Heterogeneous Selective Pressure Acting on Influenza B Victoria- and Yamagata-Like Hemagglutinins |
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Authors: | Baltazar Nunes Pedro Pechirra Anabela Coelho Carlos Ribeiro Ana Arraiolos Helena Rebelo-de-Andrade |
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Institution: | (1) Departamento de Epidemiologia, Instituto Nacional de Saúde Dr. Ricardo Jorge, I.P., Lisbon, Portugal;(2) Centro Nacional da Gripe, Instituto Nacional de Saúde Dr. Ricardo Jorge, I.P., Av. Padre Cruz, 1649-016 Lisbon, Portugal |
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Abstract: | As a consequence of immune pressure, influenza virus hemagglutinin presents some of its amino acids under positive selection.
Several authors have reported the existence of influenza A hemagglutinin codons under positive selective pressure (PSP). In
this framework, the present work objectives were to demonstrate the presence of PSP and evaluate its effects on Victoria-
and Yamagata-like influenza B viruses. Methodology adopted consisted in estimating the acceptance rate of nonsynonymous substitutions
(ω = dN/dS) that describe the strength of selective pressure and identifying codons that may be positively selected, applying a set
of continuous-time Markov chain codon-substitution models. Two groups of HA1 sequences (140 from Yamagata and 60 from Victoria
lineage) were used. All the model maximum-likelihood estimates were obtained using codeml software application (PAML 3.15). The hypothesis of no existence of sites under PSP was rejected for both lineages (p < 0.001), using likelihood ratio tests. These results demonstrate the presence of positive selection acting on hemagglutinin
of both Yamagata- and Victoria-like influenza B viruses. Several different sites were identified to be under PSP on Yamagata
and Victoria hemagglutinins. Sites found with a posterior probability > 0.95 were codons 197 and 199 in both lineages, codon
75 in the Yamagata lineage, and codon 129 in the Victoria lineage. The detected amino acids are located at or near antigenic
sites in influenza A virus H3 hemagglutinin.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Influenza B Positive selection Hemagglutinin Phylogenetic analysis Maximum likelihood |
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