Infectious Ribonucleic Acid from Mouse Brains infected with Tick-borne Encephalitis Virus

Abstract

INFECTIOUS ribonucleic acid has been prepared from several virus-infected tissues and from purified animal viruses^1–4 using the phenol extraction method of Gierer and Schramm⁵. Assuming that the tick-borne encephalitis virus contains a nucleic acid of ribose type, we have succeeded in preparing by the same method infectious ribonucleic acid from mouse brains infected with the Hypr strain of tick-borne virus isolated in Czechoslovakia. The infectivity of such preparations was about 10³–10⁵ times lower than that of virus. To be sure that the infectivity of ribonucleic acid was not caused by contamination with virus particles, the acid and virus were titrated after different treatment. The titrations were carried out in white mice by intracerebral injection of 0.03 ml. using serial ten-fold dilutions. Clarified 10 per cnet (w/v) suspension of infected brains was designated as undiluted virus for convenience in comparing the infectivities of virus and ribonucleic acid. The results are shown in Table 1.