tetano
Editor, Senior Moderator
J Virol. 2016 Jul 20. pii: JVI.00880-16. [Epub ahead of print]
[h=1]Unmasking stem-specific neutralizing epitopes by abolishing N-linked glycosylation sites of influenza hemagglutinin proteins for vaccine design.[/h] Liu WC[SUP]1[/SUP], Jan JT[SUP]2[/SUP], Huang YJ[SUP]1[/SUP], Chen TH[SUP]1[/SUP], Wu SC[SUP]3[/SUP].
[h=3]Author information[/h]
[h=3]Abstract[/h] Influenza hemagglutinin (HA) protein consists of two components-a globular head and stem region that are folded within six disulfide bonds-plus several N-linked glycans that produce a homo-trimeric complex structure. While N-linked glycosylation sites on the globular head are variable among different strains and different subtypes, N-linked glycosylation sites in the stem region are mostly well-conserved among various influenza virus strains. Targeting highly conserved HA stem regions has been proposed as a useful strategy for designing universal influenza vaccines. Since the HA stem region is constituted by a HA1 N-terminal part and a full HA2 part, we expressed a series of recombinant HA mutant proteins with deleted N-linked glycosylation sites in the HA1-stem and HA2-stem regions of H5N1 and pH1N1 viruses. Unmasking N-glycans in the HA2-stem region (H5 N484A and H1 N503A) were found to elicit more potent neutralizing antibody titers against homologous, heterologous and heterosubtypic viruses. Unmasking the HA2-stem N-glycans of H5HA but not H1HA resulted in more CR6261-like and FI6v3-like antibodies and also correlated with the increase of cell fusion inhibition activity in antisera. Only H5 N484A HA2-stem mutant protein immunization increased the numbers of antibody-secreting cells, the germinal center B cells, and the memory B cells targeting the stem helix A epitopes in splenoctyes. Unmasking the HA2-stem N-glycans of H5HA mutant proteins show a significantly improvement in the protection against homologous virus challenges, but to a less degree for the protection against heterosubtypic pH1N1 virus challenges. These results may provide useful information for designing more effective influenza vaccines.
[h=4]SIGNIFICANCE:[/h] N-linked glycosylation sites in the stem region of influenza hemagglutinin (HA) proteins are mostly well-conserved among various influenza virus strains. Targeting highly conserved HA stem regions has been proposed as a useful strategy for designing universal influenza vaccines. Our studies indicate that unmasking the HA2-stem N-glycans of recombinant HA proteins from H5N1 and pH1N1 viruses induced more potent neutralizing antibody titers against homologous and heterosubtypic viruses. However, only the immunization with the H5N1 HA2-stem mutant protein can refocus B antibody responses to the helix A epitope for inducing more CR6261-like/FI6v3-like and fusion inhibition antibodies in antisera, resulting in a significant improvement for the protection against lethal H5N1 virus challenges. These results may provide useful information for designing more effective influenza vaccines.
Copyright ? 2016, American Society for Microbiology. All Rights Reserved.
PMID: 27440889 DOI: 10.1128/JVI.00880-16
[PubMed - as supplied by publisher]
[h=1]Unmasking stem-specific neutralizing epitopes by abolishing N-linked glycosylation sites of influenza hemagglutinin proteins for vaccine design.[/h] Liu WC[SUP]1[/SUP], Jan JT[SUP]2[/SUP], Huang YJ[SUP]1[/SUP], Chen TH[SUP]1[/SUP], Wu SC[SUP]3[/SUP].
[h=3]Author information[/h]
[h=3]Abstract[/h] Influenza hemagglutinin (HA) protein consists of two components-a globular head and stem region that are folded within six disulfide bonds-plus several N-linked glycans that produce a homo-trimeric complex structure. While N-linked glycosylation sites on the globular head are variable among different strains and different subtypes, N-linked glycosylation sites in the stem region are mostly well-conserved among various influenza virus strains. Targeting highly conserved HA stem regions has been proposed as a useful strategy for designing universal influenza vaccines. Since the HA stem region is constituted by a HA1 N-terminal part and a full HA2 part, we expressed a series of recombinant HA mutant proteins with deleted N-linked glycosylation sites in the HA1-stem and HA2-stem regions of H5N1 and pH1N1 viruses. Unmasking N-glycans in the HA2-stem region (H5 N484A and H1 N503A) were found to elicit more potent neutralizing antibody titers against homologous, heterologous and heterosubtypic viruses. Unmasking the HA2-stem N-glycans of H5HA but not H1HA resulted in more CR6261-like and FI6v3-like antibodies and also correlated with the increase of cell fusion inhibition activity in antisera. Only H5 N484A HA2-stem mutant protein immunization increased the numbers of antibody-secreting cells, the germinal center B cells, and the memory B cells targeting the stem helix A epitopes in splenoctyes. Unmasking the HA2-stem N-glycans of H5HA mutant proteins show a significantly improvement in the protection against homologous virus challenges, but to a less degree for the protection against heterosubtypic pH1N1 virus challenges. These results may provide useful information for designing more effective influenza vaccines.
[h=4]SIGNIFICANCE:[/h] N-linked glycosylation sites in the stem region of influenza hemagglutinin (HA) proteins are mostly well-conserved among various influenza virus strains. Targeting highly conserved HA stem regions has been proposed as a useful strategy for designing universal influenza vaccines. Our studies indicate that unmasking the HA2-stem N-glycans of recombinant HA proteins from H5N1 and pH1N1 viruses induced more potent neutralizing antibody titers against homologous and heterosubtypic viruses. However, only the immunization with the H5N1 HA2-stem mutant protein can refocus B antibody responses to the helix A epitope for inducing more CR6261-like/FI6v3-like and fusion inhibition antibodies in antisera, resulting in a significant improvement for the protection against lethal H5N1 virus challenges. These results may provide useful information for designing more effective influenza vaccines.
Copyright ? 2016, American Society for Microbiology. All Rights Reserved.
PMID: 27440889 DOI: 10.1128/JVI.00880-16
[PubMed - as supplied by publisher]