Non-classical MHC-I human leukocyte antigen (HLA-G) in hepatotropic viral infections and in hepatocellular carcinoma

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.

Extrahepatic Malignancies Are the Leading Cause of Death in Patients with Chronic Hepatitis B without Cirrhosis: A Large Population-Based Cohort Study

(1) Background: Accurate statistics on the causes of death in patients with chronic hepatitis B (CHB) are lacking. We investigated mortality rates and causes of death over time. (2) Methods: Data on patients newly diagnosed with CHB from 2007 to 2010 (cohort 1, n = 223,424) and 2012 to 2015 (cohort 2, n = 177,966) were retrieved from the Korean National Health Insurance Service. Mortality data were obtained from Statistics Korea. The causes of death were classified as liver-related (hepatic decompensation or hepatocellular carcinoma [HCC]) or extrahepatic (cardiovascular-related, cerebrovascular-related, or extrahepatic malignancy-related). (3) Results: Over a 10-year follow-up period of 223,424 patients (cohort 1) with CHB, the overall mortality was 1.54 per 100 person-years. The mortality associated with HCC was the highest (0.65 per 100 person-years), followed by mortality related to extrahepatic malignancies (0.26 per 100 person-years), and cardio/cerebrovascular diseases (0.18 per 100 person-years). In the non-cirrhotic CHB (87.4%), 70% (11,198/15,996) of patients died due to non-liver-related causes over ten years. The 10-year overall mortality was 0.86 per 100 person-years. Among these, mortality due to extrahepatic malignancies had the highest rate (0.23 per 100 person-years), followed by mortality related to HCC (0.20 per 100 person-years), and cardio/cerebrovascular diseases (0.16 per 100 person-years). The 5-year mortality associated with extrahepatic malignancies increased from 0.36 per 100 person-years (cohort 1) to 0.40 per 100 person-years (cohort 2). (4) Conclusions: Mortality related to HCC decreased, whereas mortality related to extrahepatic malignancies increased in the antiviral era. Extrahepatic malignancies were the leading cause of death among patients with CHB without cirrhosis.

HLA-G 3'UTR haplotype analyses in HCV infection and HCV-derived cirrhosis, hepatocellular carcinoma and fibrosis

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease. Chronic HCV infection is also an important cause of hepatic fibrosis, cirrhosis and hepatocellular carcinoma (HCC). HCV has the capacity to evade immune surveillance by altering the host immune response. Moreover, variations in immune-related genes can lead to differential susceptibility to HCV infection as well as interfere on the susceptibility to the development of hepatic fibrosis, cirrhosis and HCC. The human leucocyte antigen G (HLA-G) gene codes for an immunomodulatory protein known to be expressed in the maternal-foetal interface and in immune-privileged tissues. The HLA-G 3' untranslated region (3'UTR) is important for mRNA stability, and variants in this region are known to impact gene expression. Studies, mainly focusing in a 14 bp insertion/deletion polymorphism, have correlated HLA-G 3'UTR with susceptibility to viral infections, but other polymorphic variants in the HLA-G 3'UTR might also affect HCV infection as they are inherited as haplotypes. The present study evaluated HLA-G 3'UTR polymorphisms and performed linkage disequilibrium test and haplotype assembly in 286 HCV infected patients who have developed fibrosis, cirrhosis or HCC, as well as in 129 healthy control subjects. Haplotypes UTR-1, UTR-2 and UTR-3 were the most observed in HCV+ patients, in the frequencies of 0.276, 0.255 and 0.121, respectively. No statistically significant difference was observed between HCV+ and control subjects, even when patients were grouped according to outcome (HCC, cirrhosis or fibrosis). Despite that, some trends in the results were observed, and therefore, we cannot rule out the possibility that variants associated to high HLA-G expression can be involved in HCV infection susceptibility.

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.

HLA-G susceptibility to hepatitis B infection and related hepatocellular carcinoma in the Japanese population

AIMS

Human leukocyte antigen (HLA)-G plays a role in various physiological immunomodulatory functions. Aberrant HLA-G expression is observed in various disease states, including tumors, autoimmune disorders, and viral infections. The present study investigated the association between HLA-G functional gene polymorphisms (rs1736933 [-486 C > A], rs1049033 [+2018 C > T], 14 bp Insertion [Ins]/Deletion [Del] [+2961 Del > Ins], and rs1063320 [+3142 C > G]) and disease susceptibility, hepatocellular carcinoma (HCC) development, and hepatitis B surface antigen (HBsAg) clearance.

METHODS

Allele discrimination of the 3 SNPs (-486 C > A, +2018 C > T, +3142 C > G) was determined by a TaqMan 5' exonuclease assay, while the 14 bp Ins/Del polymorphism was typed by fragment analysis using Genetic Analyzer and GeneMapper software. The above polymorphisms were analyzed for 325 Japanese hepatitis B virus (HBV) patients, 355 Japanese healthy subjects (Controls) as healthy controls, and 799 Japanese hepatitis C virus (HCV) patients as disease controls, respectively.

RESULTS

The 14 bp Insertion allele was significantly more frequent in HBV patients than Controls (27.1 % vs 20.6 %, odds ratio [OR] 1.43, P = 0.005) but did not differ between HCV patients and Controls. Similar results were found for the rs1063320 G allele (38.9 % vs 26.3 %, OR 1.78, P < 0.001) and the rs1736933 T allele (32.2 % vs 26.9 %, OR 1.29, P = 0.034) between HBV and Controls. The rs1049033 T allele showed a weak but significant association with HCC development in the dominant model (OR 1.95, P = 0.04). Regarding HBsAg clearance, the A allele at rs1736933 was significantly correlated in the recessive model (OR 3.23, P = 0.003).

CONCLUSIONS

This study revealed significant associations of HLA-G gene polymorphisms with disease susceptibility, HCC development, and HBsAg clearance in HBV patients.

Combined plasma levels of IL-10 and testosterone, but not soluble HLA-G5, predict the risk of death in COVID-19 patients

BACKGROUND

The identification of biomarkers correlated with coronavirus disease 2019 (COVID-19) outcomes is a relevant need for clinical management. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is characterized by elevated interleukin (IL)-6, IL-10, HLA-G, and impaired testosterone production.

OBJECTIVES

We aimed at defining the combined impact of sex hormones, interleukin-10, and HLA-G on COVID-19 pathophysiology and their relationship in male patients.

MATERIALS AND METHODS

We measured by chemiluminescence immunoassay, electrochemiluminescent assays, and enzyme-linked immunosorbent assay circulating total testosterone, 17β-estradiol (E₂ ), IL-10, and -HLAG5 as well as SARS-CoV-2 S1/S2 Immunoglobulin G from 292 healthy controls and 111 COVID-19 patients with different disease severity at hospital admission, and in 53 COVID-19 patients at 7-month follow-up.

RESULTS AND DISCUSSION

We found significantly higher levels of IL-10, HLA-G, and E₂ in COVID-19 patients compared to healthy controls and an inverse correlation between IL-10 and testosterone, with IL-10, progressively increasing and testosterone progressively decreasing with disease severity. This correlation was lost at the 7-month follow-up. The risk of death in COVID-19 patients with low testosterone increased in the presence of high IL-10. A negative correlation between SARS-CoV-2 Immunoglobulin G and HLA-G or IL-10 at hospitalization was observed. At the 7-month follow-up, IL-10 and testosterone normalized, and  HLA-G decreased.

CONCLUSION

Our findings indicate that combined evaluation of IL-10 and testosterone predicts the risk of death in men with COVID-19 and support the hypothesis that IL-10 fails to suppress excessive inflammation by promoting viral spreading.

Induction of pulmonary HLA-G expression by SARS-CoV-2 infection

The non-classical human leukocyte antigen (HLA)-G exerts immune-suppressive properties modulating both NK and T cell responses. While it is physiologically expressed at the maternal-fetal interface and in immune-privileged organs, HLA-G expression is found in tumors and in virus-infected cells. So far, there exists little information about the role of HLA-G and its interplay with immune cells in biopsies, surgical specimen or autopsy tissues of lung, kidney and/or heart muscle from SARS-CoV-2-infected patients compared to control tissues. Heterogeneous, but higher HLA-G protein expression levels were detected in lung alveolar epithelial cells of SARS-CoV-2-infected patients compared to lung epithelial cells from influenza-infected patients, but not in other organs or lung epithelia from non-viral-infected patients, which was not accompanied by high levels of SARS-CoV-2 nucleocapsid antigen and spike protein, but inversely correlated to the HLA-G-specific miRNA expression. High HLA-G expression levels not only in SARS-CoV-2-, but also in influenza-infected lung tissues were associated with a high frequency of tissue-infiltrating immune cells, but low numbers of CD8+ cells and an altered expression of hyperactivation and exhaustion markers in the lung epithelia combined with changes in the spatial distribution of macrophages and T cells. Thus, our data provide evidence for an involvement of HLA-G and HLA-G-specific miRNAs in immune escape and as suitable therapeutic targets for the treatment of SARS-CoV-2 infections.

HLAncPred: a method for predicting promiscuous non-classical HLA binding sites

Human leukocyte antigens (HLA) regulate various innate and adaptive immune responses and play a crucial immunomodulatory role. Recent studies revealed that non-classical HLA-(HLA-E & HLA-G) based immunotherapies have many advantages over traditional HLA-based immunotherapy, particularly against cancer and COVID-19 infection. In the last two decades, several methods have been developed to predict the binders of classical HLA alleles. In contrast, limited attempts have been made to develop methods for predicting non-classical HLA binding peptides, due to the scarcity of sufficient experimental data. Of note, in order to facilitate the scientific community, we have developed an artificial intelligence-based method for predicting binders of class-Ib HLA alleles. All the models were trained and tested on experimentally validated data obtained from the recent release of IEDB. The machine learning models achieved more than 0.98 AUC for HLA-G alleles on validation dataset. Similarly, our models achieved the highest AUC of 0.96 and 0.94 on the validation dataset for HLA-E*01:01 and HLA-E*01:03, respectively. We have summarized the models developed in the past for non-classical HLA and validated the performance with the models developed in this study. Moreover, to facilitate the community, we have utilized our tool for predicting the potential non-classical HLA binding peptides in the spike protein of different variants of virus causing COVID-19, including Omicron (B.1.1.529). One of the major challenges in the field of immunotherapy is to identify the promiscuous binders or antigenic regions that can bind to a large number of HLA alleles. To predict the promiscuous binders for the non-classical HLA alleles, we developed a web server HLAncPred (https://webs.iiitd.edu.in/raghava/hlancpred) and standalone package.

Immune classifier-based signatures provide good prognostic stratification and predict the clinical benefits of immune-based therapies for hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is an aggressive cancer with a high rate of death globally. The use of bioinformatics may help to identify immune cell-related genes both as targets for potential immunotherapies and for their value associated with predicting therapy responses.

METHODS

In this study, mRNA expression profiles of HCC samples from The Cancer Genome Atlas (TCGA) database were subjected to gene enrichment, cell type abundance, immune cell infiltration, and pathway enrichment analyses to determine immune cell gene features, cell type abundance, and functional annotation characteristics. We also evaluated their prognostic values using Cox regression and Kaplan-Meier analyses and assessed potential responses to chemotherapy. Four subgroups (Groups 1-4) were identified. Group 4 was associated with advanced clinical characteristics, high immune cell enrichment scores, and the poorest outcomes.

RESULTS

Differentially expressed genes (DEGs) in the HCC samples were enriched in the following pathways: antigen binding, cell surface receptor signal transduction of the immune response, and cell surface activated receptor signal transduction of the immune response. Highly expressed genes in Group 4 were enriched in elements of the WNT signalling pathway. We identified five immune-related genes (SEMA3A, TNFRSF11B, GUCA2A, SAA1, and CALCR) that were significantly related to HCC prognosis. A prognostic model based on these five genes exhibited good predictive value, with 1-year and 5-year area under the curve (AUC) values of  >  0.66. Group 4 was also potentially more sensitive to EHT 1864, FH535, and lapatinib chemotherapies than the other groups.

CONCLUSIONS

We identified and validated four HCC subgroups based on immune system-related genes and identified five genes that may be used for an immune-based prognostic model for HCC treatment.

Multi-omic analyses of hepatocellular carcinoma to determine immunological characteristics and key nodes in gene-expression network

Hepatocellular carcinoma (HCC) is a common malignant tumor worldwide, but effective immunotherapy is still limited for those affected. Therefore, there is an urgent need to explore the specific mechanisms governing tumor immunity to improve the survival rate for those diagnosed with HCC. In the present study, we performed a new immune stratification of HCC samples into two subclasses (A and B) from The Cancer Genome Atlas and the International Cancer Genome Consortium databases, and comprehensive multi-omic analyses of major histocompatibility complex genes, gene copy-number variations, somatic mutations, DNA methylation, and non-coding RNAs. Subclass A was found to have a higher survival rate compared with subclass B, and there were significant immunological differences between the two clusters. Based on these differences, we identified DRD1 and MYCN as key hub genes in the immune-phenotype gene expression regulatory network. These results provide novel ideas and evidence for HCC regulatory mechanisms that may improve immunotherapy for this cancer.

Puzzling out the COVID-19: Therapy targeting HLA-G and HLA-E

SARS-CoV2 might conduce to rapid respiratory complications challenging healthcare systems worldwide. Immunological mechanisms associated to SARS-CoV2 infection are complex and not yet clearly elucidated. Arguments are in favour of a well host-adapted virus. Here I draw a systemic immunological representation linking actual SARS-CoV2 infection literature that hopefully might guide healthcare decisions to treat COVID-19. I suggest HLA-G and HLA-E, non classical HLA class I molecules, in the core of COVID-19 complications. These molecules are powerful in immune tolerance and might inhibit/suppress immune cells functions during SARS-CoV2 infection promoting virus subversion. Dosing soluble forms of these molecules in COVID-19 patients' plasma might help the identification of critical cases. I recommend also developing new SARS-CoV2 therapies based on the use of HLA-G and HLA-E or their specific receptors antibodies in combination with FDA approved therapeutics to combat efficiently COVID-19.

Correlation between the coexpression of zinc finger and SCAN domain-containing protein 31 and transcriptional activator with PDZ-binding motif and prognosis in hepatocellular carcinoma

Background

Transcriptional coactivator with PDZ binding motif (TAZ) regulates multiple biological processes and has been found to be related to hepatocellular carcinoma (HCC). However, common signaling pathways downstream after TAZ knockdown may also be important.

Methods

TAZ was knocked down in an HCC cell line, and its potential target genes were analyzed. A decrease in the expression of zinc finger and SCAN domain-containing protein 31 (ZSCAN31) was observed. The difference in ZSCAN31 expression was evaluated, and its effect on survival in HCC patients who received surgical resection was determined.

Results

ZSCAN31 was over-expressed in HCC tissues and was associated with low overall survival (OS) in HCC patients after surgical resection. Analysis of tissue samples from 83 HCC patients who underwent surgical resection in our hospital produced similar results. High ZSCAN31 expression was significantly associated with tumor size. High expression levels of both TAZ and ZSCAN31 were related to poor OS. A positive correlation was identified between ZSCAN31 expression and TAZ expression, and the protein binding of ZSCAN31 and TAZ was confirmed by co-immunoprecipitation (Co-IP) assay using an HCC cell line.

Conclusions

ZSCAN31 is associated with TAZ expression in HCC cells, and the targeting of ZSCAN31 and TAZ may represent a novel therapeutic approach in HCC.

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.

Unconventional T Cell Targets for Cancer Immunotherapy

Most studies on the immunotherapeutic potential of T cells have focused on CD8 and CD4 T cells that recognize peptide antigens (Ag) presented by polymorphic major histocompatibility complex (MHC) class I and MHC class II molecules, respectively. However, unconventional T cells, which interact with MHC class Ib and MHC-I like molecules, are also implicated in tumor immunity, although their role therein is unclear. These include unconventional T cells targeting MHC class Ib molecules such as HLA-E and its murine ortholog Qa-1b, natural killer T (NKT) cells, mucosal associated invariant T (MAIT) cells, and γδ T cells. Here, we review the current understanding of the roles of these unconventional T cells in tumor immunity and discuss why further studies into the immunotherapeutic potential of these cells is warranted.

HLA-G gene 14-bp deletion variant protects Iranian subjects against chronic hepatitis B infection

To investigate whether 14-bp Ins/Del polymorphism in HLA-G gene is associated with the risk of chronic hepatitis B (CHB) infection. This study was performed on a total of 396 individuals including 199 CHB patients and 197 healthy subjects from a south-east Iranian population. We genotyped 14-bp Ins/Del polymorphism in the HLA-G gene using polymerase chain reaction method. The results of our study revealed that the HLA-G 14-bp deletion polymorphism was associated with a reduced risk of CHB at both allele and genotypic levels. The 14-bp Del allele and Ins/Del genotype were more frequent in control group than in CHB patients (37% vs 28% for Del allele with OR = 0.68 and p-value = .015; 73% vs 52% for Ins/Del genotype with OR = 0.43 and p-value = .001) and both were protective factors against CHB. However, no difference was found in the distribution of HLA-G 14-bp genotypes among subjects with varied levels of HBV DNA or hepatic enzymes (p > .05). Our findings, for the first time, suggest that the HLA-G 14-bp Ins/Del polymorphism may be a marker for genetic susceptibility to CHB infection.

Study on the association of the polymorphism of HLA-II gene with leukemia

We explored the association between the HLA-II gene polymorphisms and the occurrence of leukemia. For this study, we selected 53 patients with leukemia treated at Zhongnan Hospital of Wuhan University from February 2014 to September 2015 and 46 healthy patients as the control group. We used polymerase chain reaction with sequence specific primers for DNA typing which was carried out to analyze the patients HLA-A/B gene polymorphism. We also used enzyme-linked immunosorbent assay and western blotting method to measure the protein expression of different genotypes and activity. Compared to the control group, HLA-A04, B08 gene frequencies were significantly lower than those of HLA-A04, B08 gene frequencies of the observation group; results were statistically significant (χ²=16.28, P<0.05; χ²=16.47, P<0.05). However, in the control group, the frequency of HLA-A09 gene was significantly higher than that of the observation group; there was a significant difference between the two groups (χ²=15.28, P<0.05). Through the measurement of the protein expression levels of the different genotypes in the control group and the observation group, it was found that in the observation group, HLA-A04, B08 protein contents (4.6 and 3.2 µg/l) were significantly higher than those of the control group (0.13 and 0.1 µg/l). While the control group HLA-A09 genotype protein content (3.7 µg/l) was significantly higher than that of the observation group (0.2 µg/l); there were significant differences between both (P<0.05). Therefore, there is a significant correlation between HLA-II gene polymorphism and leukemia that is higher than HLA-A04 and B08 gene frequency and can help promote the occurrence of leukemia. The higher frequency of HLA-A09 gene can help to suppress the occurrence of leukemia.

Role of microRNAs on HLA-G expression in human tumors

The non-classical human leukocyte antigen G (HLA-G) known to protect the embryo from immune cell destruction leading to fetal maternal tolerance is often overexpressed in human tumors of distinct origin thereby leading to an escape from T and NK cell-mediated immune response. The molecular mechanisms controlling HLA-G expression are complex and involve deregulation at the transcriptional, epigenetic and posttranscriptional level. Using bioinformatics and high through put analyses a number of microRNAs (miRs) have been identified, which were able to bind to the 3' UTR of HLA-G with distinct efficacy. This caused by a downregulation of HLA-G surface expression, which was associated with an increased immune response thereby overcoming the HLA-G-mediated immune tolerance. Reduced expression of HLA-G-specific miRs was associated with tumor progression and metastases and appear to affect directly or indirectly tumor characteristics, such as cell proliferation, apoptosis and resistance to chemotherapy. Recently, an interaction between long non-coding RNAs, such as HOTAIR, and HLA-G-specific miRs has also been demonstrated. This review summarizes the control of HLA-G expression and function by microRNAs as well as its clinical significance.

Down-expression of miR-152 lead to impaired anti-tumor effect of NK via upregulation of HLA-G

It is known that chronic HBV infection (CHB) is the major risk factor for hepatocellular carcinoma (HCC) because CHB could not only cause liver tumorigenesis but also lead to change of local microenviroment and lower immune response to infected and cancerous cells (immune tolerance). Human leucocyte antigen-G (HLA-G) belongs to a non-classic MHC-I family and was considered to be an immune tolerance molecule, which could bind to immunosuppressive receptors of natural killer cell (NK) and T cells and trigger immunosuppressive signaling. Recently, numerous studies highlighted that microRNAs (miRNAs) were significantly differentially expressed in HCC tumorigenesis, and the expression was tissue-specific, indicating that miRNAs may cause great epigenetic changes in HCC tumorigenesis. In this study, we found that the expression of HLA-G was upregulated by hepatitis B virus (HBV) infection and miR-152; a HLA-G-targeting miRNA was downregulated by HBV infection. And high expression of HLA-G further suppressed NK against cancer cells, providing a new concept that miR-152 was involved in HBV-induced hepatocellular carcinoma.