In a previous publication from this laboratory (Nishimura & Tagaya, 1960) it was reported that a bacterial protease “Nagarse” inactivated vaccinia virus by log 2.0 to 3.0 at 37°C, beyond which no further inactivation could be obtained by further incubation or repeated treatments with the enzyme. An attempt to isolate enzyme-resistant variants by serial passages of the survivors after Nagarse-treatment failed, giving an unaltered survival rate by the enzyme treatment after 10 selective passages. The phenomenon suggested an intervention of the reactivation of virus particles with differently impaired surface structures, and investigations on the reactivation of Nagarse-inactivated vaccinia virus by a simultaneous inoculation of ultraviolet (UV) -inactivated virus of the homologous or its mutant strain were carried out. A part of this work was puplished recently (Kitamura, 1963) and the present paper deals with the full description of the experimental results.

View full abstract

In the previous publication (Ikegami et al., 1963) it was reported that the rate of the stabilizing effect of L-cystine on various strains belonging to the same immunogenic type was different from each other, and that the difference of the rate was a rather stable genetic entity, which remained unchanged after human passages of the vaccine virus, suggesting its applicability for the differentiation of the vaccine-derived strains of types 1 and 2 polioviruses from wild ones.
The present communication deals with the results of two kinds of experiments aimed at elucidating the mechanism of the effect of L-cystine on poliovirus. One concerns the experimental data that would give support to the hypothesis that the stabilizing effect of cystine on poliovirus results from the combination of the compound with the protein portion of the virus particle. The other concerns the relationship between the existence of L-cystine and the selection of thermoresistant poliovirus variants, by alternating heating and passages of virus in monkey kidney tissue cultures.

View full abstract