Restriction of poliovirus RNA translation in a human monocytic cell line

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Abstract
The infection of the human monocytic cell line U‐937 by poliovirus was characterized by a low level of virus production and a slow progression of the cytopathic effect. Infection took place in > 99% of the cells as revealed by a limiting dilution assay. No viral protein synthesis was evident in the infected U‐937 cells when analyzed by polyacrylamide gel electrophoresis. However, a low level of poliovirus RNA translation was detected by immunofluorescence analysis using a mixture of polyclonal antisera against non‐structural proteins. Although there was only a low level of viral protein synthesis, a gradual accumulation of viral mRNA took place in U‐937 cells as revealed by RNA blot analysis. Similar results were obtained when the erythroleukemic cell line K‐562 was used as a host cell for poliovirus. RNA extracted from infected U‐937 cells was efficiently translated in rabbit reticulocyte extracts giving rise to a pattern of viral polypeptides similar to that detected when virion‐purified RNA was the template used for the in vitro translation assay, suggesting that the poliovirus RNA present in infected U‐937 cells is functional. The existence in U‐937 cells of a discriminatory mechanism which differentially interferes with poliovirus RNA translation is discussed.