Dextran Sulfate Plaque Variants of Attenuated Type 1 Poliovirus

Abstract

Analysis of a stock of the NIH reference attenuated, type 1 poliovirus, NA-2 (Sabin strain) by a previously described procedure employing dextran sulfate (dex-s) in the overlay medium, showed that it consisted of three different plaque types. Two of the enhanced (10 mm) and two of the inhibited (less than 1 mm) plaque types were examined for their behavior in tests using the d and rct/40 markers. The enhanced or ds⁺ virus was found to be d⁺, rct/40^-, whereas the inhibited or ds^- virus was d^-, rct/40^-. One of the ds⁺ viruses produced histologic lesions of poliomyelitis but no paralysis in a high proportion (55%) of the monkeys after intrathalamic inoculation, whereas the other produced no lesions; the two ds^- types caused minimal or no lesions.