Sara Lai

HLA-G Gene Polymorphism in Human Placentas: Possible Association of G*0106 Allele with Preeclampsia and Miscarriage

Abstract 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.

The human leucocyte antigen-G 14-basepair polymorphism correlates with graft-versus-host disease in unrelated bone marrow transplantation for thalassaemia

The presence of the 14‐bp insertion polymorphism of the human leucocyte antigen (HLA)‐G gene (HLA‐G) promotes immune tolerance through increased synthesis of HLA‐G molecules. We investigated this polymorphism in a large cohort of 53 thalassaemia patients transplanted from an unrelated donor. Sixteen patients (30·2%) homozygous for the 14‐bp deletion had a higher risk of developing acute graft‐versus‐host disease (aGvHD) than patients homozygous for the 14‐bp insertion (−14‐bp/−14‐bp vs +14‐bp/+14‐bp: Relative Risk = 15·0; 95% confidence interval 1·59–141·24; P = 0·008). Therefore, the 14‐bp polymorphism could be an important predictive factor for aGvHD following bone marrow transplantation.

Killer immunoglobulin-like receptors can predict TKI treatment-free remission in chronic myeloid leukemia patients

Several factors are predictive of treatment-free remission (TFR) in chronic myeloid leukemia (CML), but few data exist on the role of natural killer (NK) cells and their killer-cell immunoglobulin-like receptors (KIRs). KIR and human leukocyte antigen (HLA) genotypes were investigated in 36 CML patients who discontinued tyrosine kinase inhibitor (TKI) treatment after achieving deep molecular response (MR(4.5)). Cumulative TFR was significantly higher in patients homozygous for KIR A haplotype (85.7% vs. 45.5%; p = 0.029). Younger age, Bx haplotype, and the combination KIR3DS1/KIR3DL1 present/HLA-Bw4 present were significantly associated with relapse. KIR genotypes could prove useful in identifying patients that are likely to maintain MR(4.5) after discontinuing TKI treatment.

Exploring the Role of Killer Cell Immunoglobulin-Like Receptors and Their HLA Class I Ligands in Autoimmune Hepatitis

Background Natural killer cells are involved in the complex mechanisms underlying autoimmune diseases but few studies have investigated their role in autoimmune hepatitis. Killer immunoglobulin-like receptors are key regulators of natural killer cell-mediated immune responses. Methods and Findings KIR gene frequencies, KIR haplotypes, KIR ligands and combinations of KIRs and their HLA Class I ligands were investigated in 114 patients diagnosed with type 1 autoimmune hepatitis and compared with a group of 221 healthy controls. HLA Class I and Class II antigen frequencies were compared to those of 551 healthy unrelated families representative of the Sardinian population. In our cohort, type 1 autoimmune hepatitis was strongly associated with the HLA-B18, Cw5, DR3 haplotype. The KIR2DS1 activating KIR gene and the high affinity HLA-C2 ligands were significantly higher in patients compared to controls. Patients also had a reduced frequency of HLA-Bw4 ligands for KIR3DL1 and HLA-C1 ligands for KIR2DL3. Age at onset was significantly associated with the KIR2DS1 activating gene but not with HLA-C1 or HLA-C2 ligand groups. Conclusions The activating KIR gene KIR2DS1 resulted to have an important predictive potential for early onset of type 1 autoimmune hepatitis. Additionally, the low frequency of the KIR-ligand combinations KIR3DL1/HLA-Bw4 and KIR2DL3/HLA-C1 coupled to the high frequency of the HLA-C2 high affinity ligands for KIR2DS1 could contribute to unwanted NK cell autoreactivity in AIH-1.

Identification of a new HLA DRB1 allele (HLA-DRB1*1167) in a potential hematopoietic stem cell donor from Iraqi Kurdistan

High-resolution polymerase chain reaction sequence-specific primer typing and sequence-based typing of the human leukocyte antigen (HLA) gene DRB1 in a potential hematopoietic stem cell donor of Kurdish ethnicity revealed a new allelic variant of HLA-DRB1*11. The sequence was named DRB1*1167, and comparison with previously described DRB1 alleles demonstrated a mixed pattern shared with some DRB1*08 alleles.

KIR and their HLA Class I ligands: Two more pieces towards completing the puzzle of chronic rejection and graft loss in kidney transplantation

Background Kidney transplantation is a life-saving treatment for patients with end-stage renal disease. However, despite progress in surgical techniques and patient management, immunological rejection continues to have a negative impact on graft function and overall survival. Incompatibility between donors and recipients for human leukocyte antigens (HLA) of the major histocompatibility complex (MHC) generates a series of complex cellular and humoral immune response mechanisms that are largely responsible for rejection and loss of graft function. Within this context, a growing amount of evidence shows that alloreactive natural killer (NK) cells play a critical role in the immune response mechanisms elicited by the allograft. Killer immunoglobulin-like receptors (KIRs) are prominent mediators of NK cell alloreactivity. Methods and findings A cohort of 174 first cadaveric kidney allograft recipients and their donors were selected from a total cohort of 657 transplanted patients for retrospective immunogenetic analyses. Patients with HLA Class II mismatches were excluded. HLA Class I allele frequencies were compared among patients with chronic rejection, patients with stable graft function and a group of 2388 healthy controls. Activating and inhibitory KIR gene frequencies, KIR haplotypes, KIR-HLA ligand matches/mismatches and combinations of recipient KIRs and donor HLA Class I ligands were compared among patients with and without chronic rejection and a group of 221 healthy controls. Patients transplanted from donors homozygous for HLA-C1 antigens had a significantly higher risk for chronic rejection than patients transplanted from donors homozygous or heterozygous for HLA-C2 antigens or with epitopes belonging to the HLA-Bw4 ligand group. The Kaplan-Meier curves obtained by dividing the patients into 3 groups according to the presence or absence of one or both of the combinations of recipient KIRs and donor HLA ligands (rKIR2DL1/dHLA-C2 and rKIR3DL1/dHLA-Bw4) showed a significantly higher cumulative incidence of chronic rejection in the group of patients completely lacking these functional units. These patients showed a progressively stronger decline in modification of diet in renal disease-estimated glomerular filtration rate. Conclusions KIR genotyping should be performed at the time of enrolment of patients on the waiting list for organ transplantation. In our study, a significantly higher risk of chronic rejection after kidney transplantation was observed when recipient (r) and donor (d) pairs completely lacked the two functional rKIR-dHLA ligand combinations rKIR2DL1/dHLA-C2 and rKIR3DL1/dHLA-Bw4. This immunogenetic profile corresponds to low levels of NK cell inhibition. Therefore, patients with this high risk profile could benefit from immunosuppressive therapy aimed at reducing NK-cell cytotoxicity.

HLA-G molecules and clinical outcome in Chronic Myeloid Leukemia

The human leukocyte antigen-G (HLA-G) gene encodes a tolerogenic protein known to promote tumor immune-escape. We investigated HLA-G polymorphisms and soluble molecules (sHLA-G) in 68 chronic myeloid leukemia (CML) patients. Patients with G*01:01:01 or G*01:01:02 allele had higher value of sHLA-G compared to G*01:01:03 (109.2±39.5 vs 39.9±8.8 units/ml; p=0.03), and showed lower event free survival (EFS) (62.3% vs 90.0%; p=0.02). The G*01:01:03 allele was associated with higher rates and earlier achievement of deep molecular response (MR)4.5 (100% vs 65%, median of 8 vs 58 months, p=0.001). HLA-G alleles with higher secretion of sHLA-G seem associated with lower EFS, possibly because of an inhibitory effect on the immune system. Conversely, lower levels of sHLA-G promoted achievement of MR4.5, suggesting increased cooperation with immune system.

Distribution of HLA alleles and haplotypes in the Maldivian population

The study of human leukocyte antigen (HLA), allele and haplotype frequencies within populations provides an important source of information for anthropological investigation, organ and hematopoietic stem-cell transplantation purposes as well as disease association studies. As of today, there are no data available in the literature on the HLA structure of the Maldivian population. Altogether 106 families were studied. We used the parents of each family (212 unrelated individuals) to analyze the frequencies of HLA class I and class II allele groups and haplotypes.

AIF-1 gene does not confer susceptibility to Behçet’s disease: Analysis of extended haplotypes in Sardinian population

Background Behçet’s disease (BD) is a polygenic immune-mediated disorder characterized by a close association with the HLA-B*51 allele. The HLA region has a strong linkage disequilibrium (LD) and carries several genetic variants (e.g. MIC-A, TNF-α genes) identified as associated to BD because of their LD with HLA-B*51. In fact, the HLA-B*51 is inherited as part of extended HLA haplotypes which are well preserved in patients with BD. Sardinian population is highly differentiated from other Mediterranean populations because of a distinctive genetic structure with very highly preserved HLA haplotypes. Patients and methods In order to identify other genes of susceptibility to BD within the HLA region we investigated the distribution of human Allograft Inflammatory Factor-1 (AIF-1) gene variants among BD patients and healthy controls from Sardinia. Six (rs2736182; rs2259571; rs2269475; rs2857597; rs13195276; rs4711274) AIF-1 single nucleotide polymorphisms (SNPs) and related extended haplotypes have been investigated as well as their LD within the HLA region and with HLA-B*51. Overall, 64 BD patients, 43 HLA-B*51 positive healthy controls (HC) and 70 random HC were enrolled in the study. Results HLA-B*51 was the only allele with significantly higher frequency (pc = 0.0021) in BD patients (40.6%) than in HC (9.8%). The rs2259571T AIF-1 variant had a significantly reduced phenotypic, but not allelic frequency in BD patients (72.1%; pc = 0.014) compared to healthy population (91.3%). That was likely due to the LD between HLA-B*51 and rs2259571G (pc = 9E-5), even though the rs2259571G distribution did not significantly differ between BD patients and HC. Conclusion No significant difference in distribution of AIF-1 SNPs haplotypes was observed between BD patients and HC and between HLA-B*51 positive BD patients and HLA-B*51 positive HC. Taken together, these results suggest that AIF-1 gene is not associated with susceptibility to BD in Sardinia.

THU0223 Genetics of behçet’s disease in sardinia: two distinct extended hla haplotypes harbor the B*51 allele in normal population and in patients

Background Several observations suggest that genes other than HLA-B*51 might be implicated in BD susceptibility and pathogenesis. In particular, as a consequence of the strong linkage disequilibrium characterizing the MHC region, it cannot be ruled out that HLA-B*51 is included in haplotypes with other functional genes partly responsible of genetic susceptibility to BD. The distribution of HLA alleles in Sardinian natives is characterized by highly preserved haplotypes. Objectives To define the contribution of HLA genes and extended HLA haplotypes conferring susceptibility to Behçet’s Disease (BD), through analysis of Sardinian subjects. Methods Forty-five unrelated Sardinian patients with BD, diagnosed according to the ISG criteria, 45 HLA-B*51 positive and 185 unselected healthy controls were enrolled in the study. DNA samples were typed for HLA class I and class II alleles and genotyped for microsatellites (MICA-TM) and single-nucleotide polymorphisms (rs1264457 HLA–E; rs2281820 motilin; rs1799724 at -857, rs361525 at -238 TNF-alpha) spanning the HLA region. Statistical analysis was carried out using Chi-square test with Yates’ correction or Fischer’s exact test. The strength of association was estimated by calculating the Odds Ratio (OR) with 95% Confidence Interval (95% CI). A value of p<0.05 was considered statistically significant where Bonferroni’s correction was applied. The LD between pairs of loci was calculated performing a likelihood-ratio test, whose empirical distribution is obtained by a permutation procedure using the statistical software Arlequin (version 3.11, Bern, Switzerland). The significance (p<0.01) of the observed likelihood ratio is found by computing the null distribution of this ratio under the hypothesis of LD, using a permutation procedure. All markers were in Hardy-Weinberg equilibrium. Maximum-likelihood haplotype frequencies and their distribution were estimated using an Expectation-Maximization algorithm and polymorphic alleles within each investigated HLA locus were constructed into extended haplotypes. Results The HLA-B*51 allele, in particular the B*51:01, was the only allele conferring susceptibility to BD (pc=0.0042; OR =4.4; 95% CI =2.0 to 9.6), among those investigated. The B*51 allele was more frequently carried by a haplotype (A2; Cw2; B*51:01; DRB1*11; DQA1*05; DQB1*03) that reached its highest frequency in patients with BD.Linkage disequilibrium analysis showed the existence of a B*51 haplotype (A2; Cw2; B*51:01; DRB1*04; DQA1*03; DQB1*03) not associated with susceptibility to the disease (figure 1). None of the investigated microsatellites and SNPs showed a different distribution in B*51 haplotypes characterizing healthy controls and BD patients. Conclusions We confirmed that B*51 is the major genetic susceptibility factor to BD and we described a significant low frequency of A2; Cw2; B*51:01; DRB1*04; DQA1*03; DQB1*03 haplotype in our patients. It might be speculated this haplotype lacks a hypothetical co-susceptibility genetic factor to BD in Sardinian natives. Disclosure of Interest None Declared