Effect of HLA incompatibility on graft-versus-host disease, relapse, and survival after marrow transplantation for patients with leukemia or lymphoma

A special report: histocompatibility testing guidelines for hematopoietic stem cell transplantation using volunteer donors. Quality Assurance and Donor Registries Working Groups of the World Marrow Donor Association

The World Marrow Donor Association has formulated guidelines for establishing the extent and quality of histocompatibility testing for unrelated donor registries, umbilical cord blood banks, and transplant centers involved in international exchange of hematopoietic stem cells for allogeneic transplantation. Registry and cord blood bank guidelines suggest that, at a minimum, initial HLA typing should be performed for three HLA loci, HLA-A, -B, and -DR, at low resolution/split antigen level. DNA-based testing methods should be utilized for HLA-DR typing. DNA-based testing for HLA-A and -B should replace serologic testing of new volunteer donors and cord blood units as robust protocols and reagents become available to the laboratories. Transplant center guidelines for typing of patient, family and to confirm the HLA types of potential unrelated donors should include, at the minimum, typing HLA-A, B, and -DR loci using primarily DNA-based testing methods at allele level resolution for DRB1 and low resolution/split antigen level for HLA-A and -B. It is strongly recommended that the typing of a patient and the selected donor be performed using the same set of reagents, methodology, and interpretation criteria with fresh tissue samples to ensure HLA identity. Guidelines for laboratory accreditation, approaches to quality assurance and quality control for HLA testing, and suggestions for the format of the HLA database of donor types are also outlined.

Reconstruction of the block matching profiles

Block matching is a valuable tool for selecting donors for bone marrow transplantation. Identical, electrophoretic profiles of unrelated bone marrow donor-recipient pairs have been shown to be associated with long-term survival and a reduction of graft versus host disease (GVHD). This study was undertaken to determine the sequences of the PCR products which are generated. PCR products obtained with beta-block primers following the amplification of DNA extracted from cell lines homozygous for 7.1 and 8.1 ancestral haplotypes were cloned and sequenced. The PCR products were characterised and the beta block profiles reconstructed. The data indicate that the profiles consist of homoduplexes and heteroduplexes which are formed by the products of probably 3 different sequence locations.

DNA Typing for HLA-A and HLA-B Identifies Disparities Between Patients and Unrelated Donors Matched by HLA-A and HLA-B Serology and HLA-DRB1

High incidences of graft failure and graft-versus-host disease in the recipients of bone marrow transplantations (BMT) from unrelated donors (URD) may reflect the existence of allelic disparities between the patient and the URD despite apparent HLA identity at HLA-A, HLA-B, and HLA-DRB1 loci. To identify the extent and pattern of allelic disparities at HLA-A and HLA-B loci, 128 patients and 484 potential URD were evaluated by DNA typing. DNA typing for HLA-A, HLA-B, and HLA-DRB1 was performed at Memorial Sloan Kettering Cancer Center. HLA-A and HLA-B serotyping on URD was provided by the registries. By original typing (serology for HLA-A and HLA-B; DNA typing for DRB1) 187, 164, and 133 URD were 6/6, 5/6, and 4/6 matches, respectively. Following DNA typing, however, only 52.9% of the originally 6/6 matched URD remained 6/6, while 38.5%, 7.5%, and 1.1% were found to be 5/6, 4/6, and 3/6 matches. The level of disparity was higher in the originally 5/6 (P< .01) and 4/6 (P < .01) matched URD. A higher level of disparity was seen for HLA-B as compared to HLA-A. In addition, a serotype related variation was also noticed. For example, 24.1% of HLA-A2 and 60.1% of HLA-B35 seromatched URD were genotypically disparate, but no disparities were seen for HLA-A1 and HLA-B8. A higher percentage of HLA-A (67.4%) compared with HLA-B (35.4%) serologic homozygous URD remained genotypically homozygous (P = .01). The level of allelic disparity was lower (P < .01 for 6/6; P = .02 for 5/6) if the patient had one of the 15 most common haplotypes (A1B8DR3, A2B7DR15, A3B7DR15, etc) in comparison to the rest of the group. Outcome studies will answer the question whether these disparities are associated with a higher rate of immunological complications seen with URD-BMT.

DNA Typing for HLA-A and HLA-B Identifies Disparities Between Patients and Unrelated Donors Matched by HLA-A and HLA-B Serology and HLA-DRB1

High incidences of graft failure and graft-versus-host disease in the recipients of bone marrow transplantations (BMT) from unrelated donors (URD) may reflect the existence of allelic disparities between the patient and the URD despite apparent HLA identity at HLA-A, HLA-B, and HLA-DRB1 loci. To identify the extent and pattern of allelic disparities at HLA-A and HLA-B loci, 128 patients and 484 potential URD were evaluated by DNA typing. DNA typing for HLA-A, HLA-B, and HLA-DRB1 was performed at Memorial Sloan Kettering Cancer Center. HLA-A and HLA-B serotyping on URD was provided by the registries. By original typing (serology for HLA-A and HLA-B; DNA typing for DRB1) 187, 164, and 133 URD were 6/6, 5/6, and 4/6 matches, respectively. Following DNA typing, however, only 52.9% of the originally 6/6 matched URD remained 6/6, while 38.5%, 7.5%, and 1.1% were found to be 5/6, 4/6, and 3/6 matches. The level of disparity was higher in the originally 5/6 (P< .01) and 4/6 (P < .01) matched URD. A higher level of disparity was seen for HLA-B as compared to HLA-A. In addition, a serotype related variation was also noticed. For example, 24.1% of HLA-A2 and 60.1% of HLA-B35 seromatched URD were genotypically disparate, but no disparities were seen for HLA-A1 and HLA-B8. A higher percentage of HLA-A (67.4%) compared with HLA-B (35.4%) serologic homozygous URD remained genotypically homozygous (P = .01). The level of allelic disparity was lower (P < .01 for 6/6; P = .02 for 5/6) if the patient had one of the 15 most common haplotypes (A1B8DR3, A2B7DR15, A3B7DR15, etc) in comparison to the rest of the group. Outcome studies will answer the question whether these disparities are associated with a higher rate of immunological complications seen with URD-BMT.

Are pretransplant psychological variables related to survival after bone marrow transplantation? A prospective study of 123 consecutive patients

Few studies have investigated relationships between psychological variables and survival after bone marrow transplantation (BMT). There is some evidence that psychological variables play a role in the course of cancer, and also after BMT. The present study focused on relationships between psychological variables and survival after BMT, in addition to prognostic disease, treatment, and demographic variables. In a consecutive sample of 123 patients undergoing BMT between 1987 and 1992, psychological variables were assessed before BMT. None of the psychological variables was univariately related to survival when entered into a Cox proportional hazards model as continuous variables. When divided into four groups of equal size, based on the 25th, 50th, and 75th percentiles, low self-esteem tended to be related to shorter survival. In multivariate analyses, none of the psychosocial variables measured before BMT was significant. Our data do not support the view that psychological variables influence survival after BMT.

Association Between Pretransplant Interferon-α and Outcome After Unrelated Donor Marrow Transplantation for Chronic Myelogenous Leukemia in Chronic Phase

Treatment options for patients diagnosed with chronic myelogenous leukemia (CML) in chronic phase (CP) who lack a suitable related donor for marrow transplantation include hydroxyurea, interferon-α (IFN-α), or transplantation from an unrelated donor (URD). Most studies support the view that treatment with IFN-α results in prolonged survival compared with hydroxyurea therapy. Some patients are offered URD transplantation as a second-line treatment; however, the impact of pretransplant IFN-α on the outcome of URD transplantation is uncertain. To address this question, we evaluated the effect of pretransplant IFN-α therapy in 184 patients undergoing URD transplantation for CML in CP at a single center. Of the 184 patients, 114 did not receive IFN-α, whereas 22, 23, and 25 patients received IFN-α for, respectively, 1 to 5, 6 to 12, and more than 12 months before transplant. Pretransplant IFN-α therapy administered for ≥6 months was associated with an increased risk of severe (grades III-IV) acute graft-versus-host disease (GVHD; relative risk [RR], 3.0; 95% confidence interval [CI], 1.4 to 6.2; P = .004) and mortality (RR, 2.1; 95% CI, 1.3 to 3.5; P = .003) relative to less than 6 months or no IFN-α therapy. Increased mortality occurred between 100 and 365 days after transplant (P = .005), was limited to patients with severe acute GVHD, and was due to chronic GVHD refractory to immunosuppressive therapy. Other variables associated with mortality included HLA-DRB1 or DQB1 (but not HLA-A or B) mismatched donors, age greater than 50 years, weight ≥110% of ideal body weight, and the absence of cytomegalovirus (CMV) or fungal prophylaxis. For patients treated with IFN-α for less than 6 months before transplant, who were ≤50 years of age, received a HLA-A, B, DRB1, and DQB1 matched URD transplant, and received CMV and fungal prophylaxis after transplant (n = 48), survival was 87% ± 5% at 5 years. These data provide a rationale for immediate transplantation in preference to extended treatment with IFN-α when the patient is ≤50 years of age and has an HLA-compatible unrelated volunteer donor.

Association Between Pretransplant Interferon-α and Outcome After Unrelated Donor Marrow Transplantation for Chronic Myelogenous Leukemia in Chronic Phase

Treatment options for patients diagnosed with chronic myelogenous leukemia (CML) in chronic phase (CP) who lack a suitable related donor for marrow transplantation include hydroxyurea, interferon-α (IFN-α), or transplantation from an unrelated donor (URD). Most studies support the view that treatment with IFN-α results in prolonged survival compared with hydroxyurea therapy. Some patients are offered URD transplantation as a second-line treatment; however, the impact of pretransplant IFN-α on the outcome of URD transplantation is uncertain. To address this question, we evaluated the effect of pretransplant IFN-α therapy in 184 patients undergoing URD transplantation for CML in CP at a single center. Of the 184 patients, 114 did not receive IFN-α, whereas 22, 23, and 25 patients received IFN-α for, respectively, 1 to 5, 6 to 12, and more than 12 months before transplant. Pretransplant IFN-α therapy administered for ≥6 months was associated with an increased risk of severe (grades III-IV) acute graft-versus-host disease (GVHD; relative risk [RR], 3.0; 95% confidence interval [CI], 1.4 to 6.2; P = .004) and mortality (RR, 2.1; 95% CI, 1.3 to 3.5; P = .003) relative to less than 6 months or no IFN-α therapy. Increased mortality occurred between 100 and 365 days after transplant (P = .005), was limited to patients with severe acute GVHD, and was due to chronic GVHD refractory to immunosuppressive therapy. Other variables associated with mortality included HLA-DRB1 or DQB1 (but not HLA-A or B) mismatched donors, age greater than 50 years, weight ≥110% of ideal body weight, and the absence of cytomegalovirus (CMV) or fungal prophylaxis. For patients treated with IFN-α for less than 6 months before transplant, who were ≤50 years of age, received a HLA-A, B, DRB1, and DQB1 matched URD transplant, and received CMV and fungal prophylaxis after transplant (n = 48), survival was 87% ± 5% at 5 years. These data provide a rationale for immediate transplantation in preference to extended treatment with IFN-α when the patient is ≤50 years of age and has an HLA-compatible unrelated volunteer donor.

Unrelated and HLA-nonidentical related donor marrow transplantation for thalassemia and leukemia. A combined report from the Seattle Marrow Transplant Team and the International Bone Marrow Transplant Registry

Allogeneic marrow transplantation is curative therapy for thalassemia, but fewer than 30% of patients have an HLA-identical sibling marrow donor. Selection of alternative donors of hematopoietic stem cells (unrelated individuals or HLA-nonidentical family members) has been aided by establishment of world-wide donor registries now exceeding 3.6 million volunteers and by DNA-based HLA typing to more closely match potential donors. Coupled with improved methods to control graft-versus-host disease and prevent fungal and cytomegalovirus infection, remarkable progress has been made in alternative donor transplantation. For patients 50 years of age or younger, with recently diagnosed chronic myelogenous leukemia (CML) in chronic phase, 1- and 5-year survivals after HLA-A, B, DRB1 identical unrelated marrow transplantation in Seattle are 82% and 74%, respectively. These results are essentially identical to outcome in similar patients given HLA-matched sibling allografts. However, the world-wide number of alternative donor transplants for thalassemia remains limited to date: 4 unrelated and 60 HLA-nonidentical related transplants have been reported to the IBMTR since 1969 with actuarial overall survival of 75%. Using the paradigm of CML, it is likely that access to curative therapy of thalassemia will improve with optimal HLA typing and donor selection early in the course of disease.

Effect of HLA matching on outcome of related and unrelated donor transplantation therapy for chronic myelogenous leukemia

This article examines the diversity and biologic role of human lymphocyte antigen (HLA) genes as related to marrow transplantation for chronic myelogenous leukemia (CML). A better understanding of the nature and function of HLA variation is necessary as unrelated marrow transplantation evolves into a safe and effective treatment for CML. HLA matching is an important aspect of donor selection criteria and has a role in engraftment as well as the development of graft-versus-host disease and tolerance after transplant.

MHC haplotype analysis by artificial neural networks

Conventional matching is based on numbers of alleles shared between donor and recipient. This approach, however, ignores the degree of relationship between alleles and haplotypes, and therefore the actual degree of difference. To address this problem, we have compared family members using a block matching technique which reflects differences in genomic sequences. All parents and siblings had been genotyped using conventional MHC typing so that haplotypes could be assigned and relatives could be classified as sharing 0, 1 or 2 haplotypes. We trained an Artificial Neural Network (ANN) with subjects from 6 families (85 comparisons) to distinguish between relatives. Using the outputs of the ANN, we developed a score, the Histocompatibility Index (HI), as a measure of the degree of difference. Subjects from a further 3 families (106 profile comparisons) were tested. The HI score for each comparison was plotted. We show that the HI score is trimodal allowing the definition of three populations corresponding to approximately 0, 1 or 2 haplotype sharing. The means and standard deviations of the three populations were found. As expected, comparisons between family members sharing 2 haplotypes resulted in high HI scores with one exception. More interestingly, this approach distinguishes between the 1 and 0 haplotype groups, with some informative exceptions. This distinction was considered too difficult to attempt visually. The approach provides promise in the quantification of degrees of histocompatibility.

HLA homozygosity and the risk of graft-versus-host disease

We explored the relationship between HLA homozygosity and risk of graft-versus-host disease (GVHD) after allogeneic marrow transplantation from an HLA-genotypically identical sibling. If the variety of minor histocompatibility antigens is decreased by the restricted diversity of major histocompatibility complex (MHC) molecules capable of presenting allogeneic peptides in HLA-homozygous individuals, then the risk of GVHD should be decreased in comparison to HLA-heterozygous marrow transplant recipients. Contrary to expectations, we found that HLA-homozygous individuals and HLA-heterozygous individuals have comparable risks of GVHD. We propose that the unexpectedly high incidence of GVHD in HLA-homozygous individuals can be explained by determinant density effects that enable certain peptide-MHC complexes to function as minor antigens on HLA-homozygous antigen-presenting cells but not on HLA-heterozygous antigen-presenting cells. Thus the variety of minor antigens expressed by the two types of cells might be similar, despite the differences in the diversity of HLA molecules.

Dimorphic primers derived from intron 1 for use in the molecular typing of HLA-B alleles

We have identified a dimorphic site in intron 1 of the HLA-B gene. Oligotyping was performed on about 3000 samples using primers derived from this dimorphic site in combination with a locus-specific primer derived from intron 3. The distribution of B-alleles bearing each of the dimorphic sequences was approximately equal. These primers were mutually exclusive and yielded approximately 50% of the heterozygous samples as apparently homozygous in PCR products. Intermediate and almost high-resolution oligotyping of HLA-B alleles was achieved using 35 and 63 hybridization probes, respectively. This dimorphic site will provide a useful tool for other PCR-based HLA-B typing approaches.

Recognition of major histoincompatibilities after transplantation with marrow from HLA closely matched donors

BACKGROUND

To determine the extent to which major histoincompatibilities are recognized after bone marrow transplantation, we characterized the specificity of the cytotoxic T lymphocytes isolated during graft-versus-host disease. We studied three patients transplanted with marrow from donors who were histoincompatible for different types of HLA antigens.

METHODS

Patient 1 was mismatched for one "ABDR-antigen" (HLA-A2 versus A3). Two patients were mismatched for antigens that would usually not be taken into account by standard selection procedures: patient 2 was mismatched for an "HLA-A subtype" (A*0213 versus A*0201), whereas patient 3 was mismatched for HLA-C (HLA-C*0501 versus HLA-C*0701). All three HLA class I mismatches were detected by a pretransplant cytotoxic precursor test.

RESULTS

Analysis of the specificity of the cytotoxic T lymphocyte clones isolated after transplantation showed that the incompatibilities detected by the pretransplant cytotoxic precursor assay were the targets recognized during graft-versus-host disease.

CONCLUSIONS

Independent of whether the incompatibility consisted of a "full" mismatch, a "subtype" mismatch, or an HLA-C mismatch, all clones recognized the incompatible HLA molecule. In addition, some of these clones had undergone antigen selection and were clearly of higher specificity than the ones established before transplantation, indicating that they had been participating directly in the antihost immune response.

Hematopoietic stem cell transplants from unrelated donors

Transplantation of hematopoietic stem cells is now well established as life-saving therapy for patients with several different genetic and acquired diseases. This has been possible largely because of the identification of HLA as the human major histocompatibility system and the application of new technologies for improving the accuracy of HLA typing and matching. Clinical advances including the development of more effective immune suppression therapy and improvements in supportive care have also been critically important. The lack of HLA-identical sibling donors for most patients and the extensive polymorphism of HLA genes have necessitated establishing very large registries of HLA-typed volunteers. With more than 3 million donors now available worldwide, the number of patients identifying HLA matches has increased substantially. Despite a higher incidence of graft-versus-host disease (GVHD), the results of unrelated donor transplants are favorable when performed under optimal conditions with a well-matched donor. In order to provide transplants for all patients, improved methods for GVHD prophylaxis are needed that will make it possible to safely perform transplants even across limited degrees of HLA disparity.

Allografting for chronic myeloid leukaemia

Marrow transplantation from human leukocyte antigen (HLA) matched related donors offers a high probability of prolonged treatment-free survival for patients with chronic myeloid leukaemia in chronic phase. Delay, patient and donor gender, patient age and previous palliation with busulphan predict outcome in this setting. Because of the median age at diagnosis and the genetics of the HLA system, transplants from HLA-matched related donors are available to less than 15% of newly diagnosed patients. Alternative donors include relatives with minor degrees of incompatibility and HLA-compatible unrelated volunteers. The probability of finding suitable unrelated donors has increased with the development of a network of registries now containing more than 3.6 million donors worldwide. Survival prospects will be improved by transplantation earlier in the course of the disease, better-matched donors and the discovery of new approaches for the prevention of graft-versus-host disease and opportunistic infections.

Factors influencing the outcome of donor marrow transplantation in adults from less than ideal donors: experience from two Australian centres

BACKGROUND

This paper reports the results of 78 marrow transplants in two Australian hospitals between 1991 and 1996, using unrelated (n = 54) or mismatched related (n = 24) donors. Twenty-six patients received granulocyte-macrophage colony stimulating factor (GM-CSF) post-transplant as part of a phase II study. Fifty-four patients (74%) had advanced disease.

AIMS

To identify factors associated with a superior outcome post-transplant, to evaluate the effect of GM-CSF on engraftment and other transplant parameters, and to compare the overall results with those of published series.

METHODS

Review of patient records, a Medline search of the relevant literature and appropriate statistical analysis.

RESULTS

The probability of overall survival and event-free survival (EFS) at three years was 35 +/- 6% and 22 +/- 6% respectively. Pre-transplant factors significantly associated with an inferior EFS were advanced disease, poorer performance status and age > 30 years. The EFS in patients with standard risk disease was 51 +/- 13% versus 10 +/- 5% in patients with advanced disease, p < 0.0001. Severe acute graft-versus-host disease was also associated with a poorer outcome. Neutrophil engraftment was faster in patients who received GM-CSF but there was no difference in any other transplant parameters.

CONCLUSIONS

These results are consistent with reported series elsewhere and suggest that an extended family or unrelated donor transplant should generally be limited to patients with a good performance status and early phase but otherwise incurable haematological disease.

The Role of B7 Costimulation by Murine Acute Myeloid Leukemia in the Generation and Function of a CD8+ T-Cell Line With Potent In Vivo Graft-Versus-Leukemia Properties

Relapse is more frequent after autologous than allogeneic bone marrow transplantation (BMT), due in part to lack of T-lymphocyte mediated allogeneic graft-versus-leukemia (GVL) effects. Infusions of leukemia-reactive T cells to patients after autologous BMT may be a means for providing a GVL effect. Costimulation of T cells by binding of the CD28 receptor on T cells with B7-counter receptors on antigen presenting cells amplifies antigen-specific T-cell responses. To enhance generation of leukemia reactive cytotoxic T lymphocytes (CTL), the murine B7-1– and B7-2–costimulatory molecule cDNAs were introduced into the MHC class I+, class II−, murine meyloid leukemia cell line C1498. B7-1 expression greatly enhanced the ability of the leukemia cells to generate and expand leukemia reactive CTL in vitro. A highly cytolytic and C1498 specific CD8+ CTL line was generated by B7-1 costimulation. This CTL line proliferated autonomously and produced interleukin-2 when provided B7-1 or B7-2 costimulation by C1498 leukemia cells. To test the in vivo antileukemia properties of this CTL line, irradiated syngeneic BMT recipients were given graded doses of leukemia cells on day 0, followed by CTL infusions beginning on day 1 post-BMT. Recipients of 107 CTL had a 3 log reduction in leukemia burden such that 100% of mice were protected from a supralethal leukemic cell dose. Sustained immune responses were detectable up to 3 months postinfusion of the CTL line. B7-1 or B7-2 costimulation in vivo did not augment antileukemia effects of infused CTL post BMT. These results suggest that B7 costimulation of leukemia reactive CTL may be important for their ex vivo generation and expansion for use in human adoptive immunotherapy of leukemia.

Molecular analysis of HLA-B35 alleles and their relationship to HLA-B15 alleles

The HLA-B35 serotype is one of the largest allelic groups of HLA class I molecules and includes four isotypes. Of the four, the B35 variant isoform is relatively rare and is the most acidic form. DNA sequencing of the rare isoforms revealed three alleles, B*1522, B*3511, and B*3517. A phylogenetic tree of HLA-B15- and HLA-B35-related alleles for the exon 2 and 3 nucleotide sequences showed that exon 2 of B*1522 clusters with B35 alleles whereas exon 3 clusters with B15 alleles. Branches of the tree suggest that the serodeterminants of B35, B62, B63, and B70 may reside in the alpha 1 domain, encoded by exon 2. The B*1520 and B*1522 genes, which type as B62 and B35, respectively, are hybrid molecules alternatively using exon 2 and exon 3 sequences of B*3501 and B*1501. A comparison of intron 2 sequences for B*3501, B*1501 and B*1522 suggests that the recombination site may have been in the region at the 3' end of intron 2. Despite being flanked by two highly polymorphic exons (exons 2 and 3), intron 2 is relatively well conserved in the B-locus, and it is characterized by seven to eight tandem repeats of the CGGGG pentanucleotide. A high degree of sequence homology and repetitive sequences are essential for a significant frequency of recombination. In this report, we reveal more about the complex evolutionary history of the HLA-B alleles.

Steroid-refractory cutaneous graft-versus-host disease after transplantation of haploidentical parental CD34+ cells in children with Down's syndrome and recurrent acute leukemia

PURPOSE

This study evaluated the feasibility of performing haploidentical CD34+ selected transplants for children with Down's syndrome (DS) and recurrent leukemia.

PATIENTS AND METHODS

Within a cohort of 15 children, two patients had DS. Transplantation of CD34+ cells from haploidentical parents was performed after the children were conditioned with fractionated total body irradiation, cyclophosphamide, and antithymocyte globulin (ATG). Graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporine and a short course of methotrexate.

RESULTS

The preparative regimen was well tolerated, and engraftment of polymorphonuclear cells and platelets took place promptly (by day 20) in both patients with DS. However, both patients with DS experienced severe grade IV GVHD that was limited to the skin and was refractory to salvage with high-dose methylprednisolone therapy. In one patient, GVHD responded to second-line salvage therapy with ATG, but the patient died on day 234 from leukemic relapse. The second patient had GVHD that did not respond to ATG and died of multisystem organ failure and refractory GVHD on day 44. Two of two DS patients had steroid refractory severe acute GVHD of the skin, while only one of 11 evaluated and identically treated non-DS patients had severe GVHD (p < 0.05).

CONCLUSION

These observations in patients who underwent mismatched bone marrow transplantation suggests that patients with DS have an increased risk of severe acute GVHD of the skin in this context.

HLA-DPB1 mismatch at position 69 is associated with high helper T lymphocyte precursor frequencies in unrelated bone marrow transplant pairs

HLA incompatibility between bone marrow recipient and unrelated donor pairs is often associated with severe acute graft-versus-host disease following bone marrow transplantation. Due to the extensive polymorphism of HLA genes, finding genotypically identical pairs is a difficult challenge. Therefore, it is crucial to single out the relevance of each HLA gene and, within each sequence, the polymorphic positions that induce a T-cell response. Among HLA class II genes, the relevance of HLA-DPB1 in inducing graft-versus-host disease is still controversial. In this study, we selected 37 bone marrow transplant pairs on the basis of HLA class I A and B identity as determined by isoelectric focusing and of class II identity as determined by serology and by low-resolution genomic typing. We analyzed them for the possible relationship between frequency of cytotoxic T lymphocyte and helper T lymphocyte precursors (CTLp and HTLp, respectively) and genomically determined class II mismatches. Seventeen pairs had high numbers of both CTLp and HTLp. They were not further considered because of the difficulty in determining whether the T-cell response was induced by class I or class II mismatches. Of the remaining pairs with low CTLp and high HTLp, six had disparities at HLA-DRB1 and HLA-DPB1 genes, and 14 differed only at the HLA-DPB1 locus. Among the latter pairs, we found a correlation between HLA-DPB1 mismatches and HTLp frequency, thus suggesting that disparity at this locus influences the alloreactive T-cell response. When the HTLp frequency was correlated with each single mismatch found in the 14 pairs, it appeared that the nature of the amino acid at position beta69 played a relevant role in inducing alloreactivity.

Acute graft versus host disease due to T lymphocytes recognizing a single HLA-DPB1*0501 mismatch

Analysis of a large number of unrelated bone marrow transplantations (BMT) has shown that HLA-DP incompatibility did not detectably influence the risk for acute graft-versus-host disease (aGVHD). Accordingly, it was proposed that HLA-DP determinants did not function as transplantation antigens in the same way as HLA-A, -B, or -DR. We have previously shown that HLA-DP (as well as HLA-A, -B, -DQ, or -DR)-specific T cells could be isolated from skin biopsies of patients who developed an aGVHD after semiallogeneic BMT. Nevertheless, whether a single HLA-DP mismatched allele could induce a detectable allo-specific reaction in vivo after BMT remained to be established. To directly address this issue we studied one patient who presented aGVHD after receiving purified CD34+ bone marrow (BM) cells from an unrelated donor with a single HLA-DP mismatch in the GVHD direction. To characterize the immunological events associated with GVHD, we analyzed the peripheral T cell repertoire, the T cell receptor Vbeta diversity, and the specificity of T cells invading a skin biopsy at the onset of GVHD. Our results demonstrated that a large fraction of skin-infiltrating lymphocytes, which expressed diverse T cell receptors, were reactive against this single HLA-DPB1 *0501 mismatch and consequently that a single HLA-DP mismatch between BM donor and recipient can activate a strong T cell response in vivo.

Bone Marrow Transplantation for Cancer—An Update

The number of allogeneic and autologous bone marrow transplants continues to grow worldwide. Bone marrow transplantation (BMT) has become standard therapy for many patients with leukemia, lymphoma, multiple myeloma and testicular cancer. Encouraging results of autologous BMT in treating patients with poor-risk breast cancer have led to this approach being tested in nationwide randomized trials. In order to increase availability and efficacy of BMT, other sources of hematopoietic cells are explored for transplantation, such as from HLA-matched unrelated volunteer donors, partially matched related donors, placental/umbilical cord blood and allogeneic peripheral blood. Relapse of original malignancy remains the main obstacle for the success of BMT. Recent clinical investigations have demonstrated that donor-derived peripheral blood leukocytes are effective in inducing remissions in patients with hematological malignancies who relapse after allogeneic BMT. BMT procedures are associated with significant complexity and should be carried out only in transplant units that meet adequate standards. In order to better define the role of BMT in treating cancer, more phase III clinical trials are needed. The future of BMT will depend on further improvements in its efficacy and economic constraints.

An apparent functional correlation between variations in amino acid residues in HLA-DR4.1 and 4.2 serological subtypes and oligonucleotide characterization

HLA-DR4 can be subdivided serologically into two specificities, DR4.1 and DR4.2, using well-defined monospecific alloantisera used in the 11th International Histocompatibility Workshop. In this study, a total of 1095 random DR4-positive individuals from several ethnic groups were tested first for serotype DR4.1/4.2 and then for DRB1*04 alleles using polymerase chain reaction (PCR) followed by sequence-specific oligonucleotide probe hybridization (SSOPH). An almost 100% correlation between samples testing positive for DR4.1 and the presence of alanine at position 74 was observed, while samples testing positive for DR4.2 correlated with the presence of glutamic acid at position 74. DRB1*04 alleles 0401, 0402, 0404, 0405, 0408, 0409 and 0410 are aligned in functional groups which coincide with the serological subtype of DR4.1. DRB1*04 alleles 0403, 0406, 0407 and 0411 coincide with subtype DR4.2. Amino acid substitutions at positions 57, 71 and 86 indicate other significant variations between alleles within the serological subgroup of DR4.1 and define five minor subgroups. The serologic and oligonucleotide allelic subgroups are in turn correlated with recognized cellular Dw antigens. While sequence data provide evidence of structural differences, data on cellular antigens support a functional association between these designated groups and their significance in transplantation and GVHD. Testing results are categorized by ethnic group in order to establish frequency data for donor selection criteria.

Transplantation of CD34+ hematopoietic progenitor cells

We have developed an avidin-biotin immunoadsorption technique in conjunction with a monoclonal anti-CD34 antibody that is capable of selecting CD34+ progenitor cells from marrow and mobilized peripheral blood. Clinical studies with these CD34+ selected cells have shown that the cells are capable of rapid and durable engraftment. In addition, there is significantly less infusional toxicity to the patient because the volume in which the CD34+ selected cells are contained is much less than that of a typical marrow or apheresis buffy coat. Selection of CD34+ progenitor cells also offers other potential advantages, including T-cell depletion of allografts and tumor cell depletion of autografts. CD34+ selection can also be used to facilitate other manipulations of marrow and peripheral blood, including gene transfection, ex vivo stem cell expansion, tumor purging, and progenitor cell banking. Future graft engineering studies are expected to clarify these relationships and enable refinement of the graft to the point at which GVHD can be minimized, graft survival maximized, and relapse-free survival prolonged.

Evaluation of the mixed lymphocyte culture (MLC) assay as a method for selecting unrelated donors for marrow transplantation

The utility of the MLC assay as a test of HLA-D region matching and predictor of graft-versus-host disease (GvHD) was evaluated in 435 patients receiving marrow grafts from unrelated donors. Donors and recipients were phenotyped for HLA-A, B and DR antigens by serology, tested in MLC, and retrospectively genotyped for DRB1, B3, B4, B5, DQB1 and DPB1 alleles by PCR/SSOP. Of the 244 HLA-A, B, DR-identical donor-recipient pairs with valuable MLC and DRB1 typing results available, 208 were matched for HLA-A, B and DRB1, while 36 were matched for HLA-A and B and mismatched for a DRB1 allele. Donor anti-recipient relative responses (RR) in MLC, corresponding to the GvHD vector in marrow transplantation, ranged from 7.2 to 100%, with a median of 4.0%. A comparison of reactivity in MLC between pairs matched versus mismatched for DRB1 alleles showed a significant overlap in the distribution of RRs. Using optimally-defined RR cutoffs of 4 and 16%, no correlation between MLC results and risk of developing clinically significant grades III-IV GvHD (p=0.6 and 0.5, respectively) was found when the contribution of DRB1 mismatch was accounted for. Matching for DRB1 alleles, in contrast, was a better predictor of clinically significant GvHD, with DRB1-matched transplant recipients less likely to develop grades III-IV GvHD than DRB1-mismatched recipients (p=0.14). Among the 208 patients and donors matched for DRB1 alleles, the MLC, although reactive (RR > 4.0%) in 45% of cases, did not predict GvHD. Overall, these results underscore the limitations in using the MLC to predict DRB1 matching or risk of clinically significant GvHD among patients receiving unrelated marrow grafts. The availability of DRB1 allele matching by sequence-specific oligonucleotide probes (SSOP) or by direct sequencing provides a method for donor matching that is rapid, precise and superior to the MLC for predicting clinically relevant outcome.

Progress of unrelated bone marrow donor search at the University Hospital of Essen (1991-1994)

The development of unrelated bone marrow donor search (UMDS) was analyzed in a retrospective single-center study covering the period from 1991 to 1994. The data files of the 285 enrolled UMDS patients were evaluated for the patients' underlying disease, HLA phenotype frequency, year of search start, UMDS duration/outcome, and the origin of identified donors. Within 3 months after UMDS start, a donor was found in 5%, 10%, 19%, and 49% of the searches started in 1991 (n = 57), 1992 (n = 73), 1993 (n = 77), and 1994 (n = 78, until September), respectively. The total UMDS success rate increased from 53% (1991 group) to 67% (1994 group), with 5% and 54%, respectively, of the accepted donors being supplied by German registries. Thus, the current UMDS procedure provides a suitable donor for the majority of the patients lacking a related donor, and the majority of the donors are now facilitated by national donor centers.

Immunogenetic analysis of successful and rejected bone marrow grafts within one family

We report the case of an Indonesian patient who required urgent bone marrow transplantation for acute leukaemia and who received successive transplants from two siblings. The first transplant failed while the second was successful. There were some uncertainties in serological typing due to the presence of cross-reacting HLA-B alleles, lack of paternal typing and the use of Caucasoid sera for Indonesian patients. Distinction between the two donors was also difficult. Interestingly, the use of a new DNA technique identified the presence of differences between the patient and the first unsuccessful donor but not the second successful donor.

Effect of HLA incompatibility in marrow transplantation from unrelated and HLA-mismatched related donors

Transplants from related donors who share one HLA haplotype and are variably matched with the recipient for HLA-A, B, or DRB1 loci on the unshared haplotype are associated with increased risks of graft failure and graft-versus-host disease (GVHD) that correlate with the degree of HLA mismatch. Survival, however, is not necessarily inferior if recipient incompatibility is limited to one HLA locus. Available methods for post-transplant immunosuppression have not allowed similar success with transplants incompatible for two or three HLA loci. GVHD incidence and severity can be decreased by depletion of donor T cells from the marrow inoculum. However, the potential benefit is offset by increased graft failure and leukemia relapse with no improvement in survival. Since fewer than 30% of the patients in North America or Europe have an HLA-matched sibling and less than 5% have a one HLA-locus mismatched relative, most candidates for an allogeneic marrow transplant are in need of an unrelated donor. As of October 1993, the National Marrow Donor Program (NMDP) has accrued more than 1 million volunteers typed for HLA-A and B, including 200,000 typed for HLA-DR, and has provided donors for more than 2000 transplants. The probability of finding an HLA-A, B, DR match at the initial search has increased from 10-15% in 1987, to 50-55% in 1992. An additional 12% of patients will find a match when available HLA-A and B matched donors are typed for DR, and 20% of patients have a one HLA-locus incompatible unrelated donor. Through an international network of regional registries a search for an unrelated donor can now be conducted among 1.7 million volunteers worldwide. Unrelated donor transplants have allowed long-term disease-free survival of patients with a variety of hematological disorders. When compared to HLA-matched sibling transplants, unrelated donor transplants are associated with an increase in the incidence of graft failure and GVHD. Such an increase may be due to undetected HLA disparities or to non-HLA-linked histocompatibility genes. At our center patients with CML in chronic phase, the most common indication for unrelated donor transplantation, have a 50-55% probability of survival 2-6 years after an unrelated donor transplant, whereas patients with aplastic or refractory anemia have a 25-35% probability of survival.(ABSTRACT TRUNCATED AT 400 WORDS)

Graft-versus-host disease and the development of late complications

Graft-versus-host disease (GVHD) in both its acute and chronic forms is a severe complication after allogeneic marrow transplantation. GVHD is associated with structural and functional defects in many organs and tissues. Severe immunoincompetence may result in frequent, often severe and at times fatal infections caused by various organisms. Prolonged antibiotic prophylaxis, and possibly immunoglobulin administration are beneficial. Ocular complications, airway and pulmonary damage, and oral or dental problems may cause severe morbidity. Despite aggressive management, a proportion of patients will succumb to these complications. Severe skin disease and joint contractures are currently seen less frequently, mostly due to early treatment of the disease. Psychosocial rehabilitation of patients with chronic GVHD is a demanding and protracted challenge and should be approached by a multidisciplinary team.

HLA-B35-subtype mismatches in ABDR serologically matched unrelated donor-recipient pairs

We have characterized HLA incompatibilities in a group of 17 B35-positive patients who were ABDR matched (AB serology and oligotyping for DR1-14) with their 28 (unrelated) potential bone marrow donors. High-resolution oligotyping for DR subtypes disclosed that nine combinations were in fact DR mismatched. Cytotoxic T-lymphocyte (CTL) activity was detected in nine combinations (32%). In the group matched for DR subtypes, three (16%) of 19 combinations were CTL positive. Patient-specific cytotoxic activity appeared to be directed against HLA C (two cases) or against a subtype of B35. In the group of DR-subtype-mismatched combinations, CTL activity was found in six (67%) of nine pairs. In all four cases that were studied in detail, however, CTL reactivity appeared to be directed against a variant subtype of B35. We have studied the B35 incompatibilities recognized in five different combinations by specificity analysis of the B35-specific CTLs and by partially sequencing of relevant segments of B35 exon 3. Preliminary data show that, within this relatively small Caucasoid group, at least five B35-variant subtypes could be distinguished. This would make B35 an antigen that will be frequently subtype mismatched, in particular when DR matching is done with low resolution (DR1-14) only.

Role of the mixed lymphocyte culture (MLC) reaction in marrow donor selection: matching for transplants from related haploidentical donors

The utility of the MLC assay as a test of HLA-D region matching and predictor of acute graft-versus-host disease (GvHD) was evaluated in 157 patients receiving marrow grafts from HLA-A, B identical related haploidentical donors. All donors and recipients were tested by HLA-DR serology, by Dw phenotyping with homozygous typing cells (HTC) and by standard MLC. Ninety-nine of the donor-recipient pairs were mismatched for a serologically defined HLA-DR antigen while 109 pairs were mismatched for the HLA-DR region by HTC typing. Donor antirecipient relative responses (RR) in MLC, corresponding to the GvHD vector in marrow transplantation, ranged from -4% to 100%, with a median of 25%. A comparison of reactivity in MLC with presence or absence of matching by Dw phenotyping, however, showed a significant overlap in the distribution of RRs from HLA-Dw matched versus Dw mismatched pairs, suggesting that the MLC was not a reliable predictor of HLA-Dw matching. Using an optimally-defined cutoff of 3% RR, the MLC was correlated with risk of developing clinically significant grades II-IV acute GvHD (p = 0.03) but not with risk of developing severe grades III-IV GvHD (p = 0.18). In contrast, matching by Dw phenotype was a significant predictor of GvHD, with Dw-compatible transplant recipients less likely to develop either grades II-IV (p = 0.004) or III-IV (p = 0.036) GvHD than Dw-incompatible transplant recipients. Overall, these results underscore the difficulty in using the MLC to measure HLA-D region compatibility and predict the risk of severe graft-versus-host disease among patients receiving related haploidentical marrow grafts. HLA-D (HTC) typing results correlate primarily with DRB compatibility, and with the advent of DRB1 allele matching by sequence-specific oligonucleotide probes (SSOP) or by direct sequencing, the precision in donor matching achievable with these methods is far greater than with either HLA-D typing or direct MLC testing.

A practical approach to HLA-DR genomic typing by heteroduplex analysis and a selective cleavage at position 86

A common problem facing HLA-typing laboratories is to substitute genomic typing for serology without having to handle a large number of oligoprobes, primers, or restriction enzymes. A protocol is described for HLA-DRB1 genomic typing using a combination of PCR amplification, DNA heteroduplex analysis, and restriction enzymes. Because the core of the procedure is the analysis of the DNA heteroduplexs, it shall be termed HET typing. There are two stages: the first stage comprises two rounds of PCR amplification of the polymorphic second exon of the HLA-DRB genes directly on lysed blood cells. The first amplification is with DRB generic primers, and the second amplification with seven HLA-DRB1 group-specific primers at the 5' end and a common 3' primer. The latter is designed with two nucleotide mismatches, thus creating an artificial restriction site to differentiate between both HLA-DRB1 variants at position 86, which is of critical importance in antigen presentation. The second stage involves subjecting the final amplified product to both DNA heteroduplex formation and digestion by two single-cutter restriction endonucleases. The digested or heteroduplexed samples are run on the same polyacrylamide gel. A total of 25 HLA-DRB1 alleles can thus be differentiated with a total of 10 primers and two restriction enzymes and without the use of probes. This protocol is ideally suited to preliminary HLA class II typing of bone marrow donors.

The immunogenetics of bone marrow transplantation

It is now clear that it is not necessary to use an HLA genotypically identical donor to have a successful marrow transplant. However, it is equally clear that the likelihood of complications increases with each increment in histoincompatibility. The implication is that histocompatibility testing must be of the highest possible precision to choose the optimal donor, and to predict the risk of adverse alloreactivity. Most clinicians would seriously consider transplantation from a one locus-mismatched relative or an HLA-matched unrelated donor in virtually any situation in which transplantation from a matched sibling would be felt to be the standard of care. More thought would need to go into transplantation from a two or three locus-mismatched relative or a mismatched unrelated donor.

Selection of an unrelated donor for marrow transplantation facilitated by the molecular characterization of a novel HLA-A allele

Precise HLA typing is crucial in the selection of marrow donors for the treatment of patients with hematologic malignancy. This study was undertaken to characterize an unusual variant of HLA-A30, designated HLA-A30JS, identified in a patient with leukemia who was a candidate for unrelated donor marrow transplantation. IEF and cDNA-sequencing analyses revealed that A30JS is a novel variant differing from the IEF-defined subtype A30.1 (encoded by the A*3002 allele) by a single amino acid substitution. An unrelated marrow donor was identified who was matched with the patient for HLA-A3, B7, B18, DR2, and DR3, but mismatched within the A30 antigen family for the two distinct alleles A*3002 versus A30JS. These two alleles encode a single amino acid substitution, Arg versus Gly, at position 56 in the alpha 1 domain. Position 56 is located outside the antigen-binding cleft of the class I molecule, suggesting that this substitution may not be functionally significant. Transplantation from this donor was performed and the patient is surviving free of leukemia for more than 700 days after transplant. The maximum acute GVHD observed was scored as grade II, but immunosuppressive therapy is still required for control of chronic GVHD. This study demonstrates how the molecular characterization of a novel HLA-A allele in a patient could facilitate the selection of an unrelated donor. Lacking this information, it would not have been possible to select a donor for this patient, and thus apparently successful marrow transplant could not have occurred.