The degree of matching at HLA-DPB1 predicts for acute graft-versus-host disease and disease relapse following haematopoietic stem cell transplantation.

The importance of matching for HLA-DPB1 in unrelated donor haematopoietic stem cell (HSC) transplantation is little understood. Most transplant centres do not, currently, prospectively match for DPB1, but emerging data show that DPB1 matching does play a role in determining outcome. We studied the impact of HLA-DPB1 matching on outcome in 143 recipients of T-cell depletion transplants, who matched with their respective unrelated donors (allelic level) at HLA-A, -B, -C, -DRB1 and -DQB1. Of those matched at DPB1, 47.2% (17/36) developed acute graft-versus-host disease (aGvHD) as compared to 66.3% (55/83) of those who were mismatched. This led to a 19.1% (95% CI 0.1-38.3%) increase in the chance of developing aGvHD in mismatched patients (P=0.049). Relapse of the original disease occurred in 51 recipients; 23 of 37 (62%) matched at both DPB1 alleles, 28 of 82 (34%) were mismatched at one or two DPB1 alleles. Thus, there was a significantly higher relapse rate (P=0.0011) in transplant recipients who matched at both DPB1 alleles. In conclusion, a donor/recipient DPB1 match was associated with a significantly lower incidence of aGvHD and a significantly higher incidence of disease relapse. This study provides further evidence for an immunogenic role of HLA-DPB1 in HSC transplants.

Comparison of outcomes of unrelated bone marrow and umbilical cord blood transplants in children with acute leukemia.

In order to compare the outcomes of unrelated umbilical cord blood transplants (UCBTs) or bone marrow transplants, 541 children with acute leukemia (AL) transplanted with umbilical cord blood (n = 99), T-cell-depleted unrelated bone marrow transplants (T-UBMT) (n = 180), or nonmanipulated (UBMT) (n = 262), were analyzed in a retrospective multicenter study. Comparisons were performed after adjustment for patient, disease, and transplant variables. The major difference between the 3 groups was the higher number in the UCBT group of HLA mismatches (defined by serology for class I and molecular typing for DRB1). The donor was HLA mismatched in 92% of UCBTs, in 18% of UBMTs, and in 43% of T-UBMTs (P <.001). Other significant differences were observed in pretransplant disease characteristics, preparative regimens, graft-versus-host disease (GVHD) prophylaxis, and number of cells infused. Nonadjusted estimates of 2-year survival and event-free survival rates were 49% and 43%, respectively, in the UBMT group, 41% and 37% in the T-UBMT group, and 35% and 31% in the UCBT group. After adjustment, differences in outcomes appeared in the first 100 days after the transplantation. Compared with UBMT recipients, UCBT recipients had delayed hematopoietic recovery (Hazard ratio [HR] = 0.37; 95% confidence interval [95CI]: 0.27-0.52; P <.001), increased 100 day transplant-related mortality (HR = 2.13; 95CI: 1.20-3.76; P <.01) and decreased acute graft-versus-host disease (aGVHD) (HR = 0.50; 95CI: 0.34-0.73; P <.001). T-UBMT recipients had decreased aGVHD (HR = 0.25; 95CI: 0.17-0.36; P <.0001) and increased risk of relapse (HR = 1.96; 95CI: 1.11-3.45; P =.02). After day 100 posttransplant, the 3 groups achieved similar results in terms of relapse. Chronic GVHD was decreased after T-UBMT (HR = 0.21; 95CI: 0.11-0.37; P <.0001) and UCBT (HR = 0.24; 95CI: 0.01-0.66; P =.002), and overall mortality was higher in T-UBMT recipients (HR = 1.39; 95CI: 0.97-1.99; P <.07). In conclusion, the use of UCBT, as a source of hematopoietic stem cells, is a reasonable option for children with AL lacking an acceptably matched unrelated marrow donor.

Reference strand mediated conformation analysis resolves HLA-DRB1 typing ambiguities when matching for unrelated bone marrow transplantation.

We show here the use of reference strand mediated conformation analysis (RSCA) to unambiguously resolve the HLA-DRB1 typing of two individuals which were selected as potential unrelated donors for bone marrow transplantation (BMT). In the first case, both sequence-specific primer (SSP) amplification and sequence-specific oligonucleotide probing (SSO), routinely used in different tissue typing laboratories gave, for the two unrelated donors, the same ambiguous typing of HLA-DRB1*04011+*0403 or DRB1*0407+*0413. In this case sequence-based typing (SBT) was not the method of choice to resolve the situation, due to the sequence ambiguities of these two given combinations. RSCA of both samples, using homozygous typing cells (HTCs) for DRB1*04011, *0403 and *0407 as internal controls, gave the unambiguous result that both donors were HLA-DRB1*04011+*0403. In the second case, a donor was typed as DRB1*1102+1103 by SSP, while SSO excluded the DRB1*1102 allele. The patient was unambiguously typed as DRB1*1101+1103 by both techniques. RSCA, using DNA from reference cell lines as internal controls, gave the unambiguous typing that the donor was DRB1*1103 homozygous.

Mutation detection and typing of polymorphic loci through double-strand conformation analysis.

Variations, such as nucleotide substitutions, deletions and insertions, within genes can affect the function of the gene product and in some cases be deleterious. Screening for known allelic variation is important for determining disease and gene associations. Techniques which target specific mutations such as restriction enzyme polymorphism and oligonucleotide probe or PCR primer reactivity are useful for the detection of specific mutations, but these techniques are not generally effective for the identification of new mutations. Approaches for measuring changes in DNA conformation have been developed, based on the principle that DNA fragments which differ in nucleotide composition exhibit different mobilities after separation by polyacrylamide gel electrophoresis (PAGE). Here we describe a conformation-based mutation detection system, double-strand conformation analysis (DSCA), which provides a simple means to detect genetic variants and to type complex polymorphic loci. We demonstrate the application of DSCA to detect genetic polymorphisms such as a single-nucleotide difference within DNA fragments of up to 979 base pairs in length. We present the application of DSCA in detecting four different mutations in the cystic fibrosis gene (CFTR) and 131 different alleles encoded by HLA class I genes.

Complementary strand analysis: a new approach for allelic separation in complex polyallelic genetic systems.

We describe a method, complementary strand analysis (CSA), for separating alleles potentially from any heterozygous genetic locus. Locus specific PCR is performed generating two allelic products. The antisense strands are isolated and hybridised with a sense reference strand to form a chimeric DNA duplex for each allele which is then separated by non-denaturing PAGE. We demonstrate the application of CSA for separation of highly polymorphic HLA-A, -B and -Cw alleles and characterisation of HLA identity in related bone marrow donors and patients. CSA is capable of resolving one nucleotide differences in a DNA fragment nearly as large as a kilobase in length.