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Structural and functional bases for broad-spectrum neutralization of avian and human influenza A viruses.

Sui J, Hwang WC, Perez S, Wei G, Aird D, Chen LM, Santelli E, Stec B, Cadwell G, Ali M, Wan H, Murakami A, Yammanuru A, Han T, Cox NJ, Bankston LA, Donis RO, Liddington RC, Marasco WA - Nat. Struct. Mol. Biol. (2009)

Bottom Line: The crystal structure of one such nAb bound to H5 shows that it blocks infection by inserting its heavy chain into a conserved pocket in the stem region, thus preventing membrane fusion.Nine of the nAbs employ the germline gene VH1-69, and all seem to use the same neutralizing mechanism.Our data further suggest that this region is recalcitrant to neutralization escape and that nAb-based immunotherapy is a promising strategy for broad-spectrum protection against seasonal and pandemic influenza viruses.

View Article: PubMed Central - PubMed

Affiliation: Department of Cancer Immunology & AIDS, Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney Street JFB 826, Boston, Massachusetts 02115, USA. jianhua_sui@dfci.harvard.edu

ABSTRACT
Influenza virus remains a serious health threat, owing to its ability to evade immune surveillance through rapid genetic drift and reassortment. Here we used a human non-immune antibody phage-display library and the H5 hemagglutinin ectodomain to select ten neutralizing antibodies (nAbs) that were effective against all group 1 influenza viruses tested, including H5N1 'bird flu' and the H1N1 'Spanish flu'. The crystal structure of one such nAb bound to H5 shows that it blocks infection by inserting its heavy chain into a conserved pocket in the stem region, thus preventing membrane fusion. Nine of the nAbs employ the germline gene VH1-69, and all seem to use the same neutralizing mechanism. Our data further suggest that this region is recalcitrant to neutralization escape and that nAb-based immunotherapy is a promising strategy for broad-spectrum protection against seasonal and pandemic influenza viruses.

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>Sequence conservation in HA Groups, Clusters and Subtypes at the F10 epitopeCircles below residue numbers indicate estimated contribution to the binding energy at each position: strong=red, intermediate=yellow; neutral=blue. Residues without a circle are not directly involved in the epitope but are discussed in the text. Colored highlighting on the sequences indicates conservation within clusters and groups, with orange indicating high conservation/invariance. Other colors (eg. yellow, cyan, pink) highlight residues that are cluster/subtype specific. The network of inter-helical contacts that stabilize the fusogenic structure60 are indicated below the HA2 sequences. Subtypes that can be recognized/neutralized by F10 are indicated with “+” on the far right. “(+) or (-)” indicates a predicted positive/negative binding.
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Figure 5: >Sequence conservation in HA Groups, Clusters and Subtypes at the F10 epitopeCircles below residue numbers indicate estimated contribution to the binding energy at each position: strong=red, intermediate=yellow; neutral=blue. Residues without a circle are not directly involved in the epitope but are discussed in the text. Colored highlighting on the sequences indicates conservation within clusters and groups, with orange indicating high conservation/invariance. Other colors (eg. yellow, cyan, pink) highlight residues that are cluster/subtype specific. The network of inter-helical contacts that stabilize the fusogenic structure60 are indicated below the HA2 sequences. Subtypes that can be recognized/neutralized by F10 are indicated with “+” on the far right. “(+) or (-)” indicates a predicted positive/negative binding.

Mentions: The broad neutralizing behavior against H5 may be attributed in part to the exclusive role of VH in antigen binding and the use of a common germline gene, VH1-69, in five out of the six VHs - although their CDR3 loops are variable in sequence and length (13-17 residues) (Supplementary Fig. 6 and Supplementary Table 1). In addition, free energy calculations26 point to dominant binding contributions (~70% of the total favorable free energy) of the three conserved residues in the VH segment (Fig. 5b). In CDR-H2 derived from germline V1-69, position 55 is always Phe, and position 54 is always hydrophobic (M/I/L/V). In our nAbs, CDR-H3 always has a Tyr predicted to lie at the tip of the CDR3 loop (conserved at the 6th position). The conformation and sequence of the CDR1 loop does not seem to be critical, since the other Abs we isolated do not contain the somatic mutation (Gly26=>Glu) found in F10, and are predicted to have canonical structures. The sixth VH gene we isolated is derived from the germline gene, VH1-2; its H2 loop has the same length as VH1-69, but by virtue of a change from Ala to Arg at position 7222 it is predicted to adopt a distinct conformation (“type 3”), which presents loop residues 3 and 4 to the antigen (rather than residues 4 and 5 in type 2 loops). The specific somatic mutation at position 4, from Asn to Met, presumably promotes H5 binding. It is not possible to predict the structure of the larger H3 loop, but a tyrosine is located at the center of the loop that may play an analogous role to that in VH1-69.


Structural and functional bases for broad-spectrum neutralization of avian and human influenza A viruses.

Sui J, Hwang WC, Perez S, Wei G, Aird D, Chen LM, Santelli E, Stec B, Cadwell G, Ali M, Wan H, Murakami A, Yammanuru A, Han T, Cox NJ, Bankston LA, Donis RO, Liddington RC, Marasco WA - Nat. Struct. Mol. Biol. (2009)

>Sequence conservation in HA Groups, Clusters and Subtypes at the F10 epitopeCircles below residue numbers indicate estimated contribution to the binding energy at each position: strong=red, intermediate=yellow; neutral=blue. Residues without a circle are not directly involved in the epitope but are discussed in the text. Colored highlighting on the sequences indicates conservation within clusters and groups, with orange indicating high conservation/invariance. Other colors (eg. yellow, cyan, pink) highlight residues that are cluster/subtype specific. The network of inter-helical contacts that stabilize the fusogenic structure60 are indicated below the HA2 sequences. Subtypes that can be recognized/neutralized by F10 are indicated with “+” on the far right. “(+) or (-)” indicates a predicted positive/negative binding.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2692245&req=5

Figure 5: >Sequence conservation in HA Groups, Clusters and Subtypes at the F10 epitopeCircles below residue numbers indicate estimated contribution to the binding energy at each position: strong=red, intermediate=yellow; neutral=blue. Residues without a circle are not directly involved in the epitope but are discussed in the text. Colored highlighting on the sequences indicates conservation within clusters and groups, with orange indicating high conservation/invariance. Other colors (eg. yellow, cyan, pink) highlight residues that are cluster/subtype specific. The network of inter-helical contacts that stabilize the fusogenic structure60 are indicated below the HA2 sequences. Subtypes that can be recognized/neutralized by F10 are indicated with “+” on the far right. “(+) or (-)” indicates a predicted positive/negative binding.
Mentions: The broad neutralizing behavior against H5 may be attributed in part to the exclusive role of VH in antigen binding and the use of a common germline gene, VH1-69, in five out of the six VHs - although their CDR3 loops are variable in sequence and length (13-17 residues) (Supplementary Fig. 6 and Supplementary Table 1). In addition, free energy calculations26 point to dominant binding contributions (~70% of the total favorable free energy) of the three conserved residues in the VH segment (Fig. 5b). In CDR-H2 derived from germline V1-69, position 55 is always Phe, and position 54 is always hydrophobic (M/I/L/V). In our nAbs, CDR-H3 always has a Tyr predicted to lie at the tip of the CDR3 loop (conserved at the 6th position). The conformation and sequence of the CDR1 loop does not seem to be critical, since the other Abs we isolated do not contain the somatic mutation (Gly26=>Glu) found in F10, and are predicted to have canonical structures. The sixth VH gene we isolated is derived from the germline gene, VH1-2; its H2 loop has the same length as VH1-69, but by virtue of a change from Ala to Arg at position 7222 it is predicted to adopt a distinct conformation (“type 3”), which presents loop residues 3 and 4 to the antigen (rather than residues 4 and 5 in type 2 loops). The specific somatic mutation at position 4, from Asn to Met, presumably promotes H5 binding. It is not possible to predict the structure of the larger H3 loop, but a tyrosine is located at the center of the loop that may play an analogous role to that in VH1-69.

Bottom Line: The crystal structure of one such nAb bound to H5 shows that it blocks infection by inserting its heavy chain into a conserved pocket in the stem region, thus preventing membrane fusion.Nine of the nAbs employ the germline gene VH1-69, and all seem to use the same neutralizing mechanism.Our data further suggest that this region is recalcitrant to neutralization escape and that nAb-based immunotherapy is a promising strategy for broad-spectrum protection against seasonal and pandemic influenza viruses.

View Article: PubMed Central - PubMed

Affiliation: Department of Cancer Immunology & AIDS, Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney Street JFB 826, Boston, Massachusetts 02115, USA. jianhua_sui@dfci.harvard.edu

ABSTRACT
Influenza virus remains a serious health threat, owing to its ability to evade immune surveillance through rapid genetic drift and reassortment. Here we used a human non-immune antibody phage-display library and the H5 hemagglutinin ectodomain to select ten neutralizing antibodies (nAbs) that were effective against all group 1 influenza viruses tested, including H5N1 'bird flu' and the H1N1 'Spanish flu'. The crystal structure of one such nAb bound to H5 shows that it blocks infection by inserting its heavy chain into a conserved pocket in the stem region, thus preventing membrane fusion. Nine of the nAbs employ the germline gene VH1-69, and all seem to use the same neutralizing mechanism. Our data further suggest that this region is recalcitrant to neutralization escape and that nAb-based immunotherapy is a promising strategy for broad-spectrum protection against seasonal and pandemic influenza viruses.

Show MeSH
Related in: MedlinePlus