Soluble HLA-G in pregnancies complicated by autoimmune rheumatic diseases

Association of parental HLA-G polymorphisms with soluble HLA-G expressions and their roles on recurrent implantation failure: A systematic review and meta-analysis

Introduction

HLA-G plays a central role in immune tolerance at the maternal-fetal interface. The HLA-G gene is characterized by low allelic polymorphism and restricted tissue expression compared with classical HLA genes. HLA-G polymorphism is associated with HLA-G expression and linked to pregnancy complications. However, the association of parental HLA-G polymorphisms with soluble HLA-G (sHLA-G) expression and their roles in recurrent implantation failure (RIF) is unclear. The study aims to systematically review the association of HLA-G polymorphisms with RIF, the association of sHLA-G expression with RIF, and the association of HLA-G polymorphisms with sHLA-G expressions in patients attending in-vitro fertilization (IVF) treatment.

Methods

Studies that evaluated the association of HLA-G polymorphisms with RIF, the association between sHLA-G expression with RIF, and the association between HLA-G polymorphisms with sHLA-G expressions in patients attending IVF treatment were included. Meta-analysis was performed by random-effect models. Sensitivity analysis was performed by excluding one study each time. Subgroup analysis was performed based on ethnicity.

Results

HLA-G 14bp ins variant is associated with a lower expression of sHLA-G in seminal or blood plasma of couples attending IVF treatment. The maternal HLA-G*010101 and paternal HLA-G*010102 alleles are associated with RIF risk compared to other alleles. However, single maternal HLA-G 14bp ins/del polymorphism, HLA-G -725 C>G/T polymorphism, or circulating sHLA-G concentration was not significantly associated with RIF in the general population. HLA-G 14bp ins/ins homozygous genotype or ins variant was associated with a higher risk of RIF in the Caucasian population.

Discussion

Specific HLA-G alleles or HLA-G polymorphisms are associated with sHLA-G expression in couples attending IVF treatment. Several HLA-G polymorphisms may be related to RIF, considering different ethnic backgrounds. A combined genetic effect should be considered in future studies to confirm the association of HLA-G polymorphisms and sHLA-G expressions in relation to RIF.

Endothelial Progenitor Cell CD34+ and CD133+ Concentrations and Soluble HLA-G Concentrations During Pregnancy and in Cord Blood in Undifferentiated Connective Tissue Diseases Compared to Controls

The objective of this study is to evaluate endothelial progenitor cells (EPCs) CD34⁺ CD133^- and CD34⁺ CD133⁺ and soluble HLA-G (sHLA-G) concentrations among undifferentiated connective tissue disease (UCTD) subjects, compared to controls, during pregnancy and in cord blood. This is a case-control study including 29 controls and 29 UCTDs. CD34⁺ CD133^-, CD34⁺ CD133⁺, and sHLA-G concentrations were detected in maternal plasma and in cord blood. This study was approved by the Medical-Ethical Committee of our Institution (Current Research Project N. 901-rcr2017i-23 of IRCCS Foundation Policlinico San Matteo of Pavia). Circulating CD34⁺ CD133^- and CD34⁺ CD133⁺ counts and sHLA-G (soluble human leucocyte antigen G) concentrations in maternal peripherical blood were higher in UCTD compared to those in controls in first and third trimester of pregnancy and at delivery (p < 0.001). Maternal CD34⁺ CD133^- and CD34⁺ CD133⁺ counts were strongly and significantly correlated in UCTD (Spearman's rho = 0.79, p < 0.0001) but not in controls (Spearman's rho = 0.10, p = 0.35). Cord blood CD34⁺ CD133^- and CD34⁺ CD133⁺ median counts and median sHLA-G concentrations were higher among UCTD subjects than in controls (p < 0.001). Cord blood CD34⁺ and CD133⁺ counts were inversely and significantly correlated with sHLA-G concentrations among UCTDs, but not in controls. Early UCTD is characterized by increased EPC levels in maternal plasma and in cord blood and higher levels of sHLA-G, compared to controls. Data suggest that fetoplacental unit plays an independent role in the EPC response to a systemic autoimmune disease.

The Role of HLA-G in Human Papillomavirus Infections and Cervical Carcinogenesis

Human leukocyte antigen (HLA)-G, a non-classical HLA-class I molecule, has a low polymorphism frequency, restricted tissue distribution and immunoinhibitory property. HLA-G expression in tumor cells and cells chronically infected with virus may enable them to escape from host immune surveillance. It is well-known that the HLA-G molecule is a novel biomarker and potential therapeutic target that is relevant in various types of cancers, but its role in cervical cancer has not been fully explored. In this review, we aim to summarize and discuss the immunologic role of the HLA-G molecule in the context of HPV infections and the process of cervical cancer carcinogenesis. A better understanding of the potential impact of HLA-G on the clinical course of persistent HPV infections, cervical epithelial cell transformation, tumor growth, recurrence and metastasis is needed to identify a novel diagnostic/prognostic biomarker for cervical cancer, which is critical for cervical cancer risk screening. In addition, it is also necessary to identify HLA-G-driven immune mechanisms involved in the interactions between host and virus to explore novel immunotherapy strategies that target HLA-G/immunoglobulin-like transcript (ILT) immune checkpoints.

miR‑148a modulates the viability, migration and invasion of oral squamous cell carcinoma cells by regulating HLA‑G expression

Oral squamous cell carcinoma (OSCC) is a common malignancy of the oral and maxillofacial regions. MicroRNAs (miRs) are a group of endogenous small noncoding RNAs that inhibit gene expression by binding to the mRNA of target genes, and serve important roles in numerous biological processes. Reverse transcription-quantitative polymerase chain reaction and western blotting were used to detect gene and protein expression levels, respectively. Cell proliferation, migration and invasion were detected using MTT, wound healing and Matrigel assays, respectively. The association between miR-148a and human leukocyte antigen-G (HLA-G) was analyzed using Targetscan and Luciferase reporter assays. In the present study, miR-148a was revealed to be significantly downregulated in OSCC cells. To further investigate the functions of miR-148a in OSCC, the viability, migration, and invasive abilities of SCC-9 cells were investigated following transfection with miR-148a mimics or miR-148a inhibitor. It was revealed that transfection with miR-148a mimics significantly reduced the viability, migration and invasion of cells, whereas miR-148a inhibitor significantly enhanced these properties. In addition, HLA-G was identified as a direct target of miR-148a and demonstrated to be downregulated in OSCC cells. Furthermore, it was revealed that transfection with miR-148a mimics decreased the expression levels of HLA-G mRNA and protein in SCC-9 cells, whereas transfection with miR-148a inhibitor increased the expression of HLA-G mRNA and protein. The results indicated that there was an association between miR-148a and HLA-G expression, and suggested that miR-148a may be a potential target in the treatment of OSCC.

Undifferentiated connective tissue diseases and adverse pregnancy outcomes. An undervalued association?

Undifferentiated connective tissue diseases (UCTDs) are a heterogeneous group of disorders characterized by symptoms and signs suggestive of systemic autoimmune rheumatic disease (ARD), but which do not fulfill all the established criteria for definite diagnosis of a condition. Although a third of UCTDs can progress to a definite ARD within months or years, most UCTDs can remain stable for years with minimal disease activity. The annual incidence of UCTD in the general population ranges from 14 to 140 per 100 000 people. UCTDs are associated with the persistence of several circulating autoantibodies including antinuclear, antiphospholipid or antithyroid antibodies. Immunological evaluation of subjects with UCTDs suggests a proinflammatory state and dysregulation of the Th1/Th2 balance. Autoantibodies have well-known deleterious effects on placentation and have been associated with an increased risk of prematurity, fetal growth restriction (FGR), preeclampsia, and congenital atrioventricular heart block. Although epidemiological and biological data suggest a potential negative impact on reproductive outcomes, the relationship between UCTD and pregnancy outcomes has not been adequately studied. While awaiting definitive data from large studies, obstetricians should be aware that rheumatic disorders in their early, incomplete, or undifferentiated phases can adversely affect pregnancy outcomes, increasing the likelihood of pregnancy loss, FGR, preeclampsia, and prematurity.

The Immunosignature of Mother/Fetus Couples in Gestational Diabetes Mellitus: Role of HLA-G 14 bp ins/del and PAPP-A A/C Polymorphisms in the Uterine Inflammatory Milieu

We enrolled 151 healthy mother/newborn couples and 26 with gestational diabetes mellitus (GDM). HLA-G and PAPP-A plasma levels were measured by ELISA at first and second trimesters, at delivery, and in cord blood. HLA-G 14 bp ins/del and PAPP-A A/C polymorphisms were genotyped. HLA-G del/del and PAPP-A C/C genotypes were more frequent among GDM mothers than controls. We observed a genetic epistasis between the two polymorphisms: the HLA-G del/del and PAPP-A C/C combination was carried by 8% of GDM mothers and 1.3% of controls (OR = 9.5, 95% CI = 0.8-109, p = 0.07). GDM mothers showed increased sHLA-G levels compared to controls (p = 0.004), and those carrying the HLA-G del/del genotype produced more sHLA-G at the second trimester and at delivery (p = 0.014). A genetic pressure by fetal genotype on maternal sHLA-G production was observed in GDM mothers with heterozygous HLA-G del/ins newborns (p = 0.02). Babies born to GDM mothers showed higher sHLA-G concentrations compared to those born to healthy mothers, and those carrying HLA-G del/del showed the highest sHLA-G levels (p = 0.013). PAPP-A amounts significantly increased along pregnancy (p < 0.001), but the median levels at the first and second trimesters were significantly lower in GDM (p = 0.03). Our findings first suggest an involvement of HLA-G and PAPP-A gene-protein interaction in GDM and highlight a possible contribution of the fetus in balancing maternal inflammation.

Recent Advances in Our Understanding of HLA-G Biology: Lessons from a Wide Spectrum of Human Diseases

HLA-G is a HLA-class Ib molecule with potent immunomodulatory activities, which is expressed in physiological conditions, where modulation of the immune response is required to avoid allograft recognition (i.e., maternal-fetal interface or transplanted patients). However, HLA-G can be expressed de novo at high levels in several pathological conditions, including solid and hematological tumors and during microbial or viral infections, leading to the impairment of the immune response against tumor cells or pathogens, respectively. On the other hand, the loss of HLA-G mediated control of the immune responses may lead to the onset of autoimmune/inflammatory diseases, caused by an uncontrolled activation of the immune effector cells. Here, we have reviewed novel findings on HLA-G functions in different physiological and pathological settings, which have been published in the last two years. These studies further confirmed the important role of this molecule in the modulation of the immune system.

Soluble HLA-G concentrations in maternal blood and cervical vaginal fluid of pregnant women with preterm premature rupture of membranes

OBJECTIVE

To evaluate soluble HLA-G (sHLA-G) concentrations in maternal blood serum and cervical vaginal fluid in pregnancies complicated by preterm premature rupture of membranes (PPROM) compared to controls.

STUDY DESIGN

Case-control study of 24 women with PPROM and 40 controls.

MAIN OUTCOME MEASURES

Vaginal and serum sHLA-G and IL-6 concentrations.

FINDINGS

Women with PPROM had significantly higher serum and vaginal sHLA-G concentrations compared to controls (respectively median 31.48U\ml versus 13.9U\ml p<0.001 and 1.7U\ml versus 0.1U\ml p<0.001). Vaginal expression of IL-6 was higher in PPROM cases compared to controls (respectively, median 31.19pg\ml versus 6.67pg\ml; p<0.001). Higher serum and vaginal sHLA-G were associated with both a shorter length of pregnancy and histological chorioamnionitis in the PPROM group.

CONCLUSIONS

Higher vaginal and serum sHLA-G in PPROM cases may be a sign of local and systemic inflammation.