Reappearance and Global Spread of Variants of Influenza B/Victoria/2/87 Lineage Viruses in the 2000–2001 and 2001–2002 Seasons

Abstract

Two antigenically and genetically distinct lineages of influenza B viruses, represented by the reference strains B/Victoria/2/1987 and B/Yamagata/16/1988, have cocirculated in humans since at least 1983. Between 1992 and 2000, Victoria lineage viruses were detected only in eastern Asia. From March to September of 2001 and during the 2001-2002 influenza season, Victoria lineage viruses were detected for the first time in a decade in several countries including Canada, USA, Italy, Netherlands, Norway, Philippines, India, and Oman. Phylogenetic analysis of the hemagglutinin (HA) gene of these viruses revealed that the viruses fell into two distinct clades: one group, represented by the reference strain B/Hong Kong/330/2001, contained viruses sharing three signature amino acids, Arg116, Asn121, and Glu164, while the other group of viruses, represented by B/Oman/16296/2001, shared Thr121 compared to the previous reference strain, B/Shandong/7/97. A number of the viruses in the latter group have been found to be reassortants having a Victoria lineage HA and a Yamagata lineage NA. In the current 2001-2002 season, Victoria-like viruses have now been associated with outbreaks in Asia, Europe, and North America. The reemergence of these Victoria lineage viruses worldwide, the fact that the majority of the B/Victoria-like isolates have poor cross-reactivity to B/Sichuan/379/99-like viruses in current vaccines, and the lack of exposure of young children in many areas of the world to these viruses has resulted in a World Health Organization Northern Hemisphere recommendation for the inclusion of a B/Victoria-like strain in vaccines for the 2002-2003 influenza season.

Influenza B virus-specific CD8+ T-lymphocytes strongly cross-react with viruses of the opposing influenza B lineage

“…Although influenza B viruses cause disease in all age groups, the burden of influenza B virus infections is highest amongst children and young adults (Ambrose & Levin, 2012;Heikkinen et al, 2014;Olson et al, 2007). To prevent severe disease and mortality, annual vaccination of individuals at high risk for influenza is recommended (WHO, 2014b Shaw et al, 2002). The time-consuming process of vaccine production requires recommendation of vaccine strains months in advance of the upcoming influenza season (Russell et al, 2008).…”

Structural basis for receptor specificity of influenza B virus hemagglutinin

“…1b). Four residues from the HA1 chain, Phe-95, Trp-158, His-191, and Tyr-202, constitute the base of the receptor-binding site, all of which are absolutely conserved among all known sequences of influenza B virus HAs (35,36,(43)(44)(45)(46)(47)(48)(49)(50). In addition to -stacking interactions among these four aromatic residues, the receptor-binding site is further stabilized by a hydrogen bond between His-191 and Tyr-202 and four more hydrogen bonds between Asp-193 and Ser-240 (Fig.…”

“…On the other side of Sia-1, each of the side chains of residues Asp-193 and Ser-240 contributes one hydrogen bond with the 9-hydroxyl group of Sia-1. Except in only one case for Gly-141 (44,45), all of those residues that interact with the Sia-1 moiety are absolutely conserved among different field isolates of influenza B viruses (35,36,(43)(44)(45)(46)(47)(48)(49)(50), highlighting their importance in receptor binding for viral infection.…”

Antigenic drift in the evolution of H1N1 influenza A viruses resulting from deletion of a single amino acid in the haemagglutinin gene

“…Amino acid substitutions within the receptor-binding pocket or the 'second shell' residues, including 190, 225 and 158, may alter the specificity toward certain types of galactosidic linkages, namely a2-6Gal or a2-3Gal linkages (Aytay & Schulze, 1991; Matrosovich et al., 2000). Because of its location on the HA threedimensional structure, mutations in the receptor-binding pocket or second shell residues can alter the antigenicity of a virus in addition to, or instead of, modifying receptor specificity or affinity (Daniels et al, 1984).The HA1 domains of the HA genes from a subset of influenza A/H1N1 viruses collected worldwide from 1977 to 1999 were sequenced and analysed as described previously (Shaw et al, 2002;Xu et al, 2004). These isolates were selected to reflect the genetic and geographical distribution spectrum of influenza A/H1N1 viruses.…”

“…The HA1 domains of the HA genes from a subset of influenza A/H1N1 viruses collected worldwide from 1977 to 1999 were sequenced and analysed as described previously (Shaw et al, 2002;Xu et al, 2004). These isolates were selected to reflect the genetic and geographical distribution spectrum of influenza A/H1N1 viruses.…”