Abstract
Subtype specificity of influenza A virus (IAV) is determined by its two surface glycoproteins, hemagglutinin (HA) and neuraminidase (NA). For HA, 16 distinct subtypes (H1–H16) exist, while nine exist for NA. The epidemic strains of H1N1 IAV change frequently and cause annual seasonal epidemics as well as occasional pandemics, such as the notorious 1918 influenza pandemic. The recent introduction of pandemic A/H1N1 IAV (H1N1pdm virus) into humans re-emphasizes the public health concern about H1N1 IAV. Several studies have identified conserved epitopes within specific HA subtypes that can be used for diagnostics. However, immune specific epitopes in H1N1 IAV have not been completely assessed. In this study, linear epitopes on the H1N1pdm viral HA protein were identified by peptide scanning using libraries of overlapping peptides against convalescent sera from H1N1pdm patients. One epitope, P5 (aa 58–72) was found to be immunodominant in patients and to evoke high titer antibodies in mice. Multiple sequence alignments and in silico coverage analysis showed that this epitope is highly conserved in influenza H1 HA [with a coverage of 91.6% (9,860/10,767)] and almost completely absent in other subtypes [with a coverage of 3.3% (792/23,895)]. This previously unidentified linear epitope is located outside the five well-recognized antigenic sites in HA. A peptide ELISA method based on this epitope was developed and showed high correlation (χ2 = 51.81, P<0.01, Pearson correlation coefficient R = 0.741) with a hemagglutination inhibition test. The highly conserved H1 subtype-specific immunodominant epitope may form the basis for developing novel assays for sero-diagnosis and active surveillance against H1N1 IAVs.
Highlights
Influenza A viruses (IAVs), members of the Orthomyxoviridae family, are highly contagious to a variety of avian and mammalian species
We report the successful identification of a new epitope, which is highly conserved among the majority of IAV strains of H1 subtype
The binding between these peptides and the convalescent serum samples from 11 H1N1pdm patients were examined by ELISA using these peptides as coating antigens
Summary
Influenza A viruses (IAVs), members of the Orthomyxoviridae family, are highly contagious to a variety of avian and mammalian species. IAVs cause seasonal influenza epidemics annually and recurring pandemics with severe consequences for public health and global economy [1,2]. The 1918 Spanish flu was the most serious influenza pandemic that killed over 50 million people worldwide [3]. The latter two pandemics, mild compared to the 1918 incidence, resulted in significant mortality, with close to 2 million and 1 million deaths, respectively [4]. The latest pandemic influenza, and newest global health challenge, occurred in 2009 due to the emergence of an A/ H1N1 pandemic IAV (H1N1pdm virus). The H1N1pdm virus has been detected in more than 214 countries and territories and has caused 18,389 deaths as of July 30, 2010 [5]
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