A deletion in exon 3 results in a new HLA-A*01 null allele (A*0115N) in a Martinican woman

We report the identification of a new HLA-A null allele, HLA-A*0115N. This null allele has been identified within the A*01 group by a combination of serological and molecular typing [Polymerase chain reaction (PCR) sequence-specific primers, PCR sequence-specific oligoprobes and sequence-based typing (SBT)] in a potential intrafamilial bone marrow donor from Martinique (French West Indies). To characterize this A*01 null allele, we performed DNA typing by PCR-SBT on genomic DNA from the beginning of exon 2 (position 84) through the end of the exon 4 (position 895) and revealed a nucleotide deletion at the end of the exon 3. This sole difference between the new allele and the HLA-A*0101 generates a premature stop codon (TGA) in the beginning of exon 4. This deletion most likely explains the lack of cell surface expression of the encoded protein despite the presence of A*01 allele. The absence of correct expression of the antigen on the cell surface was confirmed by one-dimensional isoelectric focusing (1D-IEF). To date, this is the fourth null allele described within the A*01 group.     

Absence of the HLA-G*0105N allele in Amerindian populations from the Brazilian Amazon Region: a possible role of natural selection

The human leukocyte antigen G (HLA-G) null allele (G*0105N) is defined by a DeltaC deletion at exon 3. Its high frequency in populations from areas with high pathogen loads and the putative role of HLA-G in placental development suggest that the reduced G1 expression in G*0105N heterozygous placentas may improve the intrauterine defense against infections. The G*0105N allele frequencies were evaluated in 143 Amerindians from six isolated tribes that inhabit the Central Amazon to determine the existence of genotype frequencies that suggest balancing selection in favor of G*0105N heterozygotes. No copy of the null allele was found by exon 3 sequencing. Although this finding may be because of demographic or other selective factors, it also suggests no evidence of G*0105N heterozygous advantage.     

Presence of the DRB4*0103102N null allele in different DRB1*04-positive individuals

The DRB4 gene encoding the DR53 antigen is present in DRB1*04-, DRB1*07- and DRB1*09-positive individuals. Eight allelic variants of DRB4 have been recognized, 5 resulting in an expressed DR53 antigen and 3 belonging to the null alleles. So far the DRB4*0103102N null allele had been found exclusively in individuals carrying the haplotype DR7,-DQ9. High-resolution typing of HLA class II by polymerase chain reaction using sequence-specific primers (PCR-SSP) and/or sequence-based typing of kidney patients and their families revealed the presence of the DRB4*0103102N null allele segregating with DRB1*04 and DQB1*03 in 4 different families. Three different haplotypes on which the null allele was located, were recognized by family studies: DRB1*0401, DQB1*0301; DRB1*0402, DQB1*0302 and DRB1*0404, DQB1*0302. Determination of the DR53 specificity of antisera reacting with DR53-positive individuals has always been difficult due to the simultaneous presence of DR4, 7 or 9. Identification of DR4-positive DR53-negative individuals as described here, provided the serological reactions with DR53-antisera and revealed the antibody specificities in the antisera used.     

Identification of HLA-G*01:17, a new allele possibly generated by an interloci gene conversion event involving exon 3 of HLA-B

HLA-G*01:17 was discovered in a woman of Kenyan descent who was enrolled in a mother-to-child HIV-1 transmission cohort. The new allele was identical to HLA-G*01:06 at exons 2, 3, and 4 with the exception of a base pair substitution at codon 169 (CAC → CGC) resulting in a coding change from histidine to arginine and codon 171 (TAC → CAC), resulting in turn in a coding change from tyrosine to histidine. The World Health Organization (WHO) Nomenclature Committee has named this allele HLA-G*01:17.     

Unusual association of the DRB4 null allele, DRB4*0103102N, with HLA DRB1*0402 in a sample of Austrian patients

Tissue typing for HLA class II antigens is routinely performed by serological, and/or DNA-based methods. Accuracy, absence of cross-reactivity and controllable level of resolution are striking advantages of molecular methods. However, a disadvantage of molecular typing, compared to serological methods, is the identification of unexpressed alleles. Whereas serology allows a more or less direct insight into antigen presence, molecular biology is an indirect method and results must also be interpreted by considering the biological pathways of protein expression. We believe that identification of nonexpressed MHC alleles is of importance for transplantation, since nonexpressed MHC allele positive individuals could give rise to antibody formation against the respective expressed MHC product in donor tissue. Usually, the nonexpressed DRB4*0103102N is encountered in association with DRB1*0701-DQB1*03032, which facilitates correct DNA typing. Here we describe the unusual association of this unexpressed DRB4*0103102N, with DRB1*0402-DQB1*0302 in a sample of Austrian patients.     

HLA-DMB alleles and haplotypes in Ecuador (Cuenca) Amerindians: Importance for HLA and disease studies

HLA-DMB allele frequencies and HLA-DBM-DRB1-DQB1 extended haplotypes were studied for the first time in Amerindians (Cuenca city area, Ecuador). It was found that most common extended haplotypes gathered the most frequent HLA-DRB1 Amerindian alleles. HLA-DMB polymorphism studies may be important to uncover HLA and diseases pathogenesis and also in an extended HLA haplotype frameshift. HLA-DM molecule has a crucial role together with CLIP protein in HLA class II peptide presentation. HLA extended haplotypes including complement and non classical genes alleles are proposed to HLA and disease studies.     

Identification of a novel HLA-A allele,HLA-A*01:195, in a UAE national

A novel human leucocyte antigen (HLA)-A allele, HLA-A*01:195, was identified by sequence-based typing (SBT) in a UAE national subject. The novel allele is identical to its closest known allele, HLA-A*01:01:01:01, in exon 2, 3 and 4, except for a single nucleotide mutation of A to G at position 442 in exon 3 (codon 124 in the α2 domain of the α chain of the mature protein). This A to G mutation results in an amino acid change of isoleucine #124 to valine.     

Human leukocyte antigen (HLA) and pharmacogenetics: screening for HLA-B*57:01 among human immunodeficiency virus-positive patients from southern Alberta

The field of pharmacogenetics is witnessing a growing interest in the role of the human leukocyte antigen (HLA) in manifestation of adverse drug reactions (ADR). Here we report a retrospective analysis of the association of HLA-B*5701 with abacavir hypersensitivity syndrome (AHS) in a large Canadian cohort of 489 human immunodeficiency virus-1-positive patients exposed to abacavir. A total of 3.7% of abacavir-exposed patients had developed AHS. Using polymerase chain reaction sequence-specific primer-based genotyping, the HLA-B*5701 allele was observed in 20 patients (4.1%). Of the 20 HLA-B*5701(+) abacavir-treated patients, 18 (90%) had developed AHS. Carriage of the HLA-B*5701 allele indicated a strong association with abacavir hypersensitivity (p < 0.0001; odds ratio = 6,934; 95% confidence interval = 321-149,735). HLA-B*5701 genotyping demonstrated high sensitivity, specificity, and positive and negative predictive values. The data derived from the study highlight the importance of engaging histocompatibility and immunogenetics laboratories in taking a lead in mapping other less characterized HLA and immunogenetic markers associated with ADRs.     

An HLB-B null allele (B*0808N) caused by a nucleotide deletion in exon 3, found in the family of a bone marrow transplant recipient

We have identified a variant HLA-B allele, B*0808N, segregating through two generations of healthy individuals, whilst HLA typing the family of a bone marrow patient. Serological typing identified a disparity between the father (A1, A3 B7 DR7) and the brother (A1, A2 B56 DR1, DR7) of the patient. Low/medium resolution polymerase chain reaction using sequence-specific primers (PCR-SSP) revealed a B*08 allele undetectable by serological methods. High resolution DNA typing by polymerase chain reaction-sequencing based typing (PCR-SBT), revealed a nucleotide deletion at position 131 (C) in exon 3, the only difference between the new allele and B*0801. The deletion results in a frame shift in the protein coding sequence, introducing a premature termination codon (TGA) in exon 4. Although a B*08 allele is present in these individuals, the deletion prevents correct expression of the antigen on the cell surface.     

Nuclear organization of cholinergic,catecholaminergic, serotonergic and orexinergic systems in the brain of the Tasmanian devil (Sarcophilus harrisii)

This study investigated the nuclear organization of four immunohistochemically identifiable neural systems (cholinergic, catecholaminergic, serotonergic and orexinergic) within the brains of three male Tasmanian devils (Sarcophilus harrisii), which had a mean brain mass of 11.6 g. We found that the nuclei generally observed for these systems in other mammalian brains were present in the brain of the Tasmanian devil. Despite this, specific differences in the nuclear organization of the cholinergic, catecholaminergic and serotonergic systems appear to carry a phylogenetic signal. In the cholinergic system, only the dorsal hypothalamic cholinergic nucleus could be observed, while an extra dorsal subdivision of the laterodorsal tegmental nucleus and cholinergic neurons within the gelatinous layer of the caudal spinal trigeminal nucleus were observed. Within the catecholaminergic system the A4 nucleus of the locus coeruleus complex was absent, as was the caudal ventrolateral serotonergic group of the serotonergic system. The organization of the orexinergic system was similar to that seen in many mammals previously studied. Overall, while showing strong similarities to the organization of these systems in other mammals, the specific differences observed in the Tasmanian devil reveal either order specific, or class specific, features of these systems. Further studies will reveal the extent of change in the nuclear organization of these systems in marsupials and how these potential changes may affect functionality.