DRB Genes Research Articles

Characterization of major histocompatibility complex DRA and DRB genes of the forest musk deer (Moschus berezovskii)

The forest musk deer (Moschus berezovskii) is one of the most endangered species in China. Over the past decades, extensive hunting and poaching have pushed the forest musk deer to the edge of extinction, and conservation biologists are presently pursuing scientific management plans to rescue this species. The major histocompatibility complex (MHC), a cluster of genes responsible for antigen presentation, is a highly polymorphic genomic region in vertebrates that has become a popular functional marker system for studying adaptive variation. In this study, we developed locus-specific genotyping primers for exon 2 fragments of one DRA gene and one DRB locus of the forest musk deer using a suite of comprehensive methods that included universal primer amplification, genome walking, single-strand conformation polymorphism (SSCP), heteroduplex (HD) profiling, and sequence analysis. Each forest musk deer showed no more than two sequences per locus, confirming the specificity of our primers. Genotyping with these primers allowed us to identify two DRA alleles and six DRB alleles in a captive breeding population of the Sichuan Musk Deer Breeding Institution. For the DRA locus, we found a slightly higher observed heterozygosity (NO=0.154) than expected (NE=0.143). In contrast, the DRB locus showed a significant heterozygote deficiency (NO=0.508; NE=0.761; P<0.05), which was probably due to inbreeding in the captive population. An obvious excess of nonsynonymous substitutions over synonymous was observed at the antigen-binding positions of the DRA and DRB loci, showing the presence of positive selection in the forest musk deer DR genes. Finally, generation of phylogenetic trees for the DRA and DRB sequences of the forest musk deer and other ruminants revealed that the DRA and DRB loci identified in this study had homologous relationships with the known ruminant DRA and DRB genes. Based on this analysis, and to facilitate future studies, we named these novel loci Mobe-DRA and Mobe-DRB3.

The functional importance of sequence versus expression variability of MHC alleles in parasite resistance

Understanding selection processes driving the pronounced allelic polymorphism of the major histocompatibility complex (MHC) genes and its functional associations to parasite load have been the focus of many recent wildlife studies. Two main selection scenarios are currently debated which explain the susceptibility or resistance to parasite infections either by the effects of (1) specific MHC alleles which are selected frequency-dependent in space and time or (2) a heterozygote or divergent allele advantage. So far, most studies have focused only on structural variance in co-evolutionary processes although this might not be the only trait subject to natural selection. In the present study, we analysed structural variance stretching from exon1 through exon3 of MHC class II DRB genes as well as genotypic expression variance in relation to the gastrointestinal helminth prevalence and infection intensity in wild yellow-necked mice (Apodemus flavicollis). We found support for the functional importance of specific alleles both on the sequence and expression level. By resampling a previously investigated study population we identified specific MHC alleles affected by temporal shifts in parasite pressure and recorded associated changes in allele frequencies. The allele Apfl-DRB*23 was associated with resistance to infections by the oxyurid nematode Syphacia stroma and at the same time with susceptibility to cestode infection intensity. In line with our expectation, MHC mRNA transcript levels tended to be higher in cestode-infected animals carrying the allele Apfl-DRB*23. However, no support for a heterozygote or divergent allele advantage on the sequence or expression level was detected. The individual amino acid distance of genotypes did not explain individual differences in parasite loads and the genetic distance had no effect on MHC genotype expression. For ongoing studies on the functional importance of expression variance in parasite resistance, allele-specific expression data would be preferable.

IgG Autoantibody Response against Keratinocyte Cadherins in Endemic Pemphigus Foliaceus (Fogo Selvagem)

It is well established that autoantibodies against desmoglein 3 and desmoglein 1 are relevant in the pathogenesis of pemphigus vulgaris and pemphigus foliaceus, including its endemic form, Fogo Selvagem (FS). Isolated reports have shown that in certain patients with these diseases, autoantibodies against other desmosomal cadherins and E-cadherin may also be present. The goal of this investigation was to determine if FS patients and normal individuals living in endemic areas possess autoantibodies against other desmosomal cadherins and E-cadherin. Testing a large number of FS and endemic control sera by ELISA we find a consistent and specific autoantibody response against desmoglein 1 and other keratinocyte cadherins in these individuals, which is quite different from US controls. Overall, the highest correlations among the autoantibody responses tested are in the endemic controls, followed by FS patients, and lowest in the US controls. These findings suggest that multiple, perhaps cross reactive, keratinocyte cadherins are recognized by FS patients and endemic controls.

Genetic diversity analysis of DRB3.2 in domestic yak (Bos grunniens) in Qinghai-Tibetan Plateau

DRB3 gene has been extensively evaluated as a candidate marker for association with many bovine disease and immunological traits. A hemi-nested polymerase chain reaction-sequencing method was used to investigate the polymorphisms of DRB3.2 gene from 209 individuals in three different domestic yak ( Bos grunniens ) populations (62 Tianzhu white yaks, 78 Gannan yaks and 69 Datong yaks) from the Qinghai-Tibetan Plateau. Sixty-three polymorphic sites and 143 haplotypes were detected. The percentage of polymorphic sites in Gannan Yak (GNY), Tianzhu white Yak (TWY) and Datong Yak (DTY) were 21.80, 29.95 and 12.95%, while the haplotype diversity were 0.9987, 0.9984 and 0.9855, respectively. At the amino acid level, Glu had the highest content; the percentage was 12.326%, followed by Arg (10.315%), Phe (10.804%), Val (8.346%), Gly (8.315%), Leu (6.606%) and Ala (5.851%), whereas Met and Ile were below than 1%. Only 19 amino acids were found in DTY, Met was lost. Among the synonymous codons, whose third base was G and/or C had a higher usage frequency. Most variability were found in amino acid residues 11, 13, 26, 28, 30, 32, 37, 56, 57, 59, 60, 61, 67, 70, 71, 72, 73 and 74. In GNY, the residues at positions 71, 11 and 72 were highly polymorphic with 8, 7 and 7, at 50, 58, 70, 74 and 78, the residues were selectively polymorphic than other yak populations; the other polymorphic sites were common in the populations. The results of this study indicated that the Chinese domestic yak populations in the Qinghai-Tibetan Plateau have abundant polymorphism in DRB3.2, and the GNY was the highest, followed by TWY and DTY. Key words: Domestic Yak, Hemi-nested PCR, BoLA-DRB3.2, polymorphism.

Comparison of 454 pyrosequencing methods for characterizing the major histocompatibility complex of nonmodel species and the advantages of ultra deep coverage

Characterization and population genetic analysis of multilocus genes, such as those found in the major histocompatibility complex (MHC) is challenging in nonmodel vertebrates. The traditional method of extensive cloning and Sanger sequencing is costly and time-intensive and indirect methods of assessment often underestimate total variation. Here, we explored the suitability of 454 pyrosequencing for characterizing multilocus genes for use in population genetic studies. We compared two sample tagging protocols and two bioinformatic procedures for 454 sequencing through characterization of a 185-bp fragment of MHC DRB exon 2 in wolverines (Gulo gulo) and further compared the results with those from cloning and Sanger sequencing. We found 10 putative DRB alleles in the 88 individuals screened with between two and four alleles per individual, suggesting amplification of a duplicated DRB gene. In addition to the putative alleles, all individuals possessed an easily identifiable pseudogene. In our system, sequence variants with a frequency below 6% in an individual sample were usually artefacts. However, we found that sample preparation and data processing procedures can greatly affect variant frequencies in addition to the complexity of the multilocus system. Therefore, we recommend determining a per-amplicon-variant frequency threshold for each unique system. The extremely deep coverage obtained in our study (approximately 5000×) coupled with the semi-quantitative nature of pyrosequencing enabled us to assign all putative alleles to the two DRB loci, which is generally not possible using traditional methods. Our method of obtaining locus-specific MHC genotypes will enhance population genetic analyses and studies on disease susceptibility in nonmodel wildlife species.

MHC influences infection with parasites and winter survival in the root vole Microtus oeconomus

Selective pressure from parasites is thought to maintain the polymorphism of major histocompatibility complex (MHC) genes. Although a number of studies have shown a relationship between the MHC and parasitic infections, the fitness consequences of such associations are less well documented. In the present paper, we characterised the variation in exon 2 of MHC class II DRB gene in the root vole and examined the effects of that gene on parasite prevalence and winter survival. We identified 18 unique exon 2 sequences, which translated into 10 unique amino acid sequences. Phylogenetic analysis revealed the presence of three distinct clusters, and allele distributions among these individuals suggested that the clusters correspond to three different loci. Although the rate of synonymous substitutions (dS) exceeded the rate of nonsynonymous substitutions (dN) across sequences, implying purifying selection, dN was significantly elevated at antigen-binding sites, suggesting that these sites could be under positive selection. Screening for parasites revealed a moderate prevalence of infection with gastrointestinal parasites (24 % infected), but a high infection rate for blood parasites (56 % infected). Infection with the blood parasite Babesia ssp. decreased survival almost twofold (25.7 vs. 13.9 %). Animals possessing the amino acid sequence AA*08 survived better than others (44.9 vs. 22 %), and they were infected with Babesia ssp. less often (13.9 vs 25.7 %). In contrast, individuals carrying allele AA*05 were infected more often (31.7 vs. 15.3 %). Heterozygosity at one of the putative loci was associated with a lower probability of infection with Babesia ssp., but at the other locus, the association was reversed. The unexpected latter result could be at least partly explained by the increased frequency of the susceptible allele AA*05 among heterozygotes. Overall, we demonstrate that infection with Babesia ssp. is a strong predictor of winter survival and that MHC genes are important predictors of infection status as well as survival in the root vole.

Evolution of major histocompatibility complex class I and class II genes in the brown bear.

BackgroundMajor histocompatibility complex (MHC) proteins constitute an essential component of the vertebrate immune response, and are coded by the most polymorphic of the vertebrate genes. Here, we investigated sequence variation and evolution of MHC class I and class II DRB, DQA and DQB genes in the brown bear Ursus arctos to characterise the level of polymorphism, estimate the strength of positive selection acting on them, and assess the extent of gene orthology and trans-species polymorphism in Ursidae.ResultsWe found 37 MHC class I, 16 MHC class II DRB, four DQB and two DQA alleles. We confirmed the expression of several loci: three MHC class I, two DRB, two DQB and one DQA. MHC class I also contained two clusters of non-expressed sequences. MHC class I and DRB allele frequencies differed between northern and southern populations of the Scandinavian brown bear. The rate of nonsynonymous substitutions (dN) exceeded the rate of synonymous substitutions (dS) at putative antigen binding sites of DRB and DQB loci and, marginally significantly, at MHC class I loci. Models of codon evolution supported positive selection at DRB and MHC class I loci. Both MHC class I and MHC class II sequences showed orthology to gene clusters found in the giant panda Ailuropoda melanoleuca.ConclusionsHistorical positive selection has acted on MHC class I, class II DRB and DQB, but not on the DQA locus. The signal of historical positive selection on the DRB locus was particularly strong, which may be a general feature of caniforms. The presence of MHC class I pseudogenes may indicate faster gene turnover in this class through the birth-and-death process. South–north population structure at MHC loci probably reflects origin of the populations from separate glacial refugia.

Search for schizophrenia susceptibility variants at the HLA-DRB1 locus among a British population

Schizophrenia is a complex mental disorder with unknown aetiology. Both candidate gene and genome-wide association (GWA) studies suggest that the human leukocyte antigen (HLA) system may play a part in development of the illness, but the causal HLA variant(s) remain(s) unclear. Previous studies showed that the DRB1*0101 and DRB1*13 alleles might be associated with a high risk of schizophrenia. Therefore, the present study was undertaken to test their association with the disease by genotyping seven DRB1-tagging single nucleotide polymorphisms (SNPs) in a British population. The results showed that, of the previously reported variants that were associated with schizophrenia, the DRB1*1303 allele was the only one marginally associated with a protective effect on the illness in our sample set (χ² = 4.138, P = 0.042, odds ratio (OR) = 0.42, 95 % confidence interval (CI) 0.27-0.66). Interestingly, a significant association was found for rs424232 (χ² = 9.404, P = 0.002, OR = 0.69, 95 % CI 0.54-0.88), which is a tag SNP for the DRB1*1303 allele and located near to the NOTCH4 gene that is a schizophrenia susceptibility locus confirmed by GWA studies. Analysis with the Haploview program demonstrated that rs424232 was in complete linkage disequilibrium with rs3130297 and rs3131296 present in the NOTCH4 locus. While we have failed to confirm association of the candidate alleles in the DRB1 gene with a high risk of schizophrenia, the present work suggests that the association signal detected in the HLA class II locus may extend a relatively long distance, and more work is needed in order to identify the true causal variants within this region or nearby.

Allele variants of HLA II genes DRB1 and DQB1 regarding risk for type 1 diabetes mellitus in population of Bashkortostan

Aims. To estimate significance of HLA II DRB1 and DRB2 allele variants for development of type 1 diabetes mellitus (T1DM) in Bashkortostanpopulation (ethnical Russians, Tatar, Bashkir). Materials and methods. We analyzed DNA of 323 patients with T1DM and 683 healthy controls. DNA was derived from venous bloodsamples by phenol-chloroform extraction. DRB1 and DQB1 gene typing was performed by PCR method. Amplification products wereidentified with electrophoresis on a 1% agarose gel. Statistica for Windows v6.0 and MS Excel 98 software were applied for statisticalprocessing of acquired data. Results. Common markers of high risk for T1DM were found to be DRB1*04, DRB1*17, genotype DRB1*04/*17. On the contrary,lower risk was associated with DRB1*15 allele. In ethnical Russians lower risk of T1DM is also determined by DRB1*11 allele andDRB1*01 in Tatars. Predisposition by DQB1-alleles in Russians and Bashkir realizes only within DRB1*04/*17 genotype. However,in Tatar subpopulation DQB1*0302 is an independent risk marker of T1DM development. Conclusion. Common low risk markers for all three ethnic groups are DQB1*0301, DQB1*0602-08 alleles. Their presence negates riskof disease in all studied subpopulations even within DRB1*04/*17-genotype.

Large-scale MHC class II genotyping of a wild lemur population by next generation sequencing

The critical role of major histocompatibility complex (MHC) genes in disease resistance, along with their putative function in sexual selection, reproduction and chemical ecology, make them an important genetic system in evolutionary ecology. Studying selective pressures acting on MHC genes in the wild nevertheless requires population-wide genotyping, which has long been challenging because of their extensive polymorphism. Here, we report on large-scale genotyping of the MHC class II loci of the grey mouse lemur (Microcebus murinus) from a wild population in western Madagascar. The second exons from MHC-DRB and -DQB of 772 and 672 individuals were sequenced, respectively, using a 454 sequencing platform, generating more than 800,000 reads. Sequence analysis, through a stepwise variant validation procedure, allowed reliable typing of more than 600 individuals. The quality of our genotyping was evaluated through three independent methods, namely genotyping the same individuals by both cloning and 454 sequencing, running duplicates, and comparing parent–offspring dyads; each displaying very high accuracy. A total of 61 (including 20 new) and 60 (including 53 new) alleles were detected at DRB and DQB genes, respectively. Both loci were non-duplicated, in tight linkage disequilibrium and in Hardy–Weinberg equilibrium, despite the fact that sequence analysis revealed clear evidence of historical selection. Our results highlight the potential of 454 sequencing technology in attempts to investigate patterns of selection shaping MHC variation in contemporary populations. The power of this approach will nevertheless be conditional upon strict quality control of the genotyping data.

HLA class II susceptibility to cervical cancer among Tunisian women

The variability in host immunogenetic background, especially in human major histocompatibilty genes, has been shown to influence the susceptibility to human papillomavirus (HPV) infection and cervical neoplasia. Here, we conducted a case-control study in Tunisian women to examine the effect of genetic variation in HLA class II DRB1 and DQB1 genes on invasive cervical cancer (ICC) and squamous cell carcinoma (SCC). HLA genotyping was performed by PCR sequence-specific primers technique. The data revealed significant positive and negative associations, suggesting either predisposing or protective effects of these genes in the disease outcome. DRB1*15, alone or linked to DQB1*06, was associated with a 2.7- and 3.5-fold increase in risk for ICC, respectively. DRB1*13-DQB1*03 showed a similar 3.5 risk effect. Concerning SCC, we observed a relatively higher, about 1.2 times more, risk effect for these genetic markers. In contrast, only one haplotype – DRB1*13-DQB1*06 – provides evidence for a weak protection (about 0.3-fold reduction) of ICC and SCC. In conclusion, we suggest that HLA class II polymorphisms are involved in the genetic susceptibility to cervical cancer in Tunisian women.

Vitamin D Responsive Elements within the HLA-DRB1 Promoter Region in Sardinian Multiple Sclerosis Associated Alleles

Vitamin D response elements (VDREs) have been found in the promoter region of the MS-associated allele HLA-DRB1*15∶01, suggesting that with low vitamin D availability VDREs are incapable of inducing *15∶01 expression allowing in early life autoreactive T-cells to escape central thymic deletion. The Italian island of Sardinia exhibits a very high frequency of MS and high solar radiation exposure. We test the contribution of VDREs analysing the promoter region of the MS-associated DRB1 *04∶05, *03∶01, *13∶01 and *15∶01 and non-MS-associated *16∶01, *01, *11, *07∶01 alleles in a cohort of Sardinians (44 MS patients and 112 healthy subjects). Sequencing of the DRB1 promoter region revealed a homozygous canonical VDRE in all *15∶01, *16∶01, *11 and in 45/73 *03∶01 and in heterozygous state in 28/73 *03∶01 and all *01 alleles. A new mutated homozygous VDRE was found in all *13∶03, *04∶05 and *07∶01 alleles. Functionality of mutated and canonical VDREs was assessed for its potential to modulate levels of DRB1 gene expression using an in vitro transactivation assay after stimulation with active vitamin D metabolite. Vitamin D failed to increase promoter activity of the *04∶05 and *03∶01 alleles carrying the new mutated VDRE, while the *16∶01 and *03∶01 alleles carrying the canonical VDRE sequence showed significantly increased transcriptional activity. The ability of VDR to bind the mutant VDRE in the DRB1 promoter was evaluated by EMSA. Efficient binding of VDR to the VDRE sequence found in the *16∶01 and in the *15∶01 allele reduced electrophoretic mobility when either an anti-VDR or an anti-RXR monoclonal antibody was added. Conversely, the Sardinian mutated VDRE sample showed very low affinity for the RXR/VDR heterodimer. These data seem to exclude a role of VDREs in the promoter region of the DRB1 gene in susceptibility to MS carried by DRB1* alleles in Sardinian patients.

Evolution of HLA-DRB Genes

The HLA region shows diversity concerning the number and content of DRB genes present per haplotype. Similar observations are made for the equivalent regions in other primate species. To elucidate the evolutionary history of the various HLA-DRB genes, a large panel of intron sequences obtained from humans, chimpanzees, rhesus macaques, and common marmosets has been subjected to phylogenetic analyses. Special attention was paid to the presence and absence of particular transposable elements and/or to their segments. The sharing of different parts of the same long interspersed nuclear element-2 (LINE2, L2) and various Alu insertions by the species studied demonstrates that one precursor gene must have been duplicated several times before the Old World monkey (OWM) and hominid (HOM) divergence. At least four ancestral DRB gene families appear to have been present before the radiation of OWM and HOM, and one of these even predates the speciation of Old and New World primates. Two of these families represent the pseudogenes DRB6/DRB2 and DRB7, which have been locked in the genomes of various primate species over long evolutionary time spans. Furthermore, all phylogenies of different intron segments show consistently that, apart from the pseudogenes, only DRB5 genes are shared by OWM and HOM, and they demonstrate the common history of certain DRB genes/lineages of humans and chimpanzees. In contrast, the evolutionary history of some other DRB loci is difficult to decipher, thus illustrating the complex history of the evolution of DRB genes due to a combination of mutations and recombination-like events. The selected approach allowed us to shed light on the ancestral DRB gene pool in primates and on the evolutionary relationship of the various HLA-DRB genes.

Possible Extinction Vortex for a Population of Iberian Lynx on the Verge of Extirpation

Theory suggests that demographic and genetic traits deteriorate (i.e., fitness and genetic diversity decrease) when populations become small, and that such deterioration could precipitate positive feedback loops called extinction vortices. We examined whether demographic attributes and genetic traits have changed over time in one of the 2 remaining small populations of the highly endangered Iberian lynx (Lynx pardinus) in Doñana, Spain. From 1983 to 2008, we recorded nontraumatic mortality rates, litter size, offspring survival, age at territory acquisition, and sex ratio. We combined these demographic attributes with measures of inbreeding and genetic diversity at neutral loci (microsatellites) and genes subjected to selection (major histocompatibility complex). Data on demographic traits were obtained through capture and radio tracking, checking dens during breeding, track surveys, and camera trapping. For genetic analyses, we obtained blood or tissue samples from captured or necropsied individuals or from museum specimens. Over time a female-biased sex ratio developed, age of territory acquisition decreased, mean litter size decreased, and rates of nontraumatic mortality increased, but there were no significant changes in overall mortality rates, standardized individual heterozygosity declined steadily, and allelic diversity of exon 2 of class II major histocompatibility complex DRB genes remained constant (2 allelic variants present in all individuals analyzed). Changes in sex ratio and age of territory acquisition may have resulted from demographic stochasticity, whereas changes in litter size and nontraumatic mortality may be related to observed increases in inbreeding. Concomitant deterioration of both demographic attributes and genetic traits is consistent with an extinction vortex. The co-occurrence, with or without interaction, of demographic and genetic deterioration may explain the lack of success of conservation efforts with the Doñana population of Iberian lynx.

Distribution of HLA-A, -B and -DRB1 Genes and Haplotypes in the Tujia Population Living in the Wufeng Region of Hubei Province, China

BackgroundThe distribution of HLA alleles and haplotypes varies widely between different ethnic populations and geographic areas. Before any genetic marker can be used in a disease-associated study it is therefore essential to investigate allelic frequencies and establish a genetic database.Methodology/Principal FindingsThis is the first report of HLA typing in the Tujia group using the Luminex HLA-SSO method HLA–A, –B and -DRB1 allelic distributions were determined in 124 unrelated healthy Tujia individuals, and haplotypic frequencies and linkage disequilibrium parameters were estimated using the maximum-likelihood method. In total 10 alleles were detected at the HLA–A locus, 21 alleles at the HLA–B locus and 14 alleles at the HLA-DRB1 locus. The most frequently observed alleles in the HLA-I group were HLA–A*02 (35.48%), A*11 (28.23%), A*24 (15.73%); HLA–B*40 (25.00%), B*46 (16.13%), and B*15 (15.73%). Among HLA-DRB1 alleles, high frequencies of HLA-DRB1*09 (25.81%) were observed, followed by HLA-DRB1*15 (12.9%), and DRB1*12 (10.89%). The two-locus haplotypes at the highest frequency were A*02–B*46A (8.47%), followed by A*11–B*40 (7.66%), A*02–B*40 (8.87%), A*11–B*15 (6.45%), A*02–B*15 (6.05%), B*40–DRB1*09 (9.27%) and B*46–DRB1*09 (6.45%). The most common three-locus haplotypes found in the Tujia population were A*02–B*46–DRB1*09 (4.84%) and A*02–B*40–DRB1*09 (4.03%). Fourteen two-loci haplotypes had significant linkage disequilibrium. Construction of a neighbor-joining phylogenetic tree and principal component analysis using the allelic frequencies at HLA-A was performed to compare the Tujia group and twelve other previously reported populations. The Tujia population in the Wufeng of Hubei Province had the closest genetic relationship with the central Han population, and then to the Shui, the Miao, the southern Han and the northern Han ethnic groups.Conclusions/SignificanceThese results will become a valuable source of data for tracing population migration, planning clinical organ transplantation, carrying out HLA-linked disease-associated studies and forensic identification.

A Multicentre Study of Acute Kidney Injury in Severe Sepsis and Septic Shock: Association with Inflammatory Phenotype and HLA Genotype

BackgroundTo investigate the association between severity of acute kidney injury (AKI) and outcome, systemic inflammatory phenotype and HLA genotype in severe sepsis.Methodology/Principal FindingsProspective multicenter observational study done in 4 intensive care units in two university hospitals. Severe sepsis and septic shock patients with at least 2 organ failures based on the SOFA score were classified: 1) "no AKI", 2) "mild AKI" (grouping stage 1 and 2 of AKIN score) and 3) "severe AKI" (stage 3 of AKIN score). Sequential measurements: The vasopressor dependency index (VDI; dose and types of drugs) to evaluate the association between hemodynamic status and the development of early AKI; plasma levels of IL-10, macrophage migration inhibitory factor (MIF), IL-6 and HLA-DR monocyte expression. Genotyping of the 13 HLA-DRB1 alleles with deduction of presence of HLA-DRB3, -DRB4 and -DRB5 genes. We used multivariate analysis with competitive risk model to study associations. Overall, 176 study patients (146 with septic shock) were classified from AKIN score as "no AKI" (n = 43), "mild AKI" (n = 74) or "severe AKI" (n = 59). The VDI did not differ between groups of AKI. After adjustment, "mild and severe AKI" were an independent risk factor for mortality (HR 2.42 95%CI[1.01-5.83], p = 0.048 and HR 1.99 95%CI[1.30-3.03], p = 0.001 respectively). "Severe AKI" had higher levels of plasma IL-10, MIF and IL-6 compared to “no AKI” and mild AKI (p<0.05 for each), with no difference in mHLA-DR at day 0. HLA-DRB genotyping showed a significantly lower proportion of 4 HLA-DRB alleles among patients requiring renal replacement therapy (RRT) (58%) than in patients with severe AKI who did not receive RRT (84%) (p = 0.004).ConclusionsAKI severity is independently associated with mortality and plasma IL-10, MIF or IL-6 levels. Presence of 4 alleles of HLA-DRB in severe AKI patients seems associated with a lower need of RRT.

Contrasting patterns of selection acting on MHC class I and class II DRB genes in the Alpine marmot (Marmota marmota)

The major histocompatibility complex (MHC) genes code for proteins that play a critical role in the immune system response. The MHC genes are among the most polymorphic genes in vertebrates, presumably due to balancing selection. The two MHC classes appear to differ in the rate of evolution, but the reasons for this variation are not well understood. Here, we investigate the level of polymorphism and the evolution of sequences that code for the peptide-binding regions of MHC class I and class II DRB genes in the Alpine marmot (Marmota marmota). We found evidence for four expressed MHC class I loci and two expressed MHC class II loci. MHC genes in marmots were characterized by low polymorphism, as one to eight alleles per putative locus were detected in 38 individuals from three French Alps populations. The generally limited degree of polymorphism, which was more pronounced in class I genes, is likely due to bottleneck the populations undergone. Additionally, gene duplication within each class might have compensated for the loss of polymorphism at particular loci. The two gene classes showed different patterns of evolution. The most polymorphic of the putative loci, Mama-DRB1, showed clear evidence of historical positive selection for amino acid replacements. However, no signal of positive selection was evident in the MHC class I genes. These contrasting patterns of sequence evolution may reflect differences in selection pressures acting on class I and class II genes.

High-throughput, high-fidelity HLA genotyping with deep sequencing

Human leukocyte antigen (HLA) genes are the most polymorphic in the human genome. They play a pivotal role in the immune response and have been implicated in numerous human pathologies, especially autoimmunity and infectious diseases. Despite their importance, however, they are rarely characterized comprehensively because of the prohibitive cost of standard technologies and the technical challenges of accurately discriminating between these highly related genes and their many allelles. Here we demonstrate a high-resolution, and cost-effective methodology to type HLA genes by sequencing, which combines the advantage of long-range amplification, the power of high-throughput sequencing platforms, and a unique genotyping algorithm. We calibrated our method for HLA-A, -B, -C, and -DRB1 genes with both reference cell lines and clinical samples and identified several previously undescribed alleles with mismatches, insertions, and deletions. We have further demonstrated the utility of this method in a clinical setting by typing five clinical samples in an Illumina MiSeq instrument with a 5-d turnaround. Overall, this technology has the capacity to deliver low-cost, high-throughput, and accurate HLA typing by multiplexing thousands of samples in a single sequencing run, which will enable comprehensive disease-association studies with large cohorts. Furthermore, this approach can also be extended to include other polymorphic genes.

Classical HLA-DRB1 and DPB1 alleles account for HLA associations with primary biliary cirrhosis

Susceptibility to primary biliary cirrhosis (PBC) is strongly associated with HLA region polymorphisms. To determine if associations can be explained by classical HLA determinants we studied Italian 676 cases and 1440 controls with genotyped with dense single nucleotide polymorphisms (SNPs) for which classical HLA alleles and amino acids were imputed. Although previous genome-wide association studies and our results show stronger SNP associations near DQB1, we demonstrate that the HLA signals can be attributed to classical DRB1 and DPB1 genes. Strong support for the predominant role of DRB1 is provided by our conditional analyses. We also demonstrate an independent association of DPB1. Specific HLA-DRB1 genes (*08, *11 and *14) account for most of the DRB1 association signal. Consistent with previous studies, DRB1*08 (p = 1.59 × 10−11) was the strongest predisposing allele where as DRB1*11 (p = 1.42 × 10−10) was protective. Additionally DRB1*14 and the DPB1 association (DPB1*03:01) (p = 9.18 × 10−7) were predisposing risk alleles. No signal was observed in the HLA class 1 or class 3 regions. These findings better define the association of PBC with HLA and specifically support the role of classical HLA-DRB1 and DPB1 genes and alleles in susceptibility to PBC.

Low Major Histocompatibility Complex Class I (MHC I) Variation in the European Bison (Bison bonasus)

Variation in the major histocompatibility complex (MHC) class I of the European bison was characterized in a sample of 99 individuals using both classical cloning/Sanger sequencing and 454 pyrosequencing. Three common (frequencies: 0.348, 0.328, and 0.283) haplotypes contain 1-3 classical class I loci. A variable and difficult to estimate precisely number of nonclassical transcribed loci, pseudogenes, and/or gene fragments were also found. The presence of additional 2 rare haplotypes (frequency of 0.020 each), observed only in heterozygotes, was inferred. The overall organization of MHC I appears similar to the cattle system, but genetic variation is much lower with only 7 classical class I alleles, approximately one-tenth of the number known in cattle and a quarter known in the American bison. An extensive transspecific polymorphism was found. MHC I is in a strong linkage disequilibrium with previously studied MHC II DRB3 gene. The most likely explanation for the low variation is a drastic bottleneck at the beginning of the 20th century. Genotype frequencies conformed to Hardy-Weinberg expectations, and no signatures of selection in contemporary populations but strong signatures of historical positive selection in sequences of classical alleles were found. A quick and reliable method of MHC I genotyping was developed.