HLA Class Ib Molecule Research Articles

Instability of the HLA-E peptidome of HIV presents a major barrier to therapeutic targeting

Naturally occurring Tcells that recognize microbial peptides via HLA-E, a nonpolymorphic HLA class Ib molecule, could provide the foundation for new universal immunotherapeutics. However, confidence in the biological relevance of putative ligands is crucial, given that the mechanisms by which pathogen-derived peptides can access the HLA-E presentation pathway are poorly understood. We systematically interrogated the HIV proteome using immunopeptidomic and bioinformatic approaches, coupled with biochemical and cellular assays. No HIV HLA-E peptides were identified by tandem mass spectrometry analysis of HIV-infected cells. In addition, all bioinformatically predicted HIV peptide ligands (>80) were characterized by poor complex stability. Furthermore, infected cell elimination assays using an affinity-enhanced Tcell receptor bispecific targeted to a previously reported HIV Gag HLA-E epitope demonstrated inconsistent presentation of the peptide, despite normal HLA-E expression on HIV-infected cells. This work highlights the instability of the HIV HLA-E peptidome as a major challenge for drug development.

Non-Classical HLA Class 1b and Hepatocellular Carcinoma.

A number of studies are underway to gain a better understanding of the role of immunity in the pathogenesis of hepatocellular carcinoma and to identify subgroups of individuals who may benefit the most from systemic therapy according to the etiology of their tumor. Human leukocyte antigens play a key role in antigen presentation to T cells. This is fundamental to the host's defense against pathogens and tumor cells. In addition, HLA-specific interactions with innate lymphoid cell receptors, such those present on natural killer cells and innate lymphoid cell type 2, have been shown to be important activators of immune function in the context of several liver diseases. More recent studies have highlighted the key role of members of the non-classical HLA-Ib and the transcript adjacent to the HLA-F locus, FAT10, in hepatocarcinoma. The present review analyzes the major contribution of these molecules to hepatic viral infection and hepatocellular prognosis. Particular attention has been paid to the association of natural killer and Vδ2 T-cell activation, mediated by specific HLA class Ib molecules, with risk assessment and novel treatment strategies to improve immunotherapy in HCC.

Advances in the study of HLA class Ib in maternal-fetal immune tolerance.

The HLA class Ib molecule is an alloantigen that causes transplant rejection on behalf of individual human and plays an important role in maternal-fetal immune tolerance. Early studies on HLA class Ib focused on the mechanism of HLA-G-induced immune escape, but in recent years, studies on the mechanism of HLA-G have deepened and gradually explored the mechanism of HLA-E and HLA-F, which are also HLA class Ib molecules. In the maternal-fetal interface, trophoblast cells express HLA class Ib molecules to protect the fetus from maternal immune cells by binding to inhibitory receptors of decidual immune cells (DICs) and shifting Th1/Th2 balance toward Th2 bias. Further studies on the molecular mechanism of HLA class Ib molecules provide a reference for its application in the field of clinical assisted reproduction.

Higher risk for chronic graft-versus-host disease (GvHD) in HLA-G mismatched transplants following allogeneic hematopoietic stem cell transplantation: A retrospective study.

Graft-versus-host disease (GvHD) is a major complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT) and is highly influenced by the degree of HLA matching between recipient and donor. The HLA-class Ib molecule HLA-G has been shown to promote tolerogenicity through its interaction with inhibitory receptors found on several immunocompetent cells. We hypothesized that in an allo-HSCT setting, HLA-G mismatches may negatively impact the HLA-G-mediated tolerogenicity either due to inefficient interaction with the inhibitory receptors of the transplanted immune cells or due to direct allorecognition of mismatched HLA-G on host cells by the immune cells of the donor. In order to explore this hypothesis, we investigated the impact of HLA-G mismatching in 2.083 10/10 matched high resolution HLA-typed allo-HSCT transplants. We found that the risk of chronic GvHD was significantly higher in HLA-G-mismatched transplant cases as compared with the HLA-G-matched control group (HR: 1.46, 95%CI=1.11-1.91, p= 0.006). Sub-analysis of the mismatch vector revealed that this effect was only detectable in the GvH (HR: 1.89, 95%CI 1.39-2.57, p < 0.001) but not the HvG direction (HR: 1.01, 95%CI=0.63-1.63, p= 0.967). In addition, the negative impact of HLA-G mismatching on chronic GvHD was only significant in younger patients (<30y HR: 3.02, 95%CI=1.25-7.28, p=0.014; >29y HR: 1.28, 95%CI=0.94-1.72, p= 0.113). Our results indicate that HLA-G mismatches may contribute to the onset of chronic GvHD, especially in younger patients and should therefore be avoided when possible.

HLA-G and Other Immune Checkpoint Molecules as Targets for Novel Combined Immunotherapies.

HLA-G is an HLA-class Ib molecule that is involved in the establishment of tolerance at the maternal/fetal interface during pregnancy. The expression of HLA-G is highly restricted in adults, but the de novo expression of this molecule may be observed in different hematological and solid tumors and is related to cancer progression. Indeed, tumor cells expressing high levels of HLA-G are able to suppress anti-tumor responses, thus escaping from the control of the immune system. HLA-G has been proposed as an immune checkpoint (IC) molecule due to its crucial role in tumor progression, immune escape, and metastatic spread. We here review data available in the literature in which the interaction between HLA-G and other IC molecules is reported, in particular PD-1, CTLA-4, and TIM-3, but also IDO and TIGIT. Clinical trials using monoclonal antibodies against HLA-G and other IC are currently ongoing with cancer patients where antibodies and inhibitors of PD-1 and CTLA-4 showed encouraging results. With this background, we may envisage that combined therapies using antibodies targeting HLA-G and another IC may be successful for clinical purposes. Indeed, such immunotherapeutic protocols may achieve a better rescue of effective anti-tumor immune response, thus improving the clinical outcome of patients.

Variation in the HLA-F gene locus with functional impact is associated with pregnancy success and time-to-pregnancy after fertility treatment.

The aim of this study was to investigate a possible influence of three single nucleotide polymorphisms (SNPs) in the HLA-F gene locus on time-to-pregnancy and pregnancy success after fertility treatment. HLA-F SNP genotypes and HLA-F diplotypes are associated with the number of fertility treatment cycles needed to achieve pregnancy and live birth. HLA class Ib molecules, including HLA-F, which are known to be expressed by extra-villous trophoblast cells have immunomodulatory properties and play a role at the feto-maternal interface. However, a few recent studies suggest that HLA-F expressed in the mid-luteal endometrium may play a part in the establishment of pregnancy as well. Three genetic polymorphisms in the HLA-F gene locus influence the expression of HLA-F in the mid-luteal endometrium and are associated with time-to-pregnancy in healthy women. The current study included 102 female patients and 91 male patients attending for ART treatment and recruited between 2009 and 2014 at fertility clinics in a University Hospital setting, and 78 fertile female controls recruited in 2017 and 2018 at a department of Obstetrics and Gynaecology in a University Hospital. All women in the control group conceived naturally, and no other clinical data for the controls were retrieved. Genotyping of genomic DNA from blood samples was performed with Sanger sequencing for the three SNPs of interest in the HLA-F gene locus: rs1362126 (G/A), rs2523405 (T/G) and rs2523393 (A/G). Furthermore, clinical data were collected for the couples in fertility treatment. There were no significant differences in the distributions of the three HLA-F SNP genotypes and alleles between the female fertile control group and the female infertility group. We considered if the number of treatment cycles was related to the HLA-F SNP genotypes and HLA-F diplotypes in a discrete time to event analyses. A significant association with longer time-to-pregnancy, measured as number of fertility treatment cycles, was observed for women in the ART group who carried the HLA-F genotypes that are associated with a lower amount of HLA-F mRNA expressed in mid-luteal endometrium. For the rs1362126 AA genotype relative to the GG genotype, the odds ratio (OR) was 0.30 (95% CI = 0.10-0.87, P= 0.02); for the rs2523405 GG genotype relative to the TT genotype, the OR was 0.40 (95% CI = 0.15-1.04, P= 0.06); and for the rs2523393 GG genotype relative to the AA genotype, the OR was 0.27 (95% CI = 0.09-0.78, P= 0.01). In addition to comparing the HLA-F genotypes by a standard likelihood-ratio test, a trend test based on the number of G or A alleles were also performed. The HLA-F genotypes associated with longer time-to-pregnancy in these tests were as follows: number of A alleles at rs1362126 (P= 0.01), the OR was 0.56 per A allele (95% CI = 0.35-0.89); number of G alleles at rs2523405 (P= 0.05), OR was 0.65 per G allele (95% CI = 0.42-1.00); and number of G alleles at rs2523393 (P= 0.01), OR was 0.56 per G allele (95% CI = 0.36-0.86). On average, for the rs1362126 SNP, 2.1 more treatment cycles for a woman who carried the AA genotype were needed to achieve pregnancy within the first eight treatment cycles compared with a woman who carried the GG genotype. Likewise, for the rs2523405 SNP, 1.8 more cycles for the GG genotype compared with the TT genotype were needed, and for the rs2523393 SNP, 2.2 more treatment cycles for a woman who carried the GG genotype compared with a woman who carried the AA genotype were needed. Adjustments for the covariates BMI, female age, IVF (yes/no for each cycle), ICSI (yes/no for each cycle), female factor (yes/no) and male factor (yes/no), were also performed modeling the cycle-specific probabilities and the genotypes remained significant and almost unchanged. Specific types of ART will be chosen from the start of treatment, which means that the chances of achieving pregnancy could differ between the women solely due to their first line of treatment. However, multivariate analyses are performed to adjust for type of ART treatment. To our knowledge, this is the first study that shows associations between, and implications of, HLA-F gene locus variation and time-to-pregnancy and pregnancy success in a clinical setting for fertility treatment/ART. Supported by the Region Zealand Health Sciences Research foundation and by Zealand University Hospital through the ReproHealth Research Consortium ZUH. The authors declare no conflict of interest.

Between Innate and Adaptive Immune Responses: NKG2A, NKG2C, and CD8⁺ T Cell Recognition of HLA-E Restricted Self-Peptides Acquired in the Absence of HLA-Ia.

On healthy cells the non-classical HLA class Ib molecule HLA-E displays the cognate ligand for the NK cell receptor NKG2A/CD94 when bound to HLA class I signal peptide sequences. In a pathogenic situation when HLA class I is absent, HLA-E is bound to a diverse set of peptides and enables the stimulatory NKG2C/CD94 receptor to bind. The activation of CD8+ T cells by certain p:HLA-E complexes illustrates the dual role of this low polymorphic HLA molecule in innate and adaptive immunity. Recent studies revealed a shift in the HLA-E peptide repertoire in cells with defects in the peptide loading complex machinery. We recently showed that HLA-E presents a highly diverse set of peptides in the absence of HLA class Ia and revealed a non-protective feature against NK cell cytotoxicity mediated by these peptides. In the present study we have evaluated the molecular basis for the impaired NK cell inhibition by these peptides and determined the cell surface stability of individual p:HLA-E complexes and their binding efficiency to soluble NKG2A/CD94 or NKG2C/CD94 receptors. Additionally, we analyzed the recognition of these p:HLA-E epitopes by CD8+ T cells. We show that non-canonical peptides provide stable cell surface expression of HLA-E, and these p:HLA-E complexes still bind to NKG2/CD94 receptors in a peptide-restricted fashion. Furthermore, individual p:HLA-E complexes elicit activation of CD8+ T cells with an effector memory phenotype. These novel HLA-E epitopes provide new implications for therapies targeting cells with abnormal HLA class I expression.

HLA-G dimer targets Granzyme B pathway to prolong human renal allograft survival.

Human leukocyte antigen G (HLA-G), a nonclassic HLA class Ib molecule involved in the maintenance of maternal tolerance to semiallogeneic fetal tissues during pregnancy, has emerged as a potential therapeutic target to control allograft rejection. We demonstrate here that the level of soluble HLA-G dimer was higher in a group of 90 patients with a functioning renal allograft compared with 40 patients who rejected (RJ) their transplants. The HLA-G dimer level was not affected by demographic status. One of the potential mechanisms in tissue-organ allograft rejection involves the induction of granzymes and perforin, which are the main effector molecules expressed by CD8+ cytotoxic T lymphocytes and function to destroy allogeneic transplants. Using genomics and molecular and cellular analyses of cells from T-cell-mediated RJ and nonrejected kidney transplant patients, cells from leukocyte Ig-like receptor B1 (LILRB1) transgenic mice, humanized mice, and genetically engineered HLA-G dimer, we demonstrated a novel mechanism by which HLA-G dimer inhibits activation and cytotoxic capabilities of human CD8+ T cells. This mechanism implicated the down-regulation of Granzyme B expression and the essential involvement of LILRB1. Thus, HLA-G dimer has the potential to be a specific and effective therapy for prevention of allograft rejection and prolongation of graft survival.-Ajith, A., Portik-Dobos, V., Nguyen-Lefebvre, A. T., Callaway, C., Horuzsko, D. D., Kapoor, R., Zayas, C., Maenaka, K., Mulloy, L. L., Horuzsko, A. HLA-G dimer targets Granzyme B pathway to prolong human renal allograft survival.

HLA class Ia and Ib molecules and FOXP3+ TILs in relation to the prognosis of malignant melanoma patients

HLA class Ia (HLA-ABC) and HLA class Ib (HLA-E, -F and -G) molecules and FOXP3+ tumor-infiltrating lymphocytes (TILs) are often reported as relevant factors of tumor immune regulation. We investigated their expression as prognostic factors in 200 patients with primary cutaneous melanoma (PCM). In our cohort, patients with tumors showing upregulation of HLA-ABC molecules had significantly thicker tumors (32% vs 7%, P<0.001), frequent ulceration (20% vs 6%, P=0.007) and frequent nodular melanomas (20% vs 4%, P=0.001). Additionally, high expression of HLA-G in the tumor was a sign of bad prognosis for the patients, being associated with thick tumors (30% vs 12%, P=0.017), ulceration (24% vs 5%, P<0.001) and positive sentinel node (13% vs 6%, P=0.015). HLA-E, HLA-F and FOXP3+ TILs were not indicative of the prognosis in PCM. High HLA-ABC and HLA-G were associated with tumor aggressiveness and could be relevant predictive markers for effective immunotherapy of melanoma tumors.

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.

P 56 The role of anti- and pro-inflammatory cytokines on the expression of the tolerogenic HLA class Ib molecules in relation to pregnancy and preeclampsia

Introduction Preeclampsia (PE) is a multi-systemic pregnancy disorder and an important cause of fetal and maternal morbidity and mortality worldwide. Although the exact etiology behind PE is unclear, one widely accepted hypothesis propose that a maladapted immune response in the mother cause inadequate trophoblast invasion and remodeling of the spiral arteries, leading to hypoxia and ischemia. Whereas uncomplicated pregnancies is characterized by immunological tolerance towards the fetal cells established through immunological mediators such as HLA-C and the non-classical HLA-Ib molecules and regulatory immune cells, PE is characterized by the presence of pro-inflammatory leukocytes and cytokines. The direct consequence of the presence of the pro-inflammatory cytokines in the local environment and on the fetal cells is less studied. Objectives The aim is to characterize the effect of the anti- and pro-inflammatory cytokines on the expression of HLA class I molecules on the trophoblast cell line JEG-3 and primary placenta tissue. Materials and methods JEG-3 cells are incubated in the presence of various concentrations of anti- and pro-inflammatory cytokines for up to 72 h. HLA-C, -E and -G surface expression is characterized by flow cytometry, mRNA levels of HLA class Ia and Ib is quantified by droplet digital PCR, and expression of the different isoforms of HLA-G (HLA-G1-7) is analyzed by fragment analysis. Results Our preliminary data suggests an upregulation of the HLA-Ib molecules upon culture with IFN-γ, whereas IL-12 seems to slightly downregulate the expression of HLA-G. The effect on mRNA level and on expression of different isoforms of HLA-G is currently being investigated. Conclusion Expression of HLA-I molecules seems to be affected by the presence of specific cytokines in the local environment. Whether this act of balancing is also seen in primary placenta tissue from healthy pregnancies or cases of PE will be determined in nearest future.

Associations between fetal HLA-G genotype and birth weight and placental weight in a large cohort of pregnant women – Possible implications for HLA diversity

Birth weight and placental weight are crucial parameters for the survival of fetuses and newborns in mammals. High variation in the MHC is important for an effective adaptive immune response. The maternal immune system must be controlled in relation to the semi-allogenic fetus. The immunoregulatory HLA/MHC class Ib gene, HLA-G, is strongly expressed on extravillous trophoblast cells. We investigated birth weight and placental weight of the newborns in mothers heterozygous for an HLA-G 14bp insertion (Ins)/deletion (Del) gene polymorphism. Separate analyses for pregnancies without preeclampsia (n=185), pregnancies complicated by preeclampsia (n=101), and both groups combined, were performed. Interestingly, we observed the highest mean birth weight and placental weight in homozygous 14bp Del/Del newborns, and the lowest in 14bp Ins/Ins newborns (P=0.008 and P=0.009). The 14bp Del/Del genotype is also associated with high expression of HLA-G on the trophoblast membrane. In theory, fetuses and newborns with intermediate weights and sizes would be an optimal compromise for both the fetus/father and the mother compared with very high and low weights. If such fetuses/newborns more often are heterozygous at the HLA-G gene locus, then newborns with two distinct HLA haplotypes are favored, leading to a higher degree of HLA diversity. The results of the study may indicate that a compromise between an intermediate birth weight and placental weight, induction of maternal tolerance by a fetal-derived non-polymorphic HLA class Ib molecule, and favoring of HLA heterozygous offspring, have evolved in humans.

Association of HLA-A and Non-Classical HLA Class I Alleles.

The HLA-A locus is surrounded by HLA class Ib genes: HLA-E, HLA-H, HLA-G and HLA-F. HLA class Ib molecules are involved in immuno-modulation with a central role for HLA-G and HLA-E, an emerging role for HLA-F and a yet unknown function for HLA-H. Thus, the principal objective of this study was to describe the main allelic associations between HLA-A and HLA-H, -G, -F and -E. Therefore, HLA-A, -E, -G, -H and -F coding polymorphisms, as well as HLA-G UnTranslated Region haplotypes (referred to as HLA-G UTRs), were explored in 191 voluntary blood donors. Allelic frequencies, Global Linkage Disequilibrium (GLD), Linkage Disequilibrium (LD) for specific pairs of alleles and two-loci haplotype frequencies were estimated. We showed that HLA-A, HLA-H, HLA-F, HLA-G and HLA-G UTRs were all in highly significant pairwise GLD, in contrast to HLA-E. Moreover, HLA-A displayed restricted associations with HLA-G UTR and HLA-H. We also confirmed several associations that were previously found to have a negative impact on transplantation outcome. In summary, our results suggest complex functional and clinical implications of the HLA-A genetic region.

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 and HLA-E Levels in Bone Marrow Plasma Samples Are Related to Disease Stage in Neuroblastoma Patients

The role of nonclassical HLA-class Ib molecules HLA-G and HLA-E in the progression of Neuroblastoma (NB), the most common pediatric extracranial solid tumor, has been characterized in the last years. Since BM infiltration by NB cells is an adverse prognostic factor, we have here analyzed for the first time the concentration of soluble (s)HLA-G and HLA-E in bone marrow (BM) plasma samples from NB patients at diagnosis and healthy donors. sHLA-G and sHLA-E are present in BM plasma samples, and their levels were similar between NB patients and controls, thus suggesting that these molecules are physiologically released by resident or stromal BM cell populations. This hypothesis was supported by the finding that sHLA-G and sHLA-E levels did not correlate with BM infiltration and other adverse prognostic factors (MYCN amplification and age at diagnosis). In contrast, BM plasma levels of both molecules were higher in patients with metastatic disease than in patients with localized NB, thus suggesting that concentration of these molecules might be correlated with disease progression. The prognostic role of sHLA-G and sHLA-E concentration in the BM plasma for NB patients will be evaluated in future studies, by analyzing the clinical outcome of the same NB patients at follow-up.

Immunobiology of HLA Class-Ib Molecules in Transplantation

Immunobiology of HLA Class-Ib Molecules in Transplantation

Role of blister fluid soluble HLA‐E In SJS/TEN

Background Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are life-threatening hypersensitivity reactions to medications characterized by keratinocyte apoptosis, the formation of subepidermal blisters, and skin detachment. Cytotoxic lymphocytes including CTLs and NK cells seem to be the main effectors of keratinocyte killing. Natural killer cytotoxic activity is regulated through the balance of activating and inhibitory signals delivered by innate receptors, some of which recognize HLA class I antigens. Among them, inhibitory CD94/ NKG2A and activating CD94/NKG2C receptors are specific for the non-classical HLA class Ib molecule HLA-E, and are expressed not only in NK cells but also in subsets of T lymphocytes. We have previously reported that the activating receptor CD94/NKG2C is overexpressed in lymphocytes from SJS/TEN patients resulting in net activation and lysis of HLA-E+ targets. Moreover, HLA-E was found to be overexpressed in affected skin, and in agreement with previous reports showing soluble HLA-E (sHLA-E) released in response to cell activation, we found sHLA-E in blister fluids from SJS/TEN patients.

HLA-E expression in cervical adenocarcinomas: association with improved long-term survival

BackgroundCervical cancer is the third most common cancer in women worldwide. The most common histopathological subtype is cervical squamous cell carcinoma (SCC, 75-80%), followed by adenocarcinoma (AC) and adenosquamous carcinoma (ASC; together 15-20%). Rising incidence rates of AC have been observed relative and absolute to SCC and evidence is accumulating that cervical AC is a distinct clinical entity. Cervical SCC, ASC, and AC are caused by a persistent infection with high-risk human papillomavirus (HPV) and failed control of the immune system plays a pivotal role in the carcinogenesis of all three histopathological subtypes. Human leukocyte antigen E (HLA-E), a non-classical HLA class Ib molecule, plays an important role in immune surveillance and immune escape of virally infected cells. In this study we investigated HLA-E expression in three well-defined cohorts of cervical AC, ASC, and SCC patients, and determined whether HLA-E expression was associated with histopathological parameters and patient survival.Methods and resultsHLA-E expression was assessed by immunohistochemistry on formalin-fixed, paraffin-embedded tissue sections of 79 SCC, 38 ASC, and 75 AC patients. All patients included were International Federation of Gynaecology and Obstetrics stage I-II and underwent radical hysterectomy with lymphadenectomy as primary treatment. Significant differences between the histopathological subgroups were detected for age distribution, HPV positivity, HPV type distribution, tumour size, tumour infiltration depth, lymph-vascular space invasion, and adjuvant radiotherapy. High expression of HLA-E was found in 107/192 (56%) cervical carcinomas, with significantly more overexpression in cervical AC compared to SCC and ASC (37/79 SCC, 18/38 ASC, and 52/75 AC; P = 0.010). High HLA-E expression in cervical AC was associated with favourable long term disease-specific and recurrence-free survival (P = 0.005 and P = 0.001, respectively).ConclusionHigh expression of HLA-E occurred in the majority of all histopathological subtypes of cervical cancer; especially in cervical AC. High HLA-E expression in cervical AC was associated with improved patient survival. This study also highlights the importance of careful evaluation of cervical carcinomas to distinguish histopathological subtypes. In the future, insight into the biological behaviour and distinct molecular carcinogenetic processes of the AC, ASC, and SCC subtypes may contribute to the development of more tumour-specific treatment strategies.

HLA-G expressing Tregs inhibit bystander immune activation in HIV-1 infection (170.27)

Abstract T cells expressing the HLA class Ib molecule, HLA-G, represent an emerging non-classical population of regulatory T cells (Tregs). However, the functional role of these cells during HIV-1 infection remains unclear. Here, we performed a comprehensive investigation of HLA-G- expressing Tregs in patients with different rates of HIV-1 disease progression. Using flow cytometry, we found the proportion of HLA-G-expressing CD4 and CD8 T cells were significantly reduced in individuals with progressive HIV-1 infection (p&amp;lt;0.001 for both CD4 and CD8 T cells). Moreover, HLA-G expressing Tregs were inversely correlated with phenotypic markers of immune activation, CD38 and HLA-DR (p=0.026 for CD4 and p&amp;lt;0.005 for CD8 T cells), and positively correlated with CD4 T cell counts. Functional co-culture assays indicated that HLA-G-expressing CD4 and CD8 T cells were able to potently inhibit TCR-independent bystander activation, but only weakly inhibited TCR-dependent cytokine-secretion and proliferative properties of HIV-1-specific T cells. Furthermore, in vitro infection assay suggested HLA-G expressing Treg were more susceptible to HIV-1 infection (p=0.0039). These data indicate an important role of HLA-G+ Tregs for balancing bystander immune activation and anti-viral immune activity in HIV-1 infection, and suggest that the loss of these cells during advanced HIV-1 infection may contribute to immune dysregulation and HIV-1 disease progression.

MiRNA-mediated control of HLA-G expression and function.

HLA-G is a non-classical HLA class-Ib molecule expressed mainly by the extravillous cytotrophoblasts (EVT) of the placenta. The expression of HLA-G on these fetal cells protects the EVT cells from immune rejection and is therefore important for a healthy pregnancy. The mechanisms controlling HLA-G expression are largely unknown. Here we demonstrate that miR-148a and miR-152 down-regulate HLA-G expression by binding its 3′UTR and that this down-regulation of HLA-G affects LILRB1 recognition and consequently, abolishes the LILRB1-mediated inhibition of NK cell killing. We further demonstrate that the C/G polymorphism at position +3142 of HLA-G 3′UTR has no effect on the miRNA targeting of HLA-G. We show that in the placenta both miR-148a and miR-152 miRNAs are expressed at relatively low levels, compared to other healthy tissues, and that the mRNA levels of HLA-G are particularly high and we therefore suggest that this might enable the tissue specific expression of HLA-G.