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SummaryA measles-related virus was isolated from two out of three brain biopsies of patients with SSPE by the fusion of brain cells with susceptible cells. β-propiolactone-inactivated Sendai virus was used in the fusion experiments. The mechanism of activation and the characterization of the isolated agents are discussed. Their association with another virus is reported in light of the etiology of SSPE.

The early events in the interaction of simian virus 40 (SV40) with permissive cells were investigated. Evidence is presented that 30 min after infection intact virions penetrate the nuclei of infected cells. The uncoating of the virus is carried out in the nuclei with a complete dissociation of the viral genome from the protein coat. Opening of the circular parental deoxyribonucleic acid (DNA), i.e., conversion of component I to component II of SV40 DNA, takes place after uncoating, followed by the appearance of a new component sedimenting faster than component I at alkaline p H.

One of the ‘early’ effects of cellular infection by DNA-containing viruses is an increase of various enzymic activities concerned in DNA synthesis, which in most instances seems dependent upon the synthesis of virus-coded enzymes (Keir, 1968). As far as poxviruses are concerned, relevant information relates almost exclusively to the vaccinia subgroup and very little is known about other poxviruses (Joklik, 1966). The Shope fibroma virus is an oncogenic pox virus of the myxoma subgroup (Joklik, 1966) and has only recently been subjected to systematic study in tissue cultures. It has been shown to replicate in primary cell cultures of human amnion (Hodes et al. 1966; La Placa et al. 1967; Hodes & Chang, 1968) where it causes a peculiar cytopathic effect characterized by the appearance of pock-like lesions (La Placa et al. 1967). The time-course of nucleic acid synthesis (Ewton & Hodes, 1967) and the induction of DNA nucleotidyltransferase (Chang & Hodes, 1967) in cells infected with Shope fibroma virus have also been reported.

SUBACUTE sclerosing panencephalitis (SSPE), a progressive neurological disease of children, is characterized by intracytoplasmic and intranuclear inclusions in the neurones and glial cells. Although no infectious agent was isolated directly from the diseased brain tissue, a paramyxovirus, related serologically to the measles–rinderpest virus group, was recovered from SSPE brain cells maintained in tissue culture in serial passages1. These cultures were characterized by the formation of syncytia and by their capacity to undergo transformation2. Only by fusion with African green monkey kidney cells (AGMK) could an infectious syncytiogenic paramyxovirus be recovered from the brain cells.

Summary Abortive transformation of human embryonic fibroblasts was induced by Molluscum contagiosum virus. The parameters studied in order to test the establishment of a persistent infection and transformation of cells were: (1) virus interference and interferon production; (2) alterations of cell morphology and growth; (3) presence of neoantigens; (4) karyotype. The possible mechanisms leading to an abortive transformation are discussed.

A preliminary report [1] described encephalitis in ferrets injected intracerebrally with suspensions of brain tissue obtained at biopsy of 3 patients with subacute sclerosing panencephalitis (SSPE). This encephalitis, characterized by abnormal electroencephalographic (EEG) patterns and histologic lesions, was successfully transmitted serially in ferrets by intracerebral subinoculation of suspensions of ferret brain tissue. Subsequent to this report, several laboratories, including our own, succeeded in establishing cultures of brain cells from biopsies of patients with SSPE. These tissue cultures, after serial cell transfers, showed the presence of syncytia and giant cells. Cells in these cultures contained intranuclear

Evidence that the resistance of simian virus (SV40)-transformed permissive cells to superinfection with SV40 is due to lack of virus uptake is presented. When virus uptake is enhanced, the events of infection proceed as in normal permissive cells, resulting in production of infectious virus.

ALTHOUGH a viral etiology for subacute sclerosing panencephalitis (SSPE) was first postulated by Dawson 1 in 1933, the isolation of measles-like viruses from brain cell cultures established from biopsies of SSPE patients has been a recent accomplishment. 2-4 The SSPE agents, either present in brain biopsies of patients or isolated from their brain tissue maintained in culture, have been found to be pathogenic for ferrets, 5,6 with encephalitis becoming manifest after a prolonged incubation period. Because of the difficulties involved in handling ferrets and the excessive costs of their maintenance, a search became necessary for another experimental host—an animal at least as susceptible as the ferret to SSPE infection, but easier to handle and less costly to maintain. The present study shows that the hamster meets these criteria; intracerebral inoculation of hamsters with human brain culture cells carrying the SSPE agents, or with cell-free SSPE virus, produces encephalitis. Materials and