Molecular complexity of HLA-DQw3: the TA10 determinant is located on a subset of DQw3 beta chains

Use of synthetic peptides to identify measles nucleoprotein T-cell epitopes in vaccinated and naturally infected humans

Recombinant measles nucleoprotein (N) and synthetic peptides spanning the length of the N-protein-coding region were used with a proliferation assay to identify human T-cell epitopes in vaccinated and naturally infected adults. A number of epitopes were mapped to specific regions of the measles virus N. The proliferative response of at least two donors was mediated by CD4(+) T cells in association with HLA DR antigens. Over 70% of all donors tested responded to peptides representing amino acids 271-290, 367-386, 400-420, and 483-502, suggesting that these peptides may be broadly recognized within an HLA diverse population. The most frequently recognized T-cell epitopes in both naturally infected and vaccinated donors were located in the genetically heterogeneous carboxy-terminal half of the N. Analysis of patterns of peptide reactivity among vaccinated and naturally infected subjects identified several regions of potential difference between these two groups. Peptides 221-240 and 237-256 were recognized among 100% of naturally infected donors but among only 37.5% of vaccinated donors and therefore may be of further interest in studies to investigate induction of lifelong versus transient immunity to measles. Use of chimeric molecules containing multiple well-characterized T- and B-cell epitopes or genetic alteration of attenuated vaccine virus to enhance critical T-cell responses may eventually lead to the development of a vaccine candidate that can more closely model the patterns of immune response elicited by wild-type virus.

Alloreactive T-cell clones identify multiple HLA-DQw3 variants

HLA-DQw3 is a broadly defined alloantigen that has been subdivided by serological, biochemical, and molecular methods into three distinct specificities: DQw7, DQw8, and DQw9. In order to characterize functionally relevant structural polymorphisms within this family of alloantigens, we generated a series of DQw3-reactive T-cell clones that together recognize six different variants of DQw3. T-cell clones IG11 and IG9 were found to recognize three distinct functional variants associated with a majority of DQw3+ cells, while clones 21J, IE6, 64B, and IC3 recognized four more narrowly distributed functional variants associated with unique DQw7, DQw8, and DQw9 subsets. Comparison of known DQB gene sequences suggested candidate recognition sites for clones IG11 and 64B in the region of amino acid residues 66 to 71 and residue 57 of the DQ beta chain. In contrast, no unique DQB or DQA sequences were found that individually corresponded to the reactivity patterns of clones 21J, IE6, IG9, or IC3, suggesting that an interaction between DQ alpha and DQ beta chains determines allo-recognition. These data are consistent with the hypothesis that T cells recognize specific alloepitopes on HLA class II molecules, either as distinct structural elements that trigger an alloresponse or, more indirectly, as contact elements that influence alloreactivity by governing the binding of foreign peptide. The results illustrate the diversity of possible T cell responses directed toward HLA-DQ molecules and suggest that T cell recognition of the DQ heterodimer alone, or a peptide antigen bound to the DQ heterodimer, can be affected either by the individual DQ alpha and beta chains, or by a more complex interaction between the two.

DQw7 and the C4B null allele in rheumatoid arthritis and Felty's syndrome

DQ beta and C4 null alleles have been defined in patients with rheumatoid arthritis, Felty's syndrome, and in control subjects. Comparison of DR4 positive subjects shows that rheumatoid disease without extra-articular features has no preferential associations with either DQ beta or C4 null variants. In Felty's syndrome there are significant associations with both the class II major histocompatibility complex (MHC) DQw7 allele (86% of DR4 positive patients with Felty's syndrome and 53% of DR4 positive controls) and the class III MHC C4B null allele (50% of patients with Felty's syndrome and 20% of DR4 positive controls). DQw7 and the C4B null allele are in linkage disequilibrium and the B44-Bf *S-C4A*3-C4B*Q0-DR4-DQw7 haplotype accounts for five of 24 DR4 positive haplotypes assigned in subjects with Felty's syndrome. The results were not accounted for by articular disease severity and suggest that articular and extra-articular forms of rheumatoid disease may be immunogenetically heterogeneous.

HLA-DQ beta 3.1 allele is a determinant of susceptibility to DR4-associated rheumatoid arthritis

Rheumatoid arthritis is associated with HLA-DR4 in several ethnic groups. Since DR4 haplotypes encode a diverse array of class II molecules, it is of interest to characterize the nature of the primary association. We have examined molecular polymorphisms of HLA class II gene products expressed by normals and rheumatoid arthritis patients using monoclonal antibodies and two-dimensional electrophoresis. Most homozygous DR4 rheumatoid arthritis patients express DR beta 1 molecules associated with Dw4 or Dw14 mixed lymphocyte culture determinants. In Caucasoids, two DR4-linked DQw3-associated beta-chain alleles are defined by two-dimensional electrophoresis. These variants, designated DQ beta 3.1 and 3.2, are associated with the serologic determinants DQw7 and DQw8, respectively. A panel of 40 DR4-positive normals was also examined for nucleotide sequence polymorphisms associated with DQB3.1 and 3.2 genes using the polymerase chain reaction and specific oligonucleotide probes. At the DQ beta level the rheumatoid arthritis panel was distinguished by enrichment for the DQ beta 3.1 allele with 100% of patients positive for DQw7. Results presented here suggest that specific DQ beta alleles may modify the effect of HLA-DR4 beta 1 alleles in conferring susceptibility to rheumatoid arthritis in a phenotype-specific fashion.

HLA-DQw3-related determinants: analysis of subunit and spatial relationships

More polymorphism exists among DQ region gene products than is suggested by present serologic definitions of these class II molecules. DQ beta polymorphism among haplotypes carrying the DQw3 specificity is considerable. The TA10 specificity is present on one allele of at least three different DQ beta alleles that carry the DQw3 specificity. We have examined a series of monoclonal antibodies directed against different DQ beta alleles carrying the DQw3 specificity to determine subunit and spatial relationship among the epitopes detected by these antibodies. The antibodies were examined by Western blotting and for their ability to inhibit the binding of fluoresceinated antibodies on either TA10+ or TA10- DQw3 haplotypes. Our results reveal that (1) multiple DQw3-related epitopes exist; (2) several anti-DQw3-related antibodies generated against TA10- DQw3 molecules are unable to inhibit the binding of a TA10-specific antibody on a TA10+ haplotype while strongly inhibiting binding of an antibody detecting the reciprocal DQ beta polymorphism on a TA10- DQw3 haplotype; and (3) there is a strong requirement for three-dimensional conformation in the formation of the majority of the epitopes examined here. Analysis of previously published amino acid sequences for the haplotypes investigated here suggest that charge changes at amino acids 45, and 57, respectively, may have a significant effect in changing the spatial relationship between the DQw3-related epitope(s) and other polymorphic determinants on DQ beta chains.

Sequence analysis of HLA class II domains: characterization of the DQw3 family of DQB genes

HLA class II allelic variants within the DQw3-related family of genes carry distinct allo-specificities and have been implicated in specific HLA-disease associations, such as insulin-dependent diabetes mellitus. To investigate the nucleotide variations which characterize DQw3 genes, we applied a novel cDNA cloning strategy that uses a single-stranded vector/primer system to facilitate DNA sequencing of allelically variable gene families. Using a DQB-specific primer sequence and M13 bacteriophage as the cloning vector, direct cloning and sequencing of multiple DQB genes was performed without the need for second strand synthesis or for subcloning. Sequence analysis from eight lymphoblastoid cell lines selected to represent different ethnic backgrounds revealed three DQw3-related DQB genes, DQB3.1, 3.2, and 3.3, corresponding to the newly designated HLA-DQw7, w8, and w9 specificities, respectively. An unusual Pro-Pro couplet at codons 55-56 is characteristic of all DQw3-positive sequences and may be contributing to the broad DQw3 allospecificity. Comparisons among ethnically disparate DQw3-related sequences showed no additional expressed or silent nucleotide substitutions among these DQB alleles. Thus, polymorphism within the DQw3 family of genes appears to be extremely limited, with a paucity of nucleotide variations accumulated by evolutionary distance.

Mutational analysis of the HLA-DQ3.2 insulin-dependent diabetes mellitus susceptibility gene

The human major histocompatibility complex includes approximately 14 class II HLA genes within the HLA-D region, most of which exist in multiple allelic forms. One of these genes, the DQ3.2 beta gene, accounts for the well-documented association of HLA-DR4 with insulin-dependent diabetes mellitus and is the single allele most highly correlated with this disease. We analyzed the amino acid substitutions that lead to the structural differences distinguishing DQ3.2 beta from its nondiabetogenic, but closely related allele, DQ3.1 beta. Site-directed mutagenesis of the DQ3.2 beta gene was used to convert key nucleotides into DQ3.1 beta codons. Subsequent expression studies of these mutated DQ3.2 beta clones using retroviral vectors defined amino acid 45 as critical for generating serologic epitopes characterizing the DQw3.1 beta and DQw3.2 beta molecules.

Unambiguous typing for HLA-DQ TA10 and 2B3 specificities using specific oligonucleotide probes

Oligonucleotide probes specific for the serologically defined TA10 and 2B3 specificities were selected based on a comparison of the available HLA-DQ beta sequences. Panel and family segregation studies confirm a complete correlation between the reactivities of the selected probes and the TA10/IIB3 antibodies. The Glu residue at position 45 of the HLA-DQ beta chain is specific for the TA10 determinants, and a DQ beta Gly-Val-Tyr sequence is found at position 45-47 for all 2B3-positive DQ beta chains.

Regulatory role of monomorphic and polymorphic determinants of HLA class I antigens in the proliferation of T cells stimulated by autologous and allogeneic B and T lymphoid cells

Monoclonal antibodies (mAb's) to monomorphic and polymorphic determinants of HLA Class I antigens were shown to inhibit proliferation of T cells stimulated with autologous and allogeneic B and T lymphocytes. Inhibition of proliferative responses was lower when T cells were used as stimulators than when B cells were used. The inhibitory activity was similar for mAb's to monomorphic and polymorphic determinants of HLA Class I antigens, suggesting that the density of antigen-antibody complexes on the cell membrane does not play a major role in the phenomenon. The anti-HLA Class I mAb's exerted their inhibitory effect at the level of both the responding and the stimulating cells. Addition of exogenous interleukin 2 to the mixed cultures did not affect the mAb-mediated inhibition.

Molecular analysis of DQ beta 3.1 genes

HLA class II genes have been implicated in susceptibility to a number of diseases. We have previously identified two allelic variants of DQw3 and have shown that DR4-DQ beta 3.2 haplotypes are associated with increased risk of IDDM whereas DR4-DQ beta 3.1 haplotypes are not. DR5 and DR8 DQw3+ individuals are exclusively DQ beta 3.1 and share numerous restriction sites within the DQ beta genes with DR4-DQ beta 3.1 individuals. In order to compare the DQ beta 3.1 genes associated with different haplotypes, we have sequenced coding and noncoding regions of the DQ beta genes from a DR4-DQ beta 3.1 HTC (ER) and a DR8-DQ beta 3.1 HTC (LUY). LUY and ER DQ beta genes share nucleotide substitutions in both the beta 1 and beta 2 exons, yielding six amino acid replacements distinguishing them from DQ beta 3.2. In the noncoding regions as well, LUY and ER share nucleotide substitutions distinguishing their DQ beta 3.1 genes from DQ beta 3.2. These data support the concept that the DQ beta 3.1 allele was introduced onto different backgrounds via homologous recombination.

DQw3 variants defined by cloned alloreactive T cells

The polymorphism of HLA class II molecules expressing the serologically defined alloantigen DQw3 was studied using cloned proliferative T lymphocytes. Two clones, IG9 and IC3, were selectively primed against DQw3-associated determinants and tested against a panel of 92 HLA-D homozygous cells. Both clones were specific for DQw3, but each showed a distinct response pattern. Clone IG9 recognized a DQw3-associated determinant expressed on a subset of DR4 and DR5 haplotypes and on all DRw6, 7, w8, and w9 haplotypes tested. In contrast, clone IC3 recognized a distinct DQw3-associated determinant expressed only on a subset of DR4 haplotypes. In monoclonal antibody inhibition experiments, anti-DQ, but not anti-DR or anti-DP antibodies, blocked reactivity of both clones IG9 and IC3, further demonstrating that the determinants defined by these clones are associated with DQ molecules. In DNA hybridization studies using a DQ beta probe, a correlation was observed between restriction site polymorphisms in the DQ beta gene, designated DQw"3.1" and "3.2," and the expression of the T-cell-defined IG9 and IC3 determinants. It is, thus, possible to demonstrate by cloned T-cell reactivity functionally relevant recognition sites on DQw3+ molecules that are associated with structural polymorphisms defined by molecular and genomic analysis.