Minor Histocompatibility Antigens: Molecular targets for immunomodulation in tissue transplantation and tumor therapy

Do FY antigens act as minor histocompatibility antigens in the graft-versus-host disease paradigm after human leukocyte antigen-identical sibling hematopoietic stem cell transplantation?

FY antigens are candidate minor histocompatibility antigens relevant to renal allograft rejection, but no data have been reported about their role in graft-versus-host disease (GVHD) incidence after human leukocyte antigen (HLA)-identical siblings hematopoietic stem cell transplantation (HSCT). The aim of this study was to examine the effect of donor/recipient disparity at FY antigens on the incidence of GVHD in Tunisian patients receiving an HLA-identical HSCT. This work enrolled 105 Tunisian pairs of recipients and their HLA-identical sibling donors of HSCs. FY genotyping was performed with the polymerase chain reaction-sequence-specific primer method and donor/recipient disparity for these antigens was analyzed at two levels: incompatibility and nonidentity. The case-control analyses showed no significant correlation between FY disparity and the incidence of either acute or chronic GVHD. Sample size calculation showed that 572 cases and 1716 controls would be necessary to be able to detect a significant association with 80% power and two-sided type I error level of 5% (α=0.05). The lack of association in the studied cohort may be explained by the low immunogenicity of FY antigens in HSCT context, compared with other antigens such as HA-1 and CD31.

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.

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

OBJECTIVE

The 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.

DESIGN AND METHODS

This 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).

RESULTS

The 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 donor's PECAM-1 SNPs and GVHD incidence in recipient.

CONCLUSION

The 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.

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.

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 (Fisher's 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.

Effects of mismatching for minor histocompatibility antigens on clinical outcomes in HLA-matched, unrelated hematopoietic stem cell transplants

Several studies in HLA-matched sibling hematopoietic stem cell transplantation (HSCT) have reported an association between mismatches in minor histocompatibility antigens (mHAg) and outcomes. We assessed whether single and multiple minor mHAg mismatches are associated with outcomes in 730 unrelated donor, HLA-A, B, C, DRB1, and DQB1 allele-matched hematopoietic stem cell transplants (HSCT) facilitated by the National Marrow Donor Program (NMDP) between 1996 and 2003. Patients had acute and chronic leukemia or myelodysplastic syndrome (MDS), received myeloablative conditioning regimens and calcineurin inhibitor-based graft-versus-host-disease (GVHD) prophylaxis, and most received bone marrow (BM; 85%). Donor and recipient DNA samples were genotyped for mHAg including: HA-1, HA-2, HA-3, HA-8, HB-1 and CD31(125/563). Primary outcomes included grades III-IV acute GVHD (aGVHD) and survival; secondary outcomes included chronic GVHD (cGVHD), engraftment, and relapse. Single disparities at HA-1, HA-2, HA-3, HA-8, and HB-1 were not significantly associated with any of the outcomes analyzed. In HLA-A2-positive individuals, single CD31(563) or multiple mHAg mismatches in the HVG vector were associated with lower risk of grades III-IV aGVHD. Based on these data, we conclude that mHAg incompatibility at HA-1, HA-2, HA-3, HA-8, HB-1, and CD31 has no detectable effect on the outcome of HLA matched unrelated donor HSCT.