HLA-G Genotype Research Articles

HLA-G UTR Haplotype Conservation in the Malian Population: Association with Soluble HLA-G

The HLA-G molecule plays an important role in immunomodulation. In a previous study carried out on a southern French population our team showed that HLA-G haplotypes, defined by SNPs in the coding region and specific SNPs located in 5′URR and 3′UTR regulatory regions, are associated with differential soluble HLA-G expression (sHLA-G). Furthermore, the structure of these HLA-G haplotypes appears to be conserved in geographically distant populations.The aim of our study is to confirm these expectations in a sub-Saharan African population and to explore additional factors, such as HLA-A alleles, that might influence sHLA-G expression.DNA and plasma samples were collected from 229 Malians; HLA-G and HLA-A genotyping were respectively performed by the Snap Shot® method and by Luminex™ technology. sHLA-G dosage was performed using an ELISA kit. HLA-G and HLA-A allelic and haplotypic frequencies were estimated using an EM algorithm from the Gene[Rate] program. Associations between genetic and non genetic parameters with sHLA-G were performed using a non-parametric test with GRAPH PAD Prism 5.Our results reveal a good conservation of the HLA-G UTR haplotype structure in populations with different origins and demographic histories. These UTR haplotypes appear to be involved in different sHLA-G expression patterns. Specifically, the UTR-2 haplotype was associated with low sHLA-G levels, displaying a dominant negative effect. Furthermore, an allelic effect of both HLA-G and HLA-A, as well as non genetic parameters, such as age and gender possibly linked to osteogenesis and sexual hormones, also seem to be involved in the modulation of sHLA-G.These data suggest that further investigation in larger cohorts and in populations from various ethnical backgrounds is necessary not only to detect new functional polymorphism in HLA-G regulatory regions, but also to reveal the extent of biological phenomena that influence sHLA-G secretion and this might therefore have an impact on transplantation practice.

88-P: HIGH FREQUENCY OF THE +3010 G AND +3142 C ALLELES OF THE 3’ UNTRANSLATED REGION OF THE HLA-G GENE AND VARIABLE LEVELS OF SOLUBLE sHLA-G IN CHILDHOOD ACUTE MYELOID LEUKEMIA

Polymorphisms at the 3’Untranslated region (UTR) of the HLA-G gene may influence the plasma sHLA-G. Although high levels of plasma sHLA-G have been associated with less favorable outcome in malignant hematological disorders, no information is available regarding sHLA-G in bone marrow aspirates. We evaluated the HLA-G 3’UTR allele, genotype and haplotype frequencies and bone marrow aspirate sHLA-G levels in patients exhibiting childhood acute myeloid leukemia. The HLA-G 3’UTR polymorphisms were studied in 109 children with acute myeloid leukemia followed-up at the IMIP Hospital in Recife, and 76 healthy children from the same Brazilian region. Leukemia cells were characterized by flow cytometry, and molecular biology for the detection of chromosomal translocation and gene mutations. The HLA-G polymorphism was detected by sequencing analysis and sHLA-G was detected by ELISA. Leukemia was classified in LMA-M5 (28%) and -M3 (23%) in most cases. Genetic alteration was identified in 55% of cases. Leukemia parameters of complete remission (56%), relapse (35%), second neoplasia (9%) and death (61%) illustrate the disease prognosis in this setting. The +3010 G-G ( p =0.007; OR=3.8) and +3142 C-C ( p = 0.003, OR=4.33) 3’UTR HLAG genotypes, and UTR-6 haplotype ( p = 0.019 and OR=4.63) were overrepresented in myeloid leukemia study group. Normal bone marrow of 12 children age 0 to 13 years showed average level of sHLA-G of 197 U/mL ± 23 U/mL, however, the. sHLA-G production in leukemic environmental was variable. From 40 pathological bone marrow analysed, 29 showed lower levels of sHLA-G, 7 presented high levels of sHLA-G and only 4 showed levels similar to the normal bone marrow control group. 3’UTR HLA-G alleles were associated with the development of childhood myeloid leukemia, however, the level of sHLA-G expression in leukemic environmental was highly variable in relation to the normal bone marrow.

AB0017 Hla-g 3′utr 14bp polymorphism and shla-g levels in tunisian patients with behçet’s disease

BackgroundBehcet’s disease (BD) is a chronic relapsing multisystemic inflammatory disease. Although the actual etiology is still unclear, BD symptoms are considered to be the resultant of genetic intrinsic factors and...

Maternal asthma and microRNA regulation of soluble HLA-G in the airway

We previously reported an interaction between maternal asthma and the child's HLA-G genotype on the child's subsequent risk for asthma. The implicated single nucleotide polymorphism at +3142 disrupted a target site for the microRNA (miR)-152 family. We hypothesized that the interaction effect might be mediated by these miRs. The objective of this study was to test this hypothesis in adults with asthma who are a subset of the same subjects who participated in our earlier family-based studies. We measured soluble HLA-G (sHLA-G) concentrations in bronchoalveolar lavage fluid (n = 36) and plasma (n = 57) from adult asthmatic subjects with and without a mother with asthma, and HLA-G and miR-152 family (miR-148a, miR-148b, and miR-152) transcript levels in airway epithelial cells from the same subjects. miR-148b levels were significantly increased in airway epithelial cells from asthmatic subjects with an asthmatic mother compared with those seen in asthmatic subjects without an asthmatic mother, and +3142 genotypes were associated with sHLA-G concentrations in bronchoalveolar lavage fluid among asthmatic subjects with an asthmatic mother but not among those with a nonasthmatic mother. Neither effect was observed in the plasma (sHLA-G) or white blood cells (miRNA). These combined results are consistent with +3142 allele-specific targeting of HLA-G by the miR-152 family and support our hypothesis that miRNA regulation of sHLA-G in the airway is influenced by both the asthma status of the subject's mother and the subject's genotype. Moreover, we demonstrate that the effects of maternal asthma on the gene regulatory landscape in the airways of the mother's children persist into adulthood.

Can HLA-G polymorphisms predict the development of cardiac allograft vasculopathy?

A 14 bp insertion/deletion polymorphism in exon 8 of the HLA-G gene is associated with mRNA stability and HLA-G expression. In cardiac transplantation, the 14 bp deletion polymorphism plays an important role in the expression of HLA-G and is associated with fewer episodes of cellular rejection. We investigated the association between the 14 bp insertion/deletion HLA-G polymorphism and cardiac allograft vasculopathy (CAV) post heart transplantation. There were no statistically significant differences in the presence of the three HLA-G genotypes (-14 bp/-14 bp, +14 bp/-14 bp, +14 bp/+14 bp) between patients without CAV and patients with CAV at 1 year (p=0.61) or 5 years (p=0.76) post-transplant. We found no correlation between HLA-G genotypes and CAV progression from baseline to 5 years post-transplant (p=0.55). HLA-G polymorphism appears to play an important role as a genetic indicator for cellular rejection post-transplant; however, it is not a reliable marker to identify patients at risk of CAV.

HLA-G haplotype structure shows good conservation between different populations and good correlation with high, normal and low soluble HLA-G expression

HLA-G molecule has considerable impact in various clinical fields, therefore many studies attempted to predict its expression based on HLA-G genotype. These studies have focused on polymorphisms in either the coding region or in one of the two untranslated regions (UTR) of the gene. The aim of our study was to determine if HLA-G haplotype defined based on SNPs 5' and 3'UTR could be used to predict soluble HLA-G expression in unstimulated individuals. Our findings showed that HLA-G haplotype structure was well conserved between distant populations and that the defined haplotypes were correlated with high, normal and low HLA-G soluble secretors. In conclusion, we showed that this genotyping strategy based on the use of a few selected SNPs rather than isolated SNP analysis allows reliable HLA-G expression in all populations. This strategy could be useful in a number of clinical settings, e.g., predicting graft compatibility immunogenetic laboratories.

The maternal HLA-G 1597ΔC null mutation is associated with increased risk of pre-eclampsia and reduced HLA-G expression during pregnancy in African-American women.

The non-classical major histocompatibility complex molecule, human leukocyte antigen (HLA)-G, is thought to contribute to maternal immune tolerance and successful placentation during pregnancy. Genetic polymorphisms in HLA-G are known to influence expression levels as well as the relative expression of individual protein isoforms. As diminished or aberrant HLA-G expression patterns may contribute to the development of certain pregnancy complications, we sought to investigate the association between functional HLA-G polymorphisms and the risk of pre-eclampsia (PE) in African-American women. The association between maternal and fetal genotype at six HLA-G polymorphisms and risk of PE was assessed in 372 pregnancies (314 normotensive; 58 pre-eclamptic). We observed an elevated risk of PE (P = 0.00027) in pregnancies where the mother carried the 1597ΔC allele, a null allele that abolishes expression of full-length HLA-G isoforms. Furthermore, the frequency of the maternal 1597ΔC allele was highest in the subset of pre-eclamptic pregnancies that were delivered preterm, suggesting an association between the null allele and the severity of PE. We then replicated the association between higher maternal 1597ΔC allele frequency and increased severity of PE (P = 0.038) in an independent sample of 533 African-American women. Finally, to investigate the mechanistic basis of this association, we measured circulating soluble HLA-G (sHLA-G) concentrations in maternal serum collected during pregnancy in 51 healthy, normotensive African-American control women and found significantly lower levels in women carrying the 1597ΔC allele (P = 0.012). These results demonstrate that maternal HLA-G genotype is significantly associated with risk of PE in African-American women and is predictive of circulating sHLA-G levels during pregnancy.

Role of HLA-G 14bp deletion/insertion and +3142C>G polymorphisms in the production of sHLA-G molecules in relapsing-remitting multiple sclerosis

HLA-G is believed to act as an anti-inflammatory molecule in Multiple Sclerosis (MS). The 3' untranslated region of the HLA-G gene is characterized by two polymorphisms, DEL/INS14bp and +3142C>G, which control soluble HLA-G (sHLA-G) production. The influence of these two HLA-G variants on sHLA-G serum and cerebrospinal fluid (CSF) levels was investigated in 69 Relapsing-Remitting MS patients grouped in magnetic resonance imaging (MRI) inactive and active disease. Serum and CSF sHLA-G levels were more elevated in high than in low DEL/INS 14bp and +3142C>G sHLA-G producers and were different among the various combined HLA-G genotypes in both MRI inactive and active diseases. The highest and the lowest sHLA-G values were identified in MS patients with C/C,DEL/DEL and G/G,INS/INS genotypes, respectively. Our preliminary findings suggest that serum and CSF sHLA-G levels in MS could be influenced by HLA-G polymorphisms irrespective of the inflammatory microenvironment.

HLA-G polymorphisms and soluble HLA-G protein levels in women with recurrent pregnancy loss from Basrah province in Iraq

HLA-G is a nonclassical, class I major histocompatibility complex (MHC) gene that exhibits immunomodulatory properties and likely plays a role in the maintenance of successful pregnancy. In this study, we investigated the role of HLA-G polymorphisms on risk for recurrent pregnancy loss (RPL) and on circulating levels of soluble (s)HLA-G in Iraqi women. DNA and plasma were obtained from blood samples collected at 9-12 weeks gestation from 50 women with RPL and 50 healthy pregnant women in Basrah province, Iraq. As measured by ELISA, median sHLA-G levels were significantly lower in the RPL cases compared to healthy controls (21.4 vs. 38.8 U/ml, respectively; P=0.025), and decreased with increasing maternal age (P=0.0051). However, HLA-G allele and haplotype frequencies did not differ significantly between cases and controls (P values ≥0.12 for all tests). In contrast, homozygosity for the C allele (CC) at a tri-allelic promoter polymorphism, -725C/G/T, was associated with lower concentrations of sHLA-G compared to the CG or CT genotypes (median levels 21.1 vs. 40.1 vs. 42.6 U/ml, respectively; P=0.0089). These results demonstrate that HLA-G genotype influences circulating sHLA-G levels during pregnancy but is not significantly associated with risk of RPL.

Allele frequencies of human leukocyte antigen‐G in a Korean population

The human leukocyte antigen (HLA)-G is a nonclassical major histocompatibility complex class I molecule with relatively limited polymorphism. The differences in allele frequency according to ethnicity and country have not been studied enough, so far. Therefore, fundamental data including allele frequencies and polymorphism are needed for studies on immunological function of HLA-G in each population. We investigated allele frequencies and 14-bp polymorphism of the HLA-G in Koreans. HLA-G alleles and 14-bp polymorphisms were determined by sequence-based typing analysis of exons 2-4 and polymerase chain reaction of exon 8 in 200 unrelated individuals. Genotyping analysis identified eight different HLA-G alleles, which indicates that the Korean population presents limited HLA-G allelic polymorphism. HLA-G*01:01:01:01 and G*01:04:01 were frequent alleles (42.5% and 34.0%), and allelic frequencies were similar to those of other Asian populations. The 14-bp deletion alleles are higher (78%) in Koreans, although the frequencies of the 14-bp insertion/deletion polymorphism have been known to be nearly equal in many Caucasian populations. HLA-G*01:01:08 was reported strong linkage disequilibrium with the 14-bp deletion in a previous report; the same allele was accompanied with 14-bp insertion in our study. There are a few studies investigating allele frequencies, and most of them were studied before high-resolution method era. This is the first study regarding HLA-G genotypes in Korean, which were identified by high-resolution method. From this study, we identified HLA-G frequencies of a Korean population and expect this study could help further investigations for immunological and clinical implications of HLA-G.

Soluble Human Leukocyte Antigen (HLA)-G and HLA-G genotype in couples undergoing treatment for infertility

Soluble Human Leukocyte Antigen (HLA)-G and HLA-G genotype in couples undergoing treatment for infertility

Lack of association between HLA-G 14-bp polymorphism and systemic lupus erythematosus in a Han Chinese population

HLA-G is a non-classical HLA-class Ib molecule with multiple immunoregulatory properties. A 14-bp insertion/deletion polymorphism in the HLA-G gene has been suggested to influence the expression of HLA-G and to associate with certain pathological conditions, including autoimmune diseases. We investigated the influence of the 14-bp insertion/deletion polymorphism in the HLA-G gene on disease susceptibility in systemic lupus erythematosus by genotyping this polymorphism in 231 patients with systemic lupus erythematosus and 367 healthy controls and analyzing the levels of soluble HLA-G in a subset of patients with systemic lupus erythematosus and healthy subjects from a Han Chinese population. No statistically significant differences were observed in the frequencies of the 14-bp insertion/deletion HLA-G alleles or genotypes between controls and patients with systemic lupus erythematosus. However, a significant increased expression of soluble HLA-G was noted in patients with systemic lupus erythematosus (mean value = 230.2 U/ml vs 118.3 U/ml in controls, p = 0.0001). Moreover, patients with high levels of soluble HLA-G presented with higher disease activity and had more neurological involvement. Our results do not support the HLA-G 14-bp insertion/deletion polymorphism as a genetic factor influencing systemic lupus erythematosus susceptibility. It is possible that the expression of soluble HLA-G in systemic lupus erythematosus is enhanced as part of a mechanism to try to restore the tolerance process towards auto-antigens and to counteract inflammation. However, the participation of this molecule in the pathological process of the disease also could not be excluded.

Tolerance versus immune response — MicroRNAs as important elements in the regulation of the HLA-G gene expression

HLA-G is a class Ib HLA which has gained much attention due to its multiple functions on the immune system. HLA-G exerts several immunomodulatory effects, being beneficially implicated in embryo implantation and fetal survival but, conversely, being potentially detrimental in tumors and viral infections. Such a two-edged sword behavior suggest that HLA-G expression is under tight regulation. However, to date, little is known about the regulation of this gene and previous works have been unable to well correlate HLA-G regulation at the mRNA level with the polymorphic variants at the genomic level. Here we present the hypothesis that an element, which was until now neglected, might play a role in HLA-G expression regulation: MicroRNAs might participate in the regulation of the HLA-G gene expression through a putative microRNA binding site at its 3′ UTR region . Inside the 20 nt region of this microRNA binding site lies a C/G polymorphism, which was shown to be responsible for differential microRNA binding affinity and translation suppression. The role of microRNA binding on the regulation of HLA-G gene expression (and therefore on tolerance versus immune response) can be easily tested through relatively simple steps: Confirming the expression of those three complementary microRNAs in human cells which express HLA-G, followed by examination of the correlation between HLA-G mRNA and protein production controlling for HLA-G genotypes and microRNA levels; finally, selective inhibition of microRNA activity with anti-sense oligos restoring HLA-G production would access microRNA influence on HLA-G expression which, if confirmed, might help in the development of strategies to the management of several conditions in which HLA-G is involved, including pregnancy complications, transplantation, and cancer.

Association Between Novel HLA-G Genotypes and Risk of Recurrent Miscarriages: A Case-Control Study in a South Indian Population

HLA-G is a nonclassical histocompatibility complex member associated with fetal tolerance of the mother observed during pregnancy. Despite its being a less polymorphic gene, a number of studies have evaluated the role of HLA-G gene polymorphisms on the risk of pregnancy-related complications. A 14-bp deletion polymorphism in exon 8 (3'UTR) was known to influence the levels of soluble HLA-G, differential splicing of the transcript, and also the induction of interleukin-10 secretion. The present study is aimed at evaluating the variations in exon 2 and exon 8 of the HLA-G gene for the risk of recurrent miscarriages in South Indian women. A total of 169 cases and 92 controls are included in the study. Six novel polymorphisms were identified, 2 of which are in intron 2 near the exon-intron junction and 4 of which are present downstream to the 14-bp deletion in 3'UTR. The exon 2 and intron polymorphisms failed to show any association. The T1570C and C1594A polymorphisms showed a significant association (P = .002 and .021) with the risk of miscarriage after categorization based on the 14-bp deletion. Linkage disequilibrium analysis showed that the T allele of T1570C is in linkage disequilibrium with the 14-bp deletion in cases but not in controls. In silico RNA folding studies indicate that the T allele forms a more stable secondary structure than the C allele, giving rise to a more stable transcript.The authors demonstrate a significant relation between the two 3'UTR polymorphisms and recurrent miscarriages.

Allele-Specific Targeting of microRNAs to HLA-G and Risk of Asthma

HLA-G is a nonclassic, class I HLA molecule that has important immunomodulatory properties. Previously, we identified HLA-G as an asthma-susceptibility gene and discovered that the risk of asthma in a child was determined by both the child's HLA-G genotype and the mother's affection status. Here we report a SNP in the 3' untranslated region of HLA-G that influences the targeting of three microRNAs (miRNAs) to this gene, and we suggest that allele-specific targeting of these miRNAs accounts, at least in part, for our earlier observations on HLA-G and the risk of asthma.

HLA‐G alleles and HLA‐G 14 bp polymorphisms in a Brazilian population

Brazilians represent one of the most heterogeneous populations in the world as the result of five centuries of interethnic crosses. We investigated the polymorphism of the HLA-G locus in a Brazilian urban sample. HLA-G alleles were determined by SBT analysis of exons 2-4 and 8 in 103 unrelated individuals. The genotyping analysis identified 11 different HLA-G alleles, including the recently described G*010110 allele, and four new variants in this population. These data indicate that this Brazilian population presents high HLA-G allelic polymorphism, suggesting increased levels of intrapopulational genetic diversity that may be because of the admixed nature of the sample. This is the first study regarding HLA-G genotyping that was performed at such refined resolution level in this heterogeneous population.

HLA‐G polymorphism in a Chinese Han population with recurrent spontaneous abortion

Reproduction is an important biological phenomenon posing an immunological paradox because the semiallogeneic fetus survives by evading maternal immune recognition. The detailed mechanisms behind this maternal-fetal immunotolerance remain elusive. Human leucocyte antigen (HLA)-G, a non-classical HLA class I antigen, initially identified as a molecule selectively expressed on extravillous cytotrophoblasts and first studied in the context of pregnancy, has long been supposed to play a critical role in fetal-maternal immunotolerance. To investigate the role of HLA-G polymorphism in this process and whether the HLA-G genotype is associated with an increased risk for a subsequent miscarriage, 69 women with three or more recurrent spontaneous abortions (RSA) and 146 fertile control women were genotyped for the HLA-G locus in this study. To our knowledge, this is the first report on HLA-G polymorphism in RSA and in normal fertile women from a Chinese Han population. Nine HLA-G alleles were detected in the fertile control group; however, the allele HLA-G*0103 was absent in the RSA group. No statistical significance was observed in the distribution of HLA-G alleles between the two groups. The frequency of the null allele HLA-G*0105 N in the RSA group and in normal fertile women is 0.7% and 1.4%, respectively. Our data suggested that there was no association of HLA-G polymorphism with RSA.

The HLA-G genotype is associated with IL-10 levels in activated PBMCs

Human leukocyte antigen (HLA)-G is an MHC class Ib molecule that is expressed at the feto-maternal interface during pregnancy. However, recent results have also shown that it may have important functions as an immuno-modulatory factor in adult life. Differences in the pattern of alternative splicing and in the stability of HLA-G mRNA transcripts have been associated with HLA-G polymorphisms, especially a 14 bp deletion/insertion polymorphism in the 3' untranslated region of the HLA-G gene. We have investigated the secretion of HLA-G5/soluble HLA-G1 and interleukin-10 (IL-10) in lipopolysaccharide (LPS)-activated peripheral blood mononuclear lymphocytes (PBMCs) in relation to the HLA-G 14 bp genotype. No HLA-G5/sHLA-G1 could be detected in the non-activated control PBMC culture media, and there were no significant differences among the three HLA-G 14 bp genotypes regarding IL-10 concentrations. In LPS-activated PBMC cultures, no significant differences among the three HLA-G 14 bp genotypes regarding HLA-G5/sHLA-G1 concentrations were observed. However, this was in contrast to the IL-10 levels (P=0.0004, Kruskal-Wallis test). The +14/+14 bp PBMC samples expressed higher levels of IL-10 when compared to the -14/+14 bp genotype and the -14/-14 bp genotype. Interestingly, the IL-10 G/G polymorphism at position -1082 was more frequent in the +14/+14 bp genotype (P=0.024, chi2 test). These results support an autocrine loop between HLA-G5/sHLA-G1 and IL-10 expression in activated PBMCs, which may result in higher IL-10 levels in +14/+14 bp HLA-G genotypes.

HLA-G expression in placenta in relation to HLA-G genotype and polymorphisms.

The expression of the non-classical human leukocyte antigen (HLA) class Ib gene, HLA-G, seems to be important at the feto-maternal interface. The HLA-G molecule is almost monomorphic and expressed in both membrane-bound and soluble isoforms. It has been shown to inhibit natural killer cell -mediated lysis and influence cytokine expression. HLA-G gene polymorphism has been linked to differences in gene expression profile of alternatively spliced HLA-G transcripts and levels of specific HLA-G messenger RNA (mRNA) isoforms. Furthermore, aberrant HLA-G expression has been reported in preeclamptic placentas. On this background it is of general interest to further elucidate any associations between HLA-G polymorphism and protein expression. We have investigated HLA-G protein expression by immunohistochemistry in HLA-G genotyped placentas from term. HLA-G mRNA expression in preeclamptic placentas and in control placentas was also studied by microarray technology. The studies of HLA-G protein expression in term placentas by immunohistochemical analysis showed no clear associations with HLA-G genotypes although this could be because of the very semi-quantitative nature of this technique. However, we found a tendency towards reduction of HLA-G mRNA expression in placentas from preeclamptic cases compared to matched controls with the use of microarray technology.

Association between human leukocyte antigen-G genotype and success of in vitro fertilization and pregnancy outcome.

To determine if a 14-bp deletion/insertion polymorphism in the 3'-untranslated region of exon 8 of the gene encoding human leukocyte antigen (HLA)-G in a homozygous form is associated with repeated, unsuccessful in vitro fertilization (IVF) treatments, and with increased risk of recurrent spontaneous abortions (RSA), 29 white women undergoing IVF treatments, 61 RSA women and 93 fertile controls were HLA-G genotype. The HLA-G genotype, homozygous for the presence of the 14 bp sequence in exon 8, was significantly associated with reduced fertility with respect to unsuccessful IVF treatments and increased risk of recurrent miscarriage (combined P < 0.01). The 14-bp insertion/deletion polymorphism is associated with differences in HLA-G mRNA alternative splicing and levels of HLA-G. This might affect a possible immunomodulatory role of HLA-G expression in both the mother and foetus during implantation and pregnancy.