HLA-G 2012 conference: the 15-year milestone update

3'UTR-HLA-G polymorphisms and circulating sHLA-G are associated with breast cancer: Evidence from a meta-analysis

BACKGROUND

Human leukocyte antigen-G (HLA-G) gene polymorphisms and circulating sHLA-G have often been linked to the risk of breast cancer (BC). However, the results remain controversial. To resolve this issue, we performed a meta-analysis of HLA-G gene polymorphisms and sHLA-G levels in BC.

METHODS

We performed a meta-analysis on the association of HLA-G 14-bp Insertion/Deletion (Ins/Del) and HLA-G +3142 C/G polymorphisms with BC as well as the relationship between sHLA-G and the disease outcome.

RESULTS

Pooled analysis showed a statistically significant association between the HLA-G 14-bp Ins/Del polymorphism and BC susceptibility for the overall population and for Caucasians. The Del allele and genotypes with at least one copy of the Del allele presented significant risks for BC. For HLA-G +3142 C/G polymorphism, the G allele significantly decreased the risk of BC for the overall population and for Caucasians, indicating that the G allele was a protective factor against BC and that the C allele was a significant risk factor for BC. The meta-analysis revealed a significantly increased level of sHLA-G patients with BC compared to the control group for the overall population, Caucasians and Asians.

CONCLUSION

The present meta-analysis showed a major association of both HLA-G 14-bp Ins/Del and +3142 C/G polymorphisms with BC susceptibility, suggesting Del and C variants as highly significant risk factors for BC. The present study also showed significantly higher sHLA-G levels in patients with BC compared to healthy controls. Our pooled results suggested a critical role of HLA-G in BC, thereby providing evidence to use HLA-G as a biomarker and a therapeutic tool.

COVID-19 reinfection after pregnancy

Background

There have been reports of COVID-19 reinfections, but the immunological characterization of these cases is partial. We report a case of reinfection with SARS-CoV-2, where the first infection occurred in the course of late pregnancy.

Case presentation

On May 27, 2020, a 37-year-old woman gave birth at full term, 3 hours after full dilatation. She developed fever (38.3 °C) after delivery. Mild biological anomalies compatible with COVID-19 were observed: lymphopenia, thrombocytopenia, elevated D-Dimers, CRP, and LDH. At 6-month follow-up, she reported having contracted COVID-19 with high fever, rhinorrhea, hand frostbites, cough, headache, dysgeusia and anosmia.

Conclusions

We report a case of COVID-19 reinfection with a first mild infection during late pregnancy and a more aggressive second infection 5 months later.

Interferon-τ regulates the expression and function of bovine leukocyte antigen by downregulating bta-miR-204

IFN-τ is a pregnancy recognition factor that regulates embryo implantation in ruminants. IFN-τ has been suggested to be involved in the expression of microRNA (miRNA/miR) and bovine leukocyte antigen (BoLA), which is an analog of the human major histocompatibility complex class I. However, little is known about whether the miRNAs are involved in the expression of BoLA in ruminants. The present study firstly verified that bta-miR-204 was downregulated and that BoLA was upregulated in the uterine tissues of dairy cows during early pregnancy. Subsequently, luciferase reporter assays, reverse transcription-quantitative PCR and western blot analysis were used to validate BoLA as the target gene of bta-miR-204. Moreover, BoLA was markedly upregulated and bta-miR-204 was downregulated in bovine endometrial epithelial cells (bEECs) treated with IFN-τ. In addition, the results indicated that when the expression level of BoLA was increased by IFN-τ, the expression level of programmed death-ligand 1 (PD-L1) and programmed death-ligand 2 (PD-L2) was also increased. Furthermore, when BoLA was silenced in bEECs by small interfering RNA, the expression of PD-L1 and PD-L2 was not affected by IFN-τ. The expression level of PD-L1 and PD-L2 was also increased in the uterine tissues of pregnant dairy cattle. In conclusion, IFN-τ may function by suppressing the expression of bta-miR-204 to increase the expression of BoLA during the embryo implantation period in cattle. IFN-τ may induce PD-L1 and PD-L2 transcription by regulating BoLA, which may influence the T cell immune response, thereby regulating pregnant cattle immunization.

HLA-G +3142 C>G polymorphism and cancer risk: Evidence from a meta-analysis and trial sequential analysis

BACKGROUND

Human leukocyte antigen-G (HLA-G) plays an important role in the development of human cancers. Several published studies have investigated the relationship between the HLA-G +3142 C>G (rs1063320) polymorphism and cancer susceptibility in different populations. However, the results have yet to reach a consensus in different types of cancers. Therefore, we performed a meta-analysis to evaluate the effect of the HLA-G +3142 C>G polymorphism on cancer risk.

METHODS

A systematic literature search was performed in PubMed, Web of Science, CNKI, VIP, and Wanfang databases to acquire eligible studies up to February 20, 2019. The pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were used to assess the correlation between the HLA-G +3142 C>G polymorphism and cancer risk in a fixed-effects or random-effects model. Publication bias assessments, sensitivity analysis and stratified analyses were performed. To reduce the risk of type I error and assess whether the present evidence of the results was adequate and conclusive, trial sequential analysis (TSA) was also performed.

RESULTS

Eight case-control studies comprising 1546 cases and 1595 controls were included in the present meta-analysis. The results revealed that the HLA-G +3142 C>G mutation significantly decreased the total cancer risk in recessive comparison model and allelic comparison model. Further stratified analyses showed that the HLA-G +3142 C>G mutation significantly decreases the risk of cancer in Asian populations. No similar relationship was found in other subgroups. No publication bias was identified in our present study. Omitting a single study at a time had no significant impact on the pooled OR of the sensitivity analysis assessing the association between the HLA-G +3142 C>G polymorphism and cancer risk, which demonstrates the stability of the current meta-analysis. TSA also identified our current findings.

CONCLUSIONS

The results of our meta-analysis show that the HLA-G +3142 C>G polymorphism plays a protect role in the occurrence of human cancers, particularly in Asian populations. More case-control studies with different types of cancer in various ethnicities are needed to verify the findings.

Genetic variation in the HLA-G 3'UTR 14-bp insertion/deletion and the associated cancer risk: evidence from 25 case-control studies

Human leucocyte antigen-G (HLA-G) plays an important role in the progression of human cancers. A growing number of published studies have investigated the correlation between the HLA-G 3′ untranslated region (3′UTR) 14-bp insertion/deletion (Ins/Del) polymorphism and the associated cancer risk in different populations. However, results from previous studies are inconclusive and inconsistent for the different type of cancers. Therefore, we undertook a meta-analysis to assess the effects of the HLA-G 14-bp Ins/Del polymorphism on cancer risk. A systematic literature search was conducted in PubMed, Web of Science, CNKI, VIP, and Wanfang databases to obtain relevant studies up to 28 January 2019. The pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were used. Twenty-five published case–control studies comprising 4981 cases and 6391 controls were included in the current meta-analysis. The results of the overall analysis revealed that the HLA–G 14–bp Ins/Ins genotype and Ins allele were associated with the total cancer risk in the homozygote comparison model (Ins/Ins vs. Del/Del: OR = 0.80, CI = 0.64–1.00; P=0.049) and the allelic comparison model (Ins vs. Del: OR = 0.89, CI = 0.81–0.99; P=0.035), with a protective role. Further subgroup analyses indicated that the HLA–G 14–bp Ins/Del polymorphism was associated with the risk of breast cancer and oesophageal cancer (EC), and significant risk of cancer was also observed in Mixed populations and population-based (PB). The results of our meta-analysis show that the HLA–G 14-bp Ins/Del polymorphism plays an important role in cancer risk, particularly in breast cancer and esophageal cancer in Mixed populations. Additional case–control studies with different types of cancer spanning different ethnicities are needed to extend the present findings.

Interferon-τ increases BoLA-I for implantation during early pregnancy in dairy cows

Interferon-τ (IFN-τ) signals pregnancy recognition in ruminants. We investigated the effects of IFN-τ produced by embryo trophoblastic cells (ETCs) on expression of bovine leukocyte antigen-I (BoLA-I), a bovine analogue of human MHC-I, in endometrial luminal epithelial cells (EECs) during early pregnancy in dairy cows. Expression of IFN-τ and BoLA-I was increased in endometrial tissues during early pregnancy. Expression of the anti-inflammatory cytokine IL-10 was increased in endometrial tissues, while expression of the pro-inflammatory cytokine IL-6 was decreased, indicating immunosuppression. Progesterone increased IFN-τ expression in EECs. IFN-τ increased p-STAT1 and p-STAT3 levels in EECs, but reduced TRAF3 levels. In addition, IFN-τ increased expression of BoLA-I and IL-10, but decreased expression of IL-6 in EECs. These results indicate that IFN-τ enables stable implantation in dairy cows by increasing expression of BoLA-I, and by immunosuppression mediated by increased IL-10 and decreased IL-6 expression.

Evolution of the levels of human leukocyte antigen G (HLA-G) in Beninese infant during the first year of life in a malaria endemic area: using latent class analysis

Background

HLA-G, a non-classical HLA class I antigen, is of crucial interest during pregnancy by inhibiting maternal immune response. Its role during infections is discussed, and it has been described that high levels of soluble HLA-G during childhood increase the risk of malaria. To explore more precisely interactions between soluble HLA-G and malaria, latent class analysis was used to test whether distinct sub-populations of children, each with distinctive soluble HLA-G evolutions may suggest the existence of groups presenting variable malaria susceptibility.

Method

A study was conducted in Benin from 2010 to 2013 and 165 children were followed from birth to 12 months. Evolution of soluble HLA-G was studied by the latent class method.

Results

Three groups of children were identified: one with consistently low levels of soluble HLA-G during follow-up, a second with very high levels and a last intermediate group. In all groups, low birth weight, high number of malaria infections and high exposure to malaria transmission were associated with high level of soluble HLA-G. Placental malaria was not. Presence of soluble HLA-G in cord blood increased the probability of belonging to the highest trajectory.

Conclusion

These results, together with previous ones, confirm the important role of HLA-G in the individual susceptibility to malaria. Assaying soluble HLA-G at birth could be a good indicator of newborns more fragile and at risk of infections during childhood.

HLA-G and MHC Class II Protein Expression in Diffuse Large B-Cell Lymphoma

The expression of human leukocyte antigen-G (HLA-G) and HLA class II protein was studied by immunohistochemical staining of lymph nodes from 148 patients with diffuse large B-cell lymphoma (DLBCL) and related to the clinical course of the disease. Negative HLA-G expression was associated with a lower probability of achieving a complete remission (p = 0.04). Patients with negative HLA-G expression tended towards a lower 3-year overall survival (OS) rate compared to those with positive expression of HLA-G (p = 0.08). When restricting the analysis to patients receiving chemotherapy with rituximab, the estimated 3-year OS rate of patients with positive HLA-G expression was 73.3 % compared with 47.5 % (p = 0.03) in those with negative expression. Patients with negative HLA class II expression presented a lower 3-year OS rate compared to subjects with positive expression (p = 0.04). The loss of HLA class II expression (p = 0.05) and belonging to the intermediate high/high IPI risk group (p = 0.001) independently increased the risk of death. HLA class II expression also retained its prognostic value in patients receiving rituximab; the 3-year OS rate was 65.3 % in patients with positive HLA class II expression versus 29.6 % (p = 0.04) in subjects that had loss of HLA class II expression. To our knowledge, for the first time, the expression of HLA-G protein in DLBCL and its association with the clinical course of the disease was demonstrated. Moreover, the link between losing HLA class II protein expression and poor survival of patients treated with immunochemotherapy was confirmed.

Human leukocyte antigen-G polymorphisms influence the clinical outcome in diffuse large B-cell lymphoma

The role of HLA-G is extensively studied in cancer due to its inhibition of the immune response. Several polymorphisms in the HLA-G gene have been reported to significantly affect its expression. We, therefore, investigated whether functionally relevant HLA-G polymorphisms, HLA-G-725C/G/T, and HLA-G 14-base pair, have any influence on the susceptibility to diffuse large B-cell lymphoma (DLBCL) and its clinical course. The polymorphisms were genotyped in 207 previously untreated patients with DLBCL and 150 unrelated controls. A significant difference in genotype distribution of HLA-G polymorphic genotypes between the patients and controls was found. The frequencies of the HLA-G-725GG or the HLA-G-725GC genotype were lower, and those of the HLA-G ins/ins genotype were higher in the patients compared with the controls. Patients carrying the HLA-G-725CC genotype presented a higher probability of overall survival (OS) than subjects with other genotype combinations of HLA-G-725C/G/T (P = 0.003). The homozygous HLA-G del/del had a lower probability of OS than subjects carrying the HLA-G deletion/insertion (del/ins) or the HLA-G ins/ins genotype (P = 0.009). Two HLA-G genotype-based risk groups were defined according to the genotype distribution. The high-risk (HR) group presented a shorter OS than low-risk (LR) patients (P = 0.001). In a multivariate analysis adjusted for International Prognostic Index (IPI) factors, both the intermediate high/high IPI-risk group (P < 0.0001) and the HR genotype group (P = 0.004) independently increased the risk of death. This is the first study indicating an important role of HLA-G polymorphisms for the clinical course of DLBCL. The potential influence of HLA-G polymorphisms on the susceptibility to DLBCL thus deserves further study.

Role of HLA-G as a predictive marker of low risk of chronic rejection in lung transplant recipients: a clinical prospective study

Human leukocyte antigen G (HLA-G) expression is thought to be associated with a tolerance state following solid organ transplantation. In a lung transplant (LTx) recipient cohort, we assessed (1) the role of HLA-G expression as a predictor of graft acceptance, and (2) the relationship between (i) graft and peripheral HLA-G expression, (ii) HLA-G expression and humoral immunity and (iii) HLA-G expression and lung microenvironment. We prospectively enrolled 63 LTx recipients (median follow-up 3.26 years [min: 0.44-max: 5.03]). At 3 and 12 months post-LTx, we analyzed graft HLA-G expression by immunohistochemistry, plasma soluble HLA-G (sHLA-G) level by enzyme-linked immunosorbent assay, bronchoalveolar lavage fluid (BALF) levels of cytokines involved in chronic lung allograft dysfunction (CLAD) and anti-HLA antibodies (Abs) in serum. In a time-dependent Cox model, lung HLA-G expression had a protective effect on CLAD occurrence (hazard ratio: 0.13 [0.03-0.58]; p = 0.008). The same results were found when computing 3-month and 1-year conditional freedom from CLAD (p = 0.03 and 0.04, respectively [log-rank test]). Presence of anti-HLA Abs was inversely associated with graft HLA-G expression (p = 0.02). Increased BALF level of transforming growth factor-β was associated with high plasma sHLA-G level (p = 0.02). In conclusion, early graft HLA-G expression in LTx recipients with a stable condition was associated with graft acceptance in the long term.

Inhibition of host immune response in colorectal cancer: Human leukocyte antigen-G and beyond

Colorectal cancer (CRC) is one of the most diffuse cancers worldwide and is still a clinical burden. Increasing evidences associate CRC clinical outcome to immune contexture represented by adaptive immune cells. Their type, density and location are summarized in the Immune Score that has been shown to improve prognostic prediction of CRC patients. The non-classical MHC class I human leukocyte antigen-G (HLA-G), is a crucial tumor-driven immune escape molecule involved in immune tolerance. HLA-G and soluble counterparts are able to exert inhibitory functions by direct interactions with inhibitory receptors present on both innate cells such as natural killer cells, and adaptive immune cells as cytotoxic T and B lymphocytes. HLA-G may play a prominent role in CRC strategies to avoid host immunosurveillance. This review highlights the current knowledge on HLA-G contribution in CRC, in related inflammatory diseases and in other type of cancers and disorders. HLA-G genetic setting (specific haplotypes, genotypes and alleles frequencies) and association with circulating/soluble profiles was highlighted. HLA G prognostic and predictive value in CRC was investigated in order to define a novel prognostic immune biomarker in CRC.

The dual role of HLA-G in cancer

We here review the current data on the role of HLA-G in cancer based on recent findings of an unexpected antitumor activity of HLA-G in hematological malignancies. For the past decade, HLA-G has been described as a tumor-escape mechanism favoring cancer progression, and blocking strategies have been proposed to counteract it. Aside from these numerous studies on solid tumors, recent data showed that HLA-G inhibits the proliferation of malignant B cells due to the interaction between HLA-G and its receptor ILT2, which mediates negative signaling on B cell proliferation. These results led to the conjecture that, according to the malignant cell type, HLA-G should be blocked or conversely induced to counteract tumor progression. In this context, we will here present (i) the dual role of HLA-G in solid and liquid tumors with special emphasis on (ii) the HLA-G active structures and their related ILT2 and ILT4 receptors and (iii) the current knowledge on regulatory mechanisms of HLA-G expression in tumors.

Expression and potential roles of HLA-G in human spermatogenesis and early embryonic development

As one of the non-classical major histocompatibility complex(MHC)-1 antigens, Human Leukocyte Antigen G (HLA-G), has been suggested as a prognostic marker to identify the embryo developmental potential. In the present study, we investigated the potential roles of HLA-G in human spermatogenesis and early embryonic development. Quantitative real-time PCR analysis revealed that HLA-G's expression was increased with increased Johnsen score in testicular tissues. There was no significant difference in HLA-G mRNA expression between testicular tissues with Johnsen score of 8–9 and normal sperm from ejaculated semen. HLA-G mRNA expression was detected in human zygotes, embryos and blastocysts but not in unfertilized oocytes. In testicular tissues where sperm was obtained by testicular sperm extraction (Johnsen score was 8 to 9), there were no correlations between HLA-G mRNA expression and fertilization, cleavage and high-quality embryo rates. At 48–72 h post-fertilization, HLA-G expression was higher in fast growing embryos. HLA-G specific siRNA injection into zygotes not only slowed down embryonic cleavage rate at 48 h post-fertilization, but also down-regulated the expression of embryo metabolism related gene (SLC2A1) and cell cycle-regulated gene (CCND2). Taken together, our findings suggested that HLA-G plays significant roles in human spermatogenesis and early embryonic development.

Molecular pathways: human leukocyte antigen G (HLA-G)

Human leukocyte antigen G (HLA-G) is a nonclassical MHC class I molecule that exerts important tolerogenic functions. Its main physiologic expression occurs in the placenta, where it participates in the maternal tolerance toward the fetus. HLA-G expression was found in embryonic tissues, in adult immune privileged organs, and in cells of the hematopoietic lineage. It is expressed in various types of primary solid (melanoma, head and neck, lung, urogenital, gastrointestinal, and breast cancers) and hematologic malignancies (acute leukemia, lymphomas) and metastases. HLA-G ectopic expression is observed in cancer, suggesting that its expression is one strategy used by tumor cells to escape immune surveillance. In this review, we will focus on HLA-G expression in cancers and its association with the prognosis. We will highlight the underlying molecular mechanisms of impaired HLA-G expression, the immune tolerant function of HLA-G in tumors, and the potential diagnostic use of membrane-bound and soluble HLA-G as a biomarker to identify tumors and to monitor disease stage. As HLA-G is a potent immunoinhibitory molecule, its blockade remains an attractive therapeutic strategy against cancer. Elimination of HLA-G-expressing cancer cells would be important in the efficacy of anticancer therapies.