ANTIGENIC DRIFT OF THE H1 SUBTYPE HAEMAGGLUTININ FROM 1977 TO 1980

Abstract

A previous analysis of an extensive set of laboratory-selected antigenic mutants of influenza virus A/PR/8/34 (H1N1 subtype) defined the location of 4 antigenic sites on the virus haemagglutinin. This chapter discusses an experiment in which to estimate the relevance of these antigenic sites to the nature of antigenic variation, which occurs during the evolution of the virus in man, a sequence analysis of the antigenic domain of a series of recent H1 subtype strains was performed. In the study, the amino acid sequence of the HA1subunit of influenza virus strains A/USSR/90/77, A/Brazil/11/78, A/Lackland/3/78, A/England/333/80, and A/India/6263/80 was derived by nucleotide sequence analysis of virion RNA. The deduced amino acid substitutions observed in the five strains were compared to the definitive HA1 domain of the haemagglutinin of A/PR/8/34. From the study, it was found that forty-two amino acid substitutions occurred between A/PR/8/34 and A/USSR/90/77 but no insertions or deletions were observed. This degree of amino acid substitution constitutes an evolutionary drift of 13%.