The objectives of this research proposal are to characterise the stragegy and antigenic determinants of the hemagglutinin of influenza B viruses, to determine how these change during antigenic variation (drift) of the virus, and to compare the mechanism of variation in influenza B variants and also those selected in the laboratory with hybridoma monoclonal antibodies. To obtain and interpret the results we will determine the complete amino acid sequence of the influenza B hemagglutinin, using both protein and nucleic acid sequencing methods, including recombinant DNA technology. The cloned DNA copies of influenza B genes and the sequence information will enable us to investigate influenza B isolates recovered from Reye's Syndrome patients.