14 bp deletion polymorphism in the HLA-G gene is a risk factor for idiopathic dilated cardiomyopathy in a Chinese Han population

Analysis of key markers: IL-10/sHLA-G in psoriasis patients and the identification of 14-bp INDEL in the HLA-G gene

BACKGROUND

Psoriasis is a chronic inflammation resulting from interactions between immunological and genetic factors. An important tolerogenic role in this autoimmunological disease is played by HLA-G, which is modulated by IL-10. Therefore, this study (N.=80) aimed to evaluate changes in the serum sHLA-G and IL-10 levels in active psoriasis vulgaris and in the early stages of treatment with Methotrexate (MTX) compared to healthy controls. The 14-bp INDEL of the HLA-G gene was evaluated to find possible associations with clinical and laboratory variables.

METHODS

The level of sHLA-G and IL-10 in serum was evaluated (ELISA tests) in patients before the first dose of MTX and at week 12 of treatment, compared to healthy control donors. The 14-bp INDEL in 3'UTR of the HLA-G gene was identified using gDNA templates isolated from full blood. HLA-G amplicons were obtained by PCR, separated by electrophoresis and sequenced.

RESULTS

The mean serum IL-10 level was 4.653±3.33 pg/mL in psoriatic patients, 13.3±9.64 pg/mL after short MTX treatment, compared to 6.23 pg/mL in healthy controls. In addition, the serum level of sHLA-G was 0.275±0.03 ng/mL and 0.332±0.06 ng/mL in patients before and after MTX treatment, respectively, and 0.302±0.08 ng/mL in the control group. A correlation was found (r=-0.43; P<0.005) between the IL-10 and BSA serum levels in psoriasis patients after MTX treatment, indicating health improvement. The three genotypes identified in the 3'UTR of the HLA-G revealed no association with sHLA-G level in serum.

CONCLUSIONS

The mean levels of sHLA-G and the key anti-inflammatory cytokine IL-10 in the blood of pretreatment psoriasis patients are low and indicate that the immunotolerance mechanisms have failed. Treatment of psoriasis patients with low systemic levels of sHLA-G and IL-10 brings them to the same or higher protein levels, respectively, as in healthy donors. Higher sHLA-G levels in healthy donors and after MTX treatment, compared to the sHLA-G levels in the acute phase of psoriasis, indicates its immune system surveillance function.

Diagnostic Value of HLA Typing in Pathogenesis of Cardiomyopathy

Development of cardiomyopathy (CM) is dependent upon several factors. However, the reaction of the immune response against myocardial tissue due to microbial and viral infections plays an important role in this disease. Therefore, the purpose of this study is to investigate the relationship between HLAs and their pathogenic mechanisms in the incidence of CM. Relevant literature was identified by a PubMed search (1989-2017) of English-language papers using the terms "Cardiomyopathy", "Human leukocyte antigen or HLA", "immune response", and "polymorphism". If CM patients are afflicted with viral and microbial infections, HLA class II molecules, which are not expressed on myocardial tissue in normal conditions, are mainly expressed on it. As a result, these HLAs present self- antigens and provoke autoimmune responses against myocardial tissue. On the other hand, the occurrence of polymorphism as well as disrupted expression of miRNAs can affect HLA expression, leading to hypertrophy and fibrosis of cardiac muscle. Finally, it is inferred that the expression evaluation of HLAs as well as identification of polymorphisms in their coding genes can be effective diagnostic factors in the detection of people susceptible to CM.

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.

The effect of genetic variants affecting NK cell function on cardiovascular health and the burden of CMV

Renal transplant recipients (RTR) display high burdens of cytomegalovirus (CMV) and accelerated cardiovascular change. NK cells can control CMV and may contribute to vascular pathologies. Polymorphisms in genes encoding the inhibitory receptor LILRB1 and its ligand HLA-G, and the activating receptor NKG2C may illuminate the role of NK cells in vascular health and CMV immunity. We assessed 81 healthy adults and 82 RTR >2 years after transplantation. RTR had higher humoral and T-cell responses to CMV, and impaired vascular health. A 14bp indel in HLA-G associated with increased flow-mediated dilatation of the brachial artery. The T allele of LILRB1 rs1061680 associated with increased carotid intimal media thickness (cIMT) in RTR and controls. A 16 kb deletion encompassing the NKG2C gene associated with lower cIMT values and higher humoral and T-cell responses to CMV. Hence all polymorphisms tested had small but discernable effects on vascular health. The NKG2C deletion may act via CMV.

"HLA-G 3'UTR gene polymorphisms and rheumatic heart disease: a familial study among South Indian population"

BACKGROUND

Rheumatic heart disease (RHD) is an autoimmune disease where cross reactive CD4⁺ T cells are involved in the pathogenesis of valvular damage. Human Leukocyte Antigen-G (HLA-G), an immunosuppressive molecule playing a crucial role in the inhibition of T cell response is associated with the pathogenesis of various autoimmune and inflammatory diseases. Genetic polymorphisms within the 3'untranslated region (UTR) of HLA-G influences its expression and thus disease pathogenesis. Hence, the present study aims to unravel the association of 14 bp Ins/Del (rs66554220) and +3142 C/G (rs1063320) polymorphisms in 3' UTR of HLA-G with RHD.

METHODS

This familial study consists of 99 RHD families (99 RHD patients, 140 parents and 126 healthy siblings). The 14 bp Ins/Del and +3142 C/G polymorphisms were evaluated by PCR using sequence specific primers and its transmission disequilibrium (TD) was tested by TD test in 70 trio families.

RESULTS

The frequency of +3142 C/C genotype was high in patients with combined valvular lesions (CVL) (OR = 5.88; p_c = 0.012) and pooled RHD patients (P: OR = 2.76; p = 0.043; p_c = 0.076) when compared to healthy siblings. Under the additive (OR = 5.50; p_c = 0.026) and recessive genetic model (OR = 5.88; p_c = 0.012), the +3142 C/C genotype was significantly associated with CVL in patients.

CONCLUSION

The results suggest that the +3142 C/C genotype may be associated with minor risk for the development of RHD and is more likely to influence the severity of the disease.

Cardiac Autoimmunity: Myocarditis

Myocarditis is the inflammation of the muscle tissues of the heart (myocardium). After a pathologic cardiac-specific inflammatory process, it may progress to chronic damage and dilated cardiomyopathy. The latter is characterized by systolic dysfunction, whose clinical correlate is heart failure. Nevertheless, other acute complications may arise as consequence of tissue damage and electrophysiologic disturbances. Different etiologies are involved in triggering myocarditis. In some cases, such as giant cell myocarditis or eosinophilic necrotizing myocarditis, it is an autoimmune process. Several factors predispose the development of autoimmune myocarditis such as systemic/local primary autoimmunity, viral infection, HLA and gender bias, exposure of cryptic antigens, mimicry, and deficient thymic training/Treg induction. Once the anti-myocardium autoimmune process is triggered, several components of the immune response orchestrate a sustained attack toward myocardial tissues with particular timing and immunopathogenic features. Innate response mediated by monocytes/macrophages, neutrophils, and eosinophils parallels the adaptive response, playing a final effector role and not only a priming function. Stromal cells like fibroblast are also involved in the process through specific cytokines. Furthermore, adaptive T cell responses have anti-paradigmatic features, as Th17 response is dispensable for acute myocarditis but is the main driver of the process leading to dilated cardiomyopathy. Humoral response, thought to be a bystander, is important in the appearance of late-stage hemodynamic complications. The complexity of that process, as well as the unspecific and variable clinical presentation, had generated difficulties for diagnosis and treatment, which remain suboptimal. In this chapter, we will discuss the most relevant immunopathogenic findings from a basic science and clinical perspective.

Human leukocyte antigen-G (HLA-G) polymorphism and expression in breast cancer patients

Human leukocyte antigen-G (HLA-G) is known to be implicated in a tumor-driven immune escape mechanism in malignancies. The purpose of this study was to investigate HLA-G polymorphism and expression in breast cancer. HLA-G alleles were determined by direct DNA sequencing procedures from blood samples of 80 breast cancer patients and 80 healthy controls. Soluble HLA-G (sHLA-G) was measured by enzyme-linked immunosorbent assay (ELISA) from serum specimens. HLA-G expression in breast cancer lesions was also analyzed by immunohistochemistry staining. The presence of HLA-G 3' untranslated region (UTR) 14-bp sequence was analyzed and found to be associated with reduced risk of breast cancer susceptibility based on HLA-G expression in tissues (P = 0.0407). Levels of sHLA-G were higher in the breast cancer group (median 117.2 U/mL) compared to the control group (median 10.1 U/mL, P<0.001). The area under the receiver operating characteristic curve (AU-ROC) values of sHLA-G for differentiating breast cancer from normal controls and for detecting metastasis from other stages of breast cancer were 0.89 and 0.79, respectively. HLA-G polymorphism and expression may be involved in breast carcinogenesis and sHLA-G concentrations could be used as a diagnostic marker for detecting breast cancer.

HLA-G 3' untranslated region polymorphisms influence the susceptibility for human papillomavirus infection

Human leukocyte antigen (HLA)-G molecule acts as a potential factor for the regulation of immune responses and its expression in virus-infected cells may enable them to escape immunosurveillance. Besides its polymorphic promoter region, the 3' untranslated region (UTR) seems to play an important role in regulating HLA-G expression. In this study, we investigated the influence of HLA-G 14 bp (rs66554220) and +3142 (rs1063320) polymorphisms in 179 women with active human papillomavirus (HPV) infection and 143 age-matched, unrelated, HPV-negative, normal Chinese Han population. Our findings showed that frequency of the allele +3142 C [31.3% vs 44.4%, odds ratio (OR) = 0.57, Pc < 0.01] and the genotype +3142 CC (10.6% vs 21.7%, OR = 0.43, Pc = 0.012) was significantly decreased in HPV infected patients compared with normal controls. Furthermore, the haplotype -14 bp/C was associated with a reduced risk for HPV infection (OR = 0.57, Pc = 0.001). Our findings also showed that HLA-G homozygous +14 bp/+14 bp genotype was significantly associated with an increased risk for HPV18 infection (OR = 12.95, P < 0.01), whereas HLA-G heterozygous +14 bp/-14 bp genotype increased risk for HPV58 (OR = 5.55, P < 0.05). Furthermore, frequency of the haplotype +14 bp/G was significantly increased in HPV18 infected patients (60.0% vs 27.3%, OR = 4.00, Pc < 0.05). Taken together, our results supported a role of the HLA-G 3' UTR polymorphisms as a susceptible factor for the active HPV infection, and suggested a possible interference of the HLA-G molecule in the response to virus infection.

Associations of human leukocyte antigen-G with resistance and susceptibility to HIV-1 infection in the Pumwani sex worker cohort

OBJECTIVE

To determine the association between human leukocyte antigens (HLA)-G genotypes and resistance or susceptibility to HIV-1.

DESIGN

A group of sex workers in Pumwani, Kenya can be epidemiologically defined as resistant to HIV-1 infection despite frequent exposure and provide an example of natural protective immunity. HLA class I and II molecules have been shown to be associated with resistance/susceptibility to infection in this cohort. HLA-G is a nonclassical class I allele that is primarily involved in mucosal and inflammatory response, which is of interest in HIV-1 resistance.

METHODS

In this study, we used a sequence-based typing method to genotype HLA-G for 667 women enrolled in this cohort and examined the influence of HLA-G genotypes on resistance or susceptibility to HIV-1 infection.

RESULTS

The G*01 : 01:01 genotype was significantly enriched in the HIV-1-resistant women [P = 0.002, Odds ratio: 2.11, 95% confidence interval (CI): 0.259-0.976], whereas the G*01 : 04:04 genotype was significantly associated with susceptibility to HIV-1 infection (P = 0.039, OR:0.502, 95% CI:0.259-0.976). Kaplan-Meier survival analysis correlated with these results. G*01 : 01:01 genotype was associated with significantly lower rate of seroconversion (P = 0.001). Whereas, G*01 : 04:04 genotype was significantly associated with an increased rate of seroconversion (P = 0.013). The associations of these HLA-G alleles are independent of other HLA class I and II alleles identified in this population.

CONCLUSION

Our study showed that specific HLA-G alleles are associated with resistance or susceptibility to HIV-1 acquisition in this high-risk population. Further studies are needed to understand its functional significance in HIV-1 transmission.

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.

Genetic variations in loci relevant to natural killer cell function are affected by ethnicity but are generally not correlated with susceptibility to HIV-1

Polymorphisms in cell surface receptors of natural killer cells and their ligands on target cells can affect susceptibility to viral infections including human immunodeficiency virus (HIV)-1. We found that the carriage of the human leukocyte antigen (HLA)-G minus 14-bp polymorphism, LILRB1 single nucleotide polymorphism rs1061680, and activating and inhibitory killer immunoglobulin-like receptors (KIRs) were different when data were compared between Caucasian, African Americans and Asian populations. However, carriage was similar when HIV-1 patients were compared with control donors, with the exception of the African American cohort.

Can immune-related genotypes illuminate the immunopathogenesis of cytomegalovirus disease in human immunodeficiency virus-infected patients?

Most human immunodeficiency virus (HIV) patients are seropositive for cytomegalovirus (CMV) but a smaller proportion experience end-organ disease. This observation may reflect variations in genes affecting inflammatory and natural killer cell responses. DNA samples were collected from 240 HIV-infected patients followed at the University Hospitals/Case Medical Center (Cleveland, OH) between 1993 and 2008. Seventy-eight patients (African Americans = 41, Caucasians = 37) experienced CMV disease. Genotypes were determined using allele-specific fluorescent probes or multiplex polymerase chain reaction sequence-specific primers. IL12B3'UTR*(1) and SLC11A1 D543N*(1,2) were associated with CMV disease in African American patients (p = 0.04 and p = 0.02, respectively). IL10-1082*(1,2) and LILRB1 I142T*(1) were associated with CMV disease in Caucasians (p = 0.02 and p = 0.07, respectively). DARC T-46C*(1) and CD14 C-159T*(2) were associated with low nadir CD4(+) T cell counts in African American patients (p = 0.002 and p = 0.01, respectively). Caucasian patients carrying TNFA-308*2, TNFA-1031*(2), IL2-330*(1), CCL2-2518*(2), or LILRB1 I142T*(1) had significantly lower nadir CD4(+) T cells in a bootstrapped multivariable model (p = 0.006-0.02). In general, polymorphisms associated with CMV disease and CD4(+) T cell counts were distinct in Caucasian and African American patients in the United States. The LILRB1 I142T polymorphism was associated with both CMV disease and low nadir CD4(+) T cell counts in Caucasians, but the clearest determinant of low nadir CD4(+) T cell count in African American patients was DARC T-46C.

Allele frequencies of human leukocyte antigen-G in a Korean population

The human leukocyte antigen (HLA)-G is a nonclassical major histocompatibility complex class I molecule with relatively limited polymorphism. The differences in allele frequency according to ethnicity and country have not been studied enough, so far. Therefore, fundamental data including allele frequencies and polymorphism are needed for studies on immunological function of HLA-G in each population. We investigated allele frequencies and 14-bp polymorphism of the HLA-G in Koreans. HLA-G alleles and 14-bp polymorphisms were determined by sequence-based typing analysis of exons 2-4 and polymerase chain reaction of exon 8 in 200 unrelated individuals. Genotyping analysis identified eight different HLA-G alleles, which indicates that the Korean population presents limited HLA-G allelic polymorphism. HLA-G*01:01:01:01 and G*01:04:01 were frequent alleles (42.5% and 34.0%), and allelic frequencies were similar to those of other Asian populations. The 14-bp deletion alleles are higher (78%) in Koreans, although the frequencies of the 14-bp insertion/deletion polymorphism have been known to be nearly equal in many Caucasian populations. HLA-G*01:01:08 was reported strong linkage disequilibrium with the 14-bp deletion in a previous report; the same allele was accompanied with 14-bp insertion in our study. There are a few studies investigating allele frequencies, and most of them were studied before high-resolution method era. This is the first study regarding HLA-G genotypes in Korean, which were identified by high-resolution method. From this study, we identified HLA-G frequencies of a Korean population and expect this study could help further investigations for immunological and clinical implications of HLA-G.

HLA-G 14 bp deletion/insertion polymorphism in celiac disease

OBJECTIVES

Nonclassical major histocompatibility class I HLA-G antigen is a tolerogenic molecule that inhibits lytic activity of natural killer (NK) cells and cytotoxic T lymphocytes. Because of its immunomodulatory and tolerogenic properties, HLA-G molecules may have a role in celiac disease (CD). We analyzed the HLA-G 14 bp deletion/insertion polymorphism, known to have a functional effect on mRNA stability, in a group of 522 CD patients, stratified for the presence of HLA-DQ2 genotype, and 400 healthy individuals to evaluate the possible effect of the polymorphism on the risk to develop the disease.

METHODS

HLA-G 14 bp deletion/insertion polymorphism (rs1704) was detected by polymerase chain reaction and double-checked by direct sequencing.

RESULTS

The 14 bp inserted (I) allele and the homozygous I/I genotype were significantly more frequent in CD patients than in healthy controls. The presence of I allele was associated with an increased risk of CD (OR 1.35) and the effect of I allele was consistent with a recessive genetic model (P<0.001).

CONCLUSIONS

Our results also indicate that the effect of the HLA-G D/I polymorphism is restricted for HLA-DQ2, and not simply due to the presence of linkage disequilibrium with the major known risk factor; moreover we found that the presence of the I allele confers an increased risk of CD in addition to the risk conferred by HLA-DQ2 alone and that subjects that carry both DQ2 and HLA-G I alleles have an increased risk of CD than subjects that carry DQ2 but not the I allele.

HLA-G*0105N allele is associated with augmented risk for HIV infection in white female patients

We analyzed HLA-G 3777G > C, HLA-G 14 bp deletion/insertion and HLA-G*0105N polymorphisms in HIV-positive white adult participants, infected through horizontal heterosexual transmission, and unexposed uninfected individuals, all from north eastern Italy. We report a new association between the HLA-G*0105N allele and HIV infection in adult white female participants, being HLA-G*0105N null allele correlated with an augmented risk (odds ratio = 4.35, 95% confidence interval = 1.38-18.07, P = 0.005) for HIV infection.

Analysis of the plasma soluble human leukocyte antigen-G and interleukin-10 levels in childhood atopic asthma

Human leukocyte antigen-G (HLA-G) has been hypothesized to be associated with the pathogenesis of asthma; however, results remain controversial. Furthermore, HLA-G expression could be modulated by the HLA-G 14-bp insertion (+)/deletion (-) polymorphism and by interleukin-10. In this study, the 14-bp polymorphism in exon 8 of the HLA-G gene, plasma soluble HLA-G, and interleukin-10 (IL-10) levels in untreated atopic asthmatic children, and in a group of age-, gender-, and ethnicity-matched normal controls were analyzed. Data showed that HLA-G 14-bp +/- polymorphism was not significant difference between the asthmatic patients and normal controls. Plasma soluble human leukocyte antigen (sHLA)-G in atopic asthma patients (n = 72; median, 179.28 U/ml) was dramatically higher compared with that of the normal controls (n = 76; median, 35.23 U/ml; p < 0.001). Receiver operating characteristic (ROC) curve analysis showed that the area under ROC curve for sHLA-G was 0.986 (p < 0.001) in atopic asthma patients versus normal controls. IL-10 levels in the asthmatic children (n = 50; median, 5.02 pg/ml) was significantly lower than that of the normal controls (n = 48; median, 12.82 pg/ml; p < 0.001). Both HLA-G 14-bp polymorphism and IL-10 levels were unrelated to plasma sHLA-G concentration in both groups. Our findings indicated that the HLA-G 14-bp polymorphism was not a risk factor, but that sHLA-G might be considered as a biomarker for the atopic asthmatic patients. Dramatically increased sHLA-G with decreased IL-10 levels may have implications in the pathogenesis of atopic asthma.

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.

HLA-G 3'-UTR SNP and 14-bp deletion polymorphisms in Portuguese and Guinea-Bissau populations

In the HLA-G locus, the 3'-untranslated region (3'-UTR) begins in the mid exon 6, and ends in exon 8. The occurrence of a 14-bp deletion within exon 8, the only mutation known until now in the 3'-UTR, has been considered a risk factor for disease and allograft rejection. To describe the polymorphism within this region, direct sequencing analysis was performed on 120 DNA samples from Portugal and Guinea-Bissau. Results indicate that exon 8 is less conserved than the coding exons. Nine single nucleotide polymorphisms and the previously described 14-bp deletion were found within exon 8 of both populations. Molecular diversity was higher in the Guinean samples than in the Portuguese; however, little differentiation was found among the populations, suggesting that local selection on exon 8 sequence variation is absent. The screening for sequence motifs suggests that polymorphism on this region may be involved in HLA-G post-transcriptional regulation and, therefore, in phenotype variation.

HLA-G 3' UTR haplotypes and HIV vertical transmission

We evaluated the possible association of human leukocyte antigen-G (HLA-G) 3777G>C and 14-bp deletion/insertion (D/I) polymorphisms haplotypes and combined genotypes with perinatal HIV transmission in Brazilian children. The 3777G>C polymorphism alone has no effect on HIV vertical transmission but, when linked with the D allele, exerts a positive role in the protection. Indeed, we identified the DC HLA-G haplotype as significantly associated with a protective effect towards HIV vertical transmission.

Human leukocyte antigen-G polymorphism in relation to expression, function, and disease

Human leukocyte antigen-G (HLA-G) is a nonclassical class Ib molecule belonging to the major histocompatibility complex. HLA-G appears to play a role in the suppression of immune responses and contribute to long-term immune escape or tolerance. The focus of this review is polymorphism in the HLA-G gene and protein and its possible importance in expression, function, and disease associations.

Epidermal growth factor receptor gene polymorphisms, R497K, but not (CA)n repeat, is associated with dilated cardiomyopathy

BACKGROUND

Epidermal growth factor receptor (EGFR) has been recently implicated in pathological tissue remodelling and sustained remodelling processes can lead to pathological outcomes, such as cardiac hypertrophy in heart failure. Dilated cardiomyopathy (DCM) is the most common form of heart muscle disease, comprising 60% of the cases of identified cardiomyopathy. This study aimed to evaluate the association between the EGFR gene polymorphisms and DCM in a Chinese population.

METHODS

Genomic DNA was extracted from whole blood samples in 163 DCM patients and 185 control subjects. EGFR R497K (Arg497Lys) and (CA)n polymorphisms were genotyped, and the difference of their allele and genotype frequencies distribution between DCM patients and controls were analyzed.

RESULTS

No significant difference was observed in the frequency distribution of genotype and allele in (CA)n repeat between DCM patients and control subjects. The frequency of Lys allele in DCM patients was significantly higher than that in controls (64.4% and 53.8%, in DCM patients and controls, respectively p = 0.005, OR = 1.556, 95% CI = 1.146-2.111). The frequency for Lys/Lys genotype was significantly overrepresented in DCM patients (p = 0.020, OR = 2.105, 95% CI = 1.134-3.905, for Lys/Lys vs. Arg/Arg).

CONCLUSION

This study suggests that the R497K polymorphism may be associated with DCM in a Chinese population.

Association between HLA-G 3'UTR 14-bp polymorphism and HIV vertical transmission in Brazilian children

OBJECTIVES

The aim of our study was to verify the possible association between an HLA-G 14-bp deletion/insertion polymorphism and perinatal HIV transmission in Brazilian children.

DESIGN

We analyzed the 14-bp deletion/insertion polymorphisms in seronegative (i.e., exposed uninfected, N = 71) and seropositive (exposed infected, N = 175) Brazilian children born from HIV-positive mothers and in healthy controls (n = 175).

METHODS

HLA-G 14-bp deletion/insertion polymorphism (rs16375) was detected by PCR amplification of the target sequence followed by agarose gel electrophoresis. All the samples were also analyzed by direct sequencing in order to validate the genotyping results.

RESULTS

HIV-exposed uninfected children showed significant differences in their allele and genotype frequencies of the HLA-G 14-bp polymorphism when compared to both seropositive children and healthy controls. The 14-bp-deleted (D) allele was more frequent in exposed uninfected children (79%) than in healthy controls (60%) and HIV-positive children (58%); the higher percentage of the D allele found in the exposed uninfected children with respect to HIV-positive individuals was significantly associated with a reduced risk of vertical transmission. This effect was ascribable to the presence of the D/D homozygous genotype.

CONCLUSION

Our findings support the possible role for the HLA-G 14-bp deletion/insertion polymorphism in the HIV vertical transmission in Brazilian children. The presence of the D allele and D/D genotype is associated with a protective effect toward HIV perinatal infection.

The 14 bp deletion polymorphisms in HLA-G gene play an important role in the expression of soluble HLA-G in plasma

Soluble human leukocyte antigen-G (sHLA-G) functions as a multiple immunoregulator. A 14 bp insertion (+14 bp)/deletion (-14 bp) polymorphism in exon 8 of the HLA-G gene has been proposed to be associated with HLA-G mRNA stability and the expression of HLA-G. In the current study, a total of 150 normal Chinese Han population had been genotyped for the +14 bp/-14 bp polymorphism, and the expression of plasma sHLA-G was determined with enzyme-linked immunosorbent assay in these case-matched plasma. Data showed that genotype of 14 bp polymorphism was significantly associated with sHLA-G expression. Plasma sHLA-G level with the +14 bp/+14 bp genotype was dramatically lower than that with +14 bp/-14 bp (P = 0.004) and -14 bp/-14 bp genotypes (P = 0.003), while no dramatic difference was observed between the +14 bp/-14 bp and -14 bp/-14 bp genotypes (P > 0.05). In both males and females, plasma sHLA-G with the +14 bp/+14 bp genotype was also significantly lower when compared with other two respective 14 bp genotypes. Data also showed that sHLA-G expression was unrelated to gender. This study suggests that the 14 bp deletion polymorphism in the HLA-G gene plays an important role in sHLA-G expression and that interpretation of the potential biological functions of sHLA-G should be made with caution, taking the polymorphism into consideration.

HLA-G gene polymorphism in human placentas: possible association of G*0106 allele with preeclampsia and miscarriage

Definite causes for several pathologies of pregnancy remain unknown. In light of several recent studies, however, diminished or aberrant HLA-G expression may be associated with certain complication of pregnancy and be linked to HLA-G polymorphism. We analyzed DNA from 60 normal placentas (controls), 140 placentas from miscarriage, 36 placentas from preeclampsia, 76 placentas from fetal hypotrophy, and 34 placentas with hypoxia for variations in coding regions (allelic groups G*0101 to G*0107) and the 14-bp deletion/insertion into the 3'-untranslated region. No statistically significant differences were observed in the distribution of allelic group between pathological placentas and controls with the exception of G*0106 allele frequency in preeclamptic compared with control placentas (21.2% and 6.6%, respectively). A greater frequency of this allele also was observed in the two subgroups of miscarriage and hypoxia compared with that in controls. In addition, presence of the 14-bp sequence was prominent in preeclampsia compared with controls (60.8% vs. 35%, respectively), and homozygotes with deletion were not detected in the pathology. The results suggest that the G*0106 allele, which is coupled with the presence of the 14-bp sequence, contributes and/or is a relevant marker in some specific complications of pregnancy, especially preeclampsia.

Genetic complexity of autoimmune myocarditis

Autoimmune myocarditis, a chronic stage of myocardial inflammation, occurs in a small subset of patients after acute cardiotropic viral infection and can lead to dilated cardiomyopathy (DCM). This disease can be recapitulated in susceptible mouse strains by infection with coxsackievirus B3, or by immunization with cardiac myosin or cardiac troponin I. The etiologies of myocarditis are multifactorial and genetically complex. Genetic linkage between susceptibility to myocarditis/DCM and the major histocompatibility complex (MHC) genes has been reported in both humans and experimentally induced mouse models. However, unlike other autoimmune diseases, the non-MHC genes seem to have greater impact than MHC genes on disease susceptibility. Several myocarditis-related non-MHC loci have been identified by our laboratory and others in different models. Most of these loci overlap with other autoimmune disease susceptibility loci, suggesting common or shared genetic traits influencing general autoimmunity. For example, we have demonstrated that Eam1 and Eam2 may influence disease susceptibility via regulating T cell apoptosis at different developmental stages. Blockade of signaling through specific genes, such as CTLA4, ICOS and PD-1, can either enhance or prevent the development of experimental autoimmune myocarditis, but it remains unclear whether functional polymorphisms in these genes are involved in predisposition to disease. In humans, mutations/deletions in immunologically important genes such as CD45, and genes encoding cardiac proteins, have been reported in patients with recurrent myocarditis or DCM. Identification of genetic polymorphisms controlling autoimmune myocarditis will help us understand the mechanisms underlying autoimmune diseases in general, thereby improving potential therapies in patients.