Abstract
Summary
The sensitivity of semipermis-sive cell cultures to SV40 infection can be enhanced by a component of uninfected, simian cells (CV-1) that are permissive for SV40 infection. Enhancement is demonstrated by 10- to 40-fold higher plating efficiency in simian cells, 10- to 30-fold increase in virus production by human cells and 3-fold increase in frequency of transformation in a line of human diploid fibroblasts after inoculation of mixtures containing CV-1 extracts and virus. The enhancer is recovered from cultured cells by a mild extraction procedure and is not sedimented by centrifugation at 20,000g for 1 hr. The active component of the supernate appears to be protein. Incubation of virus with enhancer preparations for 20 min at 23° results in the formation of a complex that is not dissociated by dilution. Although these properties of the SV40 enhancer are similar to those described previously for an enhancer of an enterovirus, the SV40 enhancer differs from the enterovirus enhancer in its host and viral specificity. These observations suggest that analogous enhancement systems may exist for other viruses.
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