Evolutionary characteristics of influenza B virus since its first isolation in 1940: dynamic circulation of deletion and insertion mechanism.
New antigenic variants of B/Yamagata/16/88-like lineage which appeared in the season of 1997 as a minor strain tended to predominate in the following season. Also, we could observe for the first time, three peaks of activity caused by H3N2 virus and two variants of B influenza virus. Antigenic and phylogenetic analyses revealed that B/Victoria/2/87-like variants appeared again in Japan in 1997 after a nine-year absence. Influenza B viruses evolved into three major lineages, including the earliest strain (I), B/Yamagata/16/88-like variants (II), which comprised of three sublineages (II-(i), II-(ii), II-(iii)), and B/Victoria/2/87-like variants (III). Evolution of influenza B virus hemagglutinin was apparently distinguishable from that of influenza A virus, showing a systematic mechanism of nucleotide deletion and insertion. This phenomenon was observed to be closely related to evolutionary pathways of I, II-(i), II-(ii), II-(iii) and III lineages. It was noteworthy to reveal that the nucleotide deletion and insertion mechanism of influenza B virus completed one cycle over a fifty-year period, and that a three nucleotide deletion was again observed in 1997 strains belonging to lineage II-(iii). It was evident that amino acid substitutions accompanying nucleotide insertions were highly conserved.
Nerome
R
R
Department of Virology I, National Institute of Infectious Diseases, Tokyo, Japan.
Hiromoto
Y
Y
Sugita
S
S
Tanabe
N
N
Ishida
M
M
Matsumoto
M
M
Lindstrom
S E
SE
Takahashi
T
T
Nerome
K
K
D000956:Antigens, Viral / Q000032:analysis; D001483:Base Sequence; D005075:Biological Evolution; D003001:Cloning, Molecular; D017353:Gene Deletion; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics*; D006801:Humans; D009981:Influenza B virus / Q000145:classification* / Q000235:genetics / Q000276:immunology; D007251:Influenza, Human / Q000453:epidemiology; D007564:Japan / Q000453:epidemiology; D008969:Molecular Sequence Data
D000956:Antigens, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus