Slama Hmida

Effect of donor CTLA-4 alleles and haplotypes on graft-versus-host disease occurrence in Tunisian patients receiving a human leukocyte antigen-identical sibling hematopoietic stem cell transplant.

The CTLA-4 genetic variation, such as single nucleotide polymorphisms (SNPs) may be critical and can affect the functional activity of cells that initiate the graft-versus-host disease (GVHD) effects. The aim of this study is to examine the effect of donor CTLA-4 alleles and haplotypes for the -318C>T and the 49A>G polymorphisms on the occurrence of GVHD in Tunisians recipients of HSCs. A total of 112 patients and their 112 respective sibling donors of HSCs were enrolled in this study. All patients had either grades 0-I or grades II-IV acute GVHD, or chronic GVHD. The SNPs genotyping assay was performed using sets of sequence specific primers (SSP-PCR). The single marker association analysis showed that the 49G allele, in a genetic recessive model, may be a potential risk factor only for the chronic GVHD (p = 0.032, odds ratio [OR] = 2.58, 95% confidence interval = 1.05-6.32). The haplotypes analyses showed that the CTLA-4 -318C49G nucleotide combination is significantly associated with the incidence of chronic GVHD (p = 0.043, χ² = 3.27). Donor CTLA-4 -318C49G haplotype may be a significant risk factor for developing chronic GVHD after allo-stem cell transplantation. We suppose that donor T cells expressing this haplotype in a homozygous state have higher proliferation than those expressing other haplotypes, especially after recognition of the recipients minor histocompatibility antigens.

HA-1 and HA-2 minor histocompatibility antigens in Tunisians

Minor histocompatibility antigens (MiHAgs), such as HA-1 and HA-2, are the main targets of immune responses after allogeneic stem cell transplantation (SCT). HA-1 and HA-2 are two hematopoietic system-restricted antigens encoded, respectively, by HMHA1 and MYO1G genes. In order to estimate their frequencies in Tunisians, we performed a molecular-based allele analysis for 160 healthy and unrelated subjects. Genomic DNAs were extracted mainly by the salting out method. Single nucleotide polymorphism (SNP) genotyping assays for selected sites at HMHA1 gene (rs3764653 and rs1801284) and at MYO1G gene (rs61739531) were performed with a sequence specific primers-polymerase chain reaction (SSP-PCR) method. Statistical analysis of our results showed that the HA-2 antigen is more frequent than the HA-1 antigen in the Tunisian population because their frequencies were 97% and 57%, respectively. Allele analysis for HMHA1 gene showed that the R variant (500T-504G) was predominant in our population (64%). For the MYO1G gene, the C allele was predominant (84%). All loci were in Hardy-Weinberg equilibrium (minimum P value = 0.06). Our frequencies were close to those reported in African and Caucasian groups.

Evidence that erythrocyte DARC-positive phenotype can affect the GVHD occurrence after HLA-identical sibling HSCT.

Chemokine receptors are very important players in the pathogenesis of GVHD. The aim of this study is to test the hypothesis that the lack of expression of the DARC receptor on erythrocytes can affect the GVHD incidence. A total of 105 recipients and their 105 respective sibling donors of HSCs were enrolled in this study. All patients were evaluated for acute and chronic GVHD. The DARC genotyping assay was performed using the SSP-PCR method. The case-control analyses showed that the donor DARC 146G allele and T(-46)G(146) haplotype, coding for the FY2 version of DARC, are very significant in the GVHD paradigm because they are associated with the incidence of acute effects of this outcome in recipients (p=0.007, χ²=7.200). It seems that this version of DARC receptor is a powerful facilitator of chemokine transcytosis and subsequently leukocyte migration into GVHD target organs.

Minor histocompatibility antigens in Tunisians: could platelet endothelial cell adhesion molecule 1 marker be one of them?

Platelet endothelial cell adhesion molecule 1 (PECAM-1/CD31) is one of the human minor histocompatibility antigens that are the main targets of alloreactive T-cells after hematopoietic stem cells or solid organs transplantation. In order to investigate its polymorphism in Tunisians, three single nucleotide polymorphisms (SNPs) (rs668, rs12953 and rs1131012) were selected to perform an allele and haplotype analysis. Hundred-and-forty-two healthy and unrelated subjects were enrolled in this survey. Genomic DNAs were extracted using salting out method. SNP genotyping assays were performed with home-designed sequence-specific primers polymerase chain reaction (SSP-PCR). As a result, molecular analysis showed that PECAM-1 is one of the most polymorphic markers in the Tunisian population because minor allele frequency was 0.3, and minimum haplotype frequency was 0.03. A low linkage disequilibrium (D = 0.45) between rs12953 and rs1131012 was noticed, although all other loci were in the Hardy-Weinberg equilibrium (minimum P value = 0.07). The frequencies were close to those reported in African-American and Caucasian groups.

Does minor histocompatibility antigen HA-1 disparity affect the occurrence of graft-versus-host disease in tunisian recipients of hematopoietic stem cells?

INTRODUCTION: Minor histocompatibility antigen HA‐1 (MiHAg‐HA‐1) disparity between a patient and his or her human leukocyte antigen (HLA) genoidentical donor has been widely associated with an increased risk of graft‐versus‐host disease following allogeneic hematopoietic stem cell transplantation. OBJECTIVE: To examine the effect of HA‐1 disparity on the incidence of both acute and chronic graft‐versus‐host disease in Tunisian recipients of hematopoietic stem cells. METHODS: A total of 60 patients and their 60 respective sibling hematopoietic stem cell donors were enrolled in this study. All patients prophylactically received cyclosporine A and/or methotrexate for graft‐versus‐host disease. An HA‐1 genotyping assay was performed with the SSP‐PCR method, and HLA‐A*0201‐ and/or HLA‐A*0206‐positive samples were identified using the Luminex HLA typing method. RESULTS: The Luminex HLA typing assay showed that 54 patients were positive for either the HLA‐A*0201 or HLA‐A*0206 alleles. Among these cases, six pairs were mismatched for MiHAg‐HA‐1. Both acute and chronic graft‐versus‐host disease occurred in four mismatched patients (Fishers p‐values were 0.044 and 0.170, respectively). A univariate logistic regression model analysis showed that only acute graft‐versus‐host disease may be affected by recipient MiHAg‐HA‐1 disparity (p: 0.041, OR: 6.727), while chronic graft‐versus‐host disease correlates with both age and recipient/donor sex mismatch (p: 0.014, OR: 8.556 and p: 0.033, OR: 8.664, respectively). CONCLUSION: Our findings support previously reported data suggesting a significant association between HA‐1 disparity and the risk of acute graft‐versus‐host disease following hematopoietic stem cell transplantation.

Acute graft-vs.-host disease correlates with the disparity for the PECAM-1 S536N polymorphism only in the HLA-B44-like positive Tunisian recipients of HSCs.

GVHD is the major cause of mortality after HLA-identical HSCT. Such complication has been widely linked to donor/recipient disparity for minor histocompatibility antigens (MiHAgs). PECAM-1 is one of potential human MiHAgs but its effect on the GVHD occurrence remains not clear. In order to examine such association in the Tunisian cohort of HSCs recipients, we performed a retrospective study on patients who undergone HLA-identical HSCT between 2000 and 2009. Genotyping of the three selected PECAM-1 polymorphisms (rs668, rs12953 and rs1131012) was performed with SSP-PCR method. Univariate analyses showed that grades II-IV acute GVHD were considerably linked to the non-identity for rs12953 only in HLA-B44-like positive patients (p=0.010, OR=10.000). Multivariate analysis for chronic GVHD showed that this outcome may be affected only by the adulthood and the conditioning regimen. Our findings support the previously reported data suggesting a significant association between the PECAM-1 disparity and the risk of acute GVHD.

Investigation of the effect of donor platelet endothelial cell adhesion molecule 1 polymorphism on the graft-vs.-host disease occurrence in Tunisian recipients of hematopoietic stem cells.

OBJECTIVEnThe aim of this study is to examine the effect of donor PECAM-1 alleles and haplotypes for the SNPs L98V, S536N, and R643G on the occurrence of GVHD in Tunisian recipients of HSCs.nnnDESIGN AND METHODSnThis study enrolled 102 patients and their 102 respective HLA-identical sibling donors of HSCs. The PECAM-1 SNPs genotyping assay was performed using sets of sequence specific primers (SSP-PCR).nnnRESULTSnThe single marker association analysis showed that the L98 allele, in a recessive genetic model, may be a potential risk factor only for acute GVHD (p=0.036, OR=2.580, 95% C.I. = 1.053-6.326). However, the haplotype analysis showed a lack of association between donors PECAM-1 SNPs and GVHD incidence in recipient.nnnCONCLUSIONnThe homozygosity state for donor PECAM-1L98 allele may be a significant risk factor for acute GVHD. This is probably due to its action on the function of donor leukocytes especially during the extravasation process.

The Investigation of the Evolutionary History of the Omani Population by Analysis of HLA Class I Polymorphism

Abstract The HLA polymorphism is a useful way to investigate the relatedness between human ethnic groups. This work aimed to study the relatedness of Omanis with other modern ethnic groups using the HLA class I system polymorphism. The study enrolled 259 healthy and unrelated individuals who were randomly selected from the Omani population. Genotyping of HLA-A and -B loci was carried out by the molecular approach for all subjects. The HLA A and B allele frequencies were estimated by the maximum-likelihood rule. The interethnic analysis was performed using genetic distances measurements, Neighbour-Joining dendrograms and extended haplotypes analysis. The HLA allele analysis showed the presence of 16 variants at the A locus and 27 variants at the B locus. Statistically, the most frequent alleles were: HLA-A*02 (19.9%) and -B*35 (15.3%); and the most frequent HLAA_ B haplotype was: A*02_B*51 (5.6%). When compared to others ethnic groups, the Omanis showed a genetic relatedness to the Mediterranean and West-Asian peoples. The relatedness between Omani, Mediterranean and West-Asian population might be explained by several historic and socio-geographic factors if we flashback on the long history of the Omani population.

HLA Class II (DRB1 and DQB1) Polymorphism in Omanis

The HLA class II polymorphism of 254 healthy unrelated Omanis was analyzed by PCR-SSP method, and thexa0detected frequencies were compared to those reported in 20 other populations. The most frequent HLA class IIxa0DRB1 alleles were DRB1*16, DRB1*03 and DRB1*15 with frequencies of 0.315, 0.224 and 0.106 respectively, whilexa0the most frequent DQB1 alleles were DQB1*05 and DQB1*02 with frequencies of 0.366 and 0.283 respectively. Thexa0haplotype analysis revealed that DRB1*03-DQB1*02 was the most common HLA class II haplotype with linkagexa0disequilibrium (a frequency of 0.206). Compared with other populations, our result, deduced from the analysis ofxa0genetic distances and the construction of neighbour joining dendrogram, indicates that Omanis are related toxa0Mediterranean and West-Asian populations. This fact might be explained by several historic and socio-geographicxa0factors if we consider on the long history of this population.

Kell Blood Group System Polymorphism in an Urban Tunisian Population

Blood group systems such as Kell are significant in clinical and basic sciences (Daniels 2005). Their importance has been widely linked to their immunogenicity in some contexts, such as transfusion, feto-maternal tolerance, and transplantation (Lee et al. 1993; Murphy and Fraser 1997; Mannessier 2003; Faas et al. 2000; Kavita and Francine 2001; Dhodapkar and Blei 2001; Daniels et al. 2003; Gariod et al. 2004; Zimring et al. 2007). Such immunogenicity was linked to individual antigens that result from genetic polymorphisms. In this regard, the Kell blood group was described as the third most polymorphic system, with a group of 31 antigens (Körmöczi et al. 2009). Incompatibility for these antigens was defined as a critical factor involved in hemolytic transfusion reactions, autoimmune hemolytic anemia, and hemolytic disease of the newborn (Kanhai et al. 1987; Lee et al. 1993). The Kell carrier molecule (CD238), a zinc endopeptidase, is a 93-kDa type II glycoprotein composed of 732 amino acids. It is encoded by the 19-exon KEL gene assigned to 7q33–35. Depending on single-nucleotide polymorphisms and resulting amino acid substitutions, several sets of antithetical KEL antigens are recognized, such as KEL1 (K) (Lee et al. 1996a) and KEL2 (k, ‘‘cellano’’) (Hessner et al. 1996); KEL3 (Kp), KEL4 (Kp), and KEL21 (Kp); KEL6 (Js) and KEL7 (Js) (Lee et al. 1995a). The most important is the KEL1 (K, ‘‘kell’’) antigen; anti-KEL1 is a commonly encountered allospecificity capable of causing hemolytic transfusion reactions, hemolytic disease of the fetus and newborn, and neonatal anemia (Win et al. 2005). Besides peripheral immunologic clearance of anti-KEL1 sensitized RBCs, it has been reported that these antibodies are able to induce myelosuppression, probably