Studies with some influenza B viruses in cell cultures, hamsters and hamster tracheal organ cultures.

Six influenza B virus strains and one recombinant vaccine strain have been compared in cell cultures, hamsters and in hamster tracheal organ cultures. In cell cultures all strains plaque well with or without trypsin. All strains are restricted in growth above 38 degrees C. The cold adapted attenuated virus, influenza B/AA/1/66, and a cold recombinant, RB77, are also restricted in growth above 37 degrees C and thus have a temperature marker. In hamsters influenza B viruses, except strain B/Lee, grow well in lungs and nasal tissues. Small differences were seen between wild type viruses and the cold adapted irus and its recombinants which may serve as additional markers for attenuation.