Genetic and immunologic aspects of type 1 diabetes mellitus

Prediction of type 1 diabetes mellitus (IDDM) and its identification in preclinical period is one of the central problems in modern medicine. They are based comprehensive genetic, immunologic and metabolic evaluations. We observed four hundred seven first-degree relatives of patients with IDDM (240 families in which one of the children or one of the parents had IDDM) have been included in the study. The study of HLA-DQA1, HLA-DQB1 polymorphic alleles and DRB1 genes and their combinations. The genetic study included searching HLA loci (HLA-DQA1, HLA-DQB1 polymorphic alleles and DRB1 genes) loci. To evaluate the genetic risk two approaches we used: first--carrying predisposing HLA-DQ alleles and DRB1-genes and it's combination (mainly associated in Russian population was DRB1*04-DQB1*0302, DRB1*04-DQA1*0301, DQA1*0301-DQB1*0302, DQA1*0301-DQB1*0302 and four susceptible alleles in A- and B- chains (Asp 57-, Arg 52+)) and second--IBD (identity by descent), in Russian population HLA-identical for 2 haplotypes sibs had risk of development of IDDM of 18%, for 1 haplotype--3%, for 0 haplotype-0.9%. The antibodies (ICA, IAA) prevalence rate has not depended on availability of predisposing HLA-DQ alleles and DRB1-genes and haploidentity of normal sibs and sibs with IDDM. However, GADA prevalence rate in groups having high predisposed alleles has been noticed as significantly higher (28.6%) comparing with 7.7% in groups that had no predisposing alleles (p < 0.05). The comparison of antibodies prevalence rate to sibs HLA-identity has shown the significant increase or GADA prevalence rate in group of siblings identical for one haplotype comparing with non-identical sibs (27.3% and 0% respectively, p < 0.001).     

Identification of T cell determinants on human type II collagen recognized by HLA-DQ8 and HLA-DQ6 transgenic mice.

HLA-DQA1*0301 and HLA-DQB1*0302 genes encoding the HLA-DQ8 molecule and HLA-DQA1*0103 and HLA-DQB1*0601 genes encoding the HLA-DQ6 molecule were introduced into H-2Abetao knockout mice. Three lines of transgenic mice were established: HLA-DQ8, HLA-DQ6, and HLA-DQ8beta6alpha. HLA-DQ8 mice are susceptible to collagen-induced arthritis, while HLA-DQ6 mice are resistant. HLA-DQ8beta6alpha mice develop polychrondritis in addition to arthritis. Transgenic mice were primed and challenged with individual synthetic peptides representing human type II collagen. A total of 101 synthetic peptides were tested in each transgenic line of mice. HLA-DQ8 mice responded to 15 synthetic peptides representing all cyanogen bromide fragments. In contrast, HLA-DQ6 mice responded to a subset of the peptides recognized by HLA-DQ8 T cells. HLA-DQ8beta6alpha mice, although exhibiting diminished responses to the majority of HLA-DQ8-restricted determinants, elicited enhanced responses to two peptides. In addition, HLA-DQ8beta6alpha mice respond to two unique peptide determinants contained within cyanogen bromide fragments CB10 and CB11 showing the significance of mixed isotype dimers in the immune response. The determinants recognized by the HLA-DQ transgenic mice are distinct from those previously identified using conventional laboratory mice. These results suggest that human class II transgenic mice offer a means of identifying human class II-restricted epitopes associated with potential human autoantigens.     

Beta 57-Asp plays an essential role in the unique SDS stability of HLA-DQA1*0102/DQB1*0602 alpha beta protein dimer, the class II MHC allele associated with protection from insulin-dependent diabetes mellitus

Studies of the stability of HLA-DQ have revealed a correlation between SDS stability of MHC class II alphabeta dimers and insulin-dependent diabetes mellitus (IDDM) susceptibility. The MHC class II alphabeta dimer encoded by HLA-DQA1*0102/DQB1*0602 (DQ0602), which is a dominant protective allele in IDDM, exhibits the greatest SDS stability among HLA-DQ molecules in EBV-transformed B-lymphoblastoid cells and PBLs. DQ0602 is also uniquely SDS stable in the HLA-DM-deficient cell line, BLS-1. We addressed the molecular mechanism of the stability of DQ0602 in BLS-1. A panel of mutants based on the polymorphic differences between HLA-DQA1*0102/DQB1*0602 and HLA-DQA1*0102/DQB1*0604 were generated and expressed in BLS-1. An Asp at beta57 was found to be critical for SDS stability, whereas Tyr at beta30, Gly at beta70, and Ala at beta86 played secondary roles. Furthermore, the level of class II-associated invariant chain peptide bound to HLA-DQ did not correlate with SDS stability, suggesting that class II-associated invariant chain peptide does not play a direct role in the unique SDS stability of DQ0602. These results support a role for DQB1 codon 57 in HLA-DQ alphabeta dimer stability and IDDM susceptibility.     

HLA—DQ分子遗传结构与中国人重症肌无力的相关性

重症肌无力与ＨＬＡⅡ类基因关联性在不同人种和民族中具有不同遗传易感性,为探讨中国人重症肌无力（ＭＧ）与ＨＬＡ０ＤＱ分子关联性,采用聚合酶链式反应－限制性片段长度多态性（ＰＣＲ－ＲＦＬＰ）方法,分析了５０例中国正常人及４９例重症肌无力患者的ＨＬＡ－ＤＱＡ１和－ＤＱＢ１座位的基因型,结果：共检出正常人ＤＱＡ１等位基因８种,ＤＱＢ１等位基因１０种,重症肌无力患者ＤＱＡ１等位基因８种,ＤＱＢ１等位基因９种     

Polymorphisms of HLA-DRB1, -DQA1 and -DQB1 in Inhabitants of Astana,the Capital City of Kazakhstan

Background

Kazakhstan has been inhabited by different populations, such as the Kazakh, Kyrgyz, Uzbek and others. Here we investigate allelic and haplotypic polymorphisms of human leukocyte antigen (HLA) genes at DRB1, DQA1 and DQB1 loci in the Kazakh ethnic group, and their genetic relationship between world populations.

Methodology/Principal Findings

A total of 157 unrelated Kazakh ethnic individuals from Astana were genotyped using sequence based typing (SBT-Method) for HLA-DRB1, -DQA1 and -DQB1 loci. Allele frequencies, neighbor-joining method, and multidimensional scaling analysis have been obtained for comparison with other world populations. Statistical analyses were performed using Arlequin v3.11. Applying the software PAST v. 2.17 the resulting genetic distance matrix was used for a multidimensional scaling analysis (MDS). Respectively 37, 17 and 19 alleles were observed at HLA-DRB1, -DQA1 and -DQB1 loci. The most frequent alleles were HLA-DRB1*07:01 (13.1%), HLA-DQA1*03:01 (13.1%) and HLA-DQB1*03:01 (17.6%). In the observed group of Kazakhs DRB1*07:01-DQA1*02:01-DQB1*02:01 (8.0%) was the most common three loci haplotype. DRB1*10:01-DQB1*05:01 showed the strongest linkage disequilibrium. The Kazakh population shows genetic kinship with the Kazakhs from China, Uyghurs, Mongolians, Todzhinians, Tuvinians and as well as with other Siberians and Asians.

Conclusions/Significance

The HLA-DRB1, -DQA1and -DQB1 loci are highly polymorphic in the Kazakh population, and this population has the closest relationship with other Asian and Siberian populations.     

Complex HLA-DR and -DQ interactions confer risk of narcolepsy-cataplexy in three ethnic groups

Human narcolepsy-cataplexy, a sleep disorder associated with a centrally mediated hypocretin (orexin) deficiency, is tightly associated with HLA-DQB1*0602. Few studies have investigated the influence that additional HLA class II alleles have on susceptibility to this disease. In this work, 1,087 control subjects and 420 narcoleptic subjects with cataplexy, from three ethnic groups, were HLA typed, and the effects of HLA-DRB1, -DQA1, and -DQB1 were analyzed. As reported elsewhere, almost all narcoleptic subjects were positive for both HLA-DQA1*0102 and -DQB1*0602. A strong predisposing effect was observed in DQB1*0602 homozygotes, across all ethnic groups. Relative risks for narcolepsy were next calculated for heterozygous DQB1*0602/other HLA class II allelic combinations. Nine HLA class II alleles carried in trans with DQB1*0602 were found to influence disease predisposition. Significantly higher relative risks were observed for heterozygote combinations including DQB1*0301, DQA1*06, DRB1*04, DRB1*08, DRB1*11, and DRB1*12. Three alleles-DQB1*0601, DQB1*0501, and DQA1*01 (non-DQA1*0102)-were found to be protective. The genetic contribution of HLA-DQ to narcolepsy susceptibility was also estimated by use of lambda statistics. Results indicate that complex HLA-DR and -DQ interactions contribute to the genetic predisposition to human narcolepsy but that additional susceptibility loci are also most likely involved. Together with the recent hypocretin discoveries, these findings are consistent with an immunologically mediated destruction of hypocretin-containing cells in human narcolepsy-cataplexy.     

HLA-DR53 molecules are associated with susceptibility to celiac disease and selectively bind gliadin-derived peptides

 Celiac disease (CD) patients usually express a DQ2 heterodimer, whose chains DQα1*0501/DQβ1*0201, are encoded by the genes HLA-DQA1*0501 and DQB1*0201, respectively. Among the DQ2 carriers, the risk of developing disease was shown to correlate with the number of DQβ1*0201 chains encoded. Studying two separate cohorts of Italian and Tunisian patients, we now show a significant association of celiac disease with expression of either the DQ2 or DR53 heterodimers. The risk is maximal for individuals that carry both DQ2 and DR53 heterodimers. When twenty synthetic peptides overlapping most of A-gliadin sequence were tested for the binding to various purified DR molecules, it was found that DR53 molecules bind selectively and with high affinity (IC50<1 μM) to A-gliadin-derived peptides. These data suggest that both HLA DQ2 and DR53 molecules are associated with increased genetic risk for CD, and provide a possible biochemical basis for this complex association. Received: 1 August 1998 / Revised: 24 February 1999     

Molecular Diversity of HLA-DQ

HLA-DQ molecules were isolated from a panel of HLA-DR-DQ homozygous cell lines, partially of consanguineous origin, derived by the use of monoclonal antibody SPV-L3, and subsequently analyzed by gel electrophoretic techniques. It is demonstrated that both the DQ alpha and beta chain exhibit an extensive isoelectric point polymorphism. Within a panel of 29 B-cell lines tested, at least 5 distinct alpha and 6 distinct DQ beta chain gene products were observed. Of the 30 theoretically possible DQ alpha-beta dimers, only 10 could be identified within the panel: 5 different dimers are associated with the DQw1 allospecificity; HLA-DQw2 and -DQw3 are associated with 2 types of dimers, whereas another DQ alpha-beta combination was expressed by a cell line with a so-called DQ-blank specificity. The relation between the specificities 2B3 and TA10 appeared to be complicated as far as DQ beta chain isoelectric point differences are concerned: monoclonal antibody IIB3 seems to be reactive with four distinct DQ beta chain alleles whereas monoclonal antibody TA10 only reacted with one type of DQ beta chain. These results suggest that the polymorphic DQ alpha and beta chains may both contribute to the definition of the HLA-DQ allospecificity. A particular DQ beta chain was present in two types of HLA-DQw1 molecules, as well as in one type of HLA-DQw2 and -DQw3 (2133 positive) molecule, and formed dimers with electrophoretic distinct DQ alpha chains. On the other hand, HLA-DQw2 molecules isolated from HLA-DR3-positive cells and one type of HLA-DQw3 (TA10 positive) molecule were found to be constructed of identical alpha chains but appeared to differ in the composition of their DQ beta chain gene products. The implications of these findings will be discussed.     

Single-cell RNA sequencing identify SDCBP in ACE2-positive bronchial epithelial cells negatively correlates with COVID-19 severity

The coronavirus disease 2019 (COVID-19), caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in many deaths throughout the world. It is vital to identify the novel prognostic biomarkers and therapeutic targets to assist with the subsequent diagnosis and treatment plan to mitigate the expansion of COVID-19. Since angiotensin-converting enzyme 2 (ACE2)-positive cells are hosts for COVID-19, we focussed on this cell type to explore the underlying mechanisms of COVID-19. In this study, we identified that ACE2-positive cells from the bronchoalveolar lavage fluid (BALF) of patients with COVID-19 belong to bronchial epithelial cells. Comparing with patients of COVID-19 showing severe symptoms, the antigen processing and presentation pathway was increased and 12 typical genes, HLA-DRB5, HLA-DRB1, CD74, HLA-DRA, HLA-DPA1, HLA-DQA1, HSP90AA1, HSP90AB1, HLA-DPB1, HLA-DQB1, HLA-DQA2, and HLA-DMA, particularly HLA-DPB1, were obviously up-regulated in ACE2-positive bronchial epithelial cells of patients with mild disease. We further discovered SDCBP was positively correlated with above 12 genes particularly with HLA-DPB1 in ACE2-positive bronchial epithelial cells of COVID-19 patients. Moreover, SDCBP may increase the immune infiltration of B cells, CD8+ T cells, CD4+ T cells, macrophages, neutrophils and dendritic cells in different lung carcinoma. Moreover, we found the expression of SDCBP was positively correlated with the expression of antigen processing and presentation genes in post-mortem lung biopsies tissues, which is consistent with previous discoveries. These results suggest that SDCBP has good potential to be further developed as a novel diagnostic and therapeutic target in the treatment of COVID-19.     

Specific amino acid residues in the second hypervariable region of HLA-DQA1 and DQB1 chain genes promote the Ro (SS-A)/La (SS-B) autoantibody responses

In order to define the HLA-DR and DQ alleles, as well as the specific DQA1 and DQB1 chain genes involved in the anti-Ro/La autoantibody responses, RFLP analysis and sequence-specific oligonucleotide typing was carried out on 58 Caucasians and 48 American blacks with SLE or Sj?gren's syndrome and anti-Ro antibodies. Among both Caucasian and black patients, the highest relative risk for the anti-Ro response (both with and without accompanying anti-La) was conferred by heterozygosity for the DQw2.1 (in linkage disequilibrium with HLA-DR3) and DQw6 (a subtype of DQw1) alleles compared with either 269 normal race-matched controls or 80 anti-Ro negative SLE/Sj?gren's syndrome patients. Analysis of individual DQA1 and DQB1 chain alleles revealed that DQA1*0501 and DQB1*0201 were most frequent, followed by DQA1 and DQB1 alleles comprising DQw6. In patients not possessing DQw2.1 and/or DQw6 alleles, HLA-DQB1*0302 and HLA-DQA1*0401 (especially in blacks) were significantly increased. Nucleotide sequence analysis of these associated alleles showed that 100% of patients with anti-Ro had a glutamine residue at position 34 of the outermost domain of the DQA1 chain and/or a leucine at position 26 of the outermost domain of the DQB1 chain. Patients with anti-Ro plus La were more likely to have all four of their DQA1/DQB1 chains containing these amino acid residues than either anti-Ro-negative SLE patients or controls. These data implicate specific amino acid residues on both DQA1 and DQB1 chains located in the floor of the Ag binding cleft of the HLA-DQA1:B1 heterodimer and further suggest a role for "gene dosage" in the anti-Ro (+/- La) autoantibody response.     

HLA class II polymorphism in autochthonous population of Gorski kotar, Croatia

The aim of this study was to examine frequencies and haplotypic associations of HLA class II alleles in autochthonous population of Gorski kotar (Croatia). HLA-DRB1, -DQA1 and -DQB1 alleles were determined by DNA based PCR typing in 63 unrelated inhabitants from Gorski kotar whose parents and ancestors were born and lived in tested area for at least over four generations. A total of 13 HLA-DRB1, 12 DQA1 and 14 DQB1 alleles were identified. The most frequent HLA class II genes in Gorski kotar population are: HLA-DRB1*13 (af = 0.150), -DRB1*03 (af = 0.142), -DRB1*07 (af = 0.119), and -DRB1*11 (af = 0.119), HLA-DQA1*0501 (af = 0.278), -DQA1*0102 (af = 0.183), -DQA1*0201 (af = 0.127) and HLA-DQB1*0301 (af = 0.157), -DQB1*0201 (af = 0.139), -DQB1*0501 (af = 0.111). We have identified 24 HLA class II three-locus haplotypes. The most common haplotypes in Gorski kotar population are DRB1*03-DQA* 0501-DQB1*0201 (0.120), DRB1*11-DQA1*0501-DQB1*0301 (0.111) and DRB1*07-DQA1*0201-DQB1*0202 (0.094). The allelic frequencies and populations distance dendrogram revealed the closest relationships of Gorski kotar population with Slovenians, Germans, Hungarians and general Croatian population, which is the result of turbulent migrations within this microregion during history.     

Analysis of normal human tonsil class II antigen glycosylation by lectin affinity chromatography

Human class II molecules include the HLA-DR, -DQ, and -DP alloantigens. Each class II molecule consists of two glycosylated polypeptide chains, the alpha chain and the beta chain. We have used lectin affinity analysis to investigate the glycosylation pattern of [3H]mannose-labeled glycopeptides derived from isolated alpha and beta chains of HLA-DR and -DQ molecules of normal tonsil cells. Glycopeptides obtained by Pronase digestion of each isolated chain were passed sequentially over columns of immobilized concanavalin A, Lens culinaris lectin, and phytohemagglutinins E and L in a prescribed manner to generate a lectin affinity profile which could be used to assign a minimal oligosaccharide structure for each glycopeptide studied. The data presented here demonstrate that a given class II polypeptide chain can bear several different oligosaccharides. Comparison of the glycosylation patterns of the HLA-DR and -DQ molecules shows that they are similar in most respects. However, there are qualitative differences in the oligosaccharides borne by HLA-DQ and -DR molecules. In addition, comparison between HLA-DQ and the homologous murine I-A molecules shows species-specific glycosylation patterns.     

P1 and P2 protein heterodimer binding to the P0 protein of Saccharomyces cerevisiae is relatively non-specific and a source of ribosomal heterogeneity

The ribosomal stalk is formed by four acidic phosphoproteins in Saccharomyces cerevisiae, P1α, P1β, P2α and P2β, which form two heterodimers, P1α/P2β and P1β/P2α, that preferentially bind to sites A and B of the P0 protein, respectively. Using mutant strains carrying only one of the four possible P1/P2 combinations, we found a specific phenotype associated to each P1/P2 pair, indicating that not all acidic P proteins play the same role. The absence of one P1/P2 heterodimer reduced the rate of cell growth by varying degrees, depending on the proteins missing. Synthesis of the 60S ribosomal subunit also decreased, particularly in strains carrying the unusual P1α-P2α or P1β-P2β heterodimers, although the distinct P1/P2 dimers are bound with similar affinity to the mutant ribosome. While in wild-type strains the B site bound P1β/P2α in a highly specific manner and the A site bound the four P proteins similarly, both the A and B binding sites efficiently bound practically any P1/P2 pair in mutant strains expressing truncated P0 proteins. The reported results support that while most ribosomes contain a P1α/P2β-P0-P1β/P2α structure in normal conditions, the stalk assembly mechanism can generate alternative compositions, which have been previously detected in the cell.     

Langerhans cells that have matured in vivo in the absence of T cells are fully capable of inducing a helper CD4 as well as a cytotoxic CD8 response

Langerhans cells (LCs) are immature dendritic cells (DCs) present in the skin epithelium. Upon Ag exposure, they migrate to the draining lymph nodes where they mature into potent stimulators of naive T cells. The aim of this study was to investigate the influence of T cells on LC migration and maturation. Therefore, the in vivo migration and maturation of LCs after sensitization with the hapten FITC was compared between C57BL/6 or BALB/c mice used as positive controls, and recombination activating gene (RAG) 1 knockout (-/-) mice or SCID mice used as T cell-deficient mice. Phenotypically, there was no difference between migrated LCs from RAG1-/- or SCID mice vs normal C57BL/6 or BALB/c mice: both populations of FITC+ cells had a dendritic morphology and a mature phenotype as they expressed high levels of MHC class II molecules and costimulatory molecules CD80, CD86, and CD54. Sorted migrated LCs of RAG1-/- or SCID mice were efficient stimulators of allogeneic T cells and Ag-specific CD4+ T cells. The same results were found if migrated LCs were fixed instead of irradiated, excluding the possibility that LCs derived from RAG1-/- or SCID mice would mature in the presence of T cells during the stimulation tests. Importantly, fixed migrated LCs of RAG1-/- mice were also efficient stimulators of cytotoxic CD8+ T cells. These data suggest that T cells are not required for full maturation of LCs.     

Association with beta 2-microglobulin controls the expression of transfected human class I genes

The genes encoding HLA-B27K and HLA-B27W were transfected into murine recipient cells. A monoclonal antibody HC-10, directed against free B-locus heavy chain, was the only reagent capable of efficiently detecting the HLA-B27 heavy chains in detergent lysates. These heavy chains were devoid of sialic acid. Trace amounts of HLA-B27 could be isolated with the anti-HLA-A,-B antibody W6/32, which reacts with the heavy chain beta 2-microglobulin complex. In marked contrast, HLA-A2 and -B7 genes, when transfected, yielded easily detectable amounts of antigen precipitable with W6/32, which carried the usual complement of sialic acids. Because the alpha 3 domains of HLA-B27 and HLA-B7 and the more COOH-terminal portions are identical in amino acid sequence, structural elements in the polymorphic alpha 1 and alpha 2 domains must control association of heavy chain with beta 2-microglobulin. Introduction of a human beta 2-microglobulin gene into L cells transfected with the HLA-B27 gene rescued the expression of HLA-B27 at the cell surface, as evidenced by reactivity with W6/32, surface staining, and the presence of sialic acid on the heavy chain.     

Dominance of an alternative CLIP sequence in the celiac disease associated HLA-DQ2 molecule

During assembly, HLA class II molecules associate with the invariant chain. As the result, the peptide-binding groove is occupied by an invariant chain peptide termed CLIP (class-II-associated invariant chain peptide; sequence MRMATPLLM). By mass spectrometry, we have now characterized peptides that are naturally present in HLA-DQ2. This analysis revealed that 22 variants of Ii-derived peptides are associated with HLA-DQ2. Strikingly, the large majority of those do not contain the conventional CLIP sequence MRMATPLLM, but instead a peptide that partially overlaps with CLIP, sequence TPLLMQALPM. Peptide binding studies indicate that this alternative CLIP peptide has superior HLA-DQ2 binding properties compared to the conventional CLIP and that the minimal nine-amino-acid binding core consists of the sequence PLLMQALPM, findings that could be corroborated by molecular simulation. The alternative CLIP peptide was also found to be present in HLA-DQ2 molecules isolated from human thymus. Moreover, the alternative CLIP peptide was also found in association with HLA-DQ8. Together, these results indicate that HLA-DQ2 and HLA-DQ8 associate with an alternative CLIP sequence, a property that may relate to the strong association between HLA-DQ molecules and human autoimmune diseases.     

Expression of the B7.1 costimulatory molecule on pancreatic beta cells abrogates the requirement for CD4 T cells in the development of type 1 diabetes

Although HLA-DQ8 has been implicated as a key determinant of genetic susceptibility to human type 1 diabetes, spontaneous diabetes has been observed in HLA-DQ8 transgenic mice that lack expression of murine MHC class II molecules (mII(-/-)) only when the potent costimulatory molecule, B7.1, is transgenically expressed on pancreatic beta cells. To study the contribution of HLA-DQ8 to the development of diabetes in this model, we crossed RIP-B7.1mII(-/-) mice with a set of transgenic mouse lines that differed in their HLA-DQ8 expression patterns on APC subpopulations, in particular dendritic cells and cortical thymic epithelial cells. Surprisingly, we found that even in the absence of HLA-DQ8 and CD4 T cells, a substantial fraction of the RIP-B7.1mII(-/-) mice developed diabetes. This disease process was remarkable for not only showing insulitis, but also inflammatory destruction of the exocrine pancreas with diffusely up-regulated expression of MHC class I and ICAM-1 molecules. Expression of HLA-DQ8 markedly increased the kinetics and frequency of diabetes, with the most severe disease in the lines with the highest levels of HLA-DQ8 on cortical thymic epithelial cells and the largest numbers of CD4 T cells. However, the adoptive transfer of diabetes was not HLA-DQ8-dependent and disease could be rapidly induced with purified CD8 T cells alone. Expression of B7.1 in the target tissue can thus dramatically alter the cellular and molecular requirements for the development of autoimmunity.     

Sequence and diversity of MHC <Emphasis Type="Italic">DQA</Emphasis> and<Emphasis Type="Italic"> DQB</Emphasis> genes of the owl monkey<Emphasis Type="Italic"> Aotus nancymaae</Emphasis>

The New World primate Aotus nancymaae has been recommended by the World Health Organization (WHO) as a model for evaluation of malaria vaccine candidates, given its susceptibility to experimental infection with the human malaria parasites Plasmodium falciparum and Plasmodium vivax. We present here the nucleotide sequences of the complete cDNA of MHC-DQA1 and of the polymorphic exon 2 segments of MHC-DQB1/DQB2. In a group of three nonrelated animals captured in the wild, five alleles of MHC-DQA1 could be identified. They all belong to one lineage, namely Aona-DQA1*27. This lineage has not been described in any other New World monkey species studied. In a group of 19 unrelated animals, 14 Aona-DQB1 alleles could be identified which are grouped into the two lineages Aona-DQB1*22 and Aona-DQB1*23. These lineages have been described previously in the common marmoset and cotton-top tamarin. In addition, two Aona-DQB2 sequences could be identified which are highly similar to HLA-DQB2 sequences. Essential amino acid residues contributing to MHC DQ peptide binding pockets number 1 and 4 are conserved or semi-conserved between HLA-DQ and Aona-DQ molecules, indicating a capacity to bind similar peptide repertoires. These results fully support the use of Aotus monkeys as an animal model for evaluation of future subunit vaccine candidates.