the SS5 line. Virus replication on passages in the WI38 cells was obvious by specific cellular changes, but only occasional virus-like particles were demonstrable by electron microscopy in the early passages. After 20 passages, abundant virus became evident as extracellular particles. When virus from the WI38 culture was introduced into a human lymphocyte suspension culture, massive virus budding from the cell membrane became evident. The virus ranged from 90–150 mμ, with most about 120 mμ in diameter, and produced a filamentous component 15 mμ in diameter. The filaments were shown to become the nucleoid of the budding virus. The virus was similar immunologically to simian virus SV5.
A biopsy specimen of an undifferentiated human sarcoma contained particles resembling type-C particles of oncornavirus. Cultures of this neoplasm grew as spindle cells that after 8 weeks transformed to epithelioid-like cells with rounded cells that piled up and were shed into the culture fluid. Cells from cultures were devoid of virus-like particles on repeated electron microscopic examination. Attempts to activate a virus by cocultivation with normal human cells or by exposure to ultraviolet or X-ray irradiation failed to yield virus, as determined by electron microscopy or focus formation of normal cells with cell-free filtrates from the culture. However, when the cells were cultured in medium containing 5-iododeoxyuridine, budding particles resembling those formed by C-type oncornavirus were observed.
Electron-dense particles, bearing some morphologic similarities to viruses described in the avian and murine leukemias, have been identified by electron microscopy in peripheral blood from 8 of 56 patients with acute leukemia, from none of 51 random normal controls, and from 1 of 36 age- and sex-matched normal controls. The particles are spherical bodies with 1 or 2 concentric membranes and often a centrally located nucleoid. Their diameter is 800 to 900 A. When material was available, negative staining with phosphotungstic acid revealed a tail-like protrusion extending from an angular head. As the viral nature of these particles remains unproved and their relationship to the etiology of acute human leukemia is not established, the present significance of this observation must be limited to its use as one criterion for the selection of human leukemic materials to undergo biological testing.
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