Potential as an aerosol vaccine of an improved Newcastle disease vaccine derived from the LaSota strain—I. In vitro studies

Abstract

After mutagenic treatment of the LaSota strain, cold-adapted mutants were selected by serial passages in eggs at 26°C. One of these mutants, RIT 4030, was attenuated for S.P.F. day-old chickens vaccinated by aerosol. In vitro studies were performed to define the properties which differentiate this mutant from the parental LaSota strain. 1. 1. The strain RIT 4030 bears a ts mutation which reduces its multiplication at 41°C. 2. 2. The strain RIT 4030 has modified infectivity properties in CEF and behaves like a “host-range” mutant. The correlation between these mutations and the reduced pathogenicity of this strain for chickens is discussed.