EFFECTS OF BASIC PROTEINS AND POLYAMINO ACIDS ON INFECTIOUS RNA OF EQUINE ENCEPHALITIS VIRUSES

Methylated bovine serum albumin has previously been shown to 'mask' reversibly the infectivity of infectious ribonucleic acid (IRNA) from Venezuelan equine encephalitis (VEE) virus and to protect the nucleic acid against inactivation by micrococcal nuclease. In studies reported here, the effects of several other basic proteins and synthetic polyamino acids on the infectivity of VEE-IRNA and eastern equine encephalitis virus IRNA have been compared. Quantitative differences were observed among the proteins and the polyamino acids in their capacity to lower infectivity. Polylysine and polyornithine completely masked infectivity, as measured by plaque formation, when present in only 0.01 to 0.001 times the concentration required for proteins to be effective. The original infectivity of the IRNA before treatment was recovered when the polylysine-IRNA complex was treated with pronase, indicating that the presence of the polyamino acid did not degrade the infectious unit. Protection of IRNA against inactivation by pancreatic ribonuclease was also demonstrated in the presence of polylysine, providing further evidence that a complex was formed between the nucleic acid and the polyamino acid.