Facilitation of infection of mouse L-cells with ribonucleic acid from encephalomyocarditis virus

Abstract

Infectious ribonucleic acid (RNA) was first extracted from tobacco mosaic virus by Gierer and Schramm (1956) by treatment of the virus with cold phenol. Subsequently, a number of viruses have been found to yield infectious RNA; however, the efficiency with which extracted RNA is capable of entering the cell is very low as compared with mature virus. Hypertonic sodium chloride treatment of enterovirus RNA to augment its infectivity for hypertonically treated human cells was reported by Sprunt et al (1959) . Dubes and Klingler (1961) reported that the infection of primary monkey kidney cells with poliovirus RNA was greatly increased by adding any one of several comparatively water-insoluble substances (which they called facilitators) to the RNA inoculum and depleting the cells of calcium. Encephalomyocarditis (EMC) virus is one of a number of animal viruses known as the Col-SK group. In experiments reported by Huppert and Sanders (1958) phenol extraction at 4°C of ascites tumor cells infected with mouse-grown EMC yielded ‘ribonucleic acid extracts’ from extracellular fluid following ultracentrifugation, although the latter was not extracted from the sedimented virus by similar treatment. In studies reported herein the facilitation method of Dubes and Klingler (1961) was employed to infect L-cells with RNA from a large plaque mutant of EMC virus. Moreover, this system was used to test infectivity of extracted supernatant and pellet following ultracentrifugation of tissue culture fluid to determine source of infectious RNA.