Ralationship between polymorphisms and diplotypes of HLA-G 3'UTR and fetuses with abnormal chromosomes or unexplained pregnancy loss (UPL)

OBJECTIVES

Human leukocyte antigen G (HLA-G) plays a crucial role in pregnancy. Pregnancy loss (PL) is caused by a variety of causes, such as fetal chromosomal abnormalities, maternal hypertension and diabetes, immune causes, spontaneous immune diseases, infections, unknown causes, etc. This study reports on the association of fetal HLA-G 3'UTR polymorphisms and diplotypes with chromosomally abnormal fetuses (CAF) or unexplained pregnancy loss (UPL).

METHODS

A total of 552 specimens were collected and grouped by next-generation sequencing technology (NGS) and fetal survival: UPL (112 cases), CAF (170 cases) and control (258 cases). The polymorphisms of HLA-G 3'UTR in all samples were detected by Sanger sequencing. The genotypes, haplotypes and diplotypes of HLA-G 3'UTR were analyzed. The classification and regression tree (CART) analysis was used to evaluate the role of HLA-G diplotypes in predicting fetal outcomes. The correlations between CAF or UPL and maternal age, paternal age, times of miscarrage, times of delivery were analyzed by logistic regression.

RESULTS

The frequencies of HLA-G + 2960del/del and + 3035CC genotypes were remarkablly increased in CAF than those in control group. The frequencies of HLA-G + 2960ins/del, + 3010CC, + 3035TC, + 3142GG, + 3187AA in CAF were significantly lower than those in normal fetuses. Through genetic models and logistic regression analysis, the dominant model of HLA-G 3'UTR genotypes [such as + 2960 (OR = 1.27, 95% CI = 1.05-1.54, p = 0.016), + 3010 (OR = 0.78, 95% CI = 0.63-0.97, p = 0.026), + 3035 (OR = 1.22, 95% CI = 1.00-1.49, p = 0.047), + 3142 (OR = 0.76, 95% CI = 0.62-0.95, p = 0.014) and + 3187 (OR = 0.80, 95% CI = 0.65-0.99, p = 0.041)] were dramatically associated with CAF. However, the frequencies of HLA-G + 3010GC, + 3142GC and + 3187AG in fetuses with UPL were memorably decreased than those in normal fetuses. No significant difference was found in the frequencies of HLA-G haplotypes in all groups. However, the frequency of UTR-1 positive specimens in CAF was significantly higher than that in UPL and control group. At the same time, the frequency of UTR-1/UTR-3 diplotypes in CAF was observably higher than that in UPL and control group, while the UTR-1/UTR-7 frequency in UPL was signally lower than that in control group. Multivariate logistic regression analysis indicated that positive HLA-G UTR-1 (OR = 1.8, 95% CI = 1.16-2.81, p = 0.009), times of abortion (OR = 1.23, 95% CI = 1.02-1.50, p = 0.035), and times of delivery (OR = 0.31, 95% CI = 0.20-0.48, p < 0.001) were correlated with CAF.

CONCLUSIONS

This study suggests that HLA-G 3'UTR polymorphisms and diplotypes play an important role in the process of successful pregnancy of the embryos with abnormal chromosomes after fertilization. At the same time, Different alleles or diplotypes also affect the development of embryos with UPL.

Insights into preeclampsia: a bioinformatics approach to deciphering genetic and immune contributions

Background

Preeclampsia (PE) is a global pregnancy concern, characterized by hypertension with an unclear etiology. This study employs Mendelian randomization (MR) and single-cell RNA sequencing (scRNA-seq) to clarify its genetic and molecular roots, offering insights into diagnosis and treatment avenues.

Methods

We integrated PE-specific genome-wide association study (GWAS) data, expression and protein quantitative trait loci (eQTL and pQTL) data, and single-cell data from peripheral blood mononuclear cells (PBMCs). We identified highly variable genes using single-cell information and employed MR to determine potential causality. We also combined pQTL and GWAS data, discerned genes positively associated with PE through scRNA-seq, and leveraged the Enrichr platform to unearth drug-gene interactions.

Results

Our scRNA-seq pinpointed notable cell type distribution variances, especially in T helper cells (Th cells), between PE and control groups. We unveiled 591 highly variable genes and 6 directly PE-associated genes. Although MR revealed correlations with PE risk, pQTL analysis was inconclusive due to data constraints. Using DSigDB, 93 potential therapeutic agents, like Retinoic acid targeting core genes (IFITM3, NINJ1, COTL1, CD69, and YWHAZ), emerged as prospective multi-target treatments.

Conclusion

Utilizing MR and scRNA-seq, this study underscores significant cellular disparities, particularly in Th cells, and identifies crucial genes related to PE. Despite some limitations, these genes have been revealed in PE's underlying mechanism. Potential therapeutic agents, such as Retinoic acid, suggest promising treatment pathways.

UP-regulated levels of sHLA-G in women with a history of RPL in mid-gestation presumably to achieve ongoing pregnancy

PROBLEM

Recurrent Pregnancy Loss (RPL) is a disorder characterized by two or more pregnancy losses within 20th week of gestation. Globally 1-5% of the couples are affected, 50% of these cases are with unknown etiology. HLA-G, an Immuno-modulatory molecule is a non-classical MHC-1 protein, expressed abundantly on extravillous trophoblastic cells, responsible for spiral artery remodeling, maintaining maternal immune tolerance and fetal growth by adjusting pro and anti-inflammatory milieu during different gestational phases.

METHOD OF STUDY

In the present case-control study CD4+HLA-G+ tTreg cells were enumerated by flow cytometry and estimation of the circulating levels of sHLA-G in the blood samples of 300 mid-gestation pregnant women with (iRPL) and without history of RPL (nRPL) by Enzyme-linked Immunosorbent assay was done. The cases included 92 primary and 58 secondary RPL cases RESULTS: A significant reduction in number of tTregs and elevated levels of circulating sHLA-G in iRPL (.03, 200.9) versus nRPL (.09, 90.32) was observed. Further, the primary cases showed higher circulating sHLA-G and no difference in relation to CD4+HLA-G+ tTregs compared to the secondary cases. Receiver operating curve (ROC) characteristics of sHLA-G (AUC = .8) was superior to CD4+HLA-G+ (AUC = .7) for iRPL patients over nRPL group.

CONCLUSIONS

Our results are suggestive of the over-expression of sHLA-G which may be caused due to its shedding from surface of trophoblast as a compensatory mechanism to save the on-going pregnancy. To realize the present outcome, studies are required on on-going pregnancy follow-up cases with favorable and unfavorable pregnancy outcome.

Role of the HLA-G regulatory region polymorphisms in idiopathic recurrent spontaneous abortions (RSA)

PROBLEM

HLA-G polymorphisms have a functional impact on its expression and may cause a breakdown of maternal tolerance towards the semi-allogenic fetus, resulting in recurrent spontaneous abortions (RSA). This study reports on the association of HLA-G regulatory region polymorphisms with idiopathic RSA.

METHODS

Seventy-five couples with ≥2 spontaneous abortions were recruited in comparison to 75 healthy couples who had normal pregnancies. About 5 mL of blood samples were collected from all the participants, and DNA was extracted. Screening of HLA-G 5'-upstream regulatory region (5'-URR) was done by direct sequencing in 50 each of RSA and healthy couples, respectively. The 14 bp deletion/insertion polymorphism in the 3'-untranslated region (3'-UTR) was genotyped in 75 each of RSA and healthy couples, respectively, by PCR amplification of HLA-G exon 8. MedCalc, GraphPad Prism, Haploview, PLINK, and multifactor dimensionality reduction were used to analyze the data.

RESULTS

HLA-G screening revealed the presence of -762C/T, -725C/G, -716T/G, -689A/G, -486C/A, and -477C/G single nucleotide polymorphisms (SNPs) in the 5'-URR. At positions -762 and -477, the frequency of CC homozygotes was significantly higher in controls compared to the patients. The 14 bp deletion/insertion polymorphism in the 3'-UTR showed an association with RSA with the heterozygous genotype being significantly higher in RSA compared to controls.

CONCLUSIONS

The study indicates a protective role of the CC genotypes of the two HLA-G 5'-URR polymorphisms, -762C/T and -477C/G, against RSA. It also suggests that women with the 14 bp deletion/insertion genotype have a significantly higher risk of RSA.

Evidence for a shift in placental HLA-G allelic dominance and the HLA-G isoform profile during a healthy pregnancy and pre-eclampsia

Human leukocyte antigen (HLA)-G is a non-classical class Ib major expressed by placental trophoblast cells plays a central role in establishing tolerance to the semi-allogeneic fetus and in placentation. HLA-G exists in different soluble or membrane-bound isoforms. Pre-eclampsia, a major cause of fetal and maternal morbidity and mortality, has been linked to insufficient placentation and an altered immune response in pregnancy, including altered HLA-G expression. The 14 bp insertion/deletion polymorphism in the 3' untranslated region of the gene and the isoform profile may affect HLA-G expression. The aim of the current pilot study was to characterize the expression patterns of HLAG mRNA, protein and isoform profile in uncomplicated term pregnancies and in cases of pre-eclampsia. Maternal sHLA-G mRNA and protein levels was slightly reduced in pre-eclampsia. No difference was found for placental blood, and no correlation between peripheral and placental sHLA-G levels was found. We observed no association between neither fetal nor maternal HLA-G 14 bp insertion/deletion genotypes and pre-eclampsia, nor a significant difference in isoform profiles. However, in HLA-G 14 bp insertion/deletion heterozygous placental samples, we observed abundant HLA-G1 14 bp insertion allele expression in the term placentae, which is contrary to previous findings in first trimester trophoblast. Increased HLA-G1 14 bp insertion allele expression in the placenta was associated with reduced levels of placental sHLA-G and an altered isoform profile with increased relative levels of HLA-G1 and -G5 and reduced levels of HLA-G3. The results indicate that an allelic shift in heterozygous individuals could represent a novel regulatory pathway.

A possible role for HLA-G in development of uteroplacental acute atherosis in preeclampsia

HLA-G, a non-classical HLA molecule expressed by extravillous trophoblasts, plays a role in the maternal immune tolerance towards fetal cells. HLA-G expression is regulated by genetic polymorphisms in the 3' untranslated region (3'UTR). Low levels of HLA-G in the maternal circulation and placental tissue are linked to preeclampsia. Our objective was to investigate whether variants of the 3'UTR of the HLA-G gene in mother and fetus are associated with acute atherosis, a pregnancy specific arterial lesion of the decidua basalis that is prevalent in preeclampsia. Paired maternal and fetal DNA samples from 83 normotensive and 83 preeclamptic pregnancies were analyzed. We sequenced the part of the HLA-G 3'UTR containing a 14-bp insertion/deletion region and seven single nucleotide polymorphisms (SNPs). Associations with acute atherosis were tested by logistic regression. The frequency of heterozygosity for the 14-bp polymorphism (Ins/Del) and the +3142 SNP (C/G) variant in the fetus are associated with acute atherosis in preeclampsia (66.7 % vs. 39.6 %, p = 0.039, and 69.0 % vs. 43.4 %, p = 0.024). Furthermore, the fetal UTR-3 haplotype, which encompasses the 14-bp deletion and the +3142G variant, is associated with acute atherosis in preeclampsia (15 % vs. 3.8 %, p = 0.016). In conclusion, HLA-G polymorphisms in the fetus are associated with acute atherosis. We hypothesize that these polymorphisms lead to altered HLA-G expression in the decidua basalis, affecting local feto-maternal immune tolerance and development of acute atherosis.

Analysis of key markers: IL-10/sHLA-G in psoriasis patients and the identification of 14-bp INDEL in the HLA-G gene

BACKGROUND

Psoriasis is a chronic inflammation resulting from interactions between immunological and genetic factors. An important tolerogenic role in this autoimmunological disease is played by HLA-G, which is modulated by IL-10. Therefore, this study (N.=80) aimed to evaluate changes in the serum sHLA-G and IL-10 levels in active psoriasis vulgaris and in the early stages of treatment with Methotrexate (MTX) compared to healthy controls. The 14-bp INDEL of the HLA-G gene was evaluated to find possible associations with clinical and laboratory variables.

METHODS

The level of sHLA-G and IL-10 in serum was evaluated (ELISA tests) in patients before the first dose of MTX and at week 12 of treatment, compared to healthy control donors. The 14-bp INDEL in 3'UTR of the HLA-G gene was identified using gDNA templates isolated from full blood. HLA-G amplicons were obtained by PCR, separated by electrophoresis and sequenced.

RESULTS

The mean serum IL-10 level was 4.653±3.33 pg/mL in psoriatic patients, 13.3±9.64 pg/mL after short MTX treatment, compared to 6.23 pg/mL in healthy controls. In addition, the serum level of sHLA-G was 0.275±0.03 ng/mL and 0.332±0.06 ng/mL in patients before and after MTX treatment, respectively, and 0.302±0.08 ng/mL in the control group. A correlation was found (r=-0.43; P<0.005) between the IL-10 and BSA serum levels in psoriasis patients after MTX treatment, indicating health improvement. The three genotypes identified in the 3'UTR of the HLA-G revealed no association with sHLA-G level in serum.

CONCLUSIONS

The mean levels of sHLA-G and the key anti-inflammatory cytokine IL-10 in the blood of pretreatment psoriasis patients are low and indicate that the immunotolerance mechanisms have failed. Treatment of psoriasis patients with low systemic levels of sHLA-G and IL-10 brings them to the same or higher protein levels, respectively, as in healthy donors. Higher sHLA-G levels in healthy donors and after MTX treatment, compared to the sHLA-G levels in the acute phase of psoriasis, indicates its immune system surveillance function.

Establishment and characterization of a new human first trimester Trophoblast cell line, AL07

INTRODUCTION

The limited cell number of primary trophoblasts and contamination of trophoblast cell lines promote us to develop a novel stable trophoblast cell line.

METHOD OF STUDY

Primary trophoblast cells were isolated from first-trimester placenta and telomerase-induced immortalization was used to immortalize these cells. Subsets of cells were then evaluated by flow cytometry using CK7, HLA-G, CD45 and CD14, specific markers for trophoblast cells, extra-villous trophoblast, pan leucocyte and monocyte/macrophage, respectively. Immunofluorescence staining and immunocytochemistry were used to detect CK7 expression in trophoblast cells. The level of secreted human Chorionic Gonadotropin (hCG) was measured by electrochemiluminescence (ECL). The Bio-Plex MAGPIX System was used to analyze the cytokines and chemokines produced by AL07 cell line.

RESULTS

We were able to isolate primary trophoblast cells from several first-trimester placentas. One clone, AL07 trophoblast cells, isolated from a week 7 placenta, was morphologically stable and positive for the expression of CK7 by immunofluorescence and immunocytochemistry staining. Characterization of AL07 cells reveled that they are CD45 or CD14 negative and had constitutive secretion of hCG and low HLA-G expression. Furthermore, clone AL07 secret high levels of several cytokines and chemokines, including IL-6, IL-8 and VEGF, and moderately secreted MCP-1 IP-10 and RANTES.

DISCUSSION

We report the successful isolation, immortalization and characterization of AL07 cells, a novel cell clone isolated from first trimester human placenta. The clone is free of contamination of immune cells, and exhibits similar cytokine profile as other trophoblast cell lines. This new cytotrophoblast-like AL07 cell, can be a valuable tool for in-vitro trophoblast studies in the future.

Soluble HLA-G and TGF-β in couples attending assisted reproduction - A possible role of TGF-β isoforms in semen?

Soluble isoforms of the non-classical Human Leukocyte Antigen (HLA)-G as well as Transforming Growth Factor (TGF)-β is expressed in seminal plasma possibly influencing the pregnancy potential. We wanted to examine the association of seminal plasma sHLA-G, TGF-β1, TGF-β2 and TGFβ3 with pregnancy success in a cohort of 127 couples and 4 single women attending fertility treatment with the use of assisted reproduction technologies (ART). Soluble HLA-G, TGF-β1, TGF-β2 and TGF-β3 in seminal plasma did not fluctuate significantly over time. We did not find any impact of seminal plasma sHLA-G, TGF-β1, TGF-β2 and TGF-β3 on time-to-pregnancy measured as number of treatment cycles. There was a significant association between concentrations of seminal plasma sHLA-G and HLA-G variations in the 3'untranslated region (3'UTR) of the HLA-G gene, supporting and extending previous findings. Furthermore, by comparing seminal plasma concentrations of sHLA-G, TGF-β1, TGF-β2 and TGF-β3 in male subjects with reduced semen quality, male subjects with normal semen quality, and sperm donors, we found that TGF-β2 was significantly lower, and TGF-β3 was significantly higher, in seminal plasma from sperm donors. These findings suggest that TGF-β isoforms may influence semen quality and fertility.

Next-generation sequencing of HLA-G based on long-range polymerase chain reaction

Clarifying the functional roles of HLA-G and the variation in the HLA-G gene that affects the expression are increasingly important in reproduction, cancer, organ transplantation, and autoimmune diseases. The homology between HLA genes and the genetic variability within each gene complicates the design of HLA gene-specific genotyping assays. We have designed a high-throughput, cost-efficient, robust, and specific assay for sequencing the full HLA-G gene including the 5'-upstream regulatory region, introns, and the 3'-untranslated region, using the next-generation sequencing (NGS) platform Ion Torrent PGM (Thermo Fisher Scientific, Waltham, Massachusetts). Conventional sequencing methods require the design of multiple primer pairs in order to cover the entire HLA-G gene. Designing multiple primer pairs specific for the HLA-G gene that also target all known alleles is difficult. Here, we present a setup that by the use of long-range polymerase chain reaction amplifies the whole HLA-G gene in a single reaction, which only requires a single HLA-G-specific primer pair. Enzymatic DNA shearing is used to break the long-range PCR product into shorter fragments ranging from 75 to 200 bp in length that are sequenced by NGS.

Increased HLA-G Expression in Term Placenta of Women with a History of Recurrent Miscarriage Despite Their Genetic Predisposition to Decreased HLA-G Levels

Human leukocyte antigen (HLA)-G is an immune modulating molecule that is present on fetal extravillous trophoblasts at the fetal-maternal interface. Single nucleotide polymorphisms (SNPs) in the 3 prime untranslated region (3'UTR) of the HLA-G gene can affect the level of HLA-G expression, which may be altered in women with recurrent miscarriages (RM). This case-control study included 23 women with a medical history of three or more consecutive miscarriages who delivered a child after uncomplicated pregnancy, and 46 controls with uncomplicated pregnancy. Genomic DNA was isolated to sequence the 3'UTR of HLA-G. Tissue from term placentas was processed to quantify the HLA-G protein and mRNA levels. The women with a history of RM had a lower frequency of the HLA-G 3'UTR 14-bp del/del genotype as compared to controls (Odds ratio (OR) 0.28; p = 0.039), which has previously been related to higher soluble HLA-G levels. Yet, HLA-G protein (OR 6.67; p = 0.006) and mRNA (OR 6.33; p = 0.010) expression was increased in term placentas of women with a history of RM as compared to controls. In conclusion, during a successful pregnancy, HLA-G expression is elevated in term placentas from women with a history of RM as compared to controls, despite a genetic predisposition that is associated with decreased HLA-G levels. These findings suggest that HLA-G upregulation could be a compensatory mechanism in the occurrence of RM to achieve an ongoing pregnancy.

Pericytes in the Placenta: Role in Placental Development and Homeostasis

The placenta is the most variable organ, in terms of structure, among the species. Besides it, all placental types have the same function: production of viable offspring, independent of pregnancy length, litter number, or invasion level. The angiogenesis is a central mechanism for placental functionality, due to proper maternal-fetal communication and exchanges. Much is known about the vasculature structure, but little is known about vasculature development and cellular interactions. Pericytes are perivascular cells that were described to control vasculature stability and permeability. Nowadays there are several new functions discovered, such as lymphocyte modulation and activation, macrophage-like phagocytic properties, tissue regenerative and repair processes, and also the ability to modulate stem cells, majorly the hematopoietic. In parallel, placental tissues are known to be a particularly immune microenvironment and a rich stem cell niche. The pericyte function plethora could be similar in the placental microenvironment and could have a central role in placental development and homeostasis.

The genetic diversity within the 1.4 kb HLA-G 5' upstream regulatory region moderately impacts on cellular microenvironment responses

The HLA-G 5'URR extending 1.4 kb from the ATG presents a unique set of regulatory elements among HLA genes. Several variable sites have been described that coincide with or are close to these elements, thus HLA-G 5'URR polymorphism might influence the HLA-G expression level. We cloned the ten most frequent HLA-G 5'URR haplotypes to evaluate their activity on a luciferase reporter gene in HLA-G⁺ cell lines (JEG-3/choriocarcinoma and FON⁺/melanoma). We also investigated associations between the plasma HLA-G (sHLA-G) levels and the HLA-G 5'URR variability in 157 healthy individuals. Cell lines were transfected with pGL3-Basic vector constructions containing HLA-G 5'URR sequences. The G010101a (in JEG-3) and G010101b (in FON⁺) haplotypes exhibited higher promoter activity, whereas the G010101d (in JEG-3) and G010102a (in FON⁺) haplotypes exhibited lower promoter activity. In the presence of HLA-G inducers (interferon-β and progesterone) or repressors (cyclopamine) HLA-G promoter activity was modulated, but certain haplotypes exhibited differential responses. No strict association was observed between plasma sHLA-G levels and the 5'URR haplotypes or genotypes; however, the G010101b haplotype was underrepresented among HLA-G-negative plasmas. Therefore, the HLA-G 5'URR polymorphism may have an impact on the modulation of HLA-G gene expression, but alone provides a limited predictive value for sHLA-G levels in vivo.

H558R, a common SCN5A polymorphism, modifies the clinical phenotype of Brugada syndrome by modulating DNA methylation of SCN5A promoters

BACKGROUND

A common SCN5A polymorphism H558R (c.1673 A > G, rs1805124) improves sodium channel activity in mutated channels and known to be a genetic modifier of Brugada syndrome patients (BrS). We investigated clinical manifestations and underlying mechanisms of H558R in BrS.

METHODS AND RESULTS

We genotyped H558R in 100 BrS (mean age 45 ± 14 years; 91 men) and 1875 controls (mean age 54 ± 18 years; 1546 men). We compared clinical parameters in BrS with and without H558R (H558R+ vs. H558R- group, N = 9 vs. 91). We also obtained right atrial sections from 30 patients during aortic aneurysm operations and compared SCN5A expression and methylation with or without H558R. H558R was less frequent in BrS than controls (9.0% vs. 19.2%, P = 0.028). The VF occurrence ratio was significantly lower (0% vs. 29.7%, P = 0.03) and spontaneous type 1 ECG was less observed in H558R+ than H558R- group (33.3% vs. 74.7%, P = 0.01). The SCN5A expression level was significantly higher and the methylation rate was significantly lower in sections with H558R (N = 10) than those without (0.98 ± 0.14 vs. 0.83 ± 0.19, P = 0.04; 0.7 ± 0.2% vs. 1.6 ± 0.1%, P = 0.004, respectively). In BrS with heterozygous H558R, the A allele mRNA expression was 1.38 fold higher than G allele expression.

CONCLUSION

The SCN5A polymorphism H558R may be a modifier that protects against VF occurrence in BrS. The H558R decreased the SCN5A promoter methylation and increased the expression level in cardiac tissue. An allelic expression imbalance in BrS with a heterozygous H558R may also contribute to the protective effects in heterozygous mutations.

HLA class Ib in pregnancy and pregnancy-related disorders

The HLA class Ib genes, HLA-E, HLA-F, and HLA-G, were discovered long after the classical HLA class Ia genes. The elucidation of their functions had a modest beginning. However, their basic functions and involvement in pathophysiology and a range of diseases are now emerging. Although results from a range of studies support the functional roles for the HLA class Ib molecules in adult life, especially HLA-G and HLA-F have most intensively been, and were also primarily, studied in relation to reproduction and pregnancy. The expression of HLA class Ib proteins at the feto-maternal interface in the placenta seems to be important for the maternal acceptance of the semi-allogenic fetus. In contrast to the functions of HLA class Ia, HLA-G possesses immune-modulatory and tolerogenic functions. Here, we review an accumulating amount of data describing the functions of HLA class Ib molecules in relation to fertility, reproduction, and pregnancy, and a possible role for these molecules in certain pregnancy complications, such as implantation failure, recurrent spontaneous abortions, and pre-eclampsia. The results from different kinds of studies point toward a role for HLA class Ib, especially HLA-G, throughout the reproductive cycle from conception to the birth weight of the child.

Haplotypes of the HLA-G 3' Untranslated Region Respond to Endogenous Factors of HLA-G+ and HLA-G- Cell Lines Differentially

The immune checkpoint HLA-G prevents maternal rejection of the fetus and contributes in cancer invasion and acceptance of allografts. The 5’ and 3’ regulatory regions of the HLA-G gene are polymorphic and balancing selection probably maintains this variability. It is proposed that nucleotide variations may affect the level of HLA-G expression. To investigate this issue we aimed to analyze how haplotypes of the 3’ untranslated region (3’UTR) with highest worldwide frequencies, namely UTR-1, UTR-2, UTR-3, UTR-4, UTR-5, UTR-18 and UTR-7, impact the expression of a luciferase reporter gene in vitro. Experiments performed with the HLA-G positive cell lines JEG-3 (choricarcinoma) and FON (melanoma), and with the HLA-G negative cell lines M8 (melanoma) and U251MG (glioblastoma) showed that the HLA-G 3’UTR polymorphism influences the response to endogenous cellular factors and may vary according to the cell type. UTR-5 and UTR-7 impact the activity of luciferase the most whereas UTR-2, UTR-3, UTR-4, and UTR-18 have intermediate impact, and UTR-1 has the lowest impact. These results corroborate the previous associations between amounts of plasma sHLA-G levels and 3’UTR haplotypes in healthy individuals and reinforce that 3’UTR typing may be a predictor of the genetic predisposition of an individual to express different levels of HLA-G.

Distribution of HLA-G extended haplotypes and one HLA-E polymorphism in a large-scale study of mother-child dyads with and without severe preeclampsia and eclampsia

The etiological pathways and pathogenesis of preeclampsia have rendered difficult to disentangle. Accumulating evidence points toward a maladapted maternal immune system, which may involve aberrant placental expression of immunomodulatory human leukocyte antigen (HLA) class Ib molecules during pregnancy. Several studies have shown aberrant or reduced expression of HLA-G in the placenta and in maternal blood in cases of preeclampsia compared with controls. Unlike classical HLA class Ia loci, the nonclassical HLA-G has limited polymorphic variants. Most nucleotide variations are clustered in the 5'-upstream regulatory region (5'URR) and 3'-untranslated regulatory region (3'UTR) of HLA-G and reflect a stringent expressional control. Based on genotyping and full gene sequencing of HLA-G in a large number of cases and controls (n > 900), the present study, which to our knowledge is the largest and most comprehensive performed, investigated the association between the HLA-G 14-bp ins/del (rs66554220) and HLA-E polymorphisms in mother and newborn dyads from pregnancies complicated by severe preeclampsia/eclampsia and from uncomplicated pregnancies. Furthermore, results from extended HLA-G haplotyping in the newborns are presented in order to assess whether a combined contribution of nucleotide variations spanning the 5'URR, coding region, and 3'UTR of HLA-G describes the genetic association with severe preeclampsia more closely. In contrast to earlier findings, the HLA-G 14-bp ins/del polymorphism was not associated with severe preeclampsia. Furthermore, the polymorphism (rs1264457) defining the two nonsynonymous HLA-E alleles, HLA-E*01:01:xx:xx and HLA-E*01:03:xx:xx, were not associated with severe preeclampsia. Finally, no specific HLA-G haplotypes were significantly associated with increased risk of developing severe preeclampsia/eclampsia.

14-bp ins/del polymorphism and +3142C>G SNP of the HLA-G gene have a significant impact on acute rejection after liver transplantation

Expression of human leukocyte antigen G (HLA-G) has been associated with increased graft survival and decreased rejection episodes. It has been described that the HLA-G 14-base pair (bp) insertion/deletion (ins/del) (rs66554220) and +3142C>G (rs1063320) gene polymorphisms modify the expression level of HLA-G. The aim of the study was to investigate whether these HLA-G polymorphisms have an impact on acute rejection after liver transplantation. In total, 146 liver transplant recipients (57 with acute rejection and 89 without acute rejection) and 99 corresponding liver donors were genotyped for both polymorphisms. In liver transplantation the 14-bp ins/ins and the +3142GG genotypes are more frequent in recipients without rejection compared to recipients with rejection (3.5% vs. 31.5%, p=<0.001; 12.3% vs. 41.6%, p=<0.001) demonstrating an association with protection from acute rejection. In contrast, in liver donors we could not reveal an association. We conclude that 14-bp ins/ins and +3142GG genotypes of HLA-G in liver transplant recipients are of importance for prediction of acute rejection after liver transplantation. Thus genotyping of liver recipients for both polymorphisms might be useful to stratify liver transplant recipients according to the risk of acute liver transplant rejection.

HLA-G and CD8+ regulatory T cells in the inflammatory environment of pre-eclampsia

During pregnancy, the maternal immune system is tolerant to foetal antigens via the engagement of immune regulatory mechanisms. Failure in regulating the maternal immunity to foetal antigens may lead to pre-eclampsia (PE). We addressed the role of HLA-G gene polymorphisms and protein expression as well as regulatory T cells and Th1/Th2/Th17 cytokines in healthy and pathological pregnancies. Blood samples from 26 pregnant women with PE, 25 non-PE and 7 strictly healthy pregnant women were assessed. PBMCs were phenotyped for early activation markers (CD25 and CD69), regulatory T-cell markers (CD8⁺CD28^- and CD4⁺CD25^highFoxp3⁺), ILT-2 (HLA-G receptor) and HLA-G. Lymphocyte proliferation was estimated and levels of IL-2, IL-4, IL-6, IL-10, IFN-γ, TNF-α and IL-17 were measured. HLA-G polymorphisms (rs66554220 and rs1063320) were genotyped by PCR. PE women exhibited low levels of HLA-G in PBMCs and low frequency of regulatory CD8⁺CD28^- T cells. High amounts of the pro-inflammatory cytokines IL-17, IL-2 and TNF-α as well as IL-4 and IL-10 and an increased proliferative cell activation profile were observed in PE. The allelic and genotypic frequencies of the HLA-G gene polymorphisms and the frequency of CD4⁺CD25^highFoxp3⁺ T cells did not vary among the groups. Our data suggest that the cytokine imbalance presented in PE is associated with a deficient immune regulatory profile, contributing to an impaired immune tolerance between mother and foetus.

High Amounts of Total and Extracellular Vesicle-Derived Soluble HLA-G are Associated with HLA-G 14-bp Deletion Variant in Women with Embryo Implantation Failure

PROBLEM

Human leukocyte antigen-G (HLA-G) expression is related to 14-bp insertion/deletion polymorphism at the 3'UTR of the HLA-G gene. Soluble forms of HLA-G are released as free molecules or via extracellular vesicles (EVs). Due to the crucial role of HLA-G during pregnancy, we analyzed the 14-bp polymorphism and the two secreted forms in implantation failure women (IF) and in fertile women (FW).

METHOD OF STUDY

For the genetic analysis, 49 IF and 34 FW were genotyped. For sHLA-G quantification, serum samples from 35 IF and 23 FW were available. ExoQuick(™) kit was used for EVs precipitation. The total soluble HLA-G (sHLA-Gtot ) and vesicular sHLA-GEV were quantified by ELISA. The EVs size and concentration were determined by nanoparticle tracking analysis (NTA).

RESULTS

An increased proportion of IF presented high levels of sHLA-Gtot (P = 0.02) and vesicular sHLA-GEV (P = 0.0003) compared to FW. The 14-bp deletion allele is more frequent in IF (P = 0.0002) and associated with high levels of sHLA-Gtot and vesicular sHLA-GEV .

CONCLUSION

The high expression of sHLA-Gtot and sHLA-GEV , together with the presence of the 14-bp deletion allele, might be involved in implantation failure.