MiHAs Compatibility Between Related Donor And Recipient In Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation (HSCT) is performed to reconstitute diseased or damaged hematopoietic system for hematopoietic diseases, congenital genetic disorders, autoimmune diseases, acute radiation diseases, and patient with therapy-related toxicity after high-dose radio/chemotherapy to cure malignant solid tumors. The occurrence of Graft-versus-host-disease (GVHD) is a major complication of HSCT and is the main cause of post transplant morbidity and mortality. It is the world problems to be solved that maximum extent possibly to reduce the incidence and degree of GVHD and enhance GVL when hematopoietic and immune system is reconstituted by stem sells.In clinic, it needs high-dose immunosuppressant before transplantation to restrain the accidence of graft rejection after transplantation despite donor and recipient compatibility for the HLA loci. The absolute risk of acute GVHD in HLA-identical sibling is approximately 40%, with the risk of chronic GVHD exceeding 50%. The antigens target to this part of GVHD is Minor histocompatibility antigens (MiHAs). MiHAs are peptides derived from polymorphic intracellular proteins that can be presented by HLA molecules on the cell membrane, and they are defined as alloantigens that are capable of eliciting an allogeneic T cell response in allo-geneic transplantation. The numbers of MiHAs are huge and their coding genes are in the hole genome, including autosome, Y chromosome and mitochondrial gene. So far, the identified MiHAs are only several. Except eliciting GVHD, MiHAs can also elicit graft versus leukemia (GVL) in malignant patient after HACT, which can help to reduce relapse rate of leukemia diseases and eradiate them. So far, donor was selected in clinic according to the level of HLA compatibility in recipient and donor. For selecting suitable donor for recipient taking the level of MiHAs compatibility into accoult is one of the development prospects except according to the level of HLA compatibility. Morever, study in coorelation between MiHAs and occurence of GVHD/GVL is another development direction in the clinical transplantation immunology.MiHAs are HLA-restricted antigens, that is, only presented on the cells membrane by certain HLA moleculars, can they be recognized by allogeneic T cell, if the compatibility of MiHAs is correlated with that of HLA between recipients and donors? To date, still no study get this, which has much significance for selecting suitably donor for recipient to reduce incidence of GVHD and increase possibility of occurring GVL. Studies of MiHAs disparity have largely been restricted to HLA-identical pairs and have limited by small patient numbers in which the results have no value for further researches. There have been no reports for MiHAs disparity rate in HLA-semi-matched pairs and unmatched pairs. Accordingly, in this study MiHAs disparity between recipient and donor were analyzed at gene level and phenotype level in HLA-matched pairs, HLA-semi-matched pairs and HLA-unmatched pairs respectively to identify if the compatibility of MiHAs is correlated with that of HLA in recipients and donors. Because of the different distributions of MiHAs in vary ethic populations and geospatial populations, MiHAs disparity in Chinese population was compared to other ethic populations to get the characteristic distribution of MiHAs. Furthermore, for knowing the MiHAs distribution in different populations, MiHAs frequencies in hematopoietic patients were also analyzed in this study. We are believed in that our results have significant use for effectively preventing /curing GVHD and enhancing GVL in clinic.Methods The study population consisted of 439 patients and 677 normal people and these 1116 population including 229 HLA-matched related donor and recipient, 245 HLA-semi-matched related donor and recipient, 204 HLA-unmatched related donor and recipient, which are all from HSCT recipients and their related donors having been typed for HLA in hospital affiliated to Academe of military medical sciences. First, DNA was isolated using peripheral blood, then genotyping of 14 autosomally encoded minor histocompatibility antigens including HA-1, HA-2, HA-3, HA-8, HB-1, ACC-1, ACC-2, PECAM-1(codon 125), PECAM-1(codon 563), PECAM-1(codon 670), CD62L(codon 206), CD62L(codon 213), PANE-1 and UGT2B17 was performed using the PCR-SSP technique. All PCR-SSP samples were analyzed on agarose gel. Typing data were analyzed as follows: (1) allele frequency, genotype frequency and phenotype frequency of 14 MiHAs in hematopathy population were analyzed and compared with normal population. (2) Disparity rate of MiHAs between HLA-matched related donor and recipient, HLA-semi-matched related donor and recipient, HLA-un-matched related donor and recipient were analyzed respectively at genotype level and phenotype level and compared in these three groups. (3) MiHAs disparity rate between HLA-matched related donor and recipient in Chinese population were compared with other ethnic groups. (4) Linkage analysis of the PECAM-1A (codon 125), PECAM-1A (codon 563) and PECAM-1A (codon 670) alleles were analyzed.Results (1) The statistical difference in frequency of 14 minor H antigens was not found between hematopathy population and normal population (P>0.05). (2) At genotype level, there was no statistical difference in disparity rates of MiHAs between related donor and recipient among there groups. At phenotype level, HA-1, HA-2, HA-3, HA-8, HB-1H, ACC-1, PECAM-1(codon 125), PECAM-1(codon 563), PECAM-1(codon 670), CD62L(codon 206), CD62L(codon 213), PANE-1 were observed lower in disparity rates of MiHAs between HLA-matched related donor and recipient than HLA-semi-matched related donor and recipient(P<0.01); The disparity rate of HA-1,HA-2,HA-8, ACC-1,PECAM-1(codon 125)V,PECAM-1(codon 563)N,PECAM-1(codon 670)G,CD62(codon206),CD62(codon213) in HLA-matched related donor and recipient were lower than they in HLA-unmatched related donor and recipient(P<0.01) and HA-2,HA-3,PECAM-1(codon 125)L,PECAM-1(codon 125)V,PECAM-1(codon 563)N,PECAM-1(codon 563) S,PECAM-1(codon 670) R,PECAM-1(codon 670) G,PANE-1 between HLA-semi-matched related pairs lower than they in HLA-unmatched related donor and recipient ( P<0.05 ) .(3) The frequencies of 14 MiHAs incompatibility are all below 10% in Chinese population, with HA-2, HA-3, HB-1H, ACC-2, CD62L(Condon206), PANE-1 below 1%, in which HB-1Y, ACC-2, UGT2B17 and at least one mismatch in 6 MiHAs were statistically different in white population and ACC-1 different from Asian/Pacific population, HA-1,HA-8 different from Korean (p<0.05). (4) In linkage analysis of the PECAM-1 (condon125), PECAM-1 (condon563) and PECAM-1 (condon670), the frequencies of 125V/560N/670G haplotypes were 57.14% and 125L/560S/670R haplotypes were 33.52%(r≈1), 58.85% and 40.89% for 560N/670G and 560S/670R respectively(r≈1).Conclusions (1) MiHAs distribution in hematopathy population is consistent with the normal population. (2) At gene level, MiHAs have no correlation with HLA in compatibility between recipients and their related donors. At phenotype, there is high correlation with level of MiHAs compatibility and HLA compatibility transplant pairs. (3) Compatibility in HLA-identical related pairs in Chinese population were mainly different from that in white population and Korean population because of the distribution differences of MiHAs in different ethic populations. (4) codon125L/codon563S/codon670Randcodon125V/codon563N/codon670G in three coding region of PECAM-1 has strong linkage disequilibrium, 560N/670G haplotypes and 560S/670R haplotypes were almost accordance. This is the first time that positive correlation existence between MiHAs and HLA in compatibility between recipients and their related donors was confirmed. This observation has important implication for elucidating the mechanisms of developing GVHD/GVL to select best suitably donor for recipient in clinic. Moreover, our research offers regularity of MiHAs distribution in Chinese population and information of MiHAs disparity rate between recipients and their related donors, from which more recognition were got in distributing regularity of MiHAs in vary populations. It can be concluded that these results may offer valuable experimental and theoretical data for preclinical and clinical reasearches.