Variation sites at the HLA-G 3' untranslated region confer differential susceptibility to HIV/HPV co-infection and aneuploidy in cervical cell

HLA-G - evolvement from a trophoblast specific marker to a checkpoint molecule in cancer, a narrative review about the specific role in breast- and gynecological cancer

Human leukocyte antigen G (HLA-G) is known as a non-classical molecule of the major histocompatibility complex class Ib and downregulates the mother's immune response against the fetus during pregnancy, thereby generating immune tolerance. Due to the latter effect, HLA-G is also referred to as an immune checkpoint molecule. Originally identified on extravillous trophoblasts, HLA-G is already known to induce immune tolerance at various stages of the immune response, for example through cell differentiation and proliferation, cytolysis and cytokine secretion. Because of these functions, HLA-G is involved in various processes of cancer progression, but a comprehensive review of the role of HLA-G in gynecologic cancers is lacking. Therefore, this review focuses on the existing knowledge of HLA-G in ovarian cancer, endometrial cancer, cervical cancer and breast cancer. HLA-G is predominantly expressed in cancer tissues adjacent to the extravillous trophoblast. Therefore, modulating its expression in the cancer target tissues of cancer patients could be a potential therapeutic approach to treat these diseases.

Influence of HLA-G 3' Untranslated Region Haplotypes and SNP +3422 Gene Variants as Host Genetic Factors on the Outcomes of SARS-CoV-2 Infection During Acute and Post-Acute Phases in a German Cohort

HLA-G, an important immune-checkpoint (IC) molecule that exerts inhibitory signalling on immune effector cells, has been suggested to represent a key player in regulating the immune response to Severe Acute Respiratory Syndrome Coronavirus Type 2 (SARS-CoV-2). Since specific single-nucleotide polymorphisms (SNP) in the HLA-G 3'untranslated region (UTR), which arrange as haplotypes, are crucial for the regulation of HLA-G expression, we analysed the contribution of these genetic variants as host factors in SARS-CoV-2 infection during acute and post-acute phases. HLA-G gene polymorphisms in the 3'UTR were investigated by sequencing in an unvaccinated Coronavirus Disease 2019 (COVID-19) cohort during acute SARS-CoV-2 infection (N = 505) and in the post-acute phase (N = 253). The HLA-G 3'UTR haplotype known as UTR-3 (p = 0.002) and the variant rs17875408 (also known as +3422) T variant (p = 0.004) are independent prognostic risk factors for fatal COVID-19. The +3422T variant (p = 0.006) predicted also the early loss of neutralising SARS-CoV-2 antibodies. In addition, the HLA-G 3'UTR haplotype UTR-7 (p = 0.023) emerged as an independent prognostic factor for increased susceptibility to Long-COVID symptoms after SARS-CoV-2 infection. Our study highlights that due to the variability of the 3'UTR genetic background, HLA-G has the potential to contribute to the progression of SARS-CoV-2 infection, extending to the development of Long-COVID symptoms, despite the likely alterations in the microenvironment and associated HLA-G-specific regulatory elements over the course of the disease. By spotlighting HLA-G, the importance of the genetic background of IC and their pivotal role in modulating immune responses during and after COVID-19 are emphasised.

Association of HLA-G 3'UTR polymorphisms with hepatitis B virus infection in Tunisian population

Hepatitis B virus (HBV) infection is a major public health burden. The mechanisms of immune evasion during chronic HBV (CHB) infection are poorly understood. Human leukocyte antigen (HLA)-G, an immune checkpoint molecule, plays a crucial role in the tolerance mechanisms of various infectious diseases. The 3' untranslated region (3'UTR), including the HLA-G + 3142 C > G polymorphism (rs1063320) and the 14-pb Ins/Del (rs66554220) has been strongly suggested to influence HLA-G expression. This study conducted a case-control analysis to evaluate the potential correlation between the HLA-G + 3142 C > G polymorphism and HBV infection outcome in a Tunisian cohort. The HLA-G + 3142 C > G polymorphism was analysed by PCR-RFLP in 242 patients with chronic HBV infection (116 males and 126 females), 241 healthy controls (116 males and 125 females), and 100 spontaneously resolved subjects (52 males and 48 females). Patients with chronic HBV infection showed a higher frequency of the + 3142G allele compared to healthy controls and spontaneously resolved subjects (p = 0.001 and p = 0.002, respectively). An association between the + 3142G allele and high HBV DNA levels was observed when HBV patients were stratified based on their HBV DNA levels (p = 0.016). Furthermore, the dominant model (GG + GC vs CC) was associated with liver function parameters, including AST, ALT, and high HBV DNA levels (p = 0.04, p < 0.001 and p = 0.002, respectively). However, there was no significant association found between this polymorphism and the fibrosis stage (p = 0.32). The haplotype analysis, using a subset of previously published data on the HLA-G 14-pb Ins/Del polymorphism, revealed an association between the Ins/G haplotype and chronic HBV infection (H1: InsG, p < 0.001). Our findings suggest that the + 3142G allele is a risk factor for the persistence and progression of HBV infection, while the + 3142C allele serves as a protective allele associated with the spontaneous resolution of the infection. Additionally, the HLA-G 3'UTR haplotype Ins/G is associated with chronic HBV infection in the Tunisian population.

The role of T regulatory cells in the immunopathogenesis of HIV: Clinical implications

Human Immunodeficiency Virus (HIV) infection is among the most challenging issues in the healthcare system, presenting significant financial and hygiene problems with a wide range of clinical manifestations. Despite the hopeful outcomes of Antiretroviral Therapies (ARTs), the current strategies for the treatment of patients with HIV infection have not shown clinical significance for all subjects, which is mainly due to the complexity of the disease. Therefore, the need for collaborative and interdisciplinary research focused on deciphering the multifaceted cellular, and molecular immunopathogenesis of HIV remains essential in the development of innovative and more efficacious therapeutic approaches. T-regulatory (Treg) cells function as suppressors of effector T-cell responses contributing to the inhibition of autoimmune disorders and the limitation of chronic inflammatory diseases. Notably, these cells can play substantial roles in regulating immune responses, immunopathogenesis, viral persistence and disease progression, and affect therapeutic responses in HIV patients. In this review, we aim elucidating the role of T-regulatory cells (Tregs) in the immunopathogenesis of HIV, including immunological fatigue and seroconversion. In particular, the focus of the current study is exploration of novel immunotherapeutic approaches to target HIV or related co-infections.

Role of HLA-G in tumors and upon COVID-19 infection

HLA-G expression of tumors and upon viral infections is involved in their immune escape leading to the evasion from both T and NK cell recognition. The underlying mechanisms of HLA-G expression in both pathophysiologic conditions are broad and range from genetic abnormalities to epigenetic, transcriptional and posttranscriptional regulation. This review summarizes the current knowledge of the frequency, regulation and clinical relevance of HLA-G expression upon neoplastic and viral transformation, its interaction with components of the microenvironment as well as its potential as diagnostic marker and/or therapeutic target. In addition, it discusses urgent topics, which have to be addressed in HLA-G research.

Harnessing the potential of HLA-G in cancer therapy: advances, challenges, and prospects

Immune checkpoint blockades have been prized in circumventing and ablating the impediments posed by immunosuppressive receptors, reaching an exciting juncture to be an innovator in anticancer therapy beyond traditional therapeutics. Thus far, approved immune checkpoint blockades have principally targeted PD-1/PD-L1 and CTLA-4 with exciting success in a plethora of tumors and yet are still trapped in dilemmas of limited response rates and adverse effects. Hence, unveiling new immunotherapeutic targets has aroused immense scientific interest in the hope of expanding the clinical application of immune checkpoint blockades to scale new heights. Human leukocyte antigen-G (HLA-G), a non-classical major histocompatibility complex (MHC) class I molecule, is enriched on various malignant cells and is involved in the hindrance of immune effector cells and the facilitation of immunosuppressive cells. HLA-G stands out as a crucial next-generation immune checkpoint showing great promise for the benefit of cancer patients. Here, we provide an overview of the current understanding of the expression pattern and immunological functions of HLA-G, as well as its interaction with well-characterized immune checkpoints. Since HLA-G can be shed from the cell surface or released by various cells as free soluble HLA-G (sHLA-G) or as part of extracellular vesicles (EVs), namely HLA-G-bearing EVs (HLA-GEV), we discuss the potential of sHLA-G and HLA-GEV as predictive biomarkers. This review also addresses the advancement of HLA-G-based therapies in preclinical and clinical settings, with a focus on their clinical application in cancer.

Contribution of HLA-G and FOXP3 genes and proteins in the severity of cervical intraepithelial neoplasia during HPV infection

Human Papillomavirus (HPV) persistence leads to the chronification of cervical inflammation, where HLA-G and Foxp3; immunomodulatory molecules, may contribute to the aggravation of the lesion and cancerization. Here, we evaluated the synergic effect of these two molecules in the worsening of the lesion in presence of HPV infection. Hundred and eighty (180) women cervical cells and biopsies were collected for (i) HLAG Sanger sequencing and gene expression, and (ii) HLA-G and Foxp3 molecule expressions by immunohistochemistry. 53 women were HPV+ against 127 women HPV-. HPV+ women were more at risk of having cytological changes (p ≤ 0.0123), histological changes (p < 0.0011), and cervical lesion (p = 0.0004). The HLA-G + 3142CC genotype predisposed women to infection (p = 0.0190), while HLA-G + 3142C and +3035 T alleles were associated with HLA-G5 transcript expression. Both sHLA-G (p = 0.030) and Foxp3 (p = 0.0002) proteins were higher in cervical lesion as well as in high-grade lesion. In addition, sHLA-G+ cells were positively correlated to Foxp3+ cells in presence of HPV infection and in cervical grade II/III injuries. In conclusion, HPV may use HLA-G and Foxp3 as a way of host immune escape contributing to the persistence of infection and inflammation, leading to the cervical lesion and the worsening of lesions.

The association between genetic variants at 3'-UTR and 5'-URR of HLA-G gene and the clinical outcomes of patients with leukemia receiving hematopoietic stem cell transplantation

In addition to the classical human leukocyte antigen (HLA) genes, the outcomes of post-hematopoietic stem cell transplantation (HSCT) are associated with human leukocyte antigen (HLA)-related genes and non-HLA genes involved in immune regulation. HLA-G gene plays an important role in immune tolerance, assisting immune escape of tumor cells, and decrease of transplant rejection. In this study, we explored the association of genetic variants at the 3'-untranslated region (3'-UTR) and 5'-upstream regulatory region (5'-URR) of HLA-G gene with the adverse outcomes of patients with leukemia receiving HSCT. The genomic DNAs of 164 patients who had acute leukemia and received HSCT were collected for analysis. Nine single nucleotide polymorphisms (SNPs) and six haplotypes in the 3'-UTR and 27 SNPs and 6 haplotypes in the 5'-URR were selected to investigate their relationship with the development of adverse outcomes for patients receiving HSCT, including mortality, relapse, and graft-versus-host disease. Our results revealed that two SNPs (rs371194629 and rs9380142) and one haplotype (UTR-3) located in the 3'-UTR and two SNPs (rs3823321 and rs1736934) and one haplotype (G0104a) located in the 5'-URR of HLA-G were associated with the occurrence of chronic GVHD or development of any forms of GVHD. No SNP was found to associate with the occurrence of mortality and relapse for patients receiving HSCT. These SNPs and haplotypes may play important roles in regulating immune tolerance of allografts post-HSCT that can be used to predict the risk of poor outcomes after receiving HSCT and giving preventive treatment to patients on time.

The relationship of 3'UTR HLA-G14-bp insertion/deletion and +3142 C/G polymorphisms and soluble HLA-G expression with gynecological cancers: An updated meta-analysis

OBJECTIVES

Human leukocyte antigen-G (HLA-G) is implicated in several cancers and is considered to be an immune checkpoint regulator. We determined the association between polymorphisms in the 3' untranslated region of HLA-G and soluble HLA-G (sHLA-G) expression with gynecological cancers (GCs).

METHODS

A meta-analysis was conducted to examine the association between HLA-G14-bp insertion (I)/deletion (D) and +3142C/G polymorphism in GC and to evaluate sHLA-G expression RESULTS: We revealed a significant association between the +3142C/G polymorphism and invasive cervical cancer (ICC) based on the allelic model G versus C (odds ratio [OR] = 0.738, 95% confidence interval [CI] = 0.563-0.966, p = 0.027), dominant GG+GC versus CC (OR = 0.584, 95% CI = 0.395-0.862, p = 0.007), and codominant GG versus CC (OR = 0.527, 95% CI = 0.312-0.891, p = 0.017) models, suggesting that the G allele and GG genotype are protective against ICC. In gynecological precancerous patients with human papillomavirus (HPV) infection, we found that the 14-bp I/D under the codominant DD versus DI model (OR = 0.492, 95% CI = 0.241-1.004, p = 0.051) was of borderline significance. Soluble HLA-G levels were significantly higher in patients compared with healthy controls (standardized mean differences [SMD] = 1.434, 95% CI = 0.442-2.526, p = 0.005). Stratification by cancer type revealed that the sHLA-G levels were significantly increased in cervical cancer (SMD = 4.889, 95% CI = 0.468-9.310, p = 0.030) and in subjects of Asian ethnicity (SMD = 4.889, 95% CI = 0.467-9.309, p = 0.030).

CONCLUSIONS

HLA-G14-bp I/D and +3142 C/G polymorphisms are associated with GC and HPV-associated cervical cancer. In addition, we found significantly increased sHLA-G levels in cancer patients. These results provide a basis for further studies in diagnostics and immunotherapy of GC.

Impact of HLA-G +3142C>G on the development of antibodies to blood group systems other than the Rh and Kell among sensitized patients with sickle cell disease

BACKGROUND

Patients' inflammatory history is an important factor underlying red blood cell (RBC) alloimmunization, which is a frequent transfusion complication among individuals with sickle cell disease (SCD). HLA-G has been associated with different inflammatory and auto - immune diseases. Our goal was to verify whether the HLA-G + 3142 C>G and 14-bp Ins/Del variations are associated with RBC antibody development among SCD patients.

METHODS

This was a single-center case-control study. SCD patients were randomly selected for the study and divided into two groups: 'Alloimmunized' and 'Nonalloimmunized' depending on the presence of irregular antibodies. The 'Alloimmunized'group was further divided into two subgroups according to the presence of only antibodies against the Rh and Kell blood group systems or the existence of antibodies to antigens of the other blood group systems.

RESULTS

A total of 213 patients were included in the study (110 alloimmunized and 103 non-alloimmunized). The 'Alloimmunized' and 'Non-alloimmunized' groups did not differ statistically regarding the HLA-G + 14 bp Ins/Del ( p = 0.494) and + 3142 C>G ( p = 0.334). Individuals who had only antibodies against the Rh and Kell antigens had a frequency of HLA-G + 3142GG genotype almost twice as high compared to the groupwith antibodies against less immunogenic antigens ( p = 0.043).

CONCLUSIONS

The genotype frequency of HLA-G + 3142 C>G differs among alloimmunized SCD patients, depending on the presence of antibodies against low immunogenic RBC antigens. This highlights a possible role played by the HLA-G molecule in the RBC alloimmunization process.

Systematic Evaluation of HLA-G 3'Untranslated Region Variants in Locally Advanced, Non-Metastatic Breast Cancer Patients: UTR-1, 2 or UTR-4 are Predictors for Therapy and Disease Outcome

Despite major improvements in diagnostics and therapy in early as well as in locally advanced breast cancer (LABC), metastatic relapse occurs in about 20% of patients, often explained by early micro-metastatic spread into bone marrow by disseminated tumor cells (DTC). Although neoadjuvant chemotherapy (NACT) has been a successful tool to improve overall survival (OS), there is growing evidence that various environmental factors like the non-classical human leukocyte antigen-G (HLA-G) promotes cancer invasiveness and metastatic progression. HLA-G expression is associated with regulatory elements targeting certain single-nucleotide polymorphisms (SNP) in the HLA-G 3’ untranslated region (UTR), which arrange as haplotypes. Here, we systematically evaluated the impact of HLA-G 3’UTR polymorphisms on disease status, on the presence of DTC, on soluble HLA-G levels, and on therapy and disease outcome in non-metastatic LABC patients. Although haplotype frequencies were similar in patients (n = 142) and controls (n = 204), univariate analysis revealed that the UTR-7 haplotype was related to patients with low tumor burden, whereas UTR-4 was associated with tumor sizes >T1. Furthermore, UTR-4 was associated with the presence of DTC, but UTR-3 and UTR-7 were related to absence of DTC. Additionally, increased levels of soluble HLA-G molecules were found in patients carrying UTR-7. Regarding therapy and disease outcome, univariate and multivariate analysis highlighted UTR-1 or UTR-2 as a prognostic parameter indicative for a beneficial course of disease in terms of complete response towards NACT or progression-free survival (PFS). At variance, UTR-4 was an independent risk factor for a reduced OS besides already known parameters. Taken into account the most common HLA-G 3’UTR haplotypes (UTR-1–UTR-7, UTR-18), deduction of the UTR-1/2/4 haplotypes to specific SNPs revealed that the +3003C variant, unique for UTR-4, seemed to favor a detrimental disease outcome, while the +3187G and +3196G variants, unique for UTR-1 or UTR-2, were prognostic parameters for a beneficial course of disease. In conclusion, these data suggest that the HLA-G 3’UTR variants +3003C, +3187G, and +3196G are promising candidates for the prediction of therapy and disease outcome in LABC patients.

Increased PD-1 Level in Severe Cervical Injury Is Associated With the Rare Programmed Cell Death 1 (PDCD1) rs36084323 A Allele in a Dominant Model

The high-risk oncogenic human papillomavirus (HPV) has developed mechanisms for evasion of the immune system, favoring the persistence of the infection. The chronic inflammation further contributes to the progression of tissue injury to cervical cancer. The programmed cell death protein (PD-1) after contacting with its ligands (PD-L1 and PD-L2) exerts an inhibitory effect on the cellular immune response, maintaining the balance between activation, tolerance, and immune cell-dependent lesion. We evaluated 295 patients exhibiting or not HPV infection, stratified according to the location (injured and adjacent non-injured areas) and severity of the lesion (benign, pre-malignant lesions). Additionally, we investigated the role of the promoter region PDCD1 -606G>A polymorphism (rs36084323) on the studied variables. PD-1 and PDCD1 expression were evaluated by immunohistochemistry and qPCR, respectively, and the PDCD1 polymorphism was evaluated by nucleotide sequencing. Irrespective of the severity of the lesion, PD-1 levels were increased compared to adjacent uninjured areas. Additionally, in cervical intraepithelial neoplasia (CIN) I, the presence of HPV was associated with increased (P = 0.0649), whereas in CIN III was associated with decreased (P = 0.0148) PD-1 levels, compared to the uninjured area in absence of HPV infection. The PDCD1 -606A allele was rare in our population (8.7%) and was not associated with the risk for development of HPV infection, cytological and histological features, and aneuploidy. In contrast, irrespective of the severity of the lesion, patients exhibiting the mutant PDCD1 -606A allele at single or double doses exhibited increased protein and gene expression when compared to the PDCD1 -606GG wild type genotype. Besides, the presence of HPV was associated with the decrease in PDCD1 expression and PD-1 levels in carriers of the -606 A allele presenting severe lesions, suggesting that other mediators induced during the HPV infection progression may play an additional role. This study showed that increased PD-1 levels are influenced by the -606G>A nucleotide variation, particularly in low-grade lesions, in which the A allele favors increased PDCD1 expression, contributing to HPV immune system evasion, and in the high-grade lesion, by decreasing tissue PD-1 levels.

HLA-G: Function, polymorphisms and pathology

HLA-G immune modulatory genes and molecules are presently being studied by a widespread number of research groups. In the present study, we do not aim to be exhaustive since the number of manuscripts published every year is overwhelming. Instead, our aim is pointing out facts about HLA-G function, polymorphism and pathology that have been confirmed by several different researchers, together with exposing aspects that may have been overlooked or not sufficiently remarked in this productive field of study. On the other hand, we question whether performing mainly studies on HLA-G and disease associations is going to give a clear answer in the future, since 40 years of study of classical HLA molecules association with disease has still given no definite answer on this issue.

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.