Use of N-acetylethyleneimine [AEI] for the inactivation of Semliki Forest virus in vitro.

N-Acetylethyleneimine (AEI) was used to inactivate the avirulent Togavirus Semliki Forest virus (A774 strain) grown in chick embryo, Vero, and brain cell cultures. The purity of the virus preparation affected the kinetics of inactivation. The rate of inactivation increased with a rise in temperature from 5 to 40 degrees C and in concentration of AEI from 0.025 to 0.1%. The resultant vaccine was inoculated into adult mice to test its antigenicity and into suckling mice to test for the presence of infective virus. Semliki Forest virus-specific IgG was produced equal to that of mice given live virus, and mice were protected against the lethal SFV L10 strain. No suckling mice died, and the brains of the adult mice showed no pathology.