Biochemical and serological studies of influenza B viruses: comparisons of historical and recent isolates.

The genetic characteristics of 24 representative influenza B viruses isolated in widely different geographical areas of the world between 1940 and 1980 were analysed using either RNA:RNA hybridisation or oligonucleotide mapping. Additional biochemical characterisation included electrophoretic analysis of virus-induced polypeptides and virion RNAs. A panel of monoclonal antibodies to virus HA was used to investigate serological relationships between the viruses. The influenza B viruses examined constituted a genetically and serologically related group but mutational changes were detected in all eight genes of the viruses isolated in different eras and also in genes of viruses isolated in the same epidemic year. Regardless of the overall and dominating similarities, at a higher level of discrimination it was clear that certain genetic and serological relationships were more complex than expected and, for example, some recently circulating field viruses were apparently more closely related antigenically and genetically to viruses isolated five to twelve years previously than to other viruses isolated concurrently. No evidence of recombination with hitherto undescribed influenza B viruses and with genes coding for internal proteins was detected.