Use of DPB1 T-cell epitope algorithm among italian transplant centers: A survey on behalf of Associazione Italiana di Immunogenetica e Biologia dei Trapianti.

The HLA-DPB1 locus has been demonstrated to have a significant role on patients' outcome after allogeneic HSCT, and the so-called T-cell epitope (TCE) algorithm has been incorporated in international guidelines for the selection of unrelated donors. The purpose of the present study is to measure, through a national survey conducted on behalf of the Associazione Italiana di Immunogenetica e Biologia dei Trapianti (AIBT), the extent of awareness and use of HLA-DPB1 TCE-based algorithms during the donor search. 89% of the HLA laboratories answered to a short questionnaire and the results showed a progressive increase of the laboratories typing DPB1 in patients and their potential donors during the search (from 44% to 79% during the 2010-2019 period) as well as the application of a TCE-based algorithm for the donor choice whenever possible (from 24% to 65% during the same period). The DP-permissiveness status is detailed in the official HLA typing report by 12%, 32% and 50% of laboratories in 2010, 2015 and 2019, respectively. The present data indicate an encouraging raise in the awareness of the HLA-DPB1 role in unrelated donor selection; noteworthy, mentioning the TCE-based permissiveness status in the HLA typing report of each potential unrelated donor represents a notable mean to raise awareness among transplant physicians and to support them in their task of choosing the best donor. Nonetheless, despite the compelling evidence of the predictive ability of TCE-based algorithms, further efforts are still needed to extend its application to all transplant centers in Italy.

Thymomatous myasthenia gravis: novel association with HLA DQB1*05:01 and strengthened evidence of high clinical and serological severity.

BACKGROUND: The relative prevalence of myasthenia gravis (MG) subtypes is changing, and their differential features and association with HLA class II alleles are not completely understood. METHODS: Age at onset, presence/absence of autoantibodies (Ab) and thymoma were retrospectively considered in 230 adult Italian patients. Clinical severity, assessed by MGFA scale, and the highest Ab titer were recorded. Furthermore, we performed low/high resolution typing of HLA-DRB1 and HLA-DQB1 alleles to detect associations of these loci with MG subtypes. RESULTS: There were two peaks of incidence: under 41 years of age, with female preponderance, and over 60 years, with higher male prevalence. The former group decreased and the latter increased significantly when comparing onset period 2008-2015 to 2000-2007. Thymomatous (TMG) patients showed a higher prevalence of severe phenotype and significantly higher anti-AChR Ab titer than non-thymomatous (NTMG) patients. Among the latter, those with onset after 60 years of age (LO-NTMG) displayed significantly higher Ab titers but lower MGFA grade compared to early-onset patients (< 41 years; EO-NTMG). Significant associations were found between HLA DQB1*05:01 and TMG patients and between DQB1*05:02 and DRB1*16 alleles and LO-NTMG with anti-AChR Ab. CONCLUSIONS: Two distinct cutoffs (< 41 and > 60 years) conveniently define EO-NTMG and LO-NTMG, with different characteristics. LO-NTMG is the most frequent disease subtype, with an increasing incidence. TMG patients reach higher clinical severity and higher antibody titers than NTMG patients. Moreover, TMG and LO-NTMG with anti-AChR Ab differ in their HLA-DQ association, providing further evidence that these two forms may have different etiologic mechanisms.

A new HLA-C*04 variant, HLA-C*04:01:106, discovered in an Italian hematopoietic stem cell donor.

HLA-C*04:01:106 differs from C*04:01:01:01 by a silent nucleotide substitution in exon 4.

Full-length extension of HLA allele sequences by HLA allele-specific hemizygous Sanger sequencing (SSBT).

The gold standard for typing at the allele level of the highly polymorphic Human Leucocyte Antigen (HLA) gene system is sequence based typing. Since sequencing strategies have mainly focused on identification of the peptide binding groove, full-length sequence information is lacking for >90% of the HLA alleles. One of the goals of the 17th IHIWS workshop is to establish full-length sequences for as many HLA alleles as possible. In our component "Extension of HLA sequences by full-length HLA allele-specific hemizygous Sanger sequencing" we have used full-length hemizygous Sanger Sequence Based Typing to achieve this goal. We selected samples of which full length sequences were not available in the IPD-IMGT/HLA database. In total we have generated the full-length sequences of 48 HLA-A, 45 -B and 31 -C alleles. For HLA-A extended alleles, 39/48 showed no intron differences compared to the first allele of the corresponding allele group, for HLA-B this was 26/45 and for HLA-C 20/31. Comparing the intron sequences to other alleles of the same allele group revealed that in 5/48 HLA-A, 16/45 HLA-B and 8/31 HLA-C alleles the intron sequence was identical to another allele of the same allele group. In the remaining 10 cases, the sequence either showed polymorphism at a conserved nucleotide or was the result of a gene conversion event. Elucidation of the full-length sequence gives insight in the polymorphic content of the alleles and facilitates the identification of its evolutionary origin.

The HLA-B landscape of Africa: Signatures of pathogen-driven selection and molecular identification of candidate alleles to malaria protection.

Human leukocyte antigen (HLA) genes play a key role in the immune response to infectious diseases, some of which are highly prevalent in specific environments, like malaria in sub-Saharan Africa. Former case-control studies showed that one particular HLA-B allele, B*53, was associated with malaria protection in Gambia, but this hypothesis was not tested so far within a population genetics framework. In this study, our objective was to assess whether pathogen-driven selection associated with malaria contributed to shape the HLA-B genetic landscape of Africa. To that aim, we first typed the HLA-A and -B loci in 484 individuals from 11 populations living in different environments across the Sahel, and we analysed these data together with those available for 29 other populations using several approaches including linear modelling on various genetic, geographic and environmental parameters. In addition to relevant signatures of populations' demography and migrations history in the genetic differentiation patterns of both HLA-A and -B loci, we found that the frequencies of three HLA alleles, B*53, B*78 and A*74, were significantly associated with Plasmodium falciparum malaria prevalence, suggesting their increase through pathogen-driven selection in malaria-endemic environments. The two HLA-B alleles were further identified, by high-throughput sequencing, as B*53:01:01 (in putative linkage disequilibrium with one HLA-C allele, C*04:01:01:01) and B*78:01 in all but one individuals tested, making them appropriate candidates to malaria protection. These results highlight the role of environmental factors in the evolution of the HLA polymorphism and open key perspectives for functional studies focusing on HLA peptide-binding properties.

Optimal Outcomes in Young Class 3 Patients With Thalassemia Undergoing HLA-Identical Sibling Bone Marrow Transplantation.

BACKGROUND: Bone marrow transplantation (BMT) for class 3 patients with thalassemia is challenging due to high rates of graft rejection and transplant-related mortality. Since the first studies of BMT in the late 1980s, a number of conditioning regimens have been designed to improve outcomes, but with suboptimal results. Here we report the outcome of transplantation in class 3 patients using a modified protocol. METHODS: Sixty-three patients between 5 and 16.7 years of age with class 3 thalassemia received HLA-matched sibling BMT following either the original protocol (26 patients) or the modified protocol (37 patients). Both regimens comprised preconditioning cytoreduction with hydroxyurea and azathioprine starting at -45 days pretransplant, and fludarabine from days -16 to -12. Conditioning was performed with busulfan and cyclophosphamide (original protocol) or with busulfan, thiotepa, and cyclophosphamide (modified protocol). RESULTS: The 2 groups showed similar patient demographics. At day 0, the degree of cytoreduction (lymphopenia, neuthropenia, and thrombocytopenia) achieved by the modified protocol was greater than the original protocol. The incidence of graft failure/rejection was significantly higher in the original group (15%; 95% confidence interval [95% CI], 5-32%) compared with the modified group (0%) (P = 0.014). The respective 5-year thalassemia-free survival rates were 73% (95% CI, 51-86%) and 92% (95% CI, 77-97%) (P = 0.047). Both groups showed similar incidences of grades II to IV acute graft-versus host disease. Modified protocol did not increase nonhematological toxicity or infectious complications. CONCLUSIONS: The modified treatment protocol effectively and safely prevented graft failure/rejection and significantly increased thalassemia-free survival of class 3 patients with thalassemia.

Luminex-Based Methods in High-Resolution HLA Typing.

Luminex-based technology has been applied to discriminate between the different Human Leukocyte Antigens (HLA) alleles. The typing method consists in a reverse-SSO assay: Target DNA is PCR-amplified using biotinylated group-specific primers. A single PCR reaction is used for each HLA locus. The biotinylated PCR product is chemically denatured using a pH change and allowed to rehybridize to complementary DNA probes conjugated to microspheres. These beads are characterized by two internal fluorescent dyes that create a unique combination of color, make them identifiable. Washes are performed to eliminate any additional PCR product that does not exactly match the sequence detected by the probe. The biotinylated PCR product bound to the microsphere is labelled with streptavidin conjugated with R-phycoerythrin (SAPE). A flow analyzer identifies the fluorescent intensity SAPE on each microsphere. Software is used to assign positive or negative reactions based on the strength of the fluorescent signal. The assignment of the HLA typing is based on positive and negative probe reactions compared with published HLA gene sequences. Recently kits characterized by an extensive number of probes/beads designed to potentially reduce the number of ambiguities or to directly lead to an allele level typing, have been made available.

New insights into the pharmacokinetics of intravenous busulfan in children with sickle cell anemia undergoing bone marrow transplantation.

BACKGROUND: Busulfan (Bu) is an integral part of conditioning regimens for patients with sickle cell anemia (SCA) undergoing transplantation. Patients with SCA might predispose to transplant-related neurological and pulmonary toxicities due to pre-existing disease-related cerebrovascular and lung injury. Bu therapy appears to be an important contributing factor in this context. PROCEDURE: We studied the pharmacokinetics of intravenous Bu and clinical outcomes of 36 children with SCA undergoing bone marrow transplantation. Most patients had pre-existing organ system damage. Busulfan was administered every 6 hr for 4 days with pharmacokinetic-guided dose adjustment to target a conservative area under the concentration versus time curve (AUC) range of 900-1,350 µMol*min. RESULTS: We found that the first-dose Bu clearance was significantly higher (P < 0.0005) than the subsequent daily clearance, which remained unchanged during the following days. After the first-dose, 69% of patients achieved the target range. We adapted a new dose-adjustment strategy targeting exposures to the lower end (900 µMol*min) of the AUC range after the first dose of Bu to avoid unnecessary dose increases on subsequent days due to differences in clearance. This strategy enabled most patients to maintain the AUC within therapeutic range following dose adjustments. CONCLUSIONS: Differences in Bu clearance after the first-dose and subsequent daily doses in patients with SCA should be considered for pharmacokinetic-guided dose adjustment. Conservative AUC range and targeting exposures to the lower end of the range after the first dose was associated with negligible toxicity, and high engraftment and sickle cell-free survival rates.

BAT2 and BAT3 polymorphisms as novel genetic risk factors for rejection after HLA-related SCT.

The genetic background of donor and recipient is an important factor determining the outcome of allogeneic hematopoietic SCT (allo-HSCT). We applied whole-genome analysis to investigate genetic variants-other than HLA class I and II-associated with negative outcome after HLA-identical sibling allo-HSCT in a cohort of 110 ß-Thalassemic patients. We identified two single-nucleotide polymorphisms (SNPs) in BAT2 (A/G) and BAT3 (T/C) genes, SNP rs11538264 and SNP rs10484558, both located in the HLA class III region, in strong linkage disequilibrium between each other (R(2)=0.92). When considered as single SNP, none of them reached a significant association with graft rejection (nominal P<0.00001 for BAT2 SNP rs11538264, and P<0.0001 for BAT3 SNP rs10484558), whereas the BAT2/BAT3 A/C haplotype was present at significantly higher frequency in patients who rejected as compared to those with functional graft (30.0% vs 2.6%, nominal P=1.15 × 10(-8); and adjusted P=0.0071). The BAT2/BAT3 polymorphisms and specifically the A/C haplotype may represent a novel immunogenetic factor associated with graft rejection in patients undergoing allo-HSCT.

Reduction of intramedullary apoptosis after stem cell transplantation in black african variant of pediatric sickle cell anemia.

BACKGROUND AND PURPOSE: Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative treatment for sickle cell anemia (SCA). We report our experience with transplantation in children with the Black African variant of SCA and the effects of transplant on erythroid compartment in bone marrow (BM). PATIENTS AND METHODS: Twenty-seven consecutive patients who underwent BM transplantation from HLA-identical donors following a myeloablative conditioning regimen were included. Using both CD71 and FSC parameters, we obtained three erythroid populations: EryA-C. Ery A (CD71(high) FSC(high)) are basophilic; Ery B (CD71(high) FSC(low)) are late basophilic and polychromatic; and Ery C (CD71(low) FSC(low)) are orthochromatic erythroblasts and reticulocytes. To analyze the effect of transplantation on intramedullary apoptosis, we studied Fas (CD95+) and caspase-3 expression in erythroblast subpopulations. RESULTS: All patients experienced sustained engraftment, and all surviving patients remained free of SCA-related events after transplantation. The erythroid population showed expansion in the BM at baseline. After transplant, levels decreased, especially of Ery C, in parallel to reduced Fas expression and an initial caspase 3 increase in erythroid population, similar to reported later steps of "normal" erythroid maturation. CONCLUSIONS: The results suggest a good chance of cure for children with SCA, with an excellent survival rate. We also observed "normalization" of erythroid populations in parallel with a decreased intramedullary apoptosis rate, suggesting normal erythroid maturation in ex-SCA patients after HSCT.

HLA-haploidentical stem cell transplantation after removal of αß+ T and B cells in children with nonmalignant disorders.

Twenty-three children with nonmalignant disorders received HLA-haploidentical hematopoietic stem cell transplantation (haplo-HSCT) after ex vivo elimination of αß(+) T cells and CD19(+) B cells. The median number of CD34(+), αß(+)CD3(+), and B cells infused was 16.8 × 10(6), 40 × 10(3), and 40 × 10(3) cells/kg, respectively. No patient received any posttransplantation pharmacologic prophylaxis for graft-versus-host disease (GVHD). All but 4 patients engrafted, these latter being rescued by a second allograft. Three patients experienced skin-only grade 1 to 2 acute GVHD. No patient developed visceral acute or chronic GVHD. Cumulative incidence of transplantation-related mortality was 9.3%. With a median follow-up of 18 months, 21 of 23 children are alive and disease-free, the 2-year probability of disease-free survival being 91.1%. Recovery of γδ(+) T cells was prompt, but αß(+) T cells progressively ensued over time. Our data suggest that this novel graft manipulation strategy is safe and effective for haplo-HSCT. This trial was registered at www.clinicaltrials.gov as #NCT01810120.

DQB1 locus alone explains most of the risk and protection in narcolepsy with cataplexy in Europe.

STUDY OBJECTIVE: Prior research has identified five common genetic variants associated with narcolepsy with cataplexy in Caucasian patients. To replicate and/or extend these findings, we have tested HLA-DQB1, the previously identified 5 variants, and 10 other potential variants in a large European sample of narcolepsy with cataplexy subjects. DESIGN: Retrospective case-control study. SETTING: A recent study showed that over 76% of significant genome-wide association variants lie within DNase I hypersensitive sites (DHSs). From our previous GWAS, we identified 30 single nucleotide polymorphisms (SNPs) with P < 10(-4) mapping to DHSs. Ten SNPs tagging these sites, HLADQB1, and all previously reported SNPs significantly associated with narcolepsy were tested for replication. PATIENTS AND PARTICIPANTS: For GWAS, 1,261 narcolepsy patients and 1,422 HLA-DQB1*06:02-matched controls were included. For HLA study, 1,218 patients and 3,541 controls were included. MEASUREMENTS AND RESULTS: None of the top variants within DHSs were replicated. Out of the five previously reported SNPs, only rs2858884 within the HLA region (P < 2x10(-9)) and rs1154155 within the TRA locus (P < 2x10(-8)) replicated. DQB1 typing confirmed that DQB1*06:02 confers an extraordinary risk (odds ratio 251). Four protective alleles (DQB1*06:03, odds ratio 0.17, DQB1*05:01, odds ratio 0.56, DQB1*06:09 odds ratio 0.21, DQB1*02 odds ratio 0.76) were also identified. CONCLUSION: An overwhelming portion of genetic risk for narcolepsy with cataplexy is found at DQB1 locus. Since DQB1*06:02 positive subjects are at 251-fold increase in risk for narcolepsy, and all recent cases of narcolepsy after H1N1 vaccination are positive for this allele, DQB1 genotyping may be relevant to public health policy.

Mixed chimerism evolution is associated with T regulatory type 1 (Tr1) cells in a ß-thalassemic patient after haploidentical haematopoietic stem cell transplantation.

In a cohort of ß-Thalassemia (ß-Thal) transplanted with haploidentical-HSCT we identified one transplanted patient characterized by persistent mixed chimerism (PMC) for several months after HSCT. In this unique ß-Thal patient we assessed the donor engraftment overtime after transplantation, the potential loss of the non-shared HLA haplotype, and the presence of CD49b(+)LAG-3(+) T regulatory type 1 (Tr1) cells, previously demonstrated to be associated with PMC after HLA-related HSCT for ß-Thal. The majority of the patient's erythrocytes were of donor origin, whereas T cells were initially mostly derived from the recipient, no HLA loss, but an increased frequency of circulating Tr1 cells were observed. For the first time, we showed that when the proportion of residual donor cells decreases, the frequency of CD49b(+)LAG-3(+) Tr1 cells declines, reaching the levels present in healthy subjects. These findings confirm previous results obtained in transplant related settings for ß-Thal, and supported the central role of Tr1 cells in promoting and maintaining PMC after allo-HSCT.

Bone marrow transplantation for thalassemia from alternative related donors: improved outcomes with a new approach.

Bone marrow transplantation (BMT) performance can be limited by a lack of ideal donors, and the role of alternative donor hematopoietic cell transplantation in thalassemia is not well established. Here we used a new treatment protocol (Pc 26.1) in 16 thalassemia patients to perform BMT using phenotypically HLA-identical or 1-antigen-mismatched relatives (related donors [RDs]). We compared these results with HLA-matched sibling (matched sibling donors [MSDs]) BMT in 66 patients. The entire RD group and 88% of MSD group had sustained engraftment. Rejection incidence was 0% in the RD and 12% (95% confidence interval [95% CI], 6%-21%) in MSD groups (P = .15), with respective thalassemia-free survival probabilities of 94% (95% CI, 63%-99%) and 82% (95% CI, 70%-89%) (P = .24). Transplant-related mortality was 6% (95% CI, 1%-26%) in the RD group and 8% (95% CI, 3%-16%) in the MSD group (P = .83). The intensified new protocol was not associated with increased nonhematologic toxicity. The present data show that the Pc 26.1 preparative regimen allows thalassemia patients to safely undergo BMT from RDs who are not HLA-matched siblings, with transplant outcomes similar to patients with MSD grafts.

A variable degree of autoimmunity in the pedigree of a patient with type 1 diabetes homozygous for the PTPN22 1858T variant.

We investigated whether the PTPN22 C1858T polymorphism is associated with the autoimmune conditions present in the family of a child affected by type 1 diabetes (T1D) carrying the TT genotype (index patient) and the potential immunological effect of the variant. We found that nine family members carried the CT genotype and five suffered from autoimmunity. Interestingly, anti-ZnT8 antibodies were detected in T1D patients and in three healthy relatives. In the TT patient, we showed diminished T-cell proliferation and reduced interleukin-2 (IL-2) and interferon-gamma (IFN-γ) production. A marked reduction of IL-2 was also observed for all CT relatives with autoimmunity and a lack of IFN-γ production was observed for the younger brother of the index patient, heterozygous for the polymorphism. In this family, the C1858T variant might confer a high risk of autoimmunity. Moreover, our data confirm that impaired IL-2 production upon T-cell receptor stimulation is associated with autoimmunity in the carriers of the polymorphism. This study might prompt to extend the panel of risk markers in relatives of subjects affected by T1D.

Association of HLA-DQB1∗05:02 and DRB1∗16 Alleles with Late-Onset, Nonthymomatous, AChR-Ab-Positive Myasthenia Gravis.

An association of several HLA alleles with myasthenia gravis (MG) has been reported. Aim of this work was to analyze the HLA allele profile in a survey of 76 unselected Italian MG patients and in a subgroup characterized by disease onset after the age of 50 years, absence of thymoma, and presence of antiacetylcholine receptor antibodies. We defined this subgroup by the acronym LOAb. Typing was performed at low resolution for HLA-A, -B, and -DRB1 loci with sequence-specific oligonucleotide probe (PCR-SSO); at high resolution for HLA-DQB1 locus by PCR with sequence-specific primers (PCR-SSPS). HLA allele frequencies were compared with 100 healthy controls. No correlation was observed between MG and the studied HLA class I alleles. On the contrary, a strong positive association was found for the HLA class II alleles DQB1∗05:02 (P(c) = 0.00768) and DRB1∗16 (P(c) = 0.0211) in the LOAb subgroup (n = 27) of MG patients. Association between DQB1∗05:02 and some subtypes of MG has been previously reported but not in patients with the LOAb characteristics. Therefore, the HLA allele DQB1∗05:02 might be considered as a susceptibility marker for LOAb among Italians.

HLA population genetics: a Lebanese population.

Human leukocyte antigen (HLA) typing was done in 426 Lebanese subjects of 88 families, in which 347 haplotypes were identified. The A, B, C, DRB1, DRB3/4/5, DQB1 and DPB1 loci were typed at high resolution. This study shows that information theory, as originally developed by Claude Shannon in 1948, provides a promising theoretical foundation to study the population genetics of a genetic system like HLA. Although Lebanese carry HLA alleles found in other populations, the association of these alleles into haplotypes is quite unique. Comparisons are made with the main ethnic groups. Two haplotypes well represented in the Lebanese population are not identified in any global population: L1 = {A*26:01:01 - B*35:01:01:01- C*04:01:01:01- DRB1*16:01:01 - DRB5*02:02 - DQB1*05:02:01} and L2 = {A*02:02 - B*41:01- C*17:01:01:01 -DRB1*11:04:01 - DRB3*02:02:01:01- DQB1*03:01:01:01}. By studying linkage disequilibrium in two blocks at a time, with the division of the blocks at different levels in consecutive cycles, conserved haplotypes in full linkage disequilibrium come to light, such as {A*26:01:01- B*35:01:01:01 - C*04:01:01:01 - DRB1*16:01:01 - DRB5*02:02 - DQB1*05:02:01- DPB1*03:01:01} and {A*33:01:01 - B*14:02:01 - C*08:02:01 - DRB1*01:02:01- DQB1*05:01:01:01 - DPB1*04:01:01:01}.

Tracking human migrations by the analysis of the distribution of HLA alleles, lineages and haplotypes in closed and open populations.

The human leucocyte antigen (HLA) system shows extensive variation in the number and function of loci and the number of alleles present at any one locus. Allele distribution has been analysed in many populations through the course of several decades, and the implementation of molecular typing has significantly increased the level of diversity revealing that many serotypes have multiple functional variants. While the degree of diversity in many populations is equivalent and may result from functional polymorphism(s) in peptide presentation, homogeneous and heterogeneous populations present contrasting numbers of alleles and lineages at the loci with high-density expression products. In spite of these differences, the homozygosity levels are comparable in almost all of them. The balanced distribution of HLA alleles is consistent with overdominant selection. The genetic distances between outbred populations correlate with their geographical locations; the formal genetic distance measurements are larger than expected between inbred populations in the same region. The latter present many unique alleles grouped in a few lineages consistent with limited founder polymorphism in which any novel allele may have been positively selected to enlarge the communal peptide-binding repertoire of a given population. On the other hand, it has been observed that some alleles are found in multiple populations with distinctive haplotypic associations suggesting that convergent evolution events may have taken place as well. It appears that the HLA system has been under strong selection, probably owing to its fundamental role in varying immune responses. Therefore, allelic diversity in HLA should be analysed in conjunction with other genetic markers to accurately track the migrations of modern humans.

Evaluation of DRB1 high resolution typing by a new SSO-based Luminex method.

HLA testing is an essential part of the process to identify a donor who may be a good match for the patients who need haematopoietic stem cells from bone marrow, peripheral blood or cord blood and the DNA typing in high resolution is now recommended as the Scientific Societies also describe in their standards. Recently the new PCR-Luminex HLA typing method, based on the reverse sequence specific oligonucleotide probes coupled with a microsphere beads in an array platform, has been well established. We report the data from 146 samples previously typed to a four digits level and used to evaluate the accuracy, sensitivity and performance of the new high definition DRB1 by PCR-Luminex kit. One hundred and forty-six samples from unrelated healthy donors, haematological patients or external proficiency tests were used in this study. The Luminex high definition DRB1 typing represents a versatile method and may be easily introduced in the routine, particularly when the technical team has already acquired experience on the technique. Only few HLA allelic combinations need an additional typing by PCR-SSP or SBT to solve the ambiguous results thus reducing the time necessary to produce a final report.