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Germline-encoded neutralization of a Staphylococcus aureus virulence factor by the human antibody repertoire

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ABSTRACT

Staphylococcus aureus is both an important pathogen and a human commensal. To explore this ambivalent relationship between host and microbe, we analysed the memory humoral response against IsdB, a protein involved in iron acquisition, in four healthy donors. Here we show that in all donors a heavily biased use of two immunoglobulin heavy chain germlines generated high affinity (pM) antibodies that neutralize the two IsdB NEAT domains, IGHV4-39 for NEAT1 and IGHV1-69 for NEAT2. In contrast to the typical antibody/antigen interactions, the binding is primarily driven by the germline-encoded hydrophobic CDRH-2 motifs of IGHV1-69 and IGHV4-39, with a binding mechanism nearly identical for each antibody derived from different donors. Our results suggest that IGHV1-69 and IGHV4-39, while part of the adaptive immune system, may have evolved under selection pressure to encode a binding motif innately capable of recognizing and neutralizing a structurally conserved protein domain involved in pathogen iron acquisition.

No MeSH data available.


Allelic specificity of IGHV1-69-derived NEAT2 binders.(a) Amino acid differences among functional alleles of IGHV1-69. (b) The VH of clone D2-06-N2 was germline-reverted to all alleles with amino acid differences, and tested for binding to IsdB by ELISA. All alleles with a G50R substitution lost binding. ELISA data is an average of three independent experiments. Error bars are defined as s.d. (c.) Three individual variants (G50R, F54L and T56I) of D2-06-N2 (IGHV1-69*01 germline-reverted) were generated and their binding to IsdB was tested. Only variant G50R showed significant loss of binding. ELISA data is an average of three independent experiments. Error bars are defined as s.d. (d) Analysis of the structure illustrates how a change from G to R (most frequent rotamer) at position 50 is expected to cause a steric clash in the binding to NEAT2.
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f3: Allelic specificity of IGHV1-69-derived NEAT2 binders.(a) Amino acid differences among functional alleles of IGHV1-69. (b) The VH of clone D2-06-N2 was germline-reverted to all alleles with amino acid differences, and tested for binding to IsdB by ELISA. All alleles with a G50R substitution lost binding. ELISA data is an average of three independent experiments. Error bars are defined as s.d. (c.) Three individual variants (G50R, F54L and T56I) of D2-06-N2 (IGHV1-69*01 germline-reverted) were generated and their binding to IsdB was tested. Only variant G50R showed significant loss of binding. ELISA data is an average of three independent experiments. Error bars are defined as s.d. (d) Analysis of the structure illustrates how a change from G to R (most frequent rotamer) at position 50 is expected to cause a steric clash in the binding to NEAT2.

Mentions: Moreover, we determined that the binding of IGHV1-69-derived antibodies to IsdB is strongly influenced by the allelic variation at position 50 (Fig. 3a). We found that the presence of R50, in contrast to G50 or A50 as in the antibodies described here, completely abolished the binding (Fig. 3b,c), presumably due to the steric clash between the extended side-chain of R50 and the IsdB β7-turn-β8 of NEAT2 (ref. 23; Fig. 3d). Data from the 1000 Genomes Project show that the R50 polymorphism, which abolishes NEAT2 binding, is present in 38% of the IGHV1-69 allele with a predicted homozygous rate of 14% in the general population24. This raises the possibility that there is a population-level difference in the ability to neutralize NEAT2-mediated heme-iron acquisition and therefore different susceptibility to S. aureus infection2526.


Germline-encoded neutralization of a Staphylococcus aureus virulence factor by the human antibody repertoire
Allelic specificity of IGHV1-69-derived NEAT2 binders.(a) Amino acid differences among functional alleles of IGHV1-69. (b) The VH of clone D2-06-N2 was germline-reverted to all alleles with amino acid differences, and tested for binding to IsdB by ELISA. All alleles with a G50R substitution lost binding. ELISA data is an average of three independent experiments. Error bars are defined as s.d. (c.) Three individual variants (G50R, F54L and T56I) of D2-06-N2 (IGHV1-69*01 germline-reverted) were generated and their binding to IsdB was tested. Only variant G50R showed significant loss of binding. ELISA data is an average of three independent experiments. Error bars are defined as s.d. (d) Analysis of the structure illustrates how a change from G to R (most frequent rotamer) at position 50 is expected to cause a steric clash in the binding to NEAT2.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC5120205&req=5

f3: Allelic specificity of IGHV1-69-derived NEAT2 binders.(a) Amino acid differences among functional alleles of IGHV1-69. (b) The VH of clone D2-06-N2 was germline-reverted to all alleles with amino acid differences, and tested for binding to IsdB by ELISA. All alleles with a G50R substitution lost binding. ELISA data is an average of three independent experiments. Error bars are defined as s.d. (c.) Three individual variants (G50R, F54L and T56I) of D2-06-N2 (IGHV1-69*01 germline-reverted) were generated and their binding to IsdB was tested. Only variant G50R showed significant loss of binding. ELISA data is an average of three independent experiments. Error bars are defined as s.d. (d) Analysis of the structure illustrates how a change from G to R (most frequent rotamer) at position 50 is expected to cause a steric clash in the binding to NEAT2.
Mentions: Moreover, we determined that the binding of IGHV1-69-derived antibodies to IsdB is strongly influenced by the allelic variation at position 50 (Fig. 3a). We found that the presence of R50, in contrast to G50 or A50 as in the antibodies described here, completely abolished the binding (Fig. 3b,c), presumably due to the steric clash between the extended side-chain of R50 and the IsdB β7-turn-β8 of NEAT2 (ref. 23; Fig. 3d). Data from the 1000 Genomes Project show that the R50 polymorphism, which abolishes NEAT2 binding, is present in 38% of the IGHV1-69 allele with a predicted homozygous rate of 14% in the general population24. This raises the possibility that there is a population-level difference in the ability to neutralize NEAT2-mediated heme-iron acquisition and therefore different susceptibility to S. aureus infection2526.

View Article: PubMed Central - PubMed

ABSTRACT

Staphylococcus aureus is both an important pathogen and a human commensal. To explore this ambivalent relationship between host and microbe, we analysed the memory humoral response against IsdB, a protein involved in iron acquisition, in four healthy donors. Here we show that in all donors a heavily biased use of two immunoglobulin heavy chain germlines generated high affinity (pM) antibodies that neutralize the two IsdB NEAT domains, IGHV4-39 for NEAT1 and IGHV1-69 for NEAT2. In contrast to the typical antibody/antigen interactions, the binding is primarily driven by the germline-encoded hydrophobic CDRH-2 motifs of IGHV1-69 and IGHV4-39, with a binding mechanism nearly identical for each antibody derived from different donors. Our results suggest that IGHV1-69 and IGHV4-39, while part of the adaptive immune system, may have evolved under selection pressure to encode a binding motif innately capable of recognizing and neutralizing a structurally conserved protein domain involved in pathogen iron acquisition.

No MeSH data available.