High HLA-DP Expression and Graft-versus-Host Disease

Abstract

Background: Transplantation of hematopoietic cells from unrelated donors can cure blood disorders but carries a significant risk of acute graft-versus-host disease (GVHD). The risk is higher when the recipient and donor are HLA-DPB1-mismatched, but the mechanisms leading to GVHD are unknown. The HLA-DPB1 regulatory region variant rs9277534 is associated with HLA-DPB1 expression. We tested the hypothesis that the GVHD risk correlates with the rs9277534 allele linked to the mismatched HLA-DPB1 in the recipient.

Methods: We genotyped rs9277534 in 3505 persons to define rs9277534-DPB1 haplotypes. Among 1441 recipients of transplants from HLA-A,B,C,DRB1,DQB1-matched unrelated donors with only one HLA-DPB1 mismatch, linkage of the rs9277534 A and G alleles to the mismatched HLA-DPB1 was determined. HLA-DPB1 expression was assessed by means of a quantitative polymerase-chain-reaction assay. The risk of acute GVHD among recipients whose mismatched HLA-DPB1 allele was linked to rs9277534G (high expression) was compared with the risk among recipients whose mismatched HLA-DPB1 allele was linked to rs9277534A (low expression).

Results: The mean HLA-DPB1 expression was lower with rs9277534A than with rs9277534G. Among recipients of transplants from donors with rs9277534A-linked HLA-DPB1, the risk of acute GVHD was higher for recipients with rs9277534G-linked HLA-DPB1 mismatches than for recipients with rs9277534A-linked HLA-DPB1 mismatches (hazard ratio, 1.54; 95% confidence interval [CI], 1.25 to 1.89; P<0.001), as was the risk of death due to causes other than disease recurrence (hazard ratio, 1.25; 95% CI, 1.00 to 1.57; P=0.05).

Conclusions: The risk of GVHD associated with HLA-DPB1 mismatching was influenced by the HLA-DPB1 rs9277534 expression marker. Among recipients of HLA-DPB1-mismatched transplants from donors with the low-expression allele, recipients with the high-expression allele had a high risk of GVHD. (Funded by the National Institutes of Health and others.).

Figure 1. Proposed Schema for the Role of HLA-DPB1 Expression in Graft-versus-Host Recognition

In the context of an HLA-DPB1 mismatch between a recipient and a donor (Panel A), an rs9277534G-linked (high-expression) mismatch is hypothesized to be a visible target for donor-mediated graft-versus-host (GVH) recognition. Red HLA molecules represent the mismatched HLA-DPB1 in the recipient, blue molecules represent the donor’s mismatched HLA-DPB1, and green molecules are shared (matched) between the recipient and the donor. Black arrows pointing from the donor toward the recipient represent the GVH vector of allorecognition. The size of the upward-pointing gray arrows indicates the magnitude of the GVH response. In the context of an HLA-DPB1 match between a recipient and a donor (Panel B), peptides (minor histocompatibility antigens) presented by an rs9277534G-linked (high-expression) HLA-DPB1 molecule in a recipient may be a more visible target for donor-mediated GVH recognition. Diverse peptides presented by HLA are shown as purple and blue circles and red, blue, and green triangles.

Figure 2. Direct Chromosomal Phasing of HLA-DPB1, rs9277534, rs2281389

A person with the genotype DPB1*04:01,14:01; rs9277534AG; rs2281389AG is heterozygous at all three genetic markers. The diploid genotype (both chromosomes together) can be produced by four theoretical haplotypes (Panel A). The physical linkage of HLA-DPB1, rs9277534, and rs2281389 alleles on each haplotype in a diploid sample requires separation of the chromosomes (a process known as phasing) (Panel B). The DNA was phased with the rs9277534A probe (red chromosome) and the rs9277534G probe (blue chromosome). The hap-loid DNA (one chromosome by itself) captured by the rs9277534A probe carries the HLA-DPB1*04:01 sequence (shown in reverse orientation for nucleotides 7 through 21, corresponding to residues 8 through 11 of HLA-DPβ; asterisks above the nucleotides indicate positions that distinguish DPB1*04:01 from 14:01) and is physically linked to rs9277534A (circled) and rs2281389A (circled), as ascertained by means of TaqMan genotyping. This is the HLA-DPB1*04:01-A-A haplotype. The haploid DNA captured by the rs9277534G probe carries the HLA-DPB1*14:01 allele and is physically linked to rs9277534G (circled) and rs2281389G (circled). This is the HLA-DPBl* 14:01-G-G haplotype. Controls shown for TaqMan genotyping include rs9277534AA (blue dot), rs9277534AG (green dot), rs9277534GG (red dot), and rs2281389AA (blue dot), rs2281389AG (green dot), rs2281389GG (red dot) cells from the International HLA Workshop panel (see the Materials and Methods section in the Supplementary Appendix). Black squares indicate the absence of template controls.

Figure 3. Correlation of HLA-DPB1 Expression with the rs9277534 Allele in the 3′ Untranslated Region of HLA-DPB1

HLA-DPB1 messenger RNA (mRNA) expression was determined by means of a quantitative polymerase-chain-reaction assay (TaqMan Gene Expression assay) in 81 persons: 49 with the rs9277534AA genotype and 32 with the rs9277534GG genotype. The data are presented as normalized individual data points (2^−deltaCt [delta Ct = Ct gene of interest − Ct endogenous control]) in box-and-whisker plots. The horizontal line within each box indicates the median expression value; vertical lines indicate the smallest and the largest non-outliers in these data.

Figure 4. Probability of Grade II, III, or IV Acute Graft-versus-Host Disease

The probability of grade II, III, or IV acute graft-versus-host disease (GVHD) is shown for transplant recipients with an rs9277534A-linked HLA-DPB1 mismatch (solid line) or an rs9277534G-linked HLA-DPB1 mismatch (dashed line) when the donor’s HLA-DPB1 was linked to rs9277534A (Panel A) or rs9277534G (Panel B). The effects of the mismatch were deleterious in recipients with rs9277534G-linked HLA-DPB1 (high-expression) only when the donor had rs9277534A-linked (low expression) HLA-DPB1. P values were estimated from multivariable regression models adjusted for age, source of stem cells, disease severity, T-cell depletion (yes or no), transplantation regimen, sex of recipient and donor (male–male, male-female, female–male, or female–female), cytomegalovirus serostatus, and year of transplantation.