Immunogenicity of a hepatitis A virus vaccine.

Hepatitis A virus (HAV) strain HAV/HFS/GBM was adapted to and grown in human diploid fibroblast cells. The HAV was concentrated by ammonium sulphate precipitation and high-speed centrifugation. The virus was inactivated by beta-propiolacton and purified by sedimentation through a 20% solution of sucrose and by CsCl gradient centrifugation. The immunogenicity of different preparations was tested in mice, guinea pigs, and goats. The immune response after vaccination was tested by determination of anti-HAV with RIA and of neutralizing antibodies with an appropriate test system. Results showed that anti-HAV titers of 1:1,000 and greater, as well as neutralizing antibody titers of 1:1,000 and greater, were found in sera of animals vaccinated with different preparations. It became evident that good anti-HAV titers persisted over a period of at least 1.5 years in goats and mice after immunization with a semipurified HAV vaccine, and titers up to 1:200 were present in mice 2 years after vaccination with a highly purified HAV vaccine.