HLA-E*0101 and HLA-G*010101 reduce the risk of Behcet's disease

The complex HLA-E-nonapeptide in Behçet disease

Introduction

The knowledge of the aetiology of Behçet disease (BD), an immune-mediated vasculitis, is limited. HLA-B, mainly HLA-B51, and HLA-A molecules are associated with disease, but the ultimate cause of this association remains obscure. There is evidence that NK cells participate in the etiopathology of BD. NK cells have activator and inhibitor surface receptors, like the KIR and the NKG2 families. Classical HLA-class I molecules (A, B and C) are keys in the activity control of the NK because they are KIR ligands. Most NKG2 receptors bind HLA-E, which presents only nonapeptides derived from the signal peptide of other class-I molecules.

Objective

This study investigates the contribution of the pair HLA-E and ligand, nonapeptide derived from the 3-11 sequence of the signal peptides of class I classical molecules, to the susceptibility to BD.

Methods

We analyzed the frequency of the HLA-derivated nonapeptide forms in 466 BD patients and 444 controls and an HLA-E functional dimorphism in a subgroup of patients and controls. Results: In B51 negative patients, the frequency of VMAPRTLLL was lower (70.4% versus 80.0% in controls; P=0.006, Pc=0.04, OR=0.60, 95%CI 0.41-0.86), and the frequency of VMAPRTLVL was higher (81.6% versus 71.4% in controls; P=0.004, Pc=0.03, OR=1.78, 95%CI 1.20-2.63). In homozygosity, VMAPRTLLL is protective, and VMAPRTLVL confers risk. The heterozygous condition is neutral. There were no significant differences in the distribution of the HLA-E dimorphism.

Discussion

Our results explain the association of BD with diverse HLA-A molecules, reinforce the hypothesis of the involvement of the NK cells in the disease and do not suggest a significant contribution of the HLA-E polymorphism to disease susceptibility.

HLA-E*01:01 allele is associated with better response to anti-HCV therapy while homozygous status for HLA-E*01:03 allele increases the resistance to anti-HCV treatments in frequently transfused thalassemia patients

BACKGROUND

HLA-E binding to NKG2A/CD94 induces inhibitory signals that modulate NK cells cytotoxicity against infected targets. HCV-derived peptides stabilize HLA-E molecule that favours its higher expression. However, HLA-E stability and expression vary in different genotypes where the presence of HLA-E*01:03 allele is associated with higher HLA-E expression on targets that enhances NK cells inhibition and increases the chance of virus to escape from innate immune system. Here, we aimed to investigate whether HLA-E polymorphism affects HCV infection status or its treatment in major thalassemia patients who are more vulnerable to hepatitis C.

METHODS AND MATERIALS

Study included 89 cases of major thalassemia positive for HCV-antibody; of those 17 patients were negative for HCV-PCR (spontaneously cleared) and 72 patients were HCV-PCR positive (persistent hepatitis under different anti-viral treatment). 16 major thalassemia patients without hepatitis, negative for HCV-antibody were also considered as patients control group. Genomic DNAs extracted from whole bloods were genotyped for HLA-E locus using a sequence specific primer-PCR strategy.

RESULTS

In thalassemia patients, HLA-E*01:03 allele increased susceptibility to HCV infection [p = 0.02; 4.74(1.418-15.85)]. In addition, HLA-E*01:03/*01:03 genotype predicted more resistance to HCV treatment compared to other genotypes [p = 0.037; 3.5(1.1-11.4)]. In other words, we found that the presence of HLA-E*01:01 allele favors better response to anti-HCV therapy [p = 0.037; 3.5(1.1-11.4)].

CONCLUSION

From a mechanistic point of view, the associations between HLA-E polymorphisms and susceptibility to HCV infection or its therapeutic resistance in thalassemia patients may suggest potential roles for the innate and adaptive immune responses to this infection, which are manifested by the acts of HLA-E - NKG2A/CD94 axis in the modulation of NK cell inhibitory function as well as HLA-E associated CD8+ T cell cytolytic activity against HCV, respectively. Notably, from a clinical point of view, paying attention to these associations may not only be useful in increasing the effectiveness of current anti-HCV regimens comprising direct acting antivirals (DAAs) in more complicated patients, but may also suggest antiviral prophylaxis for patients more vulnerable to HCV infection.

HLA-G: Too Much or Too Little? Role in Cancer and Autoimmune Disease

HLA-G is a non-classical HLA class I molecule with immunomodulatory properties. It was initially described at the maternal-fetal interface, and it was later found that this molecule was constitutively expressed on certain immuneprivileged tissues, such as cornea, endothelial and erythroid precursors, and thymus. The immunosuppressive effect of HLA-G is exerted through the interaction with its cognate receptors, expressed on immunocompetent cells, like ILT2, expressed on NK, B, T cells and APCs; ILT4, on APCs; KIR, found on the surface of NK cells; and finally, the co-receptor CD8. Because of these immunomodulatory functions, HLA-G has been involved in several processes, amongst which organ transplantation, viral infections, cancer progression, and autoimmunity. HLA-G neo-expression on tumors has been recently described in several types of malignancies. In fact, tumor progression is tightly linked to the presence of the molecule, as it exerts its tolerogenic function, inhibiting the cells of the immune system and favoring tumor escape. Several polymorphisms in the 3’UTR region condition changes in HLA-G expression (14bp and +3142C/G, among others), which have been associated with both the development and outcome of patients with different tumor types. Also, in recent years, several studies have shown that HLA-G plays an important role in the control of autoimmune diseases. The ability of HLA-G to limit the progression of these diseases has been confirmed and, in fact, levels of the molecule and several of its polymorphisms have been associated with increased susceptibility to the development of autoimmune diseases, as well as increased disease severity. Thus, modulating HLA-G expression in target tissues of oncology patients or patients with autoimmune diseases may be potential therapeutic approaches to treat these pathological conditions.

Correlation of Human Leukocyte Antigen-E Genomic Polymorphism with Leukemia and Functional Study of Human Leukocyte Antigen-E Different Type Promoters

Human leukocyte antigen (HLA)-E is one of the least polymorphic nonclassical major histocompatibility complex (MHC) I genes; its nucleotide variability can affect immune response. In this study, we assess the correlation between HLA-E polymorphism and leukemia and further study the transcriptional activity of promoter variation at nucleotide position-26. A total of 142 healthy blood donors and 111 leukemia patients were collected. The genomic sequence of HLA-E was amplified by high-fidelity reaction system and identified by Sanger and cloning sequencing. The dual luciferase reporter gene assay was used to detect the transcription activity of promoter variation at nucleotide position-26. In the HLA-E genomic sequence results, a total of 16 alleles and 32 genotypes were detected; the HLA-E*01:01:01:06 allele had a significantly lower frequency in leukemia patients than in healthy participants (p = 0.026 < 0.05). And the HLA-E*01:03:02:01, *01:03:02:01 genotype showed the greatest difference in frequency between the two groups of participants (p = 0.028 < 0.05). Eight HLA-E alleles were first reported worldwide in Chinese individuals. The results of the dual luciferase reporter gene experiment showed that the transcription activity of the mutant-type promoter (HLA-E*01:01:01:06 with "T" allele at nucleotide position-26) was significantly lower compared with the wild-type promoter (HLA-E*01:01:01:01 with "G" allele at nucleotide position-26) (p = 0.0242 < 0.05). HLA-E*01:01:01:06 allele has a protective effect against leukemia through decreasing transcription activity by "T" variation at nucleotide position-26.

The HLA-G Immune Checkpoint Plays a Pivotal Role in the Regulation of Immune Response in Autoimmune Diseases

The human G-leukocyte antigen (HLA-G) molecule is a non-classical major histocompatibility complex (MHC) class I molecule. The pertinence of HLA-G has been investigated in numerous studies which have sought to elucidate the relevance of HLA-G in pathologic conditions, such as autoimmune diseases, cancers, and hematologic malignancies. One of the main goals of the current research on HLA-G is to use this molecule in clinical practice, either in diagnostics or as a therapeutic target. Since HLA-G antigens are currently considered as immunomodulatory molecules that are involved in reducing inflammatory and immune responses, in this review, we decided to focus on this group of antigens as potential determinants of progression in autoimmune diseases. This article highlights what we consider as recent pivotal findings on the immunomodulatory function of HLA-G, not only to establish the role of HLA-G in the human body, but also to explain how these proteins mediate the immune response.

HLA-E typing of more than 2.5 million potential hematopoietic stem cell donors: Methods and population-specific allele frequencies

We developed a cost-efficient workflow for genotyping HLA-E by NGS and applied it for genotyping more than 2.5 million potential stem cell donors. The data obtained were used to determine HLA-E allele frequency distributions for 104 populations. Our results confirm the known dominance of the alleles E*01:01 and E*01:03, which have a combined frequency of more than 0.99 in 97 of the 104 populations. E*01:01 is more frequent in Africa and the western part of South America, E*01:03 in Southeast and East Asia. E*01:03 shows a pronounced regional substructure at the high-resolution level with E*01:03:01G being particularly common in a large connected region extending from Turkey to China, E*01:03:02G in Northwestern Europe and E*01:03:03 in Central and Eastern Europe as well as Central Asia. The presented results are relevant both as a basis for further population genetics studies and for optimizing stem cell donor searches.

Genetic polymorphism of HLA-G gene (G*01:03, G*01:04, and G*01:05N) in Iraqi patients with inflammatory bowel disease (ulcerative colitis and Crohn’s disease)

Background

Human leukocyte antigen-G (HLA-G) has been proposed to influence susceptibility to inflammatory bowel disease (IBD). Therefore, the genetic association between HLA-G alleles and two clinical phenotypes of IBD (ulcerative colitis [UC] and Crohn’s disease [CD]) was evaluated in Iraqi patients. A case-control study was performed on 50 UC and 50 CD patients and 100 healthy controls (HC). Three HLA-G alleles (G*01:03, G*01:04, and G*01:05N) were determined using sequence-specific polymerase chain reaction assay followed by product digestion with restriction endonucleases (Hinf-I, BseR-I, and PpuM-I, respectively).

Results

The G*01:03 allele was not detected in IBD patients (UC and CD) or HC, while G*01:04 and G*01:05N alleles showed polymorphic frequencies. The allele G*01:04 was significantly associated with susceptibility to UC (odds ratio [OR] = 2.55; 95% confidence interval [CI] = 1.27–5.13; corrected probability [pc] = 0.018) and CD (OR = 4.45; 95% CI = 2.11–9.41; pc < 0.001). The allele G*01:05N was also associated with increased risk of UC (OR = 4.17; 95% CI = 1.32–13.21; pc = 0.032) and CD (OR = 4.75; 95% CI = 1.53–14.78; pc = 0.014). These associations were more pronounced in IBD (UC + CD), and a significantly increased risk for IBD was found with the alleles G*01:04 (OR = 3.32; 95% CI = 1.86–5.95; pc < 0.001) and G*01:05N (OR = 4.46; 95% CI = 1.59–12.47; pc = 0.008). A stratification of IBD patients according to some demographic and clinical characteristics revealed that frequencies of both alleles showed no significant differences between the subgroups of patients in each stratum. Soluble HLA-G was not influenced by HLA-G alleles in patients or HC. UC was an exception, and the presence of G*01:04 allele was associated with a significantly higher mean of soluble HLA-G compared to patients without the allele (189.6 ± 24.0 vs. 168.6 ± 27.2 ng/mL; p = 0.033).

Conclusion

This study indicated that HLA-G*01:04 and HLA-G*01:05N alleles may influence susceptibility to UC and CD in Iraqi patients.

HLA-G in Mayas from Yucatan: An evolutionary approach

HLA-G allele frequencies were studied in Yucatán (Mexico) Maya Amerindians by a direct exon DNA sequencing technique. It is described that Mayas are probably one of the first populations together with Olmecs that populated Meso America and that important HLA genetic differences between Mexican and Guatemalan Mayas support that Maya languages were imposed to several neighbouring Amerindian groups. HLA-G*01:01:02, HLA-G*01:01:01 and HLA-G*01:04:01 are the most frequent alleles in this population. It is remarkable that HLA-G*01:05N allele was not found in the population in accordance with similar results found in another Amerindians. Also, protein allele HLA-G*01:04 frequency is found not to differ to those found in another far or close living Amerindians in contrast to other World populations. It seems that while high HLA-G*01:05N frequency is found in Iran and Middle East populations, probably where this allele appeared within an ancestral HLA-A*19 group of alleles haplotype and it is maintained by unknown evolutionary forces, Amerindians do not have a high frequency because a founder effect or because required natural evolutionary forces do not exist in America. Finally, we believe useful to study HLA-G evolution for its physiopathology understanding in addition to the many papers on statistics on HLA-G and in vitro models that are yearly published.

HLAs in Autoimmune Diseases: Dependable Diagnostic Biomarkers?

BACKGROUND

The process of antigen presentation to immune cells is an undeniable contributor to the pathogenesis of autoimmune diseases. Different studies have indicated several factors that are related to autoimmunity. Human Leukocyte Antigens (HLAs) are among such factors, which have a key role in autoimmunity because of their involvement in antigen presentation process.

METHODS

Relevant English language literature was searched and retrieved from Google Scholar search engine and PubMed database (1996-2018). The following keywords were used: "Human leukocyte antigen", "Behcet's syndrome", "Rheumatoid arthritis", "Systemic lupus erythematosus", "Type 1 diabetes", "Celiac Disease" and "Autoimmunity".

RESULTS

There is a strong association between HLA alleles and autoimmune diseases. For instance, HLA-B alleles and Behcet's syndrome are strongly correlated, and systemic lupus erythematosus and Type 1 diabetes are related to HLA-DQA1 and HLA-DQB1, respectively.

CONCLUSION

Association between numerous HLA alleles and autoimmune diseases may justify and rationalize their use as biomarkers as well as possible diagnostic laboratory parameters.

The genetic contribution of HLA-E*01:03 and HLA-E*01:03-G*01:01 to Posner-Schlossman syndrome in southern Chinese

Background

The polymorphisms of classical HLA-Ia and HLA-II loci have been associated with Posner-Schlossman syndrome (PSS) in the southern Chinese population. However, the associations of non-classical HLA-Ib (e.g., HLA-E and HLA-G) loci with PSS have not been reported for in the southern Chinese population. This study aimed to evaluate the associations of the HLA-E and HLA-G loci with PSS in a southern Chinese Han population group.

Methods

Ninety-seven unrelated patients with PSS and 90 ethnically matched control subjects were recruited from the Shenzhen Eye Hospital in China. The full-length sequences of HLA-E and HLA-G genes were amplified by long-range high-fidelity PCR, and the third exon of the HLA-E gene and the coding region of the HLA-G gene were sequenced.

Results

The allele frequency of HLA-E*01:03 in patients with PSS was significantly higher than that in the control group (P=0.017, corrected P=0.034, OR =1.66). The genotype frequencies of HLA-E*01:01/01:03 and HLA-E*01:03/01:03 in the PSS group were significantly higher than that in the control group (P=0.027, OR =2.62; P=0.011, OR =3.05; respectively). There were no significant differences in the frequency of HLA-G alleles and genotypes between the two groups (all P>0.05). The haplotype frequency of HLA-E*01:03-G*01:01 in the PSS group was significantly higher than that in the control group (P=0.019, OR =1.63), although this association did not survive the Bonferroni correction (corrected P=0.13).

Conclusions

This study proved for the first time that HLA-E*01:03 and HLA-E*01:03-G*01:01 might be risk factors for PSS.

Redundancy and Complementarity between ERAP1 and ERAP2 Revealed by their Effects on the Behcet's Disease-associated HLA-B*51 Peptidome

The endoplasmic reticulum aminopeptidases ERAP1 and ERAP2 trim peptides to be loaded onto HLA molecules, including the main risk factor for Behçet's disease HLA-B*51. ERAP1 is also a risk factor among HLA-B*51-positive individuals, whereas no association is known with ERAP2. This study addressed the mutual relationships between both enzymes in the processing of an HLA-bound peptidome, interrogating their differential association with Behçet's disease. CRISPR/Cas9 was used to generate knock outs of ERAP1, ERAP2 or both from transfectant 721.221-HLA-B*51:01 cells. The surface expression of HLA-B*51 was reduced in all cases. The effects of depleting each or both enzymes on the B*51:01 peptidome were analyzed by quantitative label-free mass spectrometry. Substantial quantitative alterations of peptide length, subpeptidome balance, N-terminal residue usage, affinity and presentation of noncanonical ligands were observed. These effects were often different in the presence or absence of the other enzyme, revealing their mutual dependence. In the absence of ERAP1, ERAP2 showed similar and significant processing of B*51:01 ligands, indicating functional redundancy. The high overlap between the peptidomes of wildtype and double KO cells indicates that a large majority of B*51:01 ligands are present in the ER even in the absence of ERAP1/ERAP2. These results indicate that both enzymes have distinct, but complementary and partially redundant effects on the B*51:01 peptidome, leading to its optimization and maximal surface expression. The distinct effects of both enzymes on the HLA-B*51 peptidome provide a basis for their differential association with Behçet's disease and suggest a pathogenetic role of the B*51:01 peptidome.

The Impact of HLA-G 3'UTR Polymorphisms in Breast Cancer in a Tunisian Population

Human leukocyte antigens G and E (HLA-G and HLA-E) are nonclassical major histocompatibility complex (MHC) class I molecules. These molecules play an important role in immune surveillance by inhibiting natural killer and cytotoxic T cells responsible for immune escape. The expression of HLA-G and HLA-E has been associated with several diseases including tumor. The main objective of the study is to evaluate the impact of three HLA-G 3'UTR potential polymorphisms: +3187 A > G (rs9380142), +3142 G > C (rs1063320), +2960 14-base pair (bp) Insertion/Deletion (Ins/Del) (rs66554220), and the HLA-E*01:01/01:03 A > G (rs1264457) polymorphism in Tunisian breast cancer population. A total of 355 patients and 381 controls were genotyping for HLA-G and HLA-E polymorphisms using a Taq Man assay. +3142 C allele and +3142 C/C genotype were significantly associated with increased risk of breast cancer (p = 0.00002; OR = 1.58; 95% CI = 27-1.97) (49% versus 35%; p = 0.0001; OR = 1.79; 95% CI = 1.32-2.44). In addition, Del allele and the homozygous state for Del/Del genotype confer a risk for breast cancer (52% versus 45%, p = 0.006; OR = 1.33, 95% CI = 1.08-1.64) (28% versus 22%, p = 0.039; OR = 1.43, 95% CI = 0.90-2.25). However, no statistical significant differences were reported for HLA-G + 3187 A > G and HLA-E variations and breast cancer in a Tunisian population. The found results indicate that HLA-G may play an important role in the breast cancer.

Genetic association between HLA-G 14-bp polymorphism and diseases: A systematic review and meta-analysis

BACKGROUND

HLA-G is an immune checkpoint molecule. Since a differential molecule expression has been reported even for healthy individuals, many studies have focused on polymorphisms at HLA-G regulatory regions, particularly the 3' untranslated region (3'UTR). The presence/absence of a 14-bp sequence was the first polymorphism described and it is the most studied in association between HLA-G and disorders.

METHODS

In this study, we performed a systematic review and meta-analysis of all association studies published regarding the HLA-G 14-bp.

RESULTS

We verified association between 14-bp alleles and diseases in the following situations: (1) presence of 14-bp (insertion) conferred susceptibility to preeclampsia (child alleles evaluated) and systemic lupus erythematosus (OR = 1.42; 95%CI = 1.04-1.93; p = 0.026 and OR = 1.13; 95%CI = 1.01-1.27, p = 0.028); (2) 14-bp absence (deletion) was associated with increased risk to breast cancer (OR = 1.23; 95%CI = 1.06-1.43; p = 0.006) and human Cytomegalovirus infection (OR = 2.06; 95%CI = 1.60-2.64; p < 0.0001); and (3) a risk association was observed between the group of reproductive disorders and the 14-bp insertion (OR = 1.12; 95%CI = 1.01-1.24; p = 0.034).

CONCLUSIONS

Considering that others 14-bp associations were inconclusive and that other variation sites observed at HLA-G 3'UTR exhibit a proven role on post-transcriptional regulation of HLA-G expression, the complete 3'UTR segment should be analyzed in terms of disease susceptibility, instead of a single polymorphism.

HSV-Induced Systemic Inflammation as an Animal Model for Behçet's Disease and Therapeutic Applications

Behçet’s disease (BD) affects multiple organs. It is mainly characterized by recurrent oral, skin, and genital aphthous ulcers, and eye involvement. Successful management of BD is increasing, although its etiology remains unclear. A number of etiologies have been proposed, including environmental, genetic, viral, and immunological factors. To understand its complex etiology and improve its management, animal models of BD have been used to enable more effective therapeutic applications with increased clinical significance. An herpes simplex virus (HSV) type 1-induced BD mouse model has shown disease characteristics similar to those seen in BD patients. An HSV-induced BD animal model has been used to test various therapeutic modalities. The applied modalities are several materials that are derived from natural products, conventional therapeutics, and possible biologics. In this review, we provided how they regulate inflammation in an HSV-induced BD model.

Soluble-HLA-E: A follow up biomarker in Takayasu arteritis, independent of HLA-E genotype

AIM

Disease activity assessment in Takayasu arteritis (TA) is challenging. Human leukocyte antigen E (HLA-E) is shed from endothelium into serum as a soluble molecule (sHLA-E) in response to inflammation. We aimed to study: (i) utility of sHLA-E as a biomarker of disease activity; and (ii) association of HLA-E polymorphism rs1264457 with clinical disease in Asian-Indian TA patients.

MATERIALS AND METHODS

In phase-1, sHLA-E levels were estimated in sera of 50 consecutive TA patients at baseline visit and 27 healthy controls. Serial estimations were performed in 27 of them. In phase-2, DNA of 150 TA patients and 264 healthy controls were genotyped for rs1264457 polymorphism.

RESULTS

At baseline visit, disease was classified as active, stable and grumbling in 23, 18 and nine patients, respectively. sHLA-E levels were higher in active TA (43; interquartile range [IQR]: 25.3-64.6) pg/mL) than stable disease (12.9; IQR: 7.6-21.6 pg/mL) (P = 0.001). At first follow-up visit, sHLA-E levels were numerically higher in active disease than stable disease (P = 0.06) but this trend was blunted at second follow-up. sHLA-E levels increased in 54% versus 25% of patients with persistently active/relapsing and persistent stable course, respectively. rs1264457 polymorphism was not associated with susceptibility to TA and did not affect sHLA-E levels.

CONCLUSION

sHLA-E level is useful as a biomarker of disease activity and course in TA patients. rs1264457 polymorphism is neither associated with susceptibility nor did it influence sHLA-E levels in TA.

HLA-G in Amerindians: Epidemiology and Worldwide Population Comparison

Background:

HLA-G molecules are immunosuppressive and avoid fetal rejection by giving negative signals to maternal immune system from fetal trophoblast cell surface. HLA-G genes have been associated to different pathologies: Spontaneous abortions, autoimmunity, tumor progression, transplant rejection and infection. In addition, different World populations show remarkable different HLA-G allele frequencies in the allele that does not produce a full HLA-G molecule (HLA-G*05N); this allele is almost absent in studied Amerindians.

Objectives:

The aim is to study HLA-A.-B,-DRB1 and –G alleles and extended haplotypes in Amerindians for the first time. This may be useful to asses HLA-G epidemiology, association to disease and Preventive Medicine in Amerindians.

Methods:

HLA-A,-B and -DRB1 have been typed by using standard automatic protocols. HLA-G alleles have been detected by direct HLA-G exon 2, exon 3 and exon 4 DNA sequencing. Computer calculations have been done by specific standard methods.

Results:

HLA-A,-B,-DRB1 and –G extended haplotypes have been calculated in Amerindians for the first time. Also, their HLA-G frequencies have been compared with worldwide populations.

Conclusion:

Low frequencies of null HLA-G*01:05N allele are found in Amerindians. The extended haplotypes with this allele bear other typical Amerindian HLA-DRB1 alleles and its origin is discussed. HLA-G allele frequency profile is closer to that of Europeans than to that of Far East Asians. Our findings are useful to Preventive Medicine and Epidemiology associated to Fertility and HLA-G associated pathology and transplantation.

Human Leukocyte Antigen-E Alleles are Associated with Hepatitis C Virus, Torque Teno Virus, and Toxoplasma Co-infections but are not Associated with Hepatitis B Virus, Hepatitis D Virus, and GB Virus C Co-infections in Human Immunodeficiency Virus Patients

Context:

Data regarding the distribution of Human Leukocyte Antigen (HLA)-E alleles and their association with blood-borne pathogen infections/co-infections are limited for many populations, including Indonesia.

Aims:

The aim of this study was to analyze the association between HLA-E allelic variants and infection with blood-borne pathogens such as hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis D virus (HDV), torque teno virus (TTV), GB virus C (GBV-C), and Toxoplasma gondii (T. gondii) in Indonesian Javanese human immunodeficiency virus (HIV) patients.

Settings and Design:

A total of 320 anti-HIV-positive blood samples were analyzed for HBV, HCV, HDV, TTV, GBV-C, and T. gondii infection status and its association with HLA-E allelic variants.

Materials and Methods:

Nucleic acid was extracted from plasma samples and used for the molecular detection of HBV DNA, HCV RNA, HDV RNA, TTV DNA, and GBV-C RNA, whereas hepatitis B surface antigen, anti-HCV, immunoglobulin M and G (IgM and IgG) anti-T. gondii were detected through serological testing. The blood samples were genotyped for HLA-E loci using a sequence-specific primer-polymerase chain reaction.

Statistical Analysis Used:

Either the Chi-square or Fisher's exact test was performed to analyze the frequency of HLA-E alleles and blood-borne pathogen infections in the population. Odds ratios (ORs) were calculated to measure the association between the antibodies found and the participants’ possible risk behaviors. A logistic regression analysis was used to assess the associations.

Results:

HLA-E*101/0101 was associated with HCV/TTV co-infection (adjusted OR [aOR]: 3.5; 95% confidence interval [CI]: 1.156-10.734; P = 0.027) and IgM/IgG anti-Toxo positivity (aOR: 27.0; 95% CI: 3.626-200.472; P = 0.001). HLA-E*103/0103 was associated with TTV co-infection (aOR: 2.7; 95% CI: 1.509-4.796; P = 0.001).

Conclusions:

HLA-E alleles in Indonesian Javanese HIV patients were found to be associated with HCV, TTV, and toxoplasma co-infections.

Regulation and trafficking of the HLA-E molecules during monocyte-macrophage differentiation

HLA-E is a nonclassical HLA-class I molecule whose best known role is to protect from the natural killer cells. More recently, an additional function more similar to that of classical HLA-class I molecules, i.e., antigen presentation to T cells, is emerging. However, much remains to be explored about the intracellular trafficking of the HLA-E molecules. With the use of 3 different cellular contexts, 2 monocytic cell lines, U937 and THP1, and peripheral blood monocytes, we show here a remarkable increase of HLA-E during monocyte-macrophage differentiation. This goes independently from the classical HLA-class I, the main source of HLA-E-specific peptides, which is found strongly up-regulated upon differentiation of peripheral blood monocytes but not at all in the case of U937 and THP1 cell lines. Although in all cases, there was a moderate increase of HLA-E expressed in the cell surface, lysis by natural killer cells is comparably restored by an anti-NKG2A antibody in untreated as well as in PMA-differentiated U937 cells. Instead, the great majority of the HLA-E is retained in the vesicles of the autophagy-lysosome network, where they colocalize with the microtubule-associated protein light chain 3, as well as with the lysosomal-associated membrane protein 1. We conclude that differently from the classical HLA-class I molecules, the primary destination of the newly synthesized HLA-E molecules in macrophages is, rather than the cell membrane, the intracellular autophagy-lysosomal vesicles where they are stored and where they can encounter the exogenous antigens.

Innate immune cells in the pathogenesis of primary systemic vasculitis

Innate immune system forms the first line of defense against foreign substances. Neutrophils, eosinophils, erythrocytes, platelets, monocytes, macrophages, dendritic cells, γδ T cells, natural killer and natural killer T cells comprise the innate immune system. Genetic polymorphisms influencing the activation of innate immune cells predispose to development of vasculitis and influence its severity. Abnormally activated innate immune cells cross-talk with other cells of the innate immune system, present antigens more efficiently and activate T and B lymphocytes and cause tissue destruction via cell-mediated cytotoxicity and release of pro-inflammatory cytokines. These secreted cytokines further recruit other cells to the sites of vascular injury. They are involved in both the initiation as well as the perpetuation of vasculitis. Evidences suggest reversal of aberrant activation of immune cells in response to therapy. Understanding the role of innate immune cells in vasculitis helps understand the potential of therapeutic modulation of their activation to treat vasculitis.

HLA Allele E*01:01 Is Associated with a Reduced Risk of EBV-Related Classical Hodgkin Lymphoma Independently of HLA-A*01/*02

BACKGROUND

An inefficient immune response against Epstein-Barr virus (EBV) infection is related to the pathogenesis of a subgroup of classical Hodgkin lymphomas (cHL). Some EBV immune-evasion mechanisms target HLA presentation, including the non-classical HLA-E molecule. HLA-E can be recognized by T cells via the TCR, and it also regulates natural killer (NK) cell signaling through the inhibitory CD94/NKG2A receptor. Some evidences indicate that EBV-infected B-cells promote the proliferation of NK subsets bearing CD94/NKG2A, suggesting a relevant function of these cells in EBV control. Variations in CD94/NKG2A-HLA-E interactions could affect NK cell-mediated immunity and, consequently, play a role in EBV-driven transformation and lymphomagenesis. The two most common HLA-E alleles, E*01:01 and E*01:03, differ by a single amino acid change that modifies the molecule function. We hypothesized that the functional differences in these variants might participate in the pathogenicity of EBV.

AIM

We studied two series of cHL patients, both with EBV-positive and-negative cases, and a cohort of unrelated controls, to assess the impact of HLA-E variants on EBV-related cHL susceptibility.

RESULTS

We found that the genotypes with at least one copy of E*01:01 (i.e., E*01:01 homozygous and heterozygous) were underrepresented among cHL patients from both series compared to controls (72.6% and 71.6% vs 83%, p = 0.001). After stratification by EBV status, we found low rates of E*01:01-carriers mainly among EBV-positive cases (67.6%). These reduced frequencies are seen independently of other factors such as age, gender, HLA-A*01 and HLA-A*02, HLA alleles positively and negatively associated with the disease (adjusted OR = 0.4, p = 0.001). Furthermore, alleles from both HLA loci exert a cumulative effect on EBV-associated cHL susceptibility.

CONCLUSIONS

These results indicate that E*01:01 is a novel protective genetic factor in EBV-associated cHL and support a role for HLA-E recognition on the control of EBV infection and lymphomagenesis.

Clinical correlates of human leucocyte antigen (HLA)-G in systemic sclerosis

Human leucocyte antigen (HLA)-G has a tolerogenic function and could play a role in the pathogenesis of immune-mediated diseases, including systemic sclerosis (SSc). The aim of this study was to evaluate HLA-G serum expression (sHLA-G) and the HLA-G gene 14 base pairs (bp) insertion/deletion (del(-)/del(+)) polymorphism in patients with Ssc, to search for possible associations with clinical and laboratory variables. sHLA-G was measured by enzyme-linked immunosorbent assay (ELISA) in sera from 77 patients with SSc and 32 healthy donors (HD); the 14 bp del(-)/del(+) polymorphism was evaluated by polymerase chain reaction (PCR) amplification of peripheral blood mononuclear cells (PBMC) genomic DNA. Receiver operating characteristics (ROC) analysis identified the HLA-G cut-off that best discriminated dichotomized clinical and serological variables, that was subsequently employed to subdivide SSc patients into HLA-G high (HLA-G(+)) and low (HLA-G(-)) profile groups. sHLA-G were not statistically different between SSc patients and HD, nor between distinct SSc autoantibody subsets. Subdividing SSc patients by HLA-G positivity or negativity yielded significant differences for the modified Rodnan skin score (mRss) (P = 0.032), 'general' (P = 0.031) and 'kidney' (P = 0.028) Medsger severity scores (MSS) and disease activity index, and especially Δ heart/lung (P = 0.005). A worse 'general' MSS (P = 0.002) and Δ heart/lung (P = 0.011) were more frequent in the low sHLA-G group. These two variables and mRss were associated with sHLA-G levels at logistic regression analysis. Treatment had no influence on sHLA-G. Moreover, a higher frequency of scleredema was detected in the del(+)/del(+) than the del(-)/del(+) group (P = 0.04). These data suggest modulatory effects of sHLA-G on SSc. Prospective studies are needed to investigate a role in predicting the disease course.

Behçet's Disease: Do Natural Killer Cells Play a Significant Role?

Behçet's disease (BD) is a complex inflammatory disease, of unknown etiology. While disease pathogenesis remains unclear, a strong relationship between BD and HLA-B*51 has been established over the last 30 years. A number of theories exist regarding the cause of BD; however, few are able to account for the increased rates of HLA-B*51 positive individuals, particularly around the Mediterranean basin and Middle-East where the prevalence is highest. This review outlines current immunogenetic data on BD and the immunoregulatory role natural killer cells may play. It also describes the interaction of the killer immunoglobulin-like receptor - KIR3DL1 with its ligand Bw4, which is found on HLA-B51. Finally, CD94/NKG2D, MICA, and ERAP are outlined with regard to their potential roles in BD.

Comprehensive analysis of polymorphisms in the HLA-G 5' upstream regulatory and 3' untranslated regions in Brazilian patients with systemic lupus erythematosus

This study aims to comprehensively analyze human leucocyte antigen (HLA)-G polymorphisms association with susceptibility to systemic lupus erythematosus (SLE) development and clinical manifestations. The HLA-G 5' upstream regulatory region (URR), 3' untranslated region (UTR) and a cytosine deletion at exon 3 (ΔC, HLA-G*0105N allele) were analyzed in 114 SLE patients and 128 healthy controls from North East Brazil. The +3003T>C (rs1707) C allele and the HG010101c extended HLA-G allele were significantly more frequent in SLE patients than healthy controls (+3003C allele frequency: 12% in SLE patients vs 6% in controls; odds ratio (OR), 2.10, 95% confidence interval (CI), 1.06-4.28, P = 0.026; HG010101c frequency: 11.8% in SLE patients and 6.3% in controls; OR, 2.14, 95% CI, 1.01-4.51, P = 0.046) and were associated with susceptibility for disease development. Other polymorphisms were associated with different clinical manifestations. Although HLA-G role in SLE disease is far from being elucidated yet, our association study results along with a systematic review and meta-analysis suggest that HLA-G might be able to slightly modulate the complex SLE phenotype (pooled OR, 1.14, 95% CI, 1.02-1.27, P = 0.021).

Do human leukocyte antigen E polymorphisms influence graft-versus-leukemia after allogeneic hematopoietic stem cell transplantation?

Hematopoietic-stem-cell transplantation (HSCT) is complicated by histocompatibility-dependent immune responses such as graft-versus-host disease, relapse, and graft rejection. The severity of these common adverse effects is directly related to the degree of human leukocyte antigen (HLA) incompatibility. In addition to the key role of classic HLA matching in influencing HSCT outcome, several lines of evidence suggest an important role for nonclassic major histocompatibility complex class I molecule, HLA-E. The interaction of HLA-E with NKG2A, its main receptor on natural killer cells, modulates cell-mediated cytotoxicity and cytokine production, an important role in innate immune responses. In addition, the HLA-E molecule can present peptides to different subtypes of T cells that may either support graft-versus-leukemia effects or be involved in bridging innate and acquired immunity. To date, the role of HLA-E and its polymorphisms in HSCT outcomes such as graft-versus-host disease, transplant-related mortality, and improved survival has been published by a number of groups. In addition, these data suggest an association between HLA-E polymorphisms and relapse. Whether the engagement of the HLA-E molecule in the modulation of donor T cells is involved in the graft-versus-leukemia effect, or whether a different mechanism of HLA-E dependent reduction of relapse is involved, requires further investigation.

Significance of association of HLA-C and HLA-E with psoriatic arthritis

Psoriatic arthritis (PsA) is a complex genetic disorder that results from an interplay between multiple genetic and environmental factors. The aim of the study was to assess the significance of the association between the HLA-C and HLA-E allelic groups and PsA. Our results confirm the association between HLA-C(∗)06 and PsA (OR=5.16, p<0.0001). Furthermore, HLA-C(∗)06-positive patients develop more severe disease (p<0.01) and more frequently present with polyarticular pattern of PsA (p=0.08). Additionally our study revealed that the HLA-C(∗)02 allele was more frequently observed in PsA patients (OR=5.40, p<0.0005) and also that the HLA-E(∗)01:01 allele was significantly over-represented among HLA-C(∗)02-negative patients in comparison to healthy individuals (OR=6.44, p=0.045). Therefore these results suggest that the HLA-E and HLA-C(∗)02 molecules may also play an important role in determination immune response contributing to the PsA development.

HLA-G Molecules in Autoimmune Diseases and Infections

Human leukocyte antigen (HLA)-G molecule, a non-classical HLA-Ib molecule, is less polymorphic when compared to classical HLA class I molecules. Human leukocyte antigen-G (HLA-G) was first detected on cytotrophoblast cells at the feto-maternal interface but its expression is prevalent during viral infections and several autoimmune diseases. HLA-G gene is characterized by polymorphisms at the 3' un-translated region and 5' upstream regulatory region that regulate its expression and are associated with autoimmune diseases and viral infection susceptibility, creating an unbalanced and pathologic environment. This review focuses on the role of HLA-G genetic polymorphisms, mRNA, and protein expression in autoimmune conditions and viral infections.

Genetics of Behçet's disease: lessons learned from genomewide association studies

PURPOSE OF REVIEW

Behçet's disease is a complex disease, and genetic susceptibility plays a critical role. This review aimed to discuss the recent genomewide association study (GWAS) findings and their implications to the pathogenesis of Behçet's disease.

RECENT FINDINGS

GWAS data confirmed the major role of HLA-B51 in Behçet's disease susceptibility, and the discovery of epistatic interactions between HLA-B51 and ERAP1 variants provided some hints about its possible pathogenic mechanisms. Investigation of human leukocyte antigen (HLA) Class I region showed weaker but independent associations around HLA-A and HLA-C regions. Genomewide studies also established associations with IL10, IL23R, CCR1, STAT4, KLRC4, GIMAP2/GIMAP4, and UBAC2 genes in Behçet's disease patients of different ethnicities. Deep resequencing of targeted genes identified additional associations with rare variants in TLR4, MEFV, and NOD2 genes.

SUMMARY

GWAS data established a major step forward by providing insights into the underlying mechanisms in Behçet's disease with the discovery of new susceptibility genes. These variations may implicate defects in the sensing and processing of microbial and endogenous danger signals as well as in the regulation of innate and adaptive immune responses in Behçet's disease. Association findings with HLA Class I antigens as well as IL23R, ERAP1, IL10, and MEFV genes also suggest shared inflammatory pathways with spondyloarthropathies.

Worldwide HLA-E nucleotide and haplotype variability reveals a conserved gene for coding and 3' untranslated regions

The human leukocyte antigen-E (HLA-E) locus is a human major histocompatibility complex (MHC) gene associated with immune-modulation and suppression of the immune response by the interaction with specific natural killer (NK) and T cell receptors (TCRs). It is considered one of the most conserved genes of the human MHC; however, this low nucleotide variability seems to be a consequence of the scarce number of studies focusing on this subject. In this manuscript we assessed the nucleotide variability at the HLA-E coding and 3' untranslated regions (3'UTRs) in Brazil and in the populations from the 1000Genomes Consortium. Twenty-eight variable sites arranged into 33 haplotypes were detected and most of these haplotypes (98.2%) are encoding one of the two HLA-E molecules found worldwide, E*01:01 and E*01:03. Moreover, three worldwide spread haplotypes, associated with the coding alleles E*01:01:01, E*01:03:01 and E*01:03:02, account for 85% of all HLA-E haplotypes, suggesting that they arose early before human speciation. In addition, the low nucleotide diversity found for the HLA-E coding and 3'UTR in worldwide populations suggests that the HLA-E gene is in fact a conserved gene, which might be a consequence of its key role in the modulation of the immune system.

Deletion of the activating NKG2C receptor and a functional polymorphism in its ligand HLA-E in psoriasis susceptibility

Psoriasis is an inflammatory, immune-mediated disease of the skin. Several studies have suggested that natural killer (NK) cells and their receptors may be important for its pathogenesis. Here, we examined whether deletion of the activating natural killer receptor gene NKG2C, which has a frequency of 20% in the European population, was associated with psoriasis susceptibility. The NKG2C deletion and a functional polymorphism in its ligand HLA-E were genotyped in a Caucasian cohort of 611 psoriasis cases and 493 controls. We found that the NKG2C deletion was significantly increased in cases compared with controls [0.258 vs 0.200, P = 0.0012, OR = 1.43 (1.15-1.79)]. The low-expressing HLA-E*01:01 allele was associated with psoriasis (P = 0.0018), although this association was dependent on HLA-C. Our findings support a potential immunoregulatory role for NK cells in psoriasis and suggest the importance of future studies to investigate the contribution of NK cells and their regulatory receptors to the pathogenesis of psoriasis.

The impact of HLA-E polymorphisms on relapse following allogeneic hematopoietic stem cell transplantation

Since relapse following allogeneic hematopoietic stem cell transplantation (HSCT) can be due to the escape of the residual malignant cells from the graft-versus-leukemia (GvL) effect and given the role of NK cells in GvL and the importance of HLA-E in the modulation of NK cell function, we investigated whether polymorphisms of HLA-E molecule could impact on the incidence of relapse and the improvement of Disease-free Survival (DFS) after allogeneic HSCT. The study group included 56 pairs of donors and patients with malignant hematological disorders undergoing HLA-E matched allogeneic HSCT. The median follow-up was 43.6 (range 20.5-113.1) months. They were genotyped for HLA-E locus using a sequence-specific primer (SSP)-PCR. We found a lower incidence of relapse (p=0.02) in the patients with HLA-E*0103/0103 genotype compared to those with other genotypes of HLA-E. We also showed an association between HLA-E*0103/0103 genotype and a better DFS (p=0.001). Our results suggest a protective role for HLA-E*0103/0103 genotype against relapse and an association between this genotype and an improved DFS following HLA-E matched allogeneic HSCT.

HLA-E*0103X is associated with susceptibility to Pemphigus vulgaris

Non-classical human leucocyte antigen-E (HLA-E) mediates natural killer and CD8+ T-cell activity, suggesting a role in the regulation of autoimmunity. HLA-E*0103X/*0103X has been associated with Behcet's disease and HLA-E *0101/*0103X with childhood onset diabetes. We investigated HLA-E allele status in 52 Caucasian and Ashkenazi Jewish Pemphigus vulgaris (PV) patients and 51 healthy controls by restriction fragment length polymorphism-polymerase chain reaction and amplification refractory mutation system. Associations were determined via chi-square test, Fisher's exact test and logistical regression analysis. HLA-E outcomes included presumed homozygous *0101/*0101 or *0103X/*0103X genotype status or *0101/*0103X heterozygous status. PV did not significantly associate with either *0101/*0101 or *0101/*0103X genotypes. HLA-E*0103X/*0103X (presumed homozygote) is significantly increased in patients with PV versus controls (P = 0.0146, OR = 3.730, 95%CI = 1.241-11.213). Our data provide the first evidence that HLA-E*0103X is a marker for genetic risk in PV.

Polymorphic variants in exon 8 at the 3' UTR of the HLA-G gene are associated with septic shock in critically ill patients

Introduction

Critically ill patients are characterized as individuals hospitalized in the Intensive Care Unit (ICU) and can evolve to sepsis, septic shock or even death. Among others, genetic factors can influence the outcome of critically ill patients. HLA-G is a non-classical class Ib molecule that has limited protein variability, presenting seven isoforms generated by alternative splicing, and presents immunomodulatory properties. Polymorphisms at the 3'UTR are thought to influence HLA-G gene expression. It was previously observed that increased sHLA-G5 levels were predictive of survival among septic shock patients. We assessed the frequencies of 7 polymorphisms in exon 8 at the 3' UTR of HLA-G and associated these variants with different clinical outcomes in critically ill patients.

Methods

Exon 8 at the 3' UTR of the HLA-G gene from 638 critically ill subjects was amplified by PCR and sequenced. Genotypes were identified using FinchTV software v.1.4.0 and the most probable haplotype constitution of each sample was determined by PHASE software v.2.1. Haplotype frequencies, linkage disequilibrium, heterozygosity test and Hardy-Weinberg Equilibrium were estimated using ARLEQUIN software v.3.5.

Results

Among all critically ill patients, an association between carriers of the +2960IN_+3142 G_+3187A haplotype and septic shock (P = 0.047) was observed. Septic patients who carried the +2960IN_+3142G_+3187A haplotype presented an increased risk for septic shock (P = 0.031).

Conclusions

The present study showed, for the first time, an association between polymorphisms in exon 8 at the 3 'UTR of HLA-G gene and outcomes of critically ill patients. These results may be important for understanding the mechanisms involved in evolution to septic shock in critically ill patients.

Characterization of HLA-E polymorphism in four distinct populations in Mainland China

In this study, human leukocyte antigen (HLA)-E allelic typing was performed for 690 individuals from two southern Chinese Han populations (Hunan Han and Guangdong Han) and two northern Chinese populations (Inner Mongolia Han and Inner Mongolia Mongol) using polymerase chain reaction-sequence-specific priming (PCR-SSP) method. Our data showed that (1) HLA-E*01:01 and HLA-E*01:03, but not E*01:04 allele, were detected in the four populations, HLA-E distribution differed significantly between each of the two southern Chinese Han populations and the Inner Mongolia Mongol population, and between Hunan Han population and Inner Mongolia Han population; (2) HLA-G*01:05N-A*30-E*01:01-C*06-B*13:02-DRB1*07 was a conserved extended haplotype in the Chinese Han populations; (3) five HLA-A-E haplotypes showed significant linkage disequilibrium (LD) in at least one population, including HLA-A*02-E*01:03 in populations except for the Inner Mongolia Mongol group, HLA-A*01-E*01:01 and HLA-A*30-E*01:01 in the Hunan Han and the Inner Mongolia Han populations, HLA-A*33-E*01:01 in the two southern Chinese Han populations and HLA-A*03-E*01:03 in the Inner Mongolia Mongol group; and (4) Ewens-Watterson homozygosity test showed a trend for balancing selection at the HLA-E locus in each of the four populations. Our data unraveled the peculiarity in terms of HLA-E allelic and haplotypic repertoire in four main ethnic groups in Mainland China, findings shown here are valuable for future studies of the potential role of HLA-E in allogeneic organ transplantation and HLA-linked disease association in related ethnic groups.

Non-classical HLA-E gene variability in Brazilians: a nearly invariable locus surrounded by the most variable genes in the human genome

The non-classical human leukocyte antigen (HLA) class I genes present a very low rate of variation. So far, only 10 HLA-E alleles encoding three proteins have been described, but only two are frequently found in worldwide populations. Because of its historical background, Brazilians are very suitable for population genetic studies. Therefore, 104 bone marrow donors from Brazil were evaluated for HLA-E exons 1-4. Seven variation sites were found, including two known single nucleotide polymorphisms (SNPs) at positions +424 and +756 and five new SNPs at positions +170 (intron 1), +1294 (intron 3), +1625, +1645 and +1857 (exon 4). Haplotyping analysis did show eight haplotypes, three of them known as E*01:01:01, E*01:03:01 and E*01:03:02:01 and five HLA-E new alleles that carry the new variation sites. The HLA-E*01:01:01 allele was the predominant haplotype (62.50%), followed by E*01:03:02:01 (24.52%). Selective neutrality tests have disclosed an interesting pattern of selective pressures in which balancing selection is probably shaping allele frequency distributions at an SNP at exon 3 (codon 107), sequence diversity at exon 4 and the non-coding regions is facing significant purifying pressure. Even in an admixed population such as the Brazilian one, the HLA-E locus is very conserved, presenting few polymorphic SNPs in the coding region.

Molecular typing of HLA-E

Human leukocyte antigen-E (HLA-E) is a non-classical HLA class I gene that shows a limited degree of polymorphism compared to the classical HLA genes. The HLA-E molecule can bind peptides derived from the leader sequence of various HLA class I alleles and some viral homologues, including CMV. The HLA-E peptide complex can act as a ligand for the CD94/NKG2 receptors expressed on the surface of natural killer cells and T cell subsets. Differences in expression levels between the different HLA-E alleles have been reported and a role for HLA-E polymorphism in stem cell transplantation has been postulated. This chapter focuses on routine technologies for HLA-E typing: the sequence-specific primer-PCR method that uses sequence-specific primers, the PCR sequence-specific oligonucleotides Luminex method, using sequence-specific probes attached to beads and the sequencing-based typing method, where sequencing of the alleles is performed.

Genetics of Behçet's Disease

Behçet's disease (BD) is a systemic inflammatory disorder characterized mainly by recurrent oral and genital ulcers and eye involvement. Although the pathogenesis remains poorly understood, a variety of studies have demonstrated that genetic predisposition is a major factor in disease susceptibility. Peculiar geographical distribution of BD along the ancient Silk Road has been regarded as evidence supporting genetic influence. The observed aggregation of BD in families of patients with BD is also supportive for a genetic component in its etiology. HLA-B51 (B510101 subtype) is the most strongly associated genetic marker for BD in countries on the Silk Road. In recent years, several genome-wide association studies and genetic polymorphism studies have also found new genetic associations with BD, which may have a supplementary role in disease susceptibility and/or severity. The author reviewed the HLA and non-HLA genetic association studies.

Clinical significance of the HLA-E and CD94/NKG2 interaction

HLA-E belongs to the non-classical HLA (class Ib family) broadly defined by a limited polymorphism and a restricted pattern of cellular expression. So far, only two functional alleles differing at only one amino acid position (non-synonymous mutation) in the α2 heavy chain domain, where an arginine in position 107 in HLA-E*0101 is replaced by a glycine in HLA-E*0103, have been reported. The interaction between non-classical HLA-E molecule and CD94/NKG2A receptor plays a crucial role in the immunological response involving natural killer (NK) cells and cytotoxic T lymphocytes. All proteins forming CD94/NKG2 receptors are encoded by genes situated in the same cluster on chromosome 12, allowing tight control over the order of their expression. The inhibitory members of the NKG2 receptor family are available on the cell surface before activating the members to prevent autoimmune incidents during immune cells' ontogenesis. In the present review, the potential role of this interaction in viral infection, pregnancy and transplantation of allogeneic hematopoietic stem cells (HSC) is presented and discussed. The review will also include the effect of HLA-E polymorphism on the outcome of HSC transplants in humans.

The genetics of pemphigus

Pemphigus vulgaris (PV) is an autoimmune blistering disorder with a complex etiology involving an interplay of genetic as well as environmental factors, most of which remain unknown. Despite the identification of several human leukocyte antigen (HLA) alleles as risk factors for disease, no other non-HLA genes have clearly been implicated in disease susceptibility. Newer candidate gene and whole-genome approaches are needed to illuminate the full palate of genetic risk elements in PV. Based on this information, genetic-based tools can be expected to provide a scientific rationale for future clinical decision-making by physicians and facilitate an era of personalized medicine.

Linkage disequilibrium between HLA-G*0104 and HLA-E*0103 alleles in Tswa Pygmies

Nonclassical human leukocyte antigen (HLA)-G and -E loci are separated by approximately 660 kb on the short arm of chromosome 6. Interestingly, some functional and expression characteristics are relatively identical or associated for both molecules. For example, expression of HLA-E on the cell surface has been linked to preferential binding of nonameric leader peptides derived from the signal sequence of HLA-G. It has been suggested that these two molecules act synergistically in modulating susceptibility to infectious or chronic inflammatory diseases. A possible explanation for these observations is that HLA-E and HLA-G are evolving under analogous selective pressures and have functions that place them under selective regimes differing from classical HLA genes. The purpose of this study was to investigate the consistency of this hypothesis based on the characterization of the molecular polymorphism of these two genes and their linkage disequilibrium (LD) in three populations, i.e. Southeastern French (n = 57), Teke Congolese (n = 84) and Tswa Pygmies (n = 74). Allelic frequencies observed for HLA-G and HLA-E and for 14-bp ins/del polymorphism in the three populations were similar to those observed in the literature for populations from corresponding geographic areas. Only one of the recently described HLA-G polymorphisms (HLA-G*01:07-01:16) was found, i.e. HLA-G*01:15 in one individual from Congo. We showed that two haplotypes in Tswa Pygmies, i.e. HLA-G*01:04-E*01:03:01 and G*01:04-E*01:01, exhibited highly significant positive and negative D' values respectively. Although these LD could have functional implications, it is more likely because of the genetic drift as the two other populations did not display any significant LD.

Genetic susceptibility to Behcet's disease: role of genes belonging to the MHC region

OBJECTIVE

To review the progress in the field of MHC-related genetic susceptibility to Behçet's disease (BD).

METHOD

Systematic review of the English literature between 1 January 1980 and 31 January 2010 using Medline. Case-control, population-based, observational cohort studies investigating the association between BD and HLA-B*51 subtypes, classical and non-classical HLA alleles and other HLA-related genes were selected. The geographical distribution of BD and these susceptibility genes was also taken into consideration. Case and familial case reports were excluded except for case series with more than two patients.

RESULTS

Ninety articles plus 17 obtained from other sources were included in the systematic review. We have found high evidence that a core component of genetic susceptibility to BD is within the MHC region being primarily related to an HLA-B*51 subtype: HLA-B*5101/B*510101. Moreover, HLA-A*26, HLA-B*15, HLA-B*5701 and TNF-α -1031C were independently associated with BD. Data suggest that other HLA (HLA-C, HLA-DR) and HLA-related [MHC Class I chain-related gene A (MIC-A), TNF-α] genes may play a role in BD co-susceptibility or pathogenesis. Finally, the distinctive geographical distribution of BD suggested an evolutionary selection of HLA-B*51 subtypes as the major susceptibility factors for BD.

CONCLUSION

Further studies must be addressed to clarify the functional relevance of the different genes found to be associated with disease susceptibility and the potential interactions between genes located within and outside the MHC region.

The role of Qa-2, the functional homolog of HLA-G, in a Behcet's disease-like mouse model induced by the herpes virus simplex

Background

It has been suggested that the HLA-G molecule is a genetic risk factor for Behcet's disease (BD). In this study, we evaluated the level of Qa-2, a murine nonclassical class I MHC molecule and possible functional homolog of HLA-G, to determine if it was associated with various symptoms of BD-like mice. In addition, we investigated siRNA (small interfering RNA) treatment to determine if it inhibited Qa-2 expression, thereby changing the symptoms of mice.

Methods

RNA interference (RNAi) and vector transfection were employed to manipulate gene expression in vivo in mice. siRNA (small interfering RNA) or Qa-2 expression vector was applied to inhibit or up-regulate Qa-2 expression, respectively.

Results

The Qa-2 levels in granulocytes were lower in BD-like mice than in normal controls. The silencing of Qa-2 by intravenous injection of siRNA (500 nmol/mouse, 4 times at 3-day intervals) specifically reduced the Qa-2 levels and worsened the BD-like symptoms.

Conclusions

Silencing Qa-2 by injecting siRNA into mice resulted in deterioration of symptoms in BD-like mice.

HLA-G polymorphism influences the susceptibility to HCV infection in sickle cell disease patients

Despite its well known monogenic etiopathogenesis, sickle cell disease (SCD) is characterized by a striking variability of clinical presentation. There is growing evidence that genetic factors may be involved in this variability. Human leukocyte antigen (HLA)-G is a non-classical HLA molecule which was shown to be expressed at sites of inflammation and in inflammatory diseases. Besides its large and highly polymorphic promoter region, the 3' UTR region seems also to play an important role on regulating HLA-G expression. We investigated the influence of the 14 pb (rs1704) and the +3142 (rs1063320) HLA-G polymorphisms in 93 SCD patients in order to evaluate its potential role on clinical parameters. Twenty-one patients presented an HCV infection. Among all SCD patients 16 (22.2%) were homozygous for the +3142C genotype, none of them hepatitis C (HCV) positive. Controlling for blood transfusions in the last year, the C allele represented a dose dependent protection effect for HCV infection (PR = 0.41; 95% CI: 0.24-0.71). The +3142C allele was also underrepresented among patients with history of respiratory-tract infections. Our results support a role of the +3142 polymorphism in the susceptibility to infections, in particular to HCV infection, and suggest a possible interference of the HLA-G molecule in the response to infections, among SCD patients.

A high-throughput Taqman approach for the discrimination of HLA-E alleles

An association between human leukocyte antigen (HLA) molecules and the incidence of various diseases has been recognized for years. Molecules of the HLA system also exert an important role on the clinical outcome after transplantation such as stem cell transplantation. The conventional HLA typing method is sequence based typing (SBT) which is reliable but laborious. The goal of this study was to develop a high-throughput Taqman assay to screen large panels for HLA-E alleles. Two functional HLA-E alleles, *0101 and *0103, have been identified. We set up the Taqman assay with genomic DNA as template to discriminate the three HLA-E genotypes: homozygous HLA-E*0101, heterozygous *0101, *0103 and homozygous *0103. This Taqman approach was validated by the comparison of results obtained with the typing results acquired by sequenced base typing (SBT). Additional screening of a large panel showed the pronounced discriminative capacity of the Taqman assay for HLA-E allele typing. The Taqman assay is a fast, reliable and consistent HLA-E allele typing method, especially useful to screen large panels.