THE STABILIZING EFFECT OF L-CYSTINE ON THE THERMAL INACTIVATION OF POLIOVIRUS. I. DIFFERENTIATION OF THE STRAINS OF POLIOVIRUS BY HEATING WITH L-CYSTINE.

Abstract

Among various problems developing during the epidemiological and virological surveys after the mass administration of live oral poliovaccine, the identification of the origin of the polioviruses isolated from vaccinees and contacts, especially from clinical specimens of suspected poliomyelitis patients, within a short period (one to two months) after vaccination is one of the most important problems. Genetic markers such as d, rct/40 and monkey neurovirulence have been found rather unstable, when the vaccine virus undergoes multicycle proliferation and passages through the human intestine, while the serological properties have been considered more stable and strain-specific under such circumstances. The inf ormations useful for the intratypic serological differentiation of the strains of poliovirus have been reported by several workers (Wenner et al., 1959; McBride, 1959; Gard et at., 1960; Wecker, 1960; Plotkin et at., 1961; Nakano and Gelf and, 1962, 1963; Wasserman and Fox, 1962; Vonka et at., 1962; Woods et at., 1962; Ozaki et at., 1963; Kitahara et at., 1963a) .During the study on the stabilizing effect of L-cystine on various strains of poliovirus against thermal inactivation, it was found that there were considerable differences in the rate of the thermal stabilization by cystine between the strains derived from the attenuated poliovaccine strain (Sabin) and other wild or virulent strains, which belonged to the same immunogenic type. This communication deals with the kinetics of the thermal inactivation of various strains of poliovirus in the presence of different concentrations of L-cystine, and the results obtained by a simplified method for intratypic differentiation of poliovirus by the use of cystine.