Molecular modelling of HLA-B*35:132.

Here we describe the molecular modelling of the new variant HLA-B*35:132. This allele shows one mismatch with B*35:01:01:01 in exon 3 at position 575 where a T is substituted by a C, which implies an amino acidic change from Leucine to Proline. This seems not to alter the molecular structure and not to compromise the HLA complex and T-cell receptor interaction.

Analysis of the motivation for hematopoietic stem cell donation.

The Italian Bone Marrow Donor Register is the institutional organization for management of unrelated hematopoietic stem cell donors. The law requires only a donor's clinical history, but not a psychosocial profile for registration. We have studied the donor's motivation for enlistment on the donor registry and the medical staff's need for this information to interact correctly with the donor. For this purpose we distributed a questionnaire to new donors at the 20 centers in the Lombardy Region over a period of 1 year. The analysis of the responses revealed a prevalence of extrinsic motivations that would not ensure continued registration for donation. Therefore, it is necessary that the donor be well informed and better educated about all aspects of donation, in order to produce a shift to an intrinsic motivation. This objective can be facilitated via professional training of health workers in communication.

The conundrum of HLA-DRB1*14:01/*14:54 and HLA-DRB3*02:01/*02:02 mismatches in unrelated hematopoietic SCT.

Uncertainty still exists on the role of polymorphisms outside the HLA-DRB1 binding site or inside the HLA-DRB3 binding groove in unrelated hematopoietic SCT (HSCT). The ideal model to solve the conundrum consists of the transplants mismatched for HLA-DRB1*14:01/*14:54 and/or for HLA-DRB3*02:01/*02:02. A task force was set up in Italy to recruit transplanted pairs defined as HLA-DRB1*14:01 before 2006, the year crucial for the proper definition of the HLA-DRB1*14:54 allele in molecular biology. Out of 2723 unrelated pairs, 189 transplanted in Italy from 1995 to 2006 were HLA-DRB1*14:01 positive; 103/189 pairs with good historical DNA were retyped for HLA-DRB1*14 and HLA-DRB3 at-high resolution level; 31/103 pairs had HLA-DRB1*14 and/or HLA-DRB3 mismatched; 99/103, having complete clinical data, underwent statistical analysis for OS, TRM, disease-free survival and acute and chronic GvHD. No significant involvement of HLA-DRB1*14:01/*14:54 or HLA-DRB3*02:01/*02:02 mismatches was found, either alone or combined. Our findings suggest that disparities at exon 3 of the HLA-DRB1 gene seem unlikely to influence the outcome after HSCT. The same may be envisaged for HLA-DRB3(*)02:01 and (*)02:02 alleles which, although differing in the Ag binding site, seem unable to modulate an appreciable immune response in an HSCT setting.

HLA-A*2626, a new allele identified through external proficiency-testing exercise.

A new allele, officially named HLA-A*2626, has been detected in a blood sample belonging to a Caucasian subject human leucocyte antigen typed for Lombardy Region external proficiency-testing exercise. The DNA sequences of exons 2, 3 and 4 of this new allele are identical to those of HLA-A*2601 except at codon 259 of exon 4 (CCT-->CTT). This variation modifies the encoded protein from proline to leucine.

Description of a new HLA-DRB1 allele, DRB1*1150.

We report the identification of a novel HLA-DRB1*11 using sequence-based typing. This new allele, officially named DRB1*1150, was detected while performing HLA-DRB1 high-resolution typing of a candidate for bone marrow transplantation. DRB1*1150 is identical to DRB1*1143 except at nucleotides 200 and 227, where a T is substituted by a C and a T by an A, respectively. These differences give rise to two amino acid substitutions at codons 38 (Val-->Ala) and 47 (Phe-->Tyr).

HLA-B*1819, a novel HLA-B allele identified by sequence-based typing.

In this brief communication, we describe a novel human leukocyte antigen-B (HLA-B) allele (HLA-B*1819). This allele, found in an Italian Caucasian individual, differs from HLA-B*180101 by three nucleotide changes in exon 3. These mutations are located at positions 527, 538, and 539 where a T, a C, and a T are substituted respectively, by an A, a T, and a G, leading to three aminoacidic substitutions at codon 152 from Valine to Glutamic Acid (GTG-->GAG), at codon 155 from Histidine to Glutamine (CAC-->CAG), and at codon 156 from Cysteine to Tryptophan (TGT-->TGG).

HLA-B*5808, a new HLA-B allele characterized by sequence based typing.

This brief communication describes a new HLA-B allele (HLA-B*5808) detected in an Italian white volunteer bone marrow donor. With serology, this subject was typed as HLA-B15,17, whereas with molecular biology B*15, B*51, B*52 and/or B*58 could be assigned. In order to clarify the results, direct and cloning sequencing of exons 2, 3 and 4 were carried out. This new allele is identical to HLA-B*5801 in exon 2 except for a silent point mutation at nucleotide 141 where a C is substituted by a T; exons 3 and 4 are typical of HLA-B*51, B*52 and B*78. The peculiar sequence of B*5808 could explain the discrepancy between the serological and molecular typing results.

Identification of a novel HLA-B allele--HLA-B*4902.

We report herein the identification of HLA-B*4902. This new allele was identified in a Caucasian individual serologically typed as B49. The allele codifying for this antigen was not clearly detectable with polymerase chain reaction using sequence-specific primers (PCR-SSP) because of an atypical amplification pattern. DNA sequencing demonstrated the presence of a new variant due to two nucleotide substitutions (from G to C and from T to C) in exon 2 at nucleotides 309 and 311 respectively. These substitutions would result in a silent mutation and in one amino acid substitution from Ile to Thr, respectively.

A nucleotide deletion in exon 4 is responsible for an HLA-A null allele (A*0105N).

We report herein the identification of a new HLA-A null allele. This allele, A*0105N, was detected during histocompatibility testing of a cord blood donor and the respective mother. Serologic typing results contrasted those obtained with DNA typing that alone showed the presence of HLA-A*01. ThisA*0105N was due to a nucleotide deletion in exon 4 that altered the reading frame, causing a premature termination.

A retrospective evaluation of HLA-A, B and -DRB1 matching in liver transplantation.

Studies on the influence of histocompatibility in liver transplantation have not produced clearcut results. We retrospectively studied the influence of HLA-A, B and -DRB1 matching on the survival of 517 liver-transplanted patients using univariate analysis. The following parameters were also considered in relation to transplant outcome: donor and recipient age, original disease, transplant center, and pretransplant blood transfusions. Twenty-four-month graft survival according to the number of HLA-A, B, DRB1 mismatches (MM) was 70.9% (n = 28) for zero to two MM, 76.6% (n = 248) for three to four MM, and 73.1% (n = 241) for five to six MM (P = 0.7). We obtained similar results when considering HLA-A, B MM alone. Survival rates according to HLA-DRB1 MM were 71.7% (n = 36) for zero MM, 73.7% (n = 236) for one MM, and 76.4% (n = 245) for two MM (P = 0.6). The same analyses, performed on cirrhotic patients alone, gave identical results. In conclusion, this study suggests, on a large series of patients, that HLA compatibility has no influence on liver transplant survival. On the contrary, an influence on transplant outcome was found for donor age, transplant center, and original disease.

Comparison of serological and molecular typing for HLA-A and -B on cord blood lymphocytes.

HLA class I typing by standard microcytotoxicity testing has been unsatisfactory for 14.5% of 1644 cord blood samples. In this study, we evaluated the capacity of PCR-SSP in solving problems in HLA-A,B typing with serological methods. With this aim we have compared serology with PCR-SSP in 100 cord blood samples with doubtful or unreliable HLA-A,B typing. PCR-SSP was successful in amplifying HLA-A,B alleles in all 100 cord blood samples. Forty-six typings gave discrepant results with the 2 methods (serology and PCR-SSP). Typings were considered discrepant also in the case of inability to define a split. For 19 specimens, no serological conclusion was drawn due to high mortality of the cell suspension, while PCR-SSP allowed the definition of a clear typing. In 6 cases it was necessary to infer information from serology to define the current typing. Finally, in 3 other cases it was impossible to exclude or attribute the antigen/allele B67 or B4802. PCR-SSP for HLA-A,B can improve the overall reliability of HLA-A,B typing requiring a small amount of blood although, with the set of sequence specific primers adopted, a number of alleles are still poorly defined.

Detection of maternal DNA in human cord blood stored for allotransplantation by a highly sensitive chemiluminescent method.

Human cord blood (CB), a rich source of hematopoietic stem and progenitor cells, is currently used for bone marrow reconstitution. However, the level of contamination of CB with maternal cells that could provoke graft-versus-host disease (GvHD) is a matter of concern. In the present study, 60 consecutive CB samples collected and stored in the Milan CB Bank, for which no maternal DNA was detected through genomic HLA typing, were examined to ascertain maternal cell contamination using polymerase chain reaction amplification of two minisatellites, apolipoprotein B gene (ApoB) and D1S80, followed by chemiluminescent detection. The sensitivity of the method employed in this study was 0.04%, comparable to that of radioactive methods. A maternal specific allele was found in 11 of the 60 CB units, at a level ranging from 1:100 to 1:2500. We could also detect the child paternal allele in 3 of the 30 mothers whose newborn was heterozygous at the loci examined. Our study indicates that maternal cells are present in 18.3% of the 60 samples examined. The clinical relevance of such a presence remains to be established. In our opinion, information on maternal cell contamination should be included within the quality control tests performed before delivering a unit.