A Variant MEF₁, Strain of Type II Poliovirus readily grown in Chicken Embyros and retaining Pathogenicity for Monkey-kidney Tissue Cultures and Mice

Abstract

A STOOL specimen was obtained from a subject (G.O.) 5 days after his ingestion of a trivalent poliovirus vaccine¹. A 20 per cent suspension of the stool was prepared in buffered saline and centrifuged for 1 h at 6,000 r.p.m. The resulting supernatant fluid was treated with penicillin (200 u/ml.) and streptomycin (200 (µg/ml.) and left at room temperature for 1 h. It was then injected into 4 tubes of monkey-kidney tissue cultures (MKTC), prepared in stationary tubes by the method of Youngner². Each tube received 0.1 ml. of the fluid. The cultures showed a cytopathic effect in 6–7 days. The cytopathic agent was again passed in MKTC and then identified as Type II poliovirus by neutralization tests with specific poliovirus antisera prepared by the Testing Department of Lederle Laboratories.