Detection of HLA-B*58:01 with TaqMan assay and its association with allopurinol-induced sCADR

An Inexpensive and Quick Method for Genotyping of HLA Variants Included in the Spanish Pharmacogenomic Portfolio of National Health System

The possibility of using the same genotyping technology (TaqMan) for all the genetic tests included in the new Spanish pharmacogenomics portfolio should enable the application of a multigenotyping platform to obtain a whole pharmacogenomics profile. However, HLA-typing is usually performed with other technologies and needs to be adapted to TaqMan assays. Our aim was to establish a set of TaqMan assays for correct typing of HLA-A*31:01, HLA-B*15:02, HLA-B*57:01, and HLA-B*58:01. Therefore, we searched for and selected SNVs described in different populations as surrogate markers for these HLA alleles, designed TaqMan assays, and tested in a set of samples with known HLA-A and HLA-B. HLA-A*31:01 was correctly typed with a combination of rs1061235 and rs17179220 (PPV 100%, 95% CI 84.6-100-%; NPV 100%, 95% CI 96.5-100.0%), HLA-B*15:02 with rs10484555 (PPV 100%, 95% CI 69.2-100.0%; NPV 100%, 95% CI 96.8-100.0%) and rs144012689 (PPV 100%, 95% CI 69.2-100.0%; NPV 100%, 95% CI 96.8-100.0%), and HLA-B*57:01 with rs2395029 (PPV 99.5%, 95% CI 72.9-99.3%; NPV 99.5%, 95% CI 98.3-100.0%). HLA-B*58:01 was typed using two allele-specific TaqMan probes mixed with a ß-Globin reference and treated as a genotyping assay (PPV 100.0%, 95% CI 81.5-100.0%; NPV 100%, 95% CI 96.8-100.0%). In conclusion, we demonstrated a clinically useful way to type HLA-A and HLA-B alleles included in the Spanish pharmacogenomics portfolio using TaqMan assays.

Genetic susceptibilities and prediction modeling of carbamazepine and allopurinol-induced severe cutaneous adverse reactions in Vietnamese

Aims: To determine genetic susceptibility markers for carbamazepine (CBZ) and allopurinol-induced severe cutaneous adverse reactions (SCARs) in Vietnamese. Methods: A case-control study was performed involving 122 patients with CBZ or allopurinol-induced SCARs and 120 drug tolerant controls. Results: HLA-B*58:01 was strongly associated with allopurinol-induced SCARs and strongly correlated with SNP rs9263726. HLA-B*15:02 was associated with CBZ-induced Stevens-Johnson syndrome/toxic epidermal necrolysis but not with drug-induced hypersensitivity syndrome/drug rash with eosinophilia and systemic symptoms. No association was found between HLA-A*31:01 and CBZ-induced SCARs. HLA-B*58:01 and rs3909184 allele A with renal insufficiency were shown to increase the risk of allopurinol-induced SCARs. Conclusion: HLA-B*58:01 and HLA-B*15:02 confer susceptibility to allopurinol-induced SCARs and CBZ-induced SJS/TEN in Vietnamese. SNP rs9263726 can be used as a surrogate marker in identifying HLA-B*58:01.

Diagnostic Test Criteria for HLA Genotyping to Prevent Drug Hypersensitivity Reactions: A Systematic Review of Actionable HLA Recommendations in CPIC and DPWG Guidelines

Introduction

Certain HLA variants are associated with an increased risk of hypersensitivity reactions to specific drugs. Both the Clinical Pharmacogenetics Implementation Consortium (CPIC) and the Dutch Pharmacogenetics Working Group (DPWG) have issued actionable HLA gene - drug interaction guidelines but diagnostic test criteria remain largely unknown. We present an overview of the diagnostic test criteria of the actionable HLA - drug pairs.

Methods

A systematic literature search was conducted in PubMed, Embase, Web of Science and Cochrane Library. Original case-control and cohort studies were selected and sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and number needed to genotype (NNG) were calculated for the actionable HLA-drug pairs.

Results

In general, the HLA tests show high specificity and NPV for predicting hypersensitivity reactions. The sensitivity of HLA tests shows a wide range, from 0-33% for HLA-B*1502 testing to predict lamotrigine induced SJS/TEN up to 100% for HLA-B*5701 to predict immunologically confirmed abacavir hypersensitivity syndrome (ABC-HSR). PPV is low for all tests except for HLA-B*5701 and ABC-HSR which is approximately 50%. HLA-B*5701 to predict ABC-HSR shows the lowest NNG followed by HLA-B*5801 for allopurinol induced severe cutaneous adverse drug reactions and HLA-B*1502 for carbamazepine induced SJS/TEN.

Discussion

This is the first overview of diagnostic test criteria for actionable HLA-drug pairs. Studies researching HLA genes and hypersensitivity are scarce for some of the HLA-drug pairs in some populations and patient numbers in studies are small. Therefore, more research is necessary to calculate the diagnostic test criteria more accurately.

Association of human leukocyte antigen variants and allopurinol-induced Stevens-Johnson syndrome and toxic epidermal necrolysis: A meta-analysis

PURPOSE

The association between human leukocyte antigen (HLA) variants and allopurinol-induced Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) was evaluated through a pooled analysis of published studies.

METHODS

A comprehensive search was performed in multiple databases, including PubMed, MEDLINE, ISI Web of Knowledge, EMBASE, Cochrane Register of Controlled Trials, and Science Direct. Studies investigating the association between HLA alleles with allopurinol-induced SJS or TEN were retrieved, and the data were independently extracted. The overall odds ratios (ORs) with corresponding 95% confidence intervals were calculated to determine the association between the presence of HLA variant in at least one allele and allopurinol-induced SJS or TEN. To test the robustness of the meta-analysis results, a sensitivity analysis was performed by removing each study one at a time and calculating the pooled ORs of the remaining studies. The fixed-effects and random-effects models were used to pool the collected data.

RESULTS

A total of 4 studies with 81 allopurinol-induced SJS or TEN cases and matched controls (allopurinol-tolerant patients) or population controls (general population) were identified. SJS and TEN were found to be significantly associated with HLA-A*33:03 and HLA-C*03:02 alleles in both groups of studies with matched controls and population controls. All of the pooled ORs were not significantly affected by the remaining studies and different modeling methods, indicating robust results.

CONCLUSION

A strong association was found between HLA-A*33:03 and HLA-C*03:02 alleles and allopurinol-induced SJS or TEN, especially in an Asian population.

Developing pharmacogenetic screening methods for an emergent country: Vietnam

BACKGROUND

The finding of strong associations between certain human leukocyte antigen (HLA) genotypes and the development of severe cutaneous adverse drug reactions (SCARs), [for example, HLA-B*57:01 and abacavir (ABC), HLA-B*15:02 and carbamazepine (CBZ) and HLA-B*58:01 and allopurinol], has led to HLA screening being used to prevent SCARs. Screening has been shown to be of great benefit in a number of studies. Clinical translation from bench to bedside, however, depends upon the development of simple, rapid and cost-effective assays to detect these risk alleles. In highly populated developing countries such as Vietnam, where there is a high prevalence of HLA-B*15:02 and HLA-B*58:01 correlating with a high incidence of CBZ- and allopurinol-induced SCARs, the crucial factor in the implementation of comprehensive screening programs to detect these major risk HLA alleles is the availability of suitable assays.

BODY

We have summarized the role and economic benefits of HLA screening, reviewed published HLA screening methods used currently in pharmacogenetic screening and examined the advantages and disadvantages of assays developed specifically for use in screening for risk alleles in the prevention of HLA-associated SCARs in Vietnam.

CONCLUSION

The optimal approach we propose may serve as a template for the development of screening programs in other emergent countries.

Clinical evaluation of a substitute of HLA-B*58:01 in different Chinese ethnic groups

The goal of this research was to investigate the linkage disequilibrium between rs9263726 and HLA-B*58:01 in different Chinese ethnic groups (Han, Tibet, and Hui) and to study the feasibility of rs9263726 replacing HLA-B*58:01 as an efficient indicator of potential allopurinol hypersensitivity syndrome. In this study, rs9263726 and HLA-B*58:01 were detected in all samples. For samples of individuals whose rs9263726 genotypes were not consistent with HLA-B*58:01, we did high-resolution typing of HLA-B gene to further confirm the correlation of rs9263726 genotype and special HLA-B alleles. We confirmed that the linkage disequilibrium between rs9263726 and HLA-B*58:01 was more significant in the Han ethnic group (r2=0.886, D'=1.0) than in the Tibet and Hui ethnic groups (for Tibetan, r2=0.606, D'=0.866; for Hui, r2=0.622, D'=0.924). For Han Chinese, samples with the GG genotype of rs9263726 did not carry HLA-B*58:01, while AA genotype samples were homozygous carriers of HLA-B*58:01. However, GA genotype samples of rs9263726 required a more sophisticated HLA-B genotyping assay before it was possible to identify whether they were HLA-B*58:01 carriers or not. For Tibetan and Hui, the linkage disequilibrium between rs9263726 and HLA-B*58:01 was not significant. Therefore, rs9263726 cannot replace HLA-B*58:01 in these two groups.

Impact of HLA-B*58:01 allele and allopurinol-induced cutaneous adverse drug reactions: evidence from 21 pharmacogenetic studies

Allopurinol is widely used for hyperuricemia and gouty arthritis, but is associated with cutaneous adverse drug reactions (CADRs). Recently, HLA-B*58:01 allele was identified as a strong genetic marker for allopurinol-induced CADRs in Han Chinese. However, the magnitude of association and diagnosis value of HLA-B*58:01 in allopurinol-induced CADRs remain inconclusive. To investigate this inconsistency, we conducted a meta-analysis of 21 pharmacogenetic studies, including 551 patients with allopurinol-induced CADRs, and 2,370 allopurinol-tolerant controls as well as 9,592 healthy volunteers. The summary OR for allopurinol-induced CADRs among HLA-B*58:01 carriers was 82.77 (95% CI: 41.63 – 164.58, P < 10⁻⁵) and 100.87 (95% CI: 63.91 – 159.21, P < 10⁻⁵) in matched and population based studies, respectively. Significant results were also observed when stratified by outcomes and ethnicity. Furthermore, the summary estimates for quantitative analysis of HLA-B*58:01 allele carriers in allopurinol-induced CADRs screening were as follows: sensitivity, 0.93 (95% CI: 0.85 – 0.97); specificity, 0.89 (95% CI: 0.87 – 0.91); positive likelihood ratio, 8.24 (95% CI: 6.92 – 9.81); negative likelihood ratio, 0.084 (95% CI: 0.039 – 0.179); and diagnostic odds ratio, 98.59 (95% CI: 43.31 – 224.41). The AUSROC was 0.92 (95% CI: 0.89–0.94), indicating the high diagnostic performance. Our results indicated that allopurinol–SCAR is strongly associated with HLA-B*58:01, and HLA-B*58:01 is a highly specific and effective genetic marker for the detection allopurinol-induced CADRs, especially for Asian descents.

Rapid and Reliable Genotyping of HLA-B*57:01 in Four Chinese Populations Using a Single-Tube Duplex Real-Time Polymerase Chain Reaction Assay

HLA-B*57:01 is strongly associated with severe adverse drug reaction induced by the anti-HIV drug abacavir (ABC) and antibiotic flucloxacillin. This study was dedicated to establishing a new method for HLA-B*57:01 genotyping and investigating the HLA-B*57:01 distribution pattern in four Chinese populations. A single-tube duplex real-time polymerase chain reaction (PCR) system was established by combining the amplification refractory mutation system and TaqMan probe. The reliability of this assay was validated by comparing the genotyping results with those by sequence-based typing. With this assay, the distribution of HLA-B*57:01 in 354 blood samples from four ethnic groups, namely, Han, Tibetan, Uighur, and Buyei, was determined. A 100% concordance was observed between the results of real-time PCR and sequence-based typing in 50 Uighur samples. As low as 0.016 ng DNA that carried HLA-B*57:01 could be detected with this assay. HLA-B*57:01 carriers identified in 100 Northern Han Chinese, 104 Buyeis, 100 Tibetans, and 50 Uighurs were 0, 1 (0.96%), 3 (3%), and 6 (12%), respectively. The carrier rate of HLA-B*57:01 in Uighur was significantly higher than those in Northern Han (p = .001) and Buyei (p = .005). The newly established real-time PCR assay provides a rapid and reliable tool for HLA-B*57:01 allele screening before the prescription of ABC and flucloxacillin in clinical practice.

Rapid and reliable screening of HLA-B*15:02 in four Chinese populations using single-tube multiplex real-time PCR assay

AIM

 HLA-B*15:02 screening should be performed to prevent antiepileptic drug induced severe cutaneous adverse reactions in populations of Asian origin. This study aimed to develop fast and reliable HLA-B*15:02 genotyping method and to investigate the distribution of HLA-B*15:02 in different Chinese ethnicities.

MATERIALS & METHODS

A single-tube multiplex real-time PCR assay for HLA-B*15:02 genotyping was established by combining allele-specific primers with TaqMan probes.

RESULTS

The HLA-B*15:02 genotyping results in Bouyei (n = 100) by the established assay were completely consistent with the corresponding PCR sequence-based typing findings. The percentage of HLA-B*15:02 carrier in Bouyei (19%; n = 100) was significantly higher than those of Han (1%; n = 100), Tibetan (0%; n = 100) and Uyghur (0%; n = 50) populations (p < 0.001).

CONCLUSION

The novel method provides rapid, reliable and cost-effective detection of HLA-B*15:02 allele in clinical applications.

Validation of a Rapid, Robust, Inexpensive Screening Method for Detecting the HLA-B*58:01 Allele in the Prevention of Allopurinol-Induced Severe Cutaneous Adverse Reactions

The HLA B^*58:01 allele has been worldwide reported as a pharmacogenetic susceptibility to allopurinol-induced severe cutaneous adverse reactions (SCARs). To prevent these life-threatening conditions, the American College of Rheumatology hingly recommended that the HLA-B^*58:01 be screened prior to the initiation of allopurinol therapy. Therefore, we developed a rapid, robust, inexpensive screening method using SYBR® Green real time PCR to detect the HLA-B^*58:01 allele. A total of 119 samples were tested. The assay has a sensitivity of 100% (95% CI: 69.15%-100%), a specificity of 100% (95% CI: 96.67%-100%), a positive predictive value of 100% (95% CI: 69.15%-100%) and a negative predictive value of 100% (95% CI: 96.67%-100%). HLA-B^*58:01 genotyping results showed 100% agreement with those obtained from Luminex SSO/SBT/SSP. The lowest limit of detection of this method is 0.8 ng/µL of DNA. The unit cost of the test is only $3.8 USD. This novel screening test using SYBR® real time PCR would be appropriate to identify individuals with the HLA-B^*58:01 allele for the prevention of allopurinol-induced SCARs.