Properties of a new type 3 attenuated poliovirus

Summary

The new attenuated type 3 poliovirus, denoted as USOL-D bac virus, was administered to a group of children, at least nine of them having been fed earlier withSabin's vaccine. The data obtained in tests on virus excretion, antibody response and genetic stability of the virus indicate:

• 1. The virus multiplied well in the alimentary tract of children without preexisting homotypic antibodies and also in those who possessed antibodies resulting from previous feedings withSabin's vaccine.

• 2. All children who excreted the virus responded with development or marked enhancement of type 3 antibody titres. Increase of type 3 antibodies was also detected in one child from which the vaccine virus was not isolated and in the infected contact child.

• 3. An alteration in rct./40⁻ character was observed only in five of 26 virus isolates tested. Ten of them were inoculated intracerebrally to 20 monkeys. No monkey was paralysed and only two animals developed slight muscular weakness. This seems to indicate a relatively high degree of genetic stability of the USOL-D bac virus during human passage.