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PubMed1998

Point mutation of a rubella virus E1 protein T-cell epitope by substitution of single amino acid reversed the restrictive HLA-DR polymorphism: a possible mechanism maintaining HLA polymorphism.

The influence of single amino acid substitutions within a rubella E1 protein T-cell epitope, E1(273-284) on T-cell recognition was studied. Substitutions of an uncharged amino acid A for an E or for a T and substitution of a T for S were found to not significantly reduce the T-cell responses. However, substitution of a charged residue such as E for hydrophobic residues (I, V, or W); D for Q; or a relatively larger size amino acid for polar residues completely abolished the cytotoxicities mediated by E1(273-284)-specific T-cell clone. A set of single amino acid-substituted peptide analogs of E1(273-284) not eliciting cytotoxicity of the T-cell clone was used to test the influence of point mutation of the epitope on HLA DR restrictions. A panel of B-cell lines with different DR4 subtypes was used as targets in cytotoxicity assays to determine the restrictive HLA molecules. Results showed that modification of the T-cell epitope by point mutation could reverse the HLA DR restriction from one allele to other alleles. A model based on these results has been proposed to explain the mechanism balancing major histocompatibility complex (MHC) polymorphism in outbred populations.

Amino Acid Substitution↗
PubMed2006

HLA-G polymorphisms and HLA-G expression in sarcoidosis.

BACKGROUND: The MHC class Ib molecule Human Leukocyte Antigen (HLA)-G may be important in induction and maintenance of immunological tolerance, and HLA-G expression may have a role in different cancers, in certain diseases with associations to HLA, and in organ transplantation. Sarcoidosis is a systemic granulomatous disease with unknown etiology but at the molecular level several studies have shown HLA associations. METHODS: In the present study, HLA-G alleles/polymorphisms were studied in sarcoidosis patients (n = 47) and controls (n = 129) by PCR techniques and HLA-G protein expression was investigated in granulomas from sarcoidosis patients with the use of immunohistochemistry. RESULTS: The HLA-G*010102/-G*0106 alleles were observed more often in sarcoidosis patients (39.4%) than in controls (26.4%), p = 0.025 (Fisher's exact test); however, not significant after correction (p(c) = 0.15). When HLA-G expression was investigated by immunohistochemistry in granulomas from sarcoidosis patients, weak HLA-G expression was observed in only one patient. CONCLUSIONS: HLA-G alleles that include a 14-bp sequence polymorphism in exon 8 of the HLA-G gene are observed more often in sarcoidosis patients than in controls. The sequence variation may influence HLA-G mRNA stability and influence the expression of soluble isoforms of HLA-G. Only rare and weak expression of HLA-G was observed in granulomas from sarcoidosis patients. More studies are needed to further elucidate the possible role for HLA-G in sarcoidosis.

Adult↗
PubMed2002

[Methods for identification of HLA antigen polymorphisms].

The HLA complex is the most polymorphic genetic system in man yet known. The variability of the HLA antigens is given by the presence of many alleles of the HLA genes. Requirements for compatibility of HLA antigens in organ and bone marrow transplantations, and also in the determination of genetic risk factors in autoimmune diseases evoke strong pressure on progress in HLA typing methods, mainly for increasing their sensitivity and resolution. For typing of the HLA antigens there are used cellular, serological, biochemical and DNA methods. For HLA class I typing there following tests are used: cytotoxic test (serological), CML (cellular), 1D--IEF (biochemical), RFLP, SSO, SSP--PCR, and SBT (DNA methods). For HLA class II typing, cytotoxic test (cellular), MLC (serological), RFLP, SSO, SSP--PCR, and SBT (DNA methods) are used. DNA methods represent the modern trend in the area of HLA typing and it will probably replace larger part of other HLA typing techniques. In our article, we describe the principles of methods that are used for HLA typing.

HLA Antigens↗
PubMed2005

PEPVAC: a web server for multi-epitope vaccine development based on the prediction of supertypic MHC ligands.

Prediction of peptide binding to major histocompatibility complex (MHC) molecules is a basis for anticipating T-cell epitopes, as well as epitope discovery-driven vaccine development. In the human, MHC molecules are known as human leukocyte antigens (HLAs) and are extremely polymorphic. HLA polymorphism is the basis of differential peptide binding, until now limiting the practical use of current epitope-prediction tools for vaccine development. Here, we describe a web server, PEPVAC (Promiscuous EPitope-based VACcine), optimized for the formulation of multi-epitope vaccines with broad population coverage. This optimization is accomplished through the prediction of peptides that bind to several HLA molecules with similar peptide-binding specificity (supertypes). Specifically, we offer the possibility of identifying promiscuous peptide binders to five distinct HLA class I supertypes (A2, A3, B7, A24 and B15). We estimated the phenotypic population frequency of these supertypes to be 95%, regardless of ethnicity. Targeting these supertypes for promiscuous peptide-binding predictions results in a limited number of potential epitopes without compromising the population coverage required for practical vaccine design considerations. PEPVAC can also identify conserved MHC ligands, as well as those with a C-terminus resulting from proteasomal cleavage. The combination of these features with the prediction of promiscuous HLA class I ligands further limits the number of potential epitopes. The PEPVAC server is hosted by the Dana-Farber Cancer Institute at the site http://immunax.dfci.harvard.edu/PEPVAC/.

Epitopes, T-Lymphocyte↗
PubMed2001

Flow cytometry in human leukocyte antigen testing.

Stem cell transplantation is a recognized treatment for many hematologic malignancies. Human leukocyte antigen (HLA) testing is a key assessment in the evaluation of potential recipients and selection of the appropriate stem cell donor. Over the past several years, technological advances have moved HLA testing from a serologic art form to a sophisticated and high-resolution molecular-based procedure. HLA typing is now performed by DNA-based methods, while flow cytometry has significantly improved our ability to detect HLA antibodies. Although DNA-based typing methods have advanced our understanding of HLA polymorphisms, HLA antibodies still play a role in both stem cell and solid organ transplantation and can lead to failed engraftment or allograft graft rejection, respectively. Flow cytometric crossmatching and HLA antigen-specific microparticle assays represent the new HLA serology. Together, these new technologies are impacting patient outcomes and are expanding our understanding of the immune response to HLA alloantigens. Semin Hematol 38:194-200.

Animals↗
PubMed1998

Mechanisms for induction of autoimmunity in humans.

The triggering or immunogenic stimulus for human autoimmune diseases is unknown. It is not even known whether the stimulus is endogenous, i.e. truly "self" or exogenous, "non-self". Many autoimmune diseases are human lymphocyte antigen (HLA)-associated and demonstrate linkage to the HLA chromosome in family investigations. For most of these diseases, evidence is strong that the association is directly dependent on specific HLA class I or II molecules rather than on other genes located in the HLA region. Since HLA polymorphic HLA molecules have so far only been shown to have two distinct functions, both of which are immunological, a HLA association supports the notion that a particular disease is autoimmune. Furthermore, an association to a specific HLA allele implies that the immunogenic stimulus for autoimmunity would be one specific HLA-binding peptide and that, at least initially, autoimmunity is dependent on the reactivity of one or a limited number of potentially autoaggressive T cell clones. These findings are encouraging and formin the basis for future preventive measures. One current theory is that autoimmune disease is precipitated by an environmental agent, such as a viral infection. Several different mechanisms to explain how a viral infection could induce autoimmune disease in humans are described and one specific example is presented for a virus-induced autoimmune disease in humans. The question of whether ITP could also be dependent on such a mechanism is briefly discussed.

Autoimmune Diseases↗
PubMed1989

Paternity exclusion using 18 genetic systems in 2124 cases in four South African population groups.

Using 18 different blood group systems, 2,124 cases of doubtful paternity, unevenly distributed among four different population groups--South African Negroes (Xhosas) 645 (30%); South African Caucasians 264 (13%); Cape Coloureds (non-Malay) 1,156 (54%), and Cape Malays 59 (3%)--were analysed. Tests for red cell antigen, plasma protein, red cell enzyme and HLA polymorphisms were done on all subjects. The overall exclusion rate was 38,23%, i.e. 812 of the 2,124 men were not biological fathers of the children ascribed to them. The capability of the individual systems to exclude a man from specific paternity was also evaluated. The polymorphic HLA system was the most useful and alone--depending on the particular population group--excluded between 93.5% and 97.8% of falsely accused men. The proportion of men excluded also varied between different population groups using the different systems, e.g. the Rhesus system alone excluded 43.9% of South African Caucasian non-fathers and only 14% of the Xhosa non-fathers. This is a reflection of the gene frequencies within a particular population. The analysis showed that the genetic systems tested in this laboratory were extremely efficient in providing evidence in proof of non-paternity.

Black People↗
PubMed1993

HLA-DQ polymorphisms do not explain HLA class II associations with multiple sclerosis in two Canadian patient groups.

Patient sharing of HLA-DQ allelic polymorphisms is a possible explanation for the association of multiple sclerosis (MS) with different HLA class II haplotypes in different populations. We used two-locus linkage analysis to investigate the relevance of three different polymorphisms to MS susceptibility in 79 French Canadian patients and 62 mixed ethnic white patients. In French Canadians, we found that an MS association with shared DQB1 sequences and a DQA1 codon for glutamine at residue 34 is secondary to an MS association with the common DR2 haplotype, DRB1*1501-DQA1*0102-DQB1*0602. In contrast, we found that an MS association in French Canadians with a DQB1 codon for leucine at residue 26 (DQ beta Leu26) is not secondary to an MS association with the DR2-bearing haplotype. Mixed ethnic whites showed a positive MS association with the DR2 haplotype but no MS association with any of these polymorphisms. We conclude that (1) the DR2 haplotype is predispositional for MS in both populations, (2) DQ beta Leu26 is an additional predispositional factor in French Canadians, and (3) none of the DQ polymorphisms fully explains the association of MS with HLA alleles in both patient groups.

Alleles↗
PubMed2001

HLA-B27 polymorphism.

HLA-B27 is a serologic specificity that encompasses 25 different alleles that encode 23 different products (proteins): HLA-B*2701 to B*2723. These alleles are also called subtypes of HLA-B27, and they may have evolved from the most widespread subtype, B*2705. These subtypes are distinguished from changes mostly in exons 2 and 3, which encode the alpha 1 and alpha 2 domains of the B27 molecule, respectively. Occurrence of ankylosing spondylitis (AS) or related spondyloarthropathy (SpA) has thus far been documented in subjects possessing any one of the first ten (B*2701 to B*2710) subtypes studied. However, B*2706 in Southeast Asian and B*2709 in the Italian island population of Sardinia seem not to be associated with AS. The 13 most recent subtypes have not yet been studied for disease association. It is important to investigate which of them are and are not associated with AS and related SpA, and whether certain subtypes show any preferential association with some of the clinical features or forms of these diseases among the various ethnic/racial populations and geographic regions of the world. This is expected to provide clues as to the mechanism of disease association, and one of the strongest reasons to study the B27 subtypes is to learn the effects of the sequence variations on the peptide-binding specificity of the molecule. Among these peptides may be the putative arthritogenic peptide(s).

Alleles↗
PubMed1986

Polymorphisms within the HLA-DR3 haplotypes. I. HLA-DR polymorphisms detected at the protein and DNA levels are reflected by T-cell recognition.

HLA-DR molecules were isolated from eight different HLA-DR3 homozygous B-cell lines by immunoprecipitation with monoclonal antibodies, and they were subsequently analyzed by two-dimensional gel electrophoresis. We found that HLA-DR3 homozygous B-cell lines of consanguineous origin express two types of HLA-DR molecules. One type of HLA-DR molecule was present in all the cell lines tested, whereas the second DR molecule appears to be polymorphic. DNA isolated from the different HLA-DR3 homozygous cell lines was studied by Southern blot analysis to determine whether any DR beta restriction fragment length polymorphism could be observed. Polymorphisms detected at both the product and genomic level have been compared to each other, and their relations to the serological (HLA-DR) and cellular (HLA-D and LB-Q1) typing data will be discussed.

Antibodies, Monoclonal↗
PubMed2006

HLA-B44 polymorphisms at position 116 of the heavy chain influence TAP complex binding via an effect on peptide occupancy.

A single residue polymorphism distinguishes HLA-B*4402(D116) from HLA-B*4405(Y116), which was suggested to allow HLA-B*4405 to acquire peptides without binding to tapasin-TAP complexes. We show that HLA-B*4405 is not inherently unable to associate with tapasin-TAP complexes. Under conditions of peptide deficiency, both allotypes bound efficiently to TAP and tapasin, and furthermore, random nonamer peptides conferred higher thermostability to HLA-B*4405 than to HLA-B*4402. Correspondingly, under conditions of peptide sufficiency, more rapid peptide-loading, dissociation from TAP complexes, and endoplasmic reticulum exit were observed for HLA-B*4405, whereas HLA-B*4402 showed greater endoplasmic reticulum retention and enhanced tapasin-TAP binding. Together, these studies suggest that position 116 HLA polymorphisms influence peptide occupancy, which in turn determines binding to tapasin and TAP. Relative to HLA-B*4405, inefficient peptide loading of HLA-B*4402 is likely to underlie its stronger tapasin dependence for cell surface expression and thermostability, and its enhanced susceptibility to pathogen interference strategies.

Animals↗
PubMed2005

Extended HLA-DPB1 polymorphism: an RNA approach for HLA-DPB1 typing.

Most of the 119 human leukocyte antigen (HLA)-DPB1 alleles are defined by polymorphism in six hypervariable regions (HVRs) in exon 2 of the HLA-DPB1 gene. We investigated how DPB1 polymorphism is represented in the entire coding region. An RNA sequencing-based typing (SBT) approach was developed for the identification of HLA-DPB1 polymorphism from the 5' untranslated region (UTR) through the 3'-UTR. B-cell lymphoblastoid cell lines, encoding 16 different DPB1 alleles, were studied. Results show additional HLA-DPB1 polymorphism in exons 1, 3, 4 and 5 and the 5' and 3'-UTR. Four new HLA-DPB1 alleles were identified, DPB1*0502, DPB1*0602, DPB1*0802 and DPB1*0902, which have exon 2 sequences identical to other DPB1 alleles but differ in the extended region. The additional polymorphism represents two main polymorphic lineages in the DPB1 alleles. Among the HVRs in exon 2, only HVR F correlates with these two main lineages.

Alleles↗
PubMed2002

[Application of the HLA system to forensic medicine--from serology to DNA polymorphism].

HLA antigens are highly polymorphic and therefore considered useful for personal identification in forensic medicine. The HLA system was first applied to forensic medicine for serological typing and is currently being applied to DNA typing. We first applied the HLA system to serological typing for paternity testing. Exclusion of paternity was confirmed in 39 of 93 cases. While serological HLA typing and other testing yielded consistent results in 37 of these 39 cases, exclusion of paternity could be confirmed only by serological HLA typing in 1 case and only by other testing in 1 case. Even in cases where exclusion could not be confirmed, it was possible to increase the probability of paternity. Bloodstains with known HLA types were then subjected to lymphocytotoxic inhibition tests to detect HLA antigens using one of the following methods: a two-stage method using an antibody and a bloodstain extract; a one-stage method where a bloodstain was allowed to react directly with an antiserum; or a washing method where washing was combined with one of the two above methods. Although HLA antigen detection was possible using any of these methods, some antisera yielded false-positive reactions, which limited the range of usable antisera. With the exception of cross-reactions, the washing method eliminated false-positive reactions. Antigens were detectable in bloodstains that were left to stand for up to 42 days. DNA typing based on the HLA system was investigated by determining DR and DQB1 types using the Hot Start PCR-SSP method with various samples of known HLA types and tissue samples collected from unidentified corpses. With bloodstains, DR typing was possible in all 61 cases, while DQB1 typing was possible in 31 of 33 cases. DR typing was possible even when bloodstains had been stored for 10 to 20 years. With saliva stains, typing was possible in all cases by purifying DNA using a Microcon 100 microconcentrator. With hair samples, typing was possible with all hair root samples and about half of hair shaft samples. With mixed stains, the detection of minor components was possible even at a low mixing ratio of 10:1. With cigarette butts, as was the case with saliva stains, typing was possible using purified DNA. Lipstick did not affect the results of DNA typing. Although DNA typing was possible in many cases using tissue samples collected from unidentified corpses, the results were affected by factors such as status of corpse, postmortem interval, postmortem change and tissue type. With some aorta samples, for example, typing was possible up to one year after death. The results of typing were also fairly favorable using bone samples.

DNA↗
PubMed1984

Polymorphism of HLA class I genes after restriction by endonucleases Eco RI, Eco RV and Hind III.

After electrophoresis and transfer onto a hybridization membrane, the restriction endonuclease fragments obtained were probed with a cDNA carrying the nucleotide sequence encoding a class I HLA gene. Polymorphism for presence or absence of various Eco RI and Eco RV and Hind III fragments was noted in a panel of unrelated Parisian people: frequent polymorphism was described for 2 Eco RI restriction fragments of sizes 16.5 and 7.7 kb, for 5 Eco RV restriction fragments of sizes 25, 20, 11.5, 7.8 and 4 kb, and for 3 Hind III restriction fragments of sizes 27.5, 23.5 and 4.7 kb. The French population studied is in Hardy-Weinberg equilibrium for the different variants described.

DNA Probes↗
PubMed1992

Family study on HLA-DPB1 polymorphism: linkage analysis with HLA-DR/DQ and two "new" alleles.

An extensive family study on HLA-DPB1 was performed in 105 families living in northeastern Japan. In a linkage study between HLA-DPB1 and other HLA loci, five apparent recombinations between DPB1 and DR/DQ loci were observed. The recombination frequency (theta) with maximum probability was estimated to be 0.017 by the lod score method. DPB1 allele and haplotype frequencies in unrelated parents were determined by direct counting. The most common allele was DPB1*0501 with the frequency of 41.2% and the second was DPB1*0201 with 24.0%. Nine DPB1-DR and six DPB1-DQ haplotypes were in significant linkage disequilibrium. Seven kinds of extended haplotypes were observed to be over 1%, in which the most common haplotype A24-B52-DR15-DQ6-DPB1*0901 occurred at 6.0%. Moreover, we found two "new" DPB1 alleles in this study. The first one possesses a single base substitution from DPB1*0501 resulting in an amino acid change. The other is most likely to be formed by an intraexonic recombination between DPB1*0301 and DPB1*0501.

Alleles↗
PubMed1995

Sequencing-based typing reveals new insight in HLA-DPA1 polymorphism.

An HLA-DPA1 sequencing-based typing (SBT) system has been developed to identify DPA1 alleles. Up to now eight DPA1 alleles have been defined. Six can be discriminated based upon exon 2 polymorphism. The three subtypes of DPA1*01: DPA1*0101, DPA1*0102 and DPA1*0103, have identical exon 2 sequences but show differences in exon 4. Exon 4 sequences were known for only the three DPA1*01 subtypes and for DPA1*0201. We now present additional sequence information for exon 4 and the unknown segments at the 3' end of exon 2. Additionally with the use of this sequencing technique it is also possible to identify previously unidentified polymorphism. We have studied the exon 2 and exon 4 polymorphism of DPA1 in 40 samples which include all known DPA1 alleles. A new allele, DPA1*01 new, was identified which differs by one nucleotide in exon 2 from DPA1*0103, resulting in an aspartic acid at codon 28. The DPA1*01 subtypes DPA1*0101 and DPA1*0102 could not be confirmed in samples which previously were used to define these subtypes, and consequently they do not exist. The exon 4 sequence of DPA1*0201 is corrected based on sequence data of DAUDI, the cell line in which DPA1*0202 was originally defined. The exon 4 regions of the remaining four alleles were resolved: the exon 4 regions of the alleles DPA1*02021 and DPA1*02022 were found to be identical to the--corrected--DPA1*0201 whereas the exon 4 region of DPA1*0301 differs by one nucleotide compared to DPA1*0103. The DPA1*0401 exon 4 region differs by one nucleotide compared to the corrected DPA1*0201.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗