Two new isolants of infectious bronchitis virus with polyvalent immunogenicity.

The immunizing capacity of two new field isolants of avian infectious bronchitis virus (IBV) was tested in vivo. Chickens vaccinated with either isolant resisted challenge with 6 serotypes of IBV, including some of the types most commonly isolated from chickens. The two new isolants, identified herein as California "G" and California "S," appear to be immunologically different from each other and from the other 6 types tested. The polyvalent immunogenicity of both G and S is noteworthy, and potentially a very promising characteristic for the development of effective vaccines. The immunogenicity is slightly better for G than for S, but both are still pathogenic for chickens. Therefore, they should be attenuated before being used as vaccines.