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Influenza Other Respir Viruses. 2012 Nov;6(6):389-95. doi: 10.1111/j.1750-2659.2011.00328.x. Epub 2012 Jan 12.

Epitope specificity of anti-HA2 antibodies induced in humans during influenza infection.

Author information

1
Institute of Virology, Slovak Academy of Sciences, Bratislava, Slovak Republic.

Abstract

BACKGROUND:

The conserved, fusion-active HA2 glycopolypeptide (HA2) subunit of influenza A hemagglutinin comprises four distinct antigenic sites. Monoclonal antibodies (MAbs) recognizing three of these sites are broadly cross-reactive and protective.

OBJECTIVES:

This study aimed to establish whether antibodies specific to these three antigenic sites were elicited during a natural influenza infection or by vaccination of humans.

METHODS:

Forty-five paired acute and convalescent sera from individuals with a confirmed influenza A (subtype H3) infection were examined for the presence of HA2-specific antibodies. The fraction of antibodies specific to three particular antigenic sites (designated IIF4, FC12, and CF2 here) was investigated using competitive enzyme immunoassay.

RESULTS:

Increased levels of antibodies specific to an ectodomain of HA2 (EHA2: N-terminal residues 23-185 of HA2) were detected in 73% of tested convalescent sera (33/45), while an increased level of antibodies specific to the HA2 fusion peptide (N-terminal residues 1-38) was induced in just 15/45 individuals (33%). Competitive assays confirmed that antibodies specific to the IIF4 epitope (within HA2 residues 125-175) prevailed in 86% (13/15) over those specific to the other two epitopes during infection. However, only a negligible increase in HA2-specific antibodies was detectable following vaccination with a current subunit vaccine.

CONCLUSIONS:

We observed that the antigenic site localized within N-terminal HA2 residues 125-175 was more immunogenic than that within residues 1-38 (HA2 fusion protein), although both are weak natural immunogens. We suggest that new anti-influenza vaccines should include HA2 (or specific epitopes localized within this glycopolypeptide) to enhance their cross-protective efficacy.

PMID:
22236105
PMCID:
PMC4941695
DOI:
10.1111/j.1750-2659.2011.00328.x
[Indexed for MEDLINE]
Free PMC Article

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