Molecular characterization of influenza B viruses circulating in northern Italy during the 2001–2002 epidemic season

Abstract

During the 2001-2002 influenza season, virological surveillance highlighted the predominant circulation of B viruses (86% of isolates) in Italy, in contrast to many other countries in Europe and North America where AH3N2 viruses were isolated most frequently, and in contrast to the infrequent isolation of B viruses in Italy during the previous two years. Associated with this predominance of influenza B was the re-emergence of B/Victoria/2/87-lineage viruses, closely related to B viruses prevalent during the 1980s, which are distinct antigenically and genetically from circulating B/Sichuan/379/99-like viruses of the B/Yamagata/16/88 lineage, which predominated in most parts of the world during the last 10 years. Ninety-four viruses isolated in two regions of northern Italy were characterized, 50 by direct sequencing of haemagglutinin (HA). Viruses of both Victoria and Yamagata lineages co-circulated throughout the 12 weeks of the influenza season. The HAs of the Yamagata-lineage viruses were heterogeneous and comprised two sublineages, represented by B/Sichuan/379/99 and B/Harbin/7/94, whereas the Victoria-lineage viruses were more homogeneous and closely related to B/Hong Kong/330/01, the current prototype vaccine strain. The antigenic and genetic characteristics of the viruses correlated with certain epidemiological features. In particular, the low age (<14 years) of individuals infected with B/Hong Kong/330/01-like viruses is likely to reflect the greater susceptibility of the youngest cohort, due to lack of previous exposure to Victoria-lineage viruses, and is consistent with the conclusion that vaccination with a B/Sichuan/379/99-like virus would give poor protection against infection with B/Hong Kong/330/01-like (Victoria-lineage) viruses.

Surveillance of influenza viruses in the post-pandemic era (2010–2012) in Northern Italy

“…Overall, B viruses presented with a mixed circulation of viral variants, since viruses belonging to both B/Victoria and B/Yamagata lineages co-circulated during these two seasons in different proportions. As previously reported by other authors, [11][12][13] this epidemiological feature -where a B virus lineage is unable to play a firm role in the epidemiological circulation -suggests that the inclusion in influenza vaccine of strains belonging to both B lineages may be advisable. However, licensed trivalent seasonal influenza vaccines contain antigens from only a single influenza B virus and thus provide limited immunity against circulating influenza B strains of the lineage not present in the vaccine.…”

“…12-1,169) influenza virus. 11,27,28 The HA nucleotide sequences were obtained by automated DNA sequencing (ABI PRISM ® 3100 Genetic Analyzer, Life Technologies). Multiple sequence alignment was conducted using ClustalX, version 2.0.10.…”

A Vaccination Model for Transmission Dynamics of Influenza

“…In this case, the DFE is the only equilibrium of the NR model if a 2 > 0 or a 2 2 − 4a 1 a 3 < 0 (Theorem 3.2). Since Ω 1 is positively invariant, it follows from Lemma 4.1 that the DFE is globally asymptotically stable.…”

“…If a 2 2 − 4a 1 a 3 > 0, then from Theorem 3.2 it follows that Q(I) has two positive roots. Thus, P (I, 0) has two positive roots if a 2 2 − 4a 1 a 3 > 0. Since P (I, ) is a cubic function of I and is a decreasing function of for I > 0, it can be seen that there is a positive * such that P (I, ) has three positive roots if 0 < < * ; two positive roots (one with multiplicity 2) if = * ; and a unique positive root if > * .…”

Neutralizing and Hemagglutination-Inhibiting Activities of Antibodies Elicited by the 2004-2005 Influenza Vaccine against Drifted Viruses

“…The molecular characterization of the globular head region of hemagglutinin was carried out by the sequence analysis of the HA1 subunit, and the antigenic characterization of isolates was carried out by HI testing, as described elsewhere (4,15). The phylogenetic tree that includes the isolates, vaccine, and reference strains is shown in Fig.…”