Roles of HLA-B, HLA-C and HLA-DPA1 incompatibilities in the outcome of unrelated stem-cell transplantation

Cytokine levels following allogeneic hematopoietic cell transplantation: a match-pair analysis of home care versus hospital care

Following allogeneic hematopoietic cell transplantation (HCT), patients living near the hospital were treated at home instead of in isolation in the hospital. We analyzed cytokines using Luminex assays for the first 3 weeks after HCT and compared patients treated at home (n = 42) with matched patients isolated in the hospital (n = 37). In the multivariate analysis, patients treated at home had decreased GM-CSF, IFN-γ (p < 0.01), IL-13, IL-5 (p < 0.05), and IL-2 (p < 0.07). Bloodstream infections, anti-thymocyte globulin, G-CSF treatment, immunosuppression, reduced-intensity conditioning (RIC), related vs. unrelated donors, and graft source affected various cytokine levels. When patients with RIC were analyzed separately, home care patients had reduced G-CSF (p = 0.04) and increased vascular endothelial growth factor (VEGF, p = 0.001) at 3 weeks compared with hospital care patients. Patients with low GM-CSF (p < 0.036) and low IFNγ (p = 0.07) had improved survival. Acute GVHD grades III-IV was seen in 7% and 16% of home care and hospital care patients, respectively. One-year transplantation-related mortality was 7% and 16% and survival at 5 years was 69% and 57% in the two groups, respectively. To conclude, patients treated in the hospital showed varying increased levels of GM-CSF, IFN-γ, IL-13, G-CSF, IL-5, and IL-2 and decreased VEGF, which may contribute to acute GVHD.

Impact of HLA-DPB1 Matching on Outcome of Unrelated Transplant for Hematologic Malignant Diseases: A Systematic Review and Meta-analysis

OBJECTIVE

Human leukocyte antigen match is the most important donor factor affecting transplant outcome. The HLA-DPB1 mismatch on the clinical outcome of hematopoietic stem cell transplant (HSCT) is less clear. This study is the first meta-analysis to investigate the impact of HLA-DPB1 loci mismatch on clinical outcome after unrelated donor HSCT for hematologic malignant disease.

METHODS

We electronically searched the PubMed, EMBASE, Cochrane Central Register of Controlled Trials, and a related database (January 1995-December 2018) for all relevant articles. Comparative studies were carried out to investigate the impact of HLA-DPB1 loci mismatch on clinical outcome after unrelated donor HSCT, that is, the disease-free survival, engraftment, graft-vs-host disease, relapse, and transplant-related mortality (TRM). We performed a meta-analysis using Review Manager 5.3.5 software and adopted funnel plot regression to assess the publication bias.

RESULTS

A total of 1570 articles were retrieved; 21 studies including 27,852 patients were assessed. Pooled comparisons of studies found that the HLA-DPB1-mismatched group had a lower rate of disease-free survival than the DPB1-matched group and lower overall survival in non-T cell-depleted transplant than the DPB1-matched group. The DPB1-mismatched group has higher incidence of acute graft-vs-host disease (aGVHD) and severe (≥ III degree) aGVHD, lower relapse rate, and higher TRM. Moreover, compared with 1-antigen mismatch, 2-antigen mismatch in DPB1 had a higher risk of TRM and a lower relapse rate, and the nonpermissive DPB1 mismatch had significantly higher rate of severe aGvHD and lower rate of disease relapse.

CONCLUSIONS

This analysis confirmed that HLA-DPB1 has important influence on survival and transplant-related complications during unrelated donor HSCT, and HLA-DPB1 donor selection strategies have been proposed based on personalized algorithm.

The Outcome of Allogeneic Hematopoietic Stem Cell Transplantation for Inherited Diseases Is Influenced by HLA Match, Year of Transplantation, and Immunized Female Donor

BACKGROUND

For many inborn errors of metabolism (IEM), allogeneic hematopoietic stem cell transplantation (HSCT) is the only cure.

METHODS

We report the outcome in 160 patients with inherited diseases, who were treated with HSCT in 3 decades. Median age was 3 years (range 0.1-63). Grafts were from matched related donors (MRDs, 56), matched unrelated donors (MUDs, 66), or HLA-mismatched donors (38).

RESULTS

Graft failure (GF) occurred in 26 patients (16%), severe acute graft-versus-host disease (GVHD) in 9 (6%), and chronic GVHD in 23 (12%). Ten-year survival was 64% before the year 2000 and 86% after that (P = 0.01). Ten-year survival for MRD grafts was 90%, as opposed to 79% for MUD grafts and 56% for HLA-mismatched grafts (P = 0.03). In multivariate analysis, GF was associated with having an HLA-mismatched donor (P < 0.05) or MUD (P = 0.015) and with reduced-intensity conditioning (P < 0.01). Death was associated with year of transplant (P = 0.015), having an HLA-mismatched donor (P < 0.001), and being a male recipient from an immune female donor (P = 0.05).

CONCLUSIONS

The outcome after HSCT for IEM depends on HLA match, year and immune female donor.

Long-term outcome in patients treated at home during the pancytopenic phase after allogeneic haematopoietic stem cell transplantation

Patients undergoing allogeneic haematopoietic stem cell transplantation (HSCT) were given the option to be treated at home during the pancytopenic phase. Daily visits by a nurse and phone calls from a physician from the unit were part of the protocol. During almost two decades, 252 patients with haematological malignancies and non-malignant disorders were included. Median age was 47 (range 0-72) years. Myeloablative conditioning was given to 102 patients and reduced intensity to 150. Donors were matched unrelated (n = 160), HLA-identical siblings (n = 71), or HLA-mismatched (n = 21). Cumulative incidence of acute graft-versus-host disease (GVHD) was 35% and that of chronic GVHD was 46%. Non-relapse mortality was 14% 10 years after HSCT. In patients with haematological malignancies (n = 229), the 10-year probability of relapse was 34%. No patients died at home. Overall survival was 59% and relapse-free survival was 50% after 10 years. We conclude that patients treated at home after HSCT have an encouraging long-term outcome.

No effect of HLA-C mismatch after allogeneic hematopoietic stem cell transplantation with unrelated donors and T-cell depletion in patients with hematological malignancies

HLA-C mismatch in unrelated donor's hematopoietic stem cell transplantation (HSCT) has been associated with poor patient outcome. However, the impact of HLA-C mismatch in the context of HSCT combined with in vivo T-cell depletion remains unclear. We therefore performed a single-center, retrospective analysis of the clinical outcome on patients with hematological malignancies treated with allo-HSCT, who underwent T-cell depletion. The majority of the patients (n=276) received a HLA-A, HLA-B, HLA-DRB1-matched graft that were either also HLA-C matched (n=260), or patients with the permissive HLA-C*03:03/03:04 mismatch (n=16), while the remaining patients (n=95) received a HLA-C-mismatched graft (excluding HLA-C*03:03/03:04 mismatches). We did not observe any significant differences between the HLA-C-matched patients (including the permissive HLA-C*03:03/03:04 mismatch) and the HLA-C-mismatched patients regarding cumulative proportion surviving, graft failure, relapse-free survival, relapse, or acute graft-versus-host disease. Our data suggest that in the context of high dose T lymphocyte-depleting agents, HLA-C matching is not essential for patients with hematological malignancies.

Reduction of Relapse after Unrelated Donor Stem Cell Transplantation by KIR-Based Graft Selection

Besides donor T cells, natural killer (NK) cells are considered to have a major role in preventing relapse after allogeneic hematopoietic stem cell transplantation (HSCT). After T-cell-depleted haploidentical HSCT, a strong NK alloreactivity has been described. These effects have been attributed to killer-cell immunoglobulin-like receptors (KIR). Abundant reports suggest a major role of KIR not only on outcome after haploidentical HSCT but also in the unrelated donor setting. In this review, we give a brief overview of the mechanism of NK cell activation, nomenclature of KIR haplotypes, human leukocyte antigen (HLA) groups, and distinct models for prediction of NK cell alloreactivity. It can be concluded that KIR-ligand mismatch seems to provoke adverse effects in unrelated donor HSCT with reduced overall survival and increased risk for high-grade acute graft-versus-host disease. The presence of activating KIR, as seen in KIR haplotype B, as well as the patient’s HLA C1/x haplotype might reduce relapse in myeloid malignancies.

Stem cell transplantation during cancer

Hematological malignancies account for approximately 9.5% of new cancers diagnosed annually. Lymphoma is the most frequent of all known categories of hematological malignancies. Worldwide, extensive research has focused on this type of cancer. However, new treatments are investigated in various clinical as well as pre-clinical studies. Hematopoietic stem cell transplantation (HSCT) is a recent and upcoming treatment strategy for patients with hematopoietic malignancies and inborn errors of metabolism or immune deficiencies. Recent studies have revealed that successful clinical outcome of this treatment strategy depends on multiple factors including the protocol applied, disease under treatment, health of the patient, source of the grafts, severity of complications such as graft versus host disease during grafting and associated infections. The scope of this review is to achieve greater understanding of various clinical effects of the disease and related mechanisms. The electronic database Pubmed was searched for pre-clinical as well as clinical controlled trials reporting efficacy of the HSCT against hematological malignancies.

Improved overall survival for pediatric patients undergoing allogeneic hematopoietic stem cell transplantation - A comparison of the last two decades

Pediatric protocols for allogeneic hematopoietic SCT have been altered during the last two decades. To compare the outcomes in children (<18 yr old), who underwent SCT at our center during 1992-2002 (P1) and 2003-2013 (P2). We retrospectively analyzed 188 patients in P1 and 201 patients in P2. The most significant protocol changes during P2 compared with P1 were a decrease in MAC protocols, particularly those containing TBI, an increase in RIC protocols, and altered GvHD prophylaxis. In addition, P2 had more patients with nonmalignant diagnoses (p = 0.002), more mismatched (MM) donors (p = 0.01), and more umbilical CB grafts (p = 0.03). Mesenchymal or DSCs were used for severe acute GvHD during P2. Three-yr OS in P1 was 58%, and in P2, it was 78% (p < 0.001). Improved OS was seen in both malignant disorders (51% vs. 68%; p = 0.05) and nonmalignant disorders (77% vs. 87%; p = 0.04). Multivariate analysis showed that SCT during P2 was associated with reduced mortality (HR = 0.57; p = 0.005), reduced TRM (HR = 0.57; p = 0.03), unchanged relapse rate, similar rate of GF, less chronic GvHD (HR = 0.49; p = 0.01), and more acute GvHD (HR = 1.77, p = 0.007). During recent years, OS has improved at our center, possibly reflecting the introduction of less toxic conditioning regimens and a number of other methodological developments in SCT.

First report on HLA-DPA1 gene allelic distribution in the general Lebanese population

Aims

HLA-DPA1 is an important marker in bone marrow and organ transplantation and a highly emerging screening parameter in histocompatibility laboratories. Being highly polymorphic, it has another significant value in detecting population origins and migrations. This is the first study to assess DPA1 allele frequencies in an Arab population.

Methods

The HLA DPA1 alleles were identified using the One-Lambda assays on a Luminex reverse SSO DNA typing system. Our study included 101 individuals coming from different Lebanese geographical areas representing the different communities and religious sects of the country.

Results

We compared the results of this study to 16 different populations and found very interesting similarities and differences between Lebanese people and individuals of European ancestry.

Conclusion

This study is the first to describe the different allelic frequencies of HLA-DPA1 in the Lebanese population and will serve as a template that can be later used for disease association studies both at the level of the country and internationally.

Quality of the hematopoietic stem cell graft affects the clinical outcome of allogeneic stem cell transplantation

BACKGROUND

In approximately two-thirds of patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) no suitable related donor can be identified but an unrelated HLA-matched donor can be found through international donor registries. HSCT grafts from unrelated donors are commonly collected at distant sites. Therefore, graft storage and transportation becomes crucial in the HSCT process. We aimed to study the impact of graft quality on clinical outcome and identify factors affecting graft quality.

STUDY DESIGN AND METHODS

We investigated the influence of graft quality on the clinical outcome in 144 HSCT patients. Graft quality was assessed by determining the viability (7-aminoactinomycin D [7AAD]) on a frozen-thawed sample from the peripheral blood stem cell (PBSC) graft.

RESULTS

Patients receiving PBSCs with inferior quality (i.e., viability < 64% in the frozen-thawed sample) more frequently developed acute graft-versus-host disease (aGVHD) Grades I to IV than patients receiving grafts with better quality (p = 0.025). The transplant-related mortality (TRM) was higher in the group receiving grafts with lower viability (p = 0.03). The viability of the frozen-thawed samples was highly variable (median, 64%; range, 24%-96%). No correlation could be observed when comparing the viability in newly arrived PBSC grafts to frozen-thawed vials. Grafts with white blood cell (WBC) count of more than 300 × 10(9) /L had lower viability than those with lower WBC counts (p < 0.001).

CONCLUSION

Graft quality affects clinical outcome. Patients receiving grafts with inferior quality had more aGVHD and higher TRM. There is a need for better analyses for assessing graft quality in routine HSCT care; analysis using 7AAD on fresh PBSC grafts is not sufficient.

Is there any impact of HLA-DPB1 disparity in 10/10 HLA-matched unrelated hematopoietic SCT? Results of a French multicentric retrospective study

We retrospectively analyzed the impact of HLA-DPB1 mismatches in a large cohort of 1342 French patients who underwent 10/10 HLA-matched unrelated HSCT. A significant impact of HLA-DPB1 allelic mismatches (2 vs 0) was observed in severe acute GVHD (aGVHDIII-IV) (risk ratio (RR)=1.73, confidence interval (CI) 95% 1.09-2.73, P=0.019) without impact on OS, TRM, relapse and chronic GVHD (cGVHD). According to the T-cell epitope 3 (TCE3)/TCE4 HLA-DPB1 disparity algorithm, 37.6% and 58.4% pairs had nonpermissive HLA-DPB1, respectively. TCE3 and TCE4 disparities had no statistical impact on OS, TRM, relapse, aGVHD and cGVHD. When TCE3/TCE4 disparities were analyzed in the graft-vs-host or host-vs-graft (HVG) direction, only a significant impact of TCE4 nonpermissive disparities in the HVG direction was observed on relapse (RR=1.34, CI 95% 1.00-1.80, P=0.048). In conclusion, this French retrospective study shows an adverse prognosis of HLA-DPB1 mismatches (2 vs 0) on severe aGVHD and of nonpermissive TCE4 HVG disparities on relapse after HLA-matched 10/10 unrelated HSCT.

Risk associations between HLA-DPB1 T-cell epitope matching and outcome of unrelated hematopoietic cell transplantation are independent of HLA-DPA1

HLA-DP antigens are beta-alpha heterodimers encoded by polymorphic HLA-DPB1 and -DPA1 alleles, respectively, in strong linkage disequilibrium (LD) with each other. Non-permissive unrelated donor (UD)-recipient HLA-DPB1 mismatches across three different T-cell epitope (TCE) groups are associated with increased mortality after hematopoietic SCT (HCT), but the role of HLA-DPA1 is unclear. We studied 1281 onco-hematologic patients after 10/10 HLA-matched UD-HCT facilitated by the National Marrow Donor Program. Non-permissive mismatches defined solely by HLA-DPB1 TCE groups were associated with significantly higher risks of TRM compared to permissive mismatches (hazard ratio (HR) 1.30, confidence interval (CI) 1.06-1.53; P=0.009) or allele matches. Moreover, non-permissive HLA-DPB1 TCE group mismatches in the graft versus host (GvH) direction significantly decreased the risk of relapse compared to permissive mismatches (HR 0.55, CI 0.37-0.80; P=0.002) or allele matches. Splitting each group into HLA-DPA1*02:01 positive or negative, in frequent LD with HLA-DPB1 alleles from two of the three TCE groups, or into HLA-DPA1 matched or mismatched, did not significantly alter the observed risk associations. Our findings suggest that the effects of clinically non-permissive HLA-DPB1 TCE group mismatches are independent of HLA-DPA1, and that selection of donors with non-permissive DPB1 TCE mismatches in GvH direction might provide some protection from disease recurrence.

Reduced plasma levels of soluble interleukin-7 receptor during graft-versus-host disease (GVHD) in children and adults

Background

Interleukin 7 (IL-7) signals via the IL-7 receptor (IL-7R) and drives homeostatic T-cell proliferation in patients after allogeneic hematopoietic stem cell transplantation (aHSCT).

Purpose

We performed a prospective study in adults (n = 33) and children (n = 29) undergoing aHSCT measuring plasma IL-7 and soluble IL-7R (sIL-7R) concentrations between 1 and 12 months after HSCT in order to investigate the link between sIL-7R and clinical events after aHSCT.

Results

sIL-7R, but not IL-7, increased with time after HSCT in plasma from all patients enrolled in the study. sIL-7R values were higher at 2, 3, and 6 months (p < 0.01) if the donor was a sibling as compared to an unrelated donor. Increased sIL-7R levels were also identified in plasma from patients who were not treated with anti-thymocyte globulin (ATG). Low sIL-7R was associated with any grade of acute graft-versus-host disease (GVHD) at 2 and 6 months (p = 0.02) and with a positive CMV PCR at 2 months after HSCT (p < 0.05). Patients with cytomegalovirus (CMV) reactivation had increased IL-7 values at 2 and 3 months (p = 0.02) after HSCT. In multivariate analysis, lower sIL-7R levels were associated with acute GVHD (relative hazard (RH): 0.70, p > 0.01) and sibling donors (RH: 2.23, p = 0.004). Recipients of sibling grafts showed high levels of IL-7 (RH: 1.38, p < 0.05) and bone marrow recipients had low IL-7 levels (RH: 0.73, p = 0.04).

Conclusions

Measurement of the sIL-7R/IL-7 axis will help in guided immune monitoring after HSCT and guided interference with sIL-7R may be explored in GVHD management.

Home care during neutropenia after allogeneic hematopoietic stem cell transplantation in children and adolescents is safe and may be more advantageous than isolation in hospital

After ASCT, children are isolated in hospital to prevent neutropenic infections. Patients living within two-h drive from the hospital were given the option of treatment at home after ASCT. Daily visits by an experienced nurse and phone calls from a physician from the unit were included in the protocol. We compared 29 children and adolescents treated at home with 58 matched hospital controls. The children spent a median time of 13 days at home (range 2-24 days) and 6 (0-35) days in hospital. The cumulative incidence of acute GVHD grades II-IV was 21% in the home-care children and 39% in the controls (p = 0.1). Chronic GVHD and probability of relapse were similar in the two groups. TRM at five yr was 11% in the home-care patients and 18% in the controls. Overall survival at three yr was 77% and 62%, respectively (p = 0.33). None of the patients died at home. Median costs were 38,748 euros in the home-care patients and 49,282 euros in those treated in the hospital (p = 0.2). We conclude that it is safe for children and adolescents to be treated at home during the pancytopenic phase after ASCT.

Hematopoietic SCT: a useful treatment for late metachromatic leukodystrophy

In metachromatic leukodystrophy (MLD), the deficiency of the lysosomal enzyme arylsulfatase A (ARSA) leads to demyelination in the central and peripheral nervous system and ultimately to death. Allogeneic hematopoietic SCT (HSCT) is currently the only treatment for adult and late-onset juvenile MLD, although it is still in question because of insufficient follow-up. We wanted to determine whether HSCT could halt the progression of adult and late-onset juvenile MLD. Four treated unrelated patients and three untreated siblings were included in the study, and followed regularly for up to 18 years after transplantation. The patients were assessed from clinical examination, ARSA enzyme levels, magnetic resonance imaging of the brain and neuropsychological and neurophysiological tests. In the treated patients, ARSA levels were normal up to 18 years after transplantation. The parameters evaluated stabilized and remained stable after a latency period of 12-24 months. Two patients live normal lives, partially in a protected environment. The other two patients stabilized at a low cognitive and functional level. One of the controls is demented, one is in a vegetative state and one died. We conclude that, in comparison with their untreated siblings, HSCT halted the progression of the disease in our treated patients.

Reduced intensity conditioning and oral care measures prevent oral mucositis and reduces days of hospitalization in allogeneic stem cell transplantation recipients

PURPOSE

Oral mucositis (OM) is a side effect of intensive chemotherapy and radiation and has been reported to affect 75-100% of hematopoietic stem cell transplantation (HSCT) recipients. The purpose of this study was to compare the incidence of OM in patients conditioned with myeloablative conditioning (MAC) to reduced-intensity conditioning (RIC) and to determine the effect of a new oral care protocol.

METHODS

The study involved 171 HSCT recipients, with hematological malignancies transplanted between 2007 and 2011. Median age of the patients was 50 years (range 12-71). Ninety-nine (58%) received RIC and 72 received MAC. Clinical features of OM were recorded from day -3 before to day +25 after HSCT using the World Health Organization (WHO) scoring system and the oral mucositis assessment score (OMAS).

RESULTS

Overall, 87% of the patients developed OM of any severity, which peaked on days 10-11. The mean WHO score was 1.7. In multivariate analysis, the severity of OM was associated with MAC (relative hazard (RH) 1.57, 95% confidence interval (CI) 1.37-1.80, p < 0.001), all donor-recipient gender combinations except female-to-male (RH = 1.26, 95% CI 1.10-1.4, p = 0.001), and early year of HSCT (RH = 0.84, 95%CI 0.7-0.96, p = 0.013). There was a correlation between long hospitalization and OM (day 15, r = 0.31, p < 0.001). There was a good correlation between the WHO and OMAS scoring systems for OM (r = 0.74, p < 0.001).

CONCLUSIONS

Oral mucositis was reduced in patients treated with RIC and in patients treated during recent years, when oral care was intensified. Increased scores of OM prolonged hospitalization.

Analysis of donor and recipient ABO incompatibility and antibody-associated complications after allogeneic stem cell transplantation with reduced-intensity conditioning

Allogeneic hematopoietic stem cell transplantation (HSCT) can be performed across the ABO blood group barrier. The impact of ABO incompatibility on clinical outcome is controversial. A retrospective analysis of 310 patients who underwent HSCT with reduced-intensity conditioning between 1998 and 2011 was performed to investigate the frequency and clinical implications of anti-RBC antibodies in passenger lymphocyte syndrome (PLS) after minor ABO mismatch (mm), persistent or recurring recipient type ABO antibodies (PRABO) after major ABO mm HSCT, and autoimmune hemolytic anemia (AIHA). Transplantation characteristics and clinical outcome were analyzed by univariate and multivariate analysis for groups with or without anti-RBC antibodies. ABO blood group incompatibility did not affect clinical outcome despite an increased requirement of blood transfusion. Twelve patients with AIHA, 6 patients with PLS, and 12 patients with PRABO post-HSCT were identified. AIHA did not affect overall survival (OS) or transplant-related mortality (TRM), but patients with AIHA had a lower incidence of grades II to IV acute graft-versus-host disease (P = .05). OS in the PLS group was 0% compared with 61% in the whole group receiving minor ABO mm transplants (P < .001). Comparing PRABO patients with those receiving a major ABO mm HSCT, the OS was 17% versus 73% (P = .002) and TRM was 50% versus 21% (P = .03). At our center, PLS after minor ABO mm and PRABO antibodies after major ABO mm HSCT are significant risk factors for decreased OS and TRM. Our results suggest that occurrence of unexpected ABO antibodies after HSCT warrant a wider investigation individual to find the underlying cause.

Chronic granulomatous disease-haematopoietic stem cell transplantation versus conventional treatment

AIM

Chronic granulomatous disease (CGD) is a rare X-linked or autosomal recessive primary immune deficiency characterized by recurrent, life-threatening bacterial and fungal infections. Mortality rates are high with conventional treatment. However, haematopoietic stem cell transplantation (HSCT) offers cure. Here, we compare the outcome of HSCT in 14 Swedish patients with CGD to that in 27 patients with CGD who were given conventional treatment.

METHODS

Forty-one patients in Sweden were diagnosed with CGD between 1990 and 2012. From 1997 to 2012, 14 patients with CGD, aged 1-35 years, underwent HSCT and received grafts either from an HLA-matched sibling donor or a matched unrelated donor.

RESULTS

Thirteen of the 14 transplanted patients are alive and well. Mean age at transplantation was 10.4 years, and the mean survival time was 7.7 years. In contrast, seven of 13 Swedish men or boys with X-linked CGD who were treated conventionally died from complications of CGD at a mean age of 19 years, while the remaining patients suffered life-threatening infections.

CONCLUSION

The outcome of the patients who underwent HSCT supports HSCT as being the preferable treatment for severe CGD. Our results advocate early HSCT for all patients with X-linked CGD, using grafts from either a matched sibling donor or a matched unrelated donor.

A prospective randomized toxicity study to compare reduced-intensity and myeloablative conditioning in patients with myeloid leukaemia undergoing allogeneic haematopoietic stem cell transplantation

BACKGROUND

To our knowledge, no randomized toxicity studies have been conducted to compare myeloablative conditioning (MAC) and reduced-intensity conditioning (RIC) in allogeneic haematopoietic stem cell transplantation (HSCT).

METHODS

Adult patients ≤60 years of age with myeloid leukaemia were randomly assigned (1 : 1) to treatment with RIC (n = 18) or MAC (n = 19) in this Phase II single-centre toxicity study.

RESULTS

There was a maximum median mucositis grade of 1 in the RIC group compared with 4 in the MAC group (P < 0.001). Haemorrhagic cystitis occurred in eight of the patients in the MAC group and none in the RIC group (P < 0.01). Results of renal and hepatic tests did not differ significantly between the two groups. RIC-treated patients had faster platelet engraftment (P < 0.01) and required fewer erythrocyte and platelet transfusions (P < 0.001) and less total parenteral nutrition (TPN) than those treated with MAC (P < 0.01). Cytomegalovirus (CMV) infection was more common in the MAC group (14/19) than in the RIC group (6/18) (P = 0.02). Donor chimerism was similar in the two groups with regard to CD19 and CD33, but was delayed for CD3 in the RIC group. Five-year transplant-related mortality (TRM) was approximately 11% in both groups, and rates of relapse and survival were not significantly different. Patients in the MAC group with intermediate cytogenetic acute myeloid leukaemia had a 3-year survival of 73%, compared with 90% among those in the RIC group.

CONCLUSION

Reduced-intensity conditioning had several advantages compared with MAC, including less mucositis, less haemorrhagic cystitis, faster platelet engraftment, the need for fewer transfusions and less TPN, and fewer CMV infections. Both regimens were tolerated and TRM was low.

A high antithymocyte globulin dose increases the risk of relapse after reduced intensity conditioning HSCT with unrelated donors

The study included 110 consecutive patients with hematological malignancies receiving fludarabine-based reduced intensity conditioning (RIC) and hematopoietic stem cell transplantation (HSCT) from matched unrelated donors. The median age was 55 yr (range 11-68) and all but 15 patients received peripheral blood stem cell grafts. Antithymocyte globulin (ATG) (Thymoglobulin, Genzyme) at a total dose of 6 mg/kg (n = 66) or 8 mg/kg (n = 44) was given to all patients according to protocol. The ATG dose did not affect time-to-neutrophil or platelet engraftment. The incidences of acute GVHD grades II-IV were 34% and 18% (p = 0.11) and of chronic GVHD were 40% and 26% (p = 0.46) in patients receiving 6 and 8 mg/kg of ATG, respectively. The five-yr relapse-free survival (RFS) was 61% and 36% (p = 0.14) in patients, given low and high ATG dose, respectively. In patients given low-dose ATG, the incidence of relapse was lower compared to those given high-dose ATG, 19% vs. 41% (p = 0.04). In multivariate analysis, age >50 yr (p < 0.001), absence of acute (p < 0.001) and chronic GVHD (p = 0.001) were correlated to relapse, and low-dose ATG was associated with improved RFS (p < 0.05). A high dose (8 mg/kg) of ATG in RIC HSCT with unrelated donors increased the risk for relapse and reduced the RFS.

Many days at home during neutropenia after allogeneic hematopoietic stem cell transplantation correlates with low incidence of acute graft-versus-host disease

Patients are isolated in the hospital during the neutropenic phase after allogeneic hematopoietic stem cell transplantation. We challenged this by allowing patients to be treated at home. A nurse from the unit visited and checked the patient. One hundred forty-six patients treated at home were compared with matched hospital control subjects. Oral intake was intensified from September 2006 and improved (P = .002). We compared 4 groups: home care and control subjects before and after September 2006. The cumulative incidence of acute graft-versus-host disease (GVHD) of grades II to IV was 15% in the "old" home care group, which was significantly lower than that of 32% to 44% in the other groups (P < .03). Transplantation-related mortality, chronic GVHD, and relapse were similar in the groups. The "new" home care patients spent fewer days at home (P = .002). In multivariate analysis, GVHD of grades 0 to I was associated with home care (hazard ratio [HR], 2.46; P = .02) and with days spent at home (HR, .92; P = .005) but not with oral nutrition (HR, .98; P = .13). Five-year survival was 61% in the home care group as compared with 49% in the control subjects (P = .07). Home care is safe. Home care and many days spent at home were correlated with a low risk of acute GVHD.

Nuclear reprogramming and induced pluripotent stem cells: a review for surgeons

Induced pluripotent stem cells (iPSCs) are generated from somatic cells by the exogenous expression of defined transcription factors. iPSCs share the defining features of embryonic stem cells (ESCs) in that they are able to self-renew indefinitely and maintain the potential to develop into all cell types of the body. These cells have key advantages over ESCs in that they are autologous to the donor cells and can be generated from individuals at any age. iPSCs also circumvent ethical and political issues surrounding the destruction of embryos that is necessary in the isolation of ESCs. This review briefly describes the advent of iPSC technology and the concepts of nuclear reprogramming, and discusses the potential application of this powerful biological tool in both surgical research and regenerative medicine.

Role of HLA in Hematopoietic Stem Cell Transplantation

The selection of hematopoietic stem cell transplantation (HSCT) donors includes a rigorous assessment of the availability and human leukocyte antigen (HLA) match status of donors. HLA plays a critical role in HSCT, but its involvement in HSCT is constantly in flux because of changing technologies and variations in clinical transplantation results. The increased availability of HSCT through the use of HLA-mismatched related and unrelated donors is feasible with a more complete understanding of permissible HLA mismatches and the role of killer-cell immunoglobulin-like receptor (KIR) genes in HSCT. The influence of nongenetic factors on the tolerability of HLA mismatching has recently become evident, demonstrating a need for the integration of both genetic and nongenetic variables in donor selection.

WITHDRAWN: Treatment with mesenchymal stromal cells does not improve long-term survival in patients with severe acute GVHD

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Improved survival after allogeneic hematopoietic stem cell transplantation in recent years. A single-center study

We analyzed the outcome of allogeneic hematopoietic stem cell transplantation (HSCT) over the past 2 decades. Between 1992 and 2009, 953 patients were treated with HSCT, mainly for a hematologic malignancy. They were divided according to 4 different time periods of treatment: 1992 to 1995, 1996 to 2000, 2001 to 2005, and 2006 to 2009. Over the years, many factors have changed considerably regarding patient age, diagnosis, disease stage, type of donor, stem cell source, genomic HLA typing, cell dose, type of conditioning, treatment of infections, use of granulocyte-colony stimulating factor (G-CSF), use of mesenchymal stem cells, use of cytotoxic T cells, and home care. When we compared the last period (2006-2009) with earlier periods, we found slower neutrophil engraftment, a higher incidence of acute graft-versus-host disease (aGVHD) of grades II-IV, and less chronic GVHD (cGHVD). The incidence of relapse was unchanged over the 4 periods (22%-25%). Overall survival (OS) and transplant-related mortality (TRM) improved significantly in the more recent periods, with the best results during the last period (2006-2009) and a 100-day TRM of 5.5%. This improvement was also apparent in a multivariate analysis. When correcting for differences between the 4 groups, the hazard ratio for mortality in the last period was 0.59 (95% confidence interval [CI]: 0.44-0.79; P < .001) and for TRM it was 0.63 (CI: 0.43-0.92; P = .02). This study shows that the combined efforts to improve outcome after HSCT have been very effective. Even though we now treat older patients with more advanced disease and use more alternative HLA nonidentical donors, OS and TRM have improved. The problem of relapse still has to be remedied. Thus, several different developments together have resulted in significantly lower TRM and improved survival after HSCT over the last few years.

Granulocyte colony-stimulating factor induced acute and chronic graft-versus-host disease

BACKGROUND

A recent experimental study in mice shed new light on the controversy as to whether granulocyte colony-stimulating factor (G-CSF) increases graft-versus-host disease (GVHD). Total body irradiation and bone marrow were found to be prerequisites for acute GVHD. This study encouraged us to perform a retrospective clinical study.

METHODS

We compared 260 patients given G-CSF prophylaxis after allogeneic hematopoietic stem-cell transplantation with 205 controls transplanted between 1993 and 2003.

RESULTS

G-CSF hastened the engraftment of neutrophils, but that of platelets was delayed (P<0.0001). The proportion of acute GVHD of grades II to IV was 29% in the G-CSF group and 19% in the controls (P<0.01) and that of chronic GVHD was 54% and 43%, respectively (P=0.019). G-CSF increased acute and chronic GVHD in patients preferentially conditioned with chemotherapy. Unexpectedly, it exacerbated acute GVHD in recipients of peripheral blood stem cells and enhanced chronic GVHD in bone marrow recipients. A multivariable analysis showed that acute GVHD (hazards ratio=1.52, P=0.03) and chronic GVHD (hazards ratio=1.51, P=0.004) were associated with G-CSF. There was no significant difference between study groups regarding nonrelapse mortality, relapse, or survival.

CONCLUSION

G-CSF increased acute and chronic GVHD in patients treated with chemotherapy but did not affect relapse or survival.

Characterization of long-term mixed donor-donor chimerism after double cord blood transplantation

Double cord blood transplantation (DCBT) with two matched or partially matched cord blood units has been implemented successfully to circumvent the limitations of graft cell dose associated with single CBT. After DCBT, sustained haematopoiesis is derived almost exclusively from only one of the donated units. None the less, we previously observed two of six evaluable DCBT patients still having mixed donor-donor chimerism at 28 and 45 months post-transplantation, respectively. In the present study we utilize flow cytometry techniques to perform the first thorough analysis of phenotype and functionality of cord blood units in patients with mixed donor-donor chimerism. Our results suggest that the two stable cord blood units are different phenotypically and functionally: one unit shows more naive T cells, lower T cell cytokine production and higher frequencies of natural killer cells, the other shows higher frequencies of well-differentiated and functional lymphocytes. Additionally, in comparison with control patients having a single prevailing cord blood unit, the patients with donor-donor chimerism exhibit less overall T cell cytokine production and a smaller fraction of memory T cells. Furthermore, our results indicate that human leucocyte antigen-C match of donor units may partly explain the development of a donor-donor mixed chimerism.

C-reactive protein levels before reduced-intensity conditioning predict outcome after allogeneic stem cell transplantation

The prognostic value of CRP levels before conditioning for allogeneic stem-cell transplantation (ASCT) was evaluated. Reduced-intensity conditioning (RIC) was given to 205 patients and conventional myeloablative conditioning (MAC) to 299 patients. Most patients had an HLA-compatible related or unrelated donor. There were 287 males and 216 females, median age 36 (1-69) years. Most patients received peripheral blood stem cells. Increased CRP levels (>10 mg/L) were detected in 129 patients (26%). Overall survival (OS) and transplant-related mortality (TRM) were worse for RIC patients with elevated CRP (67 vs. 43%, p = 0.005, and 16 vs. 30%, p = 0.036) while no difference was seen in MAC patients. An infection at the start of conditioning was seen in 27 RIC patients. We identified a subgroup of patients with an infection and elevated CRP (n = 16) and these patients had the worst outcome. In multivariate analysis, both infection and elevated CRP was the strongest factor associated with OS (HR 3.27, p < 0.001) and TRM (HR 4.35, p < 0.001). No correlation between any outcome variable and CRP was seen in MAC-treated patients. CRP may be a good prognostic factor for outcome after RIC and ASCT. It should be analyzed before conditioning, especially in patients with coexisting infection since patients with increased CRP and infection seem to have a very poor outcome after ASCT.

Lymphocyte recovery is a major determinant of outcome after matched unrelated myeloablative transplantation for myelogenous malignancies

A higher absolute lymphocyte count 1 month (LC30) after allogeneic hematopoietic stem cell transplantation (HSCT) is associated with better outcome in patients transplanted from a matched sibling. We studied 102 SCT patients with unrelated donor and matched unrelated donors and the relationship between LC30 and outcome in patients with myelogenous leukemia. Conditioning was myeloablative using cyclophosphamide (Cy) with busulfan (Bu; n=61) or total body irradiation (TBI; n=41). LC30 was low (<0.2x10(9)/L) in 18 patients, intermediate (0.2-1.0x10(9)L) in 67, and high (>1.0x10(9)/L) in 17 patients. In multivariate analysis, independent factors associated with high relapse-free survival (RFS) were high LC30, high CD34 cell-dose, and absence of acute graft-versus-host disease (aGVHD) grades II-IV. When analyzed as a continuous variable in multivariate analysis, a higher LC30 was associated with a lower transplant-related mortality (TRM; relative hazard [RH]=0.87, P < .05), higher relapse-free survival (RH=3.42, P=.036), and improved survival (RH=4.53, P=.016, excluding GVHD). In patients with high, intermediate, and low LC30, overall survival (OS) was 91% versus 60%, versus 36% (P=.02 and .001, respectively). This significant relationship was maintained in patients who did not develop GVHD by day 30. Significant risk factors to develop low LC30 was chronic myelogenous leukemia (CML; hazard ratio [HR] 0.73, P=.001), prophylaxis with granulocyte colony-stimulating factor (G-CSF; HR 0.81, P=.02) and aGVHD (HR 0.84, P=.05). These results indicate that LC30 is an independent prognostic factor for transplant outcome in matched unrelated SCT for myelogenous malignancies.

Stable mixed donor-donor chimerism after double cord blood transplantation

Double cord blood transplantation (DCBT) has been used increasingly and has proven to be both safe and efficacious. In chimerism analysis, previous studies have indicated single unit predominance early after DCBT. In the present study, we evaluated the chimeric pattern in T-, B- and myeloid cells using PCR-based chimerism analysis in seven patients after DCBT: five patients had acute leukemia and two had lymphoma. Five patients received myeloablative conditioning and two patients were given reduced intensity conditioning. All patients received anti-thymocyte globulin (ATG) before DCBT. Three of the six evaluable patients showed donor-donor mixed chimerism in all cell lineages at 90 days after DCBT. Interestingly, two patients in long-term follow-up showed mixed donor chimerism in all cell lineages at 25 and 35 months after DCBT, respectively. Both patients are doing clinically well. Neither of the two developed GVHD after DCBT. In conclusion, in this study donor-donor mixed chimerism was common after high dose ATG and DCBT. Further studies are warranted concerning the immunological consequences of the phenomenon of donor-donor mixed chimerism after DCBT.

Allogeneic stem cell transplantation in children with leukemia using human leukocyte antigen-mismatched unrelated donors

Allogeneic HSCT is a curative treatment, when chemotherapy fails, for certain malignant diseases. In Europe, only 15% of the indicated children have an HLA-matched sibling available; in 65-70% of others, HLA allele-matched (9-10/10) UDs can be identified. For the rest, it is necessary to identify other alternative donors (HLA-mismatched family or unrelated cord blood). We present our data of HSCT using HLA partially allele-mismatched (7-8/10) UDs in 24 children with leukemia. Uniform GvHD prophylaxis was used (rATG, CsA and MTX). Acute GvHD grade II was diagnosed in 70.8% of the patients and grade III-IV in 12.5%. Overall incidence of chronic GvHD was 38.7% (extensive in 30%). The probability of EFS was 60.3% (95% CI 35.5-78.1) and OS was 74.9 (95% CI 49.1-88.9). No difference in survival between PBSC and BM recipients was observed. TRM at day + 100 was 4%, and overall was 12.5%. We conclude that used combination of drugs for GvHD prophylaxis is efficient even for patients transplanted with grafts from a HLA-mismatched UDs. It enables stable engraftment, good control of GvHD, full reconstitution of immunity, and is not connected with unacceptable transplant-related mortality.

Risk factors for acute graft-versus-host disease grades II-IV after reduced intensity conditioning allogeneic stem cell transplantation with unrelated donors: a single centre study

We analysed factors associated with moderate to severe acute GVHD in 111 patients treated with fludarabin-based reduced intensity conditioning (RIC) and allogeneic haematopoietic stem cell transplantation (HSCT). Most patients had a haematological malignancy. Donors were 97 HLA-A, -B and -DRbeta1 identical unrelated and 14 HLA-A, -B or -DRbeta1 allele mismatched unrelated donors. In the univariate analysis, we found ten factors associated with acute GVHD. These were diagnosis (P=0.06), GVHD prophylaxis with combinations other than CsA+MTX (P=0.006), graft nucleated (P<0.001) and CD34 (P<0.001) cell-dose, bidirectional ABO mismatch (P=0.001), conditioning (P=0.002), hospital vs home-care (P=0.06), ATG dose (P<0.001), donor herpes virus serology (P=0.07) and an immunized female donor to male recipient (P=0.05). In the multivariate analysis, three factors remained significant: a high CD34 cell dose (P<0.001), low dose (4 mg/kg) ATG (P<0.001), and an immunized female donor to male recipient (P<0.01). Patients receiving a CD34 cell dose > or =17.0 x 10(6) per kg had a higher incidence of GVHD, 53.7%, compared to 22.3% in patients receiving a lower dose (P=0.002). In patients without any of these risk factors (n=70), the incidence of acute GVHD was 14.1%, while it was 38.0 and 85.0% in patients with one (n=29) or two (n=10) risk factors (P<0.001). We concluded that risk factors for acute GVHD using RIC are similar as using myeloablative conditioning.

Clinical significance of donor-recipient HLA matching on survival after myeloablative hematopoietic cell transplantation from unrelated donors

The application of unrelated donor hematopoietic cell transplantation can be expanded with the use of mismatched donors if human leukocyte antigen (HLA) disparity does not lead to increased morbidity and mortality. The rules that govern permissibility of HLA mismatches are not well defined. The International Histocompatibility Working Group in hematopoietic cell transplantation measured the risks associated with locus-specific disparity in 4796 patients transplanted for low, intermediate, or high-risk hematologic diseases. The permissibility of a given HLA mismatch is in part defined by the locus and by disease risk.

Major ABO blood group mismatch increases the risk for graft failure after unrelated donor hematopoietic stem cell transplantation

Two hundred twenty-four patients with leukemia transplanted with an unrelated donor between 1991 and 2003 at the Karolinska University Hospital were analyzed according to association between graft failure and ABO, RhD, MNSs, and Kidd blood group antigen compatibility. Median age was 29 years (range: 0-55). Conditioning consisted of total-body irradiation or busulfan-based myeloablative conditioning. A bone marrow graft was given to 152 patients, and 72 patients received peripheral blood stem cells. Most patients received graft-versus-host disease prophylaxis with cyclosporine and MTX. Graft failure (GF) was seen in 6 (2.7%) patients. In the multivariate analysis major ABO mismatch (odds ratio [OR] 14.9, 95% confidence interval [CI] 2.01-110, P = .008) and HLA-allele mismatch (6.42, 1.19-34.8, P = .03) was significantly associated to GF. In patients with and without major ABO mismatch the incidence of GF was 7.5% and 0.6% (P = .02), respectively. Using an ABO major mismatched graft increases the risk for GF after unrelated donor hematopoietic stem cell transplantation.

Detrimental effect of natural killer cell alloreactivity in T-replete hematopoietic cell transplantation (HCT) for leukemia patients

In hematopoietic cell transplantation (HCT), natural killer cell alloreactivity conferred by inhibitory ligands of killer immunoglobulin-like receptors (iKIRLs) may result in beneficial or detrimental outcomes. More data may contribute to resolution of this complex issue. We analyzed 378 primary allogeneic transplants with T-replete grafts for acute lymphoblastic leukemia (n = 101), acute myeloid leukemia and myelodysplastic syndrome (n = 149), and chronic myeloid leukemia (n = 128). The cohort was divided into 3 groups: in group 1, HLA class I matched at the antigen level (n = 260); in group 2, HLA class I mismatched at the antigen level (n = 57); and in group 3, HLA class I and iKIRLs mismatched (n = 61). One-year overall survival (OS) across groups 1 (59%), 2 (49%), and 3 (30%) was significantly different (P = .002). In contrast to group 2, group 3 had statistically lower OS (P = .05) and event-free survival (P = .01). Relapse and relapse-free mortality appeared to contribute to the low OS in group 3. The detrimental effect of natural killer alloreactivity was also evident when HLA-matched transplants were analyzed for patients lacking iKIRLs. One-year OS in patients lacking the HLA-Cw group 1 or 2 iKIRL was significantly lower than that in patients having the iKIRLs (55% vs 67%, n = 246, P = .01). Our observations indicate that, in T-replete unrelated HCT, iKIRL mismatches and the absence of iKIRLs confer higher risk to patients after HCT.

Phase I Study of Abagovomab in Patients with Epithelial Ovarian, Fallopian Tube, or Primary Peritoneal Cancer

PURPOSE

This open-label study assessed the safety and immunogenicity of two doses and two routes of the anti-idiotypic monoclonal antibody abagovomab (formerly ACA125) in patients with epithelial ovarian, fallopian tube, or primary peritoneal cancer.

EXPERIMENTAL DESIGN

Eligible patients from the three participating institutions were any stage at diagnosis, had relapsed, and had complete or partial response to additional chemotherapy. Patients were randomized to receive abagovomab at 2.0 versus 0.2 mg and i.m. versus s.c. for four immunizations every 2 weeks and then monthly for two additional immunizations. Planned evaluation included interval physical examinations and laboratory assessments with immune assessment, including HLA typing, human anti-mouse antibody, ELISA, and enzyme-linked immunospot. Patients were required to remain on study until week 10 (the first post-baseline Ab3 determination) to be considered for immunologic assessment. The primary end points were safety and immunogenicity primarily determined by Ab3 response.

RESULTS

Forty-two patients received at least one vaccination and were eligible for safety analysis. Thirty-three patients were available for Ab3 analysis (removed for progression of disease, 6; withdrawal of consent, 2; unrelated adverse event, 1). The most common adverse events were self-limited pain at injection site, myalgia, and fever. No hematologic or nonhematologic toxicity grade>2 related to immunization was seen. Ab3 was detectable in all patients (median, 236,794 ng/mL); none of route of administration (P=0.6268), dose (P=0.4602), or cohort (P=0.4944) was statistically significant in terms of effect on maximum post-baseline Ab3 titer. Human anti-mouse antibody was not detectable at baseline but was present in all patients at week 16 (range, 488-45,000 ng/mL).

CONCLUSIONS

Immunization with abagovomab is well tolerated and induced robust Ab3 responses at the two doses and routes tested. A phase III randomized study with abagovomab (2.0 mg s.c.) is warranted.

Frequent Loss of HLA-A2 Expression in Metastasizing Ovarian Carcinomas Associated with Genomic Haplotype Loss and HLA-A2-Restricted HER-2/neu-Specific Immunity

Defective expression of HLA class I molecules is common in tumor cells and may allow escape from CTL-mediated immunity. We here investigate alterations in expression of HLA class I and their underlying molecular mechanisms in ovarian cancer patients. The HLA class I and HLA-A2 expression levels on noncultured tumor cells of 12 patients diagnosed with ovarian carcinoma were investigated by flow cytometry. Molecular analyses of antigen-processing machinery (APM) components were done in metastatic cancer cells, and the HLA genotype was determined in both these and the primary tumor. HER-2/neu-specific immunity was evaluated by enzyme-linked immunospot assays. The metastatic tumor cells from all patients expressed low levels of HLA class I surface antigens. In six of nine HLA-A2+ patients, HLA-A2 expression was heterogeneous with a subpopulation of tumor cells exhibiting decreased or absent HLA-A2 expression. One patient-derived tumor cell line completely lacked HLA-A2 but exhibited constitutive expression of APM components and high HLA class I expression that was further inducible by IFN-gamma treatment. Genotyping showed a haplotype loss in the metastatic tumor cells, whereas tumor tissue microdissected from the primary tumor exhibited an intact HLA gene complex. Interestingly, HLA-A2-restricted HER-2/neu-specific T-cell responses were evident among the lymphocytes of this patient. Abnormalities in HLA class I antigen expression are common features during the progression of ovarian cancer, and haplotype loss was, for the first time, described as an underlying mechanism.

Real-Time PCR Using Fluorescent Resonance Emission Transfer Probes for HLA-B Typing

HLA genotyping by polymerase chain reaction (PCR) has some inherent labor-intensive and effort-demanding limitations. To overcome them, we have developed a real-time PCR with hybridization probes approach able to obtain a medium-low resolution HLA-B genotyping with fewer tubes and probes and with a shorter time requirement. Our strategy used 18 simultaneous reactions amplifying HLA-B alleles and an internal control. Monitorization of both amplifications in each tube is performed by the simultaneous application of two fluorescent resonance emission transfer probes: the first probe, different for each tube, is specific for the HLA-B locus and the second probe detects the control gene. A medium-low resolution (300 HLA-B allelic groups) typing is obtained for each sample by analyzing the melting curve patterns. Because some alleles may be determined without using the complete set of reactions, we present an alternative strategy: a first round of seven reactions and, according to the result, a second (or third) round of PCRs to solve the ambiguities. This method was validated in pretyped clinical samples and the results were completely concordant. Moreover, fewer ambiguous results were obtained. In summary, we present a new, faster, and more accurate method than currently used PCR techniques to type HLA-B alleles.