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The QTL within the H2 Complex Involved in the Control of Tuberculosis Infection in Mice Is the Classical Class II H2-Ab1 Gene.

Logunova N, Korotetskaya M, Polshakov V, Apt A - PLoS Genet. (2015)

Bottom Line: Cloning and sequencing of the H2j allelic variants of these genes demonstrated profound polymorphic variations compare to the H2b haplotype.These variations were sufficient to produce different TB-relevant phenotypes: the more susceptible B6.I-249.1.15.100 strain demonstrated shorter survival time, more rapid body weight loss, higher mycobacterial loads in the lungs and more severe lung histopathology compared to the more resistant B6.I-249.1.15.139 strain.CD4+ T cells recognized mycobacterial antigens exclusively in the context of the H2-A Class II molecule, and the level of IFN-γ-producing CD4+ T cells in the lungs was significantly higher in the resistant strain.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Immunogenetics, Central Institute for Tuberculosis, Moscow, Russia.

ABSTRACT
The level of susceptibility to tuberculosis (TB) infection depends upon allelic variations in numerous interacting genes. In our mouse model system, the whole-genome quantitative trait loci (QTLs) scan revealed three QTLs involved in TB control on chromosomes 3, 9, and in the vicinity of the H2 complex on chromosome 17. For the present study, we have established a panel of new congenic, MHC-recombinant mouse strains bearing differential small segments of chromosome 17 transferred from the TB-susceptible I/St (H2j) strain onto the genetic background of TB-resistant C57BL/6 (B6) mice (H2b). This allowed narrowing the QTL interval to 17Ch: 33, 77-34, 34 Mb, containing 36 protein-encoding genes. Cloning and sequencing of the H2j allelic variants of these genes demonstrated profound polymorphic variations compare to the H2b haplotype. In two recombinant strains, B6.I-249.1.15.100 and B6.I-249.1.15.139, recombination breakpoints occurred in different sites of the H2-Aβ 1 gene (beta-chain of the Class II heterodimer H2-A), providing polymorphic variations in the domain β1 of the Aβ-chain. These variations were sufficient to produce different TB-relevant phenotypes: the more susceptible B6.I-249.1.15.100 strain demonstrated shorter survival time, more rapid body weight loss, higher mycobacterial loads in the lungs and more severe lung histopathology compared to the more resistant B6.I-249.1.15.139 strain. CD4+ T cells recognized mycobacterial antigens exclusively in the context of the H2-A Class II molecule, and the level of IFN-γ-producing CD4+ T cells in the lungs was significantly higher in the resistant strain. Thus, we directly demonstrated for the first time that the classical H2- Ab1 Class II gene is involved in TB control. Molecular modeling of the H2-Aj product predicts that amino acid (AA) substitutions in the Aβ-chain modify the motif of the peptide-MHC binding groove. Moreover, unique AA substitutions in both α- and β-chains of the H2-Aj molecule might affect its interactions with the T-cell receptor (TCR).

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Molecular model of H2-Aj molecule in comparison to H2-Ab.Top view of structural overlay of the peptide-binding domains of H2-Ab (blue) and H2-Aj (red) alleles, bound to CLIP peptide (green). α- alpha and β–beta chains. 1 –α- subunit 310 helix, 2- β subunit region with two AA (P65E66) deletions in j-haplotype (A). Comparison of the H-bond network between H2-Ab (B) and H2-Aj (C) molecules containing CLIP peptide backbone (P-1-P10). MHC Class II conserved residues that contribute to the peptide- MHC hydrogen-bonding network are shown in stick representation. Dashed lines indicate conservative hydrogen bonds with the exception of Ab74 and Kb71 (marked red) in the H2-Aj molecule. D -Comparison of pocket structures of the MHC- binding groove between H2-Ab (blue) and H2-Aj (red). The CLIP peptide backbone is shown in green, P1, P4, P6, P7 and P9 pockets in grey. AA substitutions in the α-chain contribute mostly to the differences in the P1 structure, AA substitutions in the β-chain determine differences in P4, P6, P7 and P9 pockets (E). Potentially most important substitutions are marked and their side chains shown.
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pgen.1005672.g007: Molecular model of H2-Aj molecule in comparison to H2-Ab.Top view of structural overlay of the peptide-binding domains of H2-Ab (blue) and H2-Aj (red) alleles, bound to CLIP peptide (green). α- alpha and β–beta chains. 1 –α- subunit 310 helix, 2- β subunit region with two AA (P65E66) deletions in j-haplotype (A). Comparison of the H-bond network between H2-Ab (B) and H2-Aj (C) molecules containing CLIP peptide backbone (P-1-P10). MHC Class II conserved residues that contribute to the peptide- MHC hydrogen-bonding network are shown in stick representation. Dashed lines indicate conservative hydrogen bonds with the exception of Ab74 and Kb71 (marked red) in the H2-Aj molecule. D -Comparison of pocket structures of the MHC- binding groove between H2-Ab (blue) and H2-Aj (red). The CLIP peptide backbone is shown in green, P1, P4, P6, P7 and P9 pockets in grey. AA substitutions in the α-chain contribute mostly to the differences in the P1 structure, AA substitutions in the β-chain determine differences in P4, P6, P7 and P9 pockets (E). Potentially most important substitutions are marked and their side chains shown.

Mentions: Comparison between the H2-Aj and H2-Ab molecules suggests that the most prominent structural dissimilarities occur in two protein backbone regions: the 310 helical fragment of the α-chain and the P65E66 deletion in the H2-Aβj chain (Fig 7A). These deviations are not unique and are present in other H2 haplotypes (reviewed in Ref [51] and displayed in S3 Fig). Analysis of the hydrogen bond network between H-2A Class II molecules and, as a model, invariant CLIP peptide stabilizing the complex before an antigenic peptide is loaded, demonstrated that the conserved H-bond interactions and the total number of H-bonds are identical for the H2-Ab and H2-Aj products despite two b → j substitutions, T71K and E74A in the Aβ-chain (Fig 7B and 7C). The Aβ-position E74 is highly conserved among all known mouse H2-A haplotypes (S4 Fig) and the majority of human HLA-DQ molecules [52]. In the H2-Aj molecule, the A74-provided H-bond is lacking; however, it might be functionally substituted by the H-bond from the Aβ K71.


The QTL within the H2 Complex Involved in the Control of Tuberculosis Infection in Mice Is the Classical Class II H2-Ab1 Gene.

Logunova N, Korotetskaya M, Polshakov V, Apt A - PLoS Genet. (2015)

Molecular model of H2-Aj molecule in comparison to H2-Ab.Top view of structural overlay of the peptide-binding domains of H2-Ab (blue) and H2-Aj (red) alleles, bound to CLIP peptide (green). α- alpha and β–beta chains. 1 –α- subunit 310 helix, 2- β subunit region with two AA (P65E66) deletions in j-haplotype (A). Comparison of the H-bond network between H2-Ab (B) and H2-Aj (C) molecules containing CLIP peptide backbone (P-1-P10). MHC Class II conserved residues that contribute to the peptide- MHC hydrogen-bonding network are shown in stick representation. Dashed lines indicate conservative hydrogen bonds with the exception of Ab74 and Kb71 (marked red) in the H2-Aj molecule. D -Comparison of pocket structures of the MHC- binding groove between H2-Ab (blue) and H2-Aj (red). The CLIP peptide backbone is shown in green, P1, P4, P6, P7 and P9 pockets in grey. AA substitutions in the α-chain contribute mostly to the differences in the P1 structure, AA substitutions in the β-chain determine differences in P4, P6, P7 and P9 pockets (E). Potentially most important substitutions are marked and their side chains shown.
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pgen.1005672.g007: Molecular model of H2-Aj molecule in comparison to H2-Ab.Top view of structural overlay of the peptide-binding domains of H2-Ab (blue) and H2-Aj (red) alleles, bound to CLIP peptide (green). α- alpha and β–beta chains. 1 –α- subunit 310 helix, 2- β subunit region with two AA (P65E66) deletions in j-haplotype (A). Comparison of the H-bond network between H2-Ab (B) and H2-Aj (C) molecules containing CLIP peptide backbone (P-1-P10). MHC Class II conserved residues that contribute to the peptide- MHC hydrogen-bonding network are shown in stick representation. Dashed lines indicate conservative hydrogen bonds with the exception of Ab74 and Kb71 (marked red) in the H2-Aj molecule. D -Comparison of pocket structures of the MHC- binding groove between H2-Ab (blue) and H2-Aj (red). The CLIP peptide backbone is shown in green, P1, P4, P6, P7 and P9 pockets in grey. AA substitutions in the α-chain contribute mostly to the differences in the P1 structure, AA substitutions in the β-chain determine differences in P4, P6, P7 and P9 pockets (E). Potentially most important substitutions are marked and their side chains shown.
Mentions: Comparison between the H2-Aj and H2-Ab molecules suggests that the most prominent structural dissimilarities occur in two protein backbone regions: the 310 helical fragment of the α-chain and the P65E66 deletion in the H2-Aβj chain (Fig 7A). These deviations are not unique and are present in other H2 haplotypes (reviewed in Ref [51] and displayed in S3 Fig). Analysis of the hydrogen bond network between H-2A Class II molecules and, as a model, invariant CLIP peptide stabilizing the complex before an antigenic peptide is loaded, demonstrated that the conserved H-bond interactions and the total number of H-bonds are identical for the H2-Ab and H2-Aj products despite two b → j substitutions, T71K and E74A in the Aβ-chain (Fig 7B and 7C). The Aβ-position E74 is highly conserved among all known mouse H2-A haplotypes (S4 Fig) and the majority of human HLA-DQ molecules [52]. In the H2-Aj molecule, the A74-provided H-bond is lacking; however, it might be functionally substituted by the H-bond from the Aβ K71.

Bottom Line: Cloning and sequencing of the H2j allelic variants of these genes demonstrated profound polymorphic variations compare to the H2b haplotype.These variations were sufficient to produce different TB-relevant phenotypes: the more susceptible B6.I-249.1.15.100 strain demonstrated shorter survival time, more rapid body weight loss, higher mycobacterial loads in the lungs and more severe lung histopathology compared to the more resistant B6.I-249.1.15.139 strain.CD4+ T cells recognized mycobacterial antigens exclusively in the context of the H2-A Class II molecule, and the level of IFN-γ-producing CD4+ T cells in the lungs was significantly higher in the resistant strain.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Immunogenetics, Central Institute for Tuberculosis, Moscow, Russia.

ABSTRACT
The level of susceptibility to tuberculosis (TB) infection depends upon allelic variations in numerous interacting genes. In our mouse model system, the whole-genome quantitative trait loci (QTLs) scan revealed three QTLs involved in TB control on chromosomes 3, 9, and in the vicinity of the H2 complex on chromosome 17. For the present study, we have established a panel of new congenic, MHC-recombinant mouse strains bearing differential small segments of chromosome 17 transferred from the TB-susceptible I/St (H2j) strain onto the genetic background of TB-resistant C57BL/6 (B6) mice (H2b). This allowed narrowing the QTL interval to 17Ch: 33, 77-34, 34 Mb, containing 36 protein-encoding genes. Cloning and sequencing of the H2j allelic variants of these genes demonstrated profound polymorphic variations compare to the H2b haplotype. In two recombinant strains, B6.I-249.1.15.100 and B6.I-249.1.15.139, recombination breakpoints occurred in different sites of the H2-Aβ 1 gene (beta-chain of the Class II heterodimer H2-A), providing polymorphic variations in the domain β1 of the Aβ-chain. These variations were sufficient to produce different TB-relevant phenotypes: the more susceptible B6.I-249.1.15.100 strain demonstrated shorter survival time, more rapid body weight loss, higher mycobacterial loads in the lungs and more severe lung histopathology compared to the more resistant B6.I-249.1.15.139 strain. CD4+ T cells recognized mycobacterial antigens exclusively in the context of the H2-A Class II molecule, and the level of IFN-γ-producing CD4+ T cells in the lungs was significantly higher in the resistant strain. Thus, we directly demonstrated for the first time that the classical H2- Ab1 Class II gene is involved in TB control. Molecular modeling of the H2-Aj product predicts that amino acid (AA) substitutions in the Aβ-chain modify the motif of the peptide-MHC binding groove. Moreover, unique AA substitutions in both α- and β-chains of the H2-Aj molecule might affect its interactions with the T-cell receptor (TCR).

Show MeSH
Related in: MedlinePlus