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Variation of the factor H-binding protein of Neisseria meningitidis.

Brehony C, Wilson DJ, Maiden MC - Microbiology (Reading, Engl.) (2009)

Bottom Line: A unified nomenclature scheme was devised to catalogue this diversity.Analysis of recombination and selection on the allele sequences demonstrated that parts of the gene are subject to positive selection, consistent with immune selection on the protein generating antigenic variation, particularly in the C-terminal region of the peptide sequence.The highest levels of selection were observed in regions corresponding to epitopes recognized by previously described bactericidal monoclonal antibodies.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, University of Oxford, OX1 3PS, UK. carina.brehony@zoo.ox.ac.uk

ABSTRACT
There is currently no comprehensive meningococcal vaccine, due to difficulties in immunizing against organisms expressing serogroup B capsules. To address this problem, subcapsular antigens, particularly the outer-membrane proteins (OMPs), are being investigated as candidate vaccine components. If immunogenic, however, such antigens are often antigenically variable, and knowledge of the extent and structuring of this diversity is an essential part of vaccine formulation. Factor H-binding protein (fHbp) is one such protein and is included in two vaccines under development. A survey of the diversity of the fHbp gene and the encoded protein in a representative sample of meningococcal isolates confirmed that variability in this protein is structured into two or three major groups, each with a substantial number of alleles that have some association with meningococcal clonal complexes and serogroups. A unified nomenclature scheme was devised to catalogue this diversity. Analysis of recombination and selection on the allele sequences demonstrated that parts of the gene are subject to positive selection, consistent with immune selection on the protein generating antigenic variation, particularly in the C-terminal region of the peptide sequence. The highest levels of selection were observed in regions corresponding to epitopes recognized by previously described bactericidal monoclonal antibodies.

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Structure of the fH–fHbp complex (Schneider et al., 2009), with temperature colouring using per-site point estimates of ω for (a) subfamily B/variant 1 sequences, (b) subfamily A/variant 2 sequences and (c) subfamily A/variant 3 sequences. Peptides indicated in (a) are putative bactericidal epitopes identified elsewhere (Giuliani et al., 2005; Welsch et al., 2004; Scarselli et al., 2009). In (b) and (c), positively selected sites are indicated. Note: subfamily A/variant 2 and subfamily A/variant 3 differ in length from subfamily B/variant 1 by +4 bp (e.g. Glu151 is equivalent to Glu147 in variant 1) and +7 bp (e.g. Glu154 is equivalent to Glu147 in variant 1), respectively.
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f5: Structure of the fH–fHbp complex (Schneider et al., 2009), with temperature colouring using per-site point estimates of ω for (a) subfamily B/variant 1 sequences, (b) subfamily A/variant 2 sequences and (c) subfamily A/variant 3 sequences. Peptides indicated in (a) are putative bactericidal epitopes identified elsewhere (Giuliani et al., 2005; Welsch et al., 2004; Scarselli et al., 2009). In (b) and (c), positively selected sites are indicated. Note: subfamily A/variant 2 and subfamily A/variant 3 differ in length from subfamily B/variant 1 by +4 bp (e.g. Glu151 is equivalent to Glu147 in variant 1) and +7 bp (e.g. Glu154 is equivalent to Glu147 in variant 1), respectively.

Mentions: The fHbp locus had an average dN : dS ratio of 0.35, indicating a level of purifying selection against amino acid change. Previous estimates have been 0.51±0.7 (Bambini et al., 2009) and comparable to that of other antigenic genes such as fetA (0.314) (Thompson, 2001). Codon-by-codon analysis of selection on the gene was possible using omegamap. Separate analyses for each of the subfamilies/variants, including variant 3, indicated that in the C-terminal region (after ∼318 nt encoding 106 aa) there was diversifying immune selection (ω >1) acting on particular areas in each of the subfamilies/variants (Fig. 4a–f). Subfamily B/variant 1 and subfamily A/variant 2 (not including variant 3) shared one positively selected codon (147 and 151 in subfamily B/variant 1 and subfamily A/variant 2, respectively). Subfamily B/variant 1 displayed positive selection at the four codons 146–149 (ω 3.41–3.52) and also at codons 195–204 (ω 1.02–1.66). Subfamily A/variants 2 and 3 shared the positively selected sites from codons 169–181. The per-site point estimate of ω inferred for each of the subfamily/variant isolates was used to colour a 3D pdb file of the solution structure of a complex between a subfamily B/variant 1 GNA1870/fHbp protein and a region of the fH protein (code 2W81) (Schneider et al., 2009). The temperature colouring of the protein enabled the demonstration of the regions under positive selection on the 3D model (Fig. 5a, b and c). These regions did not overlap with residues involved in interactions with the fH molecule (Schneider et al., 2009).


Variation of the factor H-binding protein of Neisseria meningitidis.

Brehony C, Wilson DJ, Maiden MC - Microbiology (Reading, Engl.) (2009)

Structure of the fH–fHbp complex (Schneider et al., 2009), with temperature colouring using per-site point estimates of ω for (a) subfamily B/variant 1 sequences, (b) subfamily A/variant 2 sequences and (c) subfamily A/variant 3 sequences. Peptides indicated in (a) are putative bactericidal epitopes identified elsewhere (Giuliani et al., 2005; Welsch et al., 2004; Scarselli et al., 2009). In (b) and (c), positively selected sites are indicated. Note: subfamily A/variant 2 and subfamily A/variant 3 differ in length from subfamily B/variant 1 by +4 bp (e.g. Glu151 is equivalent to Glu147 in variant 1) and +7 bp (e.g. Glu154 is equivalent to Glu147 in variant 1), respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2801853&req=5

f5: Structure of the fH–fHbp complex (Schneider et al., 2009), with temperature colouring using per-site point estimates of ω for (a) subfamily B/variant 1 sequences, (b) subfamily A/variant 2 sequences and (c) subfamily A/variant 3 sequences. Peptides indicated in (a) are putative bactericidal epitopes identified elsewhere (Giuliani et al., 2005; Welsch et al., 2004; Scarselli et al., 2009). In (b) and (c), positively selected sites are indicated. Note: subfamily A/variant 2 and subfamily A/variant 3 differ in length from subfamily B/variant 1 by +4 bp (e.g. Glu151 is equivalent to Glu147 in variant 1) and +7 bp (e.g. Glu154 is equivalent to Glu147 in variant 1), respectively.
Mentions: The fHbp locus had an average dN : dS ratio of 0.35, indicating a level of purifying selection against amino acid change. Previous estimates have been 0.51±0.7 (Bambini et al., 2009) and comparable to that of other antigenic genes such as fetA (0.314) (Thompson, 2001). Codon-by-codon analysis of selection on the gene was possible using omegamap. Separate analyses for each of the subfamilies/variants, including variant 3, indicated that in the C-terminal region (after ∼318 nt encoding 106 aa) there was diversifying immune selection (ω >1) acting on particular areas in each of the subfamilies/variants (Fig. 4a–f). Subfamily B/variant 1 and subfamily A/variant 2 (not including variant 3) shared one positively selected codon (147 and 151 in subfamily B/variant 1 and subfamily A/variant 2, respectively). Subfamily B/variant 1 displayed positive selection at the four codons 146–149 (ω 3.41–3.52) and also at codons 195–204 (ω 1.02–1.66). Subfamily A/variants 2 and 3 shared the positively selected sites from codons 169–181. The per-site point estimate of ω inferred for each of the subfamily/variant isolates was used to colour a 3D pdb file of the solution structure of a complex between a subfamily B/variant 1 GNA1870/fHbp protein and a region of the fH protein (code 2W81) (Schneider et al., 2009). The temperature colouring of the protein enabled the demonstration of the regions under positive selection on the 3D model (Fig. 5a, b and c). These regions did not overlap with residues involved in interactions with the fH molecule (Schneider et al., 2009).

Bottom Line: A unified nomenclature scheme was devised to catalogue this diversity.Analysis of recombination and selection on the allele sequences demonstrated that parts of the gene are subject to positive selection, consistent with immune selection on the protein generating antigenic variation, particularly in the C-terminal region of the peptide sequence.The highest levels of selection were observed in regions corresponding to epitopes recognized by previously described bactericidal monoclonal antibodies.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, University of Oxford, OX1 3PS, UK. carina.brehony@zoo.ox.ac.uk

ABSTRACT
There is currently no comprehensive meningococcal vaccine, due to difficulties in immunizing against organisms expressing serogroup B capsules. To address this problem, subcapsular antigens, particularly the outer-membrane proteins (OMPs), are being investigated as candidate vaccine components. If immunogenic, however, such antigens are often antigenically variable, and knowledge of the extent and structuring of this diversity is an essential part of vaccine formulation. Factor H-binding protein (fHbp) is one such protein and is included in two vaccines under development. A survey of the diversity of the fHbp gene and the encoded protein in a representative sample of meningococcal isolates confirmed that variability in this protein is structured into two or three major groups, each with a substantial number of alleles that have some association with meningococcal clonal complexes and serogroups. A unified nomenclature scheme was devised to catalogue this diversity. Analysis of recombination and selection on the allele sequences demonstrated that parts of the gene are subject to positive selection, consistent with immune selection on the protein generating antigenic variation, particularly in the C-terminal region of the peptide sequence. The highest levels of selection were observed in regions corresponding to epitopes recognized by previously described bactericidal monoclonal antibodies.

Show MeSH