HLA-B*15 diversity in the Korean population

Analysis of Individual Case Safety Reports of Severe Cutaneous Adverse Reactions in Korea

PURPOSE

Despite morbidities and fatalities, nationwide epidemiologic data for severe cutaneous adverse reactions (SCARs), including Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug reaction with eosinophilia and systemic symptoms (DRESS), are not widely available. We aimed to investigate SCAR epidemiology over the last two decades in Korea.

MATERIALS AND METHODS

We analyzed individual case safety reports (ICSRs) of SCARs in the Korea Adverse Event Reporting System from 1988 to 2013. Administered drugs, demographic profiles, and causality assessment according to the World Health Organization-Uppsala Monitoring Center system were analyzed.

RESULTS

A total of 755 SCAR cases (508 SJS/TEN, 247 DRESS) were reported. The number of SCAR ICSRs has been increasing with increasing ICSRs for overall adverse drug events. Since 2010, the number of SCAR ICSRs has increased up to 100 cases/year. Allopurinol was the most common causative drug (SJS/TEN: 10.2%; DRESS: 11.3%; SCAR ICSRs: 10.6%), followed by carbamazepine (SJS/TEN: 8.7%; DRESS: 9.7%; SCAR ICSRs: 8.6%). Regarding drug groups, antiepileptics (19.5%) and antibiotics for systemic use (12.7%) were common causative drug groups. Twenty SCAR-related deaths were recorded. Antibacterials were the most common causes of deaths (8 cases), followed by antiepileptics (5 cases). The potential risk of SCARs was not specified in the drug information leaflet for 40.2% of drugs causing SJS/TEN and 82.5% causing DRESS syndrome in Korea.

CONCLUSION

The number of SCAR ICSRs has increased rapidly with recent active pharmacovigilance programs in Korea. Allopurinol and antiepileptics are the most common individual and categorical causative agents, respectively.

The Presence of HLA-B75, DR13 Homozygosity, or DR14 Additionally Increases the Risk of Allopurinol-Induced Severe Cutaneous Adverse Reactions in HLA-B*58:01 Carriers

BACKGROUND

Although HLA-B*58:01 is a well-known risk factor for the development of allopurinol-induced severe cutaneous adverse reactions (SCARs), most of the HLA-B*58:01 carriers do not suffer from SCARs despite a long-term use of allopurinol. This suggests that there are other risk factors that determine the fate of HLA-B*58:01 carriers.

OBJECTIVE

The aim of this study was to investigate the additional genetic factors that increase the risk of allopurinol-induced SCARs in HLA-B*58:01 carriers.

METHODS

The incidence of allopurinol-induced SCARs was investigated according to coexisting HLA alleles in all subjects with HLA-B*58:01 who took allopurinol between 2003 and 2017. The allopurinol tolerant group was defined as a group who took allopurinol for more than 60 days without developing hypersensitivity and was compared with the allopurinol-induced SCAR group.

RESULTS

Among the retrospective cohort consisting of 367 HLA-B*58:01 carriers treated with allopurinol, 11 (3.0%) were diagnosed with allopurinol-induced SCARs. When HLA-B75, DR13 homozygosity, or DR14 was present, the incidence of SCARs increased up to 22.2% (odds ratio [OR], 19.568; P = .015), 20.0% (OR, 38.458; P = .001), and 10.7% (OR, 19.355; P = .004), respectively. Among the 153 HLA-B*58:01 carriers with chronic renal insufficiency (CRI), the incidence of SCARs doubled to 6.5% and further increased to 40%, 30%, and 37.5% in the presence of HLA-B75, DR13 homozygosity, or DR14, respectively.

CONCLUSIONS

Secondary screening with HLA-B75, DR13 homozygosity, and DR14 in addition to primary screening with HLA-B*58:01 would enable a more accurate prediction of SCAR occurrence, especially in patients with CRI.

Association between the HLA-B alleles and carbamazepine-induced SJS/TEN: A meta-analysis

PURPOSE

From our current understanding, the association between the human leukocyte antigen (HLA), HLA-B*1502, and carbamazepine(CBZ)-induced Stevens-Jonson syndrome and toxic epidermal necrolysis (SJS/TEN) in the Asian population is quite clear. However the relationship between other HLA-B alleles and CBZ-induced severe cutaneous adverse drug reactions (SCADRs) remains unclear. We aimed to identify other non-HLA-B*1502 alleles in patients with CBZ-induced SCADRs through a meta-analysis.

MATERIALS AND METHODS

A thorough literature search was performed using Embase, PubMed, Web of Knowledge and Cochrane databases. A meta-analysis was performed from their inceptions to May 31, 2016. Studies investigating the association of HLA-B alleles and CBZ-induced SJS/TEN were retrieved. Two reviewers independently extracted the data. Overall odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were calculated using the RevMan 5.3 software.

RESULTS

A total of 11 studies met the inclusion criteria, totaling 343 CBZ-induced SJS/TEN cases, 838 CBZ tolerant controls, and 978 population controls. We observed HLA-B*1511 as a risk marker, and HLA-B*4001 and HLA-B*4601 as protective markers for the development of SJS/TEN in patients taking CBZ. SJS/TEN cases were found to be significantly associated with HLA-B*1511 in both the tolerant group (OR=17.43;95%CI=3.12-97.41;P=0.001) and the population-control group (OR=11.11; 95%CI=2.62-47.09; P=0.001). The sensitivity analysis found that HLA-B*5801 was a protective marker in the Southeast Asian population (OR=0.23; 95%CI=0.09-0.58; P=0.002).

CONCLUSION

Our study demonstrated that in the Asian population, HLA-B*4001, HLA-B*4601, HLA-B*5801 were strong protective factors in the development of CBZ-induced SJS/TEN whereas HLA-B*1511 was a risk factor. While more studies may be needed in order to confirm these findings, consideration should be taken into testing Asian patients for at-risk alleles prior to CBZ therapy initiation.

Pharmacogenetics of antiepileptic drug-induced hypersensitivity

Antiepileptic drugs can induce potentially life-threatening hypersensitivity reactions such as Stevens–Johnson syndrome at a frequency of one in 10,000 to one in 1000 treated patients. There is a considerable cross-reactivity among different antiepileptic drugs but the mechanisms are not known. In this review we have summarized current evidence on antiepileptic drug-induced hypersensitivity reactions and performed meta-analyses of published case–control studies that investigated associations between HLA alleles and several antiepileptic drugs in diverse populations. As the heterogeneity between studies was high, we conducted subsequent subgroup analyses and showed that HLA-B*15:02 was associated with carbamazepine, lamotrigine and phenytoin-induced Stevens–Johnson syndrome in Asian populations indicating that pretreatment testing may prevent cross-reactivity. Additionally, we explored the potential of new, high-throughput technologies that may help to understand the mechanisms and predict the risk of adverse drug reactions in the future.

Carbamazepine-induced severe cutaneous adverse reactions and HLA genotypes in Koreans

BACKGROUND

Although the US FDA recommends screening for HLA-B*1502 allele in most of Asian ancestry before initiating carbamazepine therapy, the HLA associations with carbamazepine hypersensitivity in non-Chinese Asian populations remain unclear. This study investigated the association between the HLA class I genotype and carbamazepine-induced severe cutaneous adverse reaction (SCAR) in Koreans.

METHODS

Twenty-four patients who had developed carbamazepine-induced SCAR (7 Stevens-Johnson syndrome (SJS), 17 drug hypersensitivity syndrome (HSS)), 50 carbamazepine-tolerant controls from the Korean Pharmacogenetic Adverse Drug Reaction Research Network and data of 485 Korean general population from a previously published study were recruited. HLA-A, -B, and -C genotyping was performed by direct DNA sequence analysis.

RESULTS

Only one of the seven SJS patients was positive for the B*1502 allele, but the frequency of B*1511 was much higher in the patients with CBZ-SJS than in the CBZ-tolerant control patients (P=0.011, P(c)=not significant; OR=18.0(2.3-141.2)). The frequencies of A*3101 in carbamazepine-induced HSS and SCAR were significantly higher than those in carbamazepine-tolerant controls (P(c)=0.011, OR=8.8(2.5-30.7) and P(c)=0.013, OR=7.3(2.3-22.5), respectively). The frequencies of B*1511 in carbamazepine-SJS and A*3101 in carbamazepine-HSS/SCAR were significantly higher than those in the general population.

CONCLUSIONS

HLA-B*1502 does not seem to be an effective predictive marker for carbamazepine-induced SCAR, while HLA-B*1511 and A*3101 was associated with carbamazepine-induced SJS and HSS/SCAR respectively in the Korean population.

Polymorphism of the HLA-B*15 group of alleles is generated following 5 lineages of evolution

Generation of the HLA-B*15 group of alleles has been analyzed using exon 1, intron 1, exon 2, intron 2, and exon 3 sequences from human and nonhuman primates. Results indicated that the 230 alleles analyzed could be grouped into 5 different lineages of evolution coming from nonhuman primate MHC-B* alleles sharing characteristic nucleotide sequences. The major evolutionary mechanism of evolution in this group of alleles is the gene conversion event with the exchange of genomic sequences present in other HLA-B*alleles. This evolutionary event reflects the importance of the exchanges between different genomic regions of distinct HLA-A*, -B*, or -C* alleles and only 1 group of HLA-B* alleles (B*15 in the present paper). These data also correlated with the geographic distribution of the lineages postulated and with the corresponding serologic specificities (B62, -63, -71, -72, -75, -76, and -77). In conclusion, the high degree of polymorphism of 1 group of alleles has a specific and simple pathway of evolution, which could result in new insight into the study of immune system functionality, disease association studies, and anthropological studies.

A new HLA-B*15 allele, HLA-B*9587, identified by sequence-based typing in a Korean individual

A new HLA-B*9587 showed one nucleotide difference from B*15010101 at nucleotide 127 with substitution G-->C (codon 19 GAG-->CAG) resulting in a coding change from Glu to Gln (E19Q).

HLA-B*15 subtypes in Burmese population by sequence-based typing

Human leukocyte antigen (HLA)-B*15 encompasses an increasing number of subtypes of more than 150. Frequency studies and a strong genetic association between HLA subtypes and susceptibility to drug hypersensitivity have been reported in different ethnic populations. To identify HLA-B*15 subtypes in Burmese using sequence-based typing (SBT) method, we selected 65 HLA-B*15-positive samples from 170 unrelated healthy Burmese who were genotyped HLA-B* by polymerase chain reaction with the sequence-specific primer method. The frequency of HLA-B*15 in Burmese was found to be 38.2%. By the SBT method, results showed 10 alleles of HLA-B*15 subtypes. Four common alleles, B*1502 (45.2%), B*1532 (16.4%), B*1525 (12.3%), and B*1501 (8.2%), were found in 82.1% of HLA-B*15-positive Burmese. Whereas the B*1501 was the highest in the Caucasians, Koreans, and Japanese, the highest frequency of HLA-B*15 alleles in Burmese was B*1502 (45.2%) that is similar to the frequency found in northeastern Thais and Vietnamese. This study is the first report of HLA-B*15 subtypes in Burmese. These results will provide the basic data in the further study in transplantations, genetic association with diseases, and drug hypersensitivity.

HLA-A, -B, -C, -DRB1 and -DQB1 alleles and haplotypes in the Kinh population in Vietnam

Allele and haplotype frequencies of the human leukocyte antigens (HLA) were studied in the Kinh Vietnamese population. We analyzed 170 unrelated healthy individuals. DNA-based HLA typing was performed using a microsphere-based array genotyping platform with sequence-specific oligonucleotide probes to distinguish HLA-A, -B, -C, -DRB1 and -DQB1 alleles. A total of 21 HLA-A, 37 HLA-B, 18 HLA-C, 25 HLA-DRB1, and 14 HLA-DQB1 alleles were identified. HLA-A*1101, A*2402, A*3303, B*1502, B*4601, Cw*0102, Cw*0702, Cw*0801, DRB1*1202, DQB1*0301, DQB1*0303, and DQB1*0501 were found with frequencies higher than 10%. Two representative haplotypes bearing two to five HLA loci were A*1101-B*1502 and A*3303-B*5801 for HLA-A-B; Cw*0801-B*1502 and Cw*0102-B*4601 for HLA-C-B; B*1502-DRB1*1202 and B*4601-DRB1*0901 for HLA-B-DRB1; DRB1*1202-DQB1*0301 and DRB1*0901-DQB1*0303 for HLA-DRB1-DQB1; A*1101-Cw*0801-B*1502 and A*3303-Cw*0302-B*5801 for HLA-A-C-B; A*1101-B*1502-DRB1*1202 and A*2901-B*0705-DRB1*1001 for HLA-A-B-DRB1, A*1101-Cw*0801-B*1502-DRB1*1202-DQB1*0301 and A*2901-Cw*1505-B*0705-DRB1*1001-DQB1*0501 for HLA-A-C-B-DRB1-DQB1. Allele distribution and haplotype analysis demonstrated that the Vietnamese population shares HLA patterns with southern Chinese, Thai, Javanese and Micronesians, while it also retains unique characteristics.

Generation of HLA-B*1516/B*1567/B*1595 and B*1517 alleles (B15 specific group) by transpecies evolution

The generation of the human leukocyte antigen (HLA)-B*1516, B*1517, B*1567, and B*1595 alleles has been analyzed using exon 1, intron 1, exon 2, intron 2, and exon 3 sequences from human and non-human primates. Results showed that at the first place three evolutionary steps would have been necessary for the generation of HLA-B*1516 and B*1517 alleles: (1) a non-human primate step with the generation of a major histocompatibility complex (MHC)-B*1516/1517-like allele; (2) a human or non-human primate step with two different ways of evolution generating a MHC-B*1516 and a MHC-B*1517 ancestors; and (3) a human step consisting of the generation of HLA-B*1516 and HLA-B*15170101 alleles. After that, HLA-B*1567, B*1595 B*151701012, and B*151702 alleles would be generated by point mutation events. In conclusion these alleles are generated by two different evolutionary pathways. The generation of these alleles points out the importance of the exons/introns in the generation of the evolution of HLA alleles.

Identification of three novel HLA class I alleles: HLA-A*0261, HLA-B*1585 and HLA-B*1587

Three novel human leucocyte antigen (HLA) class I alleles have been characterized by means of direct DNA sequencing analysis. HLA-A* 0261 showed sequence variation at conserved codon. It differs from HLA-A* 020601 by a single-nucleotide substitution at codon 57 (CCG-->GCG) resulting in an amino acid change from Pro to Ala. The sequences of HLA-B*1585 are similar to those of HLA-B*15010101, but differed five nucleotides on exon 3 resulting in three amino acid changes at residues 94 (Thr-->Ile), 95 (Leu-->Ile) and 103 (Val-->Leu). Likewise, HLA-B*1587 is identical to HLA-B*15010101 except at codons 80-83 (Asn-Leu-Arg-Gly-->Ile-Ala-Leu-Arg) which has been replaced by HLA-Bw4 motif. These alleles seemed to be generated by either a point mutation or a gene conversion-like event from alleles existing in the population with high frequencies.

Allelic and haplotypic diversity of HLA-A, -B, -C, -DRB1, and -DQB1 genes in the Korean population

High-resolution human leukocyte antigen (HLA) typing exposes the unique patterns of HLA allele and haplotype frequencies in each population. In this study, HLA-A, -B, -C, -DRB1, and -DQB1 genotypes were analyzed in 485 apparently unrelated healthy Korean individuals. A total of 20 HLA-A, 43 HLA-B, 21 HLA-C, 31 HLA-DRB1, and 14 HLA-DQB1 alleles were identified. Eleven alleles (A*0201, A*1101, A*2402, A*3303, B*1501, Cw*0102, Cw*0302, Cw*0303, DQB1*0301, DQB1*0302, and DQB1*0303) were found in more than 10% of the population. In each serologic group, a maximum of three alleles were found with several exceptions (A2, B62, DR4, DR14, and DQ6). In each serologic group exhibiting multiple alleles, two major alleles were present at 62-96% (i.e. A*0201 and A*0206 comprise 85% of A2-positive alleles). Multiple-locus haplotypes estimated by the maximum likelihood method revealed 51 A-C, 43 C-B, 52 B-DRB1, 34 DRB1-DQB1, 48 A-C-B, 42 C-B-DRB1, 46 B-DRB1-DQB1, and 30 A-C-B-DRB1-DQB1 haplotypes with frequencies of more than 0.5%. In spite of their high polymorphism in B and DRB1, identification of relatively small numbers of two-locus (B-C and DRB1-DQB1) haplotypes suggested strong associations of those two loci, respectively. Five-locus haplotypes defined by high-resolution DNA typing correlated well with previously identified serology-based haplotypes in the population. The five most frequent haplotypes were: A*3303-Cw*1403-B*4403-DRB1*1302-DQB1*0604 (4.2%), A*3303-Cw*0701/6-B*4403-DRB1*0701-DQB1*0201/2 (3.0%), A*3303-Cw*0302-B*5801-DRB1*1302-DQB1*0609 (3.0%), A*2402-Cw*0702-B*0702-DRB1*0101-DQB1*0501 (2.9%), and A*3001-Cw*0602-B*1302-DRB1*0701-DQB1*0201/2 (2.7%). Several sets of allele level haplotypes that could not be discriminated by routine HLA-A, -B, and -DRB1 low-resolution typing originated from allelic diversity of A2, B61, DR4, and DR8 serologic groups. Information obtained in this study will be useful for medical and forensic applications as well as in anthropology.

HLA-B*15 subtypes in the population of north-eastern Thailand

The HLA-B*15 group is the most polymorphic HLA-B allele and so has several subtypes. These subtypes have not been defined in the population of north-eastern Thailand (NET). In a previous study, using polymerase chain reaction-sequence-specific primers (PCR-SSP), subtypes were categorized into four groups, namely: group I: HLA-B*15 (01, 04-07, 12, 14, 19, 20, 24, 25, 26N, 27, 32, 33, 34 and 35); group II: HLA-B*15 (02, 08, 11, 15, 28 and 30); group III: HLA-B*1503/4802; group IV: HLA-B*1521. Groups I and II occurred frequently (allele frequency = 8.0 and 2.5%), and thus we optimized the polymerase chain reaction-single-stranded conformation polymorphism (PCR-SSCP) method to identify HLA-B*15 subtypes of groups I and II. Eighty samples of DNA carrying HLA-B*15 from 300 healthy unrelated individuals were tested. B*1502 (52.5%) and B*1525 (13.8%) were the most common subtypes found in NET. They also showed strong linkage disequilibrium with HLA-Cw and heterogeneity of HLA-A, DR, DQ haplotypes. Although limited conclusions can be drawn from this study because of the small number of DNA references used, the baseline data will be useful in the selection of common HLA-B*15 alleles when subtyping for unrelated donor transplantations.

Identification of two new alleles in a single Korean individual, HLA-B*1568 and HLA-DRB1*1208

We have identified a new HLA-B*15 allele and a new HLA-DRB1*12 allele, named B*1568 and DRB1*1208, respectively. The alleles were identified using a combination of sequence specific primers, reverse line sequence specific oligonucleotide probing and sequence-based typing. Both alleles were identified in a single individual of Korean origin. HLA-B*1568 appears to be an HLA-B*4801/B*1507 hybrid combining the exon 2 sequence of B*4801 and the exon 3 and 4 sequences of B*1507. Exon 2 of DRB1*1208 was most similar to DRB1*1201 or 1206, with a single mismatch at nucleotide position 165 (A to C). At the protein level, this substitution results in a phenylalanine substitution at position 26 that creates an identical amino acid sequence to DRB3*0202 between amino acid positions 17 and 36.