A simple screening approach to reduce B*5701-associated abacavir hypersensitivity on the basis of sequence variation in HIV reverse transcriptase

Human leukocyte antigen HLA-B*57:01 status in HIV-1 patients developing hypersensitivity reactions in Benin: a pilot study

BACKGROUND

Antiretroviral drugs in people living with HIV-1 (PLHIV-1) often trigger side effects which may lead to discontinuation or failure of treatment. Human Leukocyte Antigen B*57:01 (HLA-B*57:01) allele is known to predict hypersensitivity reactions to Abacavir. Very few data are available on the prevalence of HLA-B*57:01 allele in PLHIV-1 in African countries. This study aimed to screen for HLA-B*57:01 allele in PLHIV-1 in Benin.

METHODS

This pilot study was carried out on one hundred ten PLHIV-1 enrolled in two health facilities in Benin. Socio-demographic and clinical data were collected. Biological data were determined and HLA-B*57:01 allele was genotyped, using Single Specific Primer-Polymerase Chain Reaction in blood samples.

RESULTS

70% of participants were female. PLHIV-1 were under TDF + 3TC + DTG (47.2%) or TDF + 3TC + EFV (57.3%). Their median age was 41 [36-48.75] years and the average CD4 + T cell count was 249 [130-381.25] cells/µl. The average viral load in treatment failure PLHIV-1 was 4.7 [3.9-5.2] Log10. At the inclusion date, twenty-nine (26.4%) PLHIV-1 under TDF + 3TC + EFV have developed hypersensitivity reactions. None of 110 patients had shown HLA-B*5701 allele.

CONCLUSION

Our study revealed that HLA-B*57:01 allele was very rare in PLHIV-1 in Benin, suggesting that its screening before starting the Abacavir regimen did not seem necessary.

Development of multiplex pyrosequencing for HLA-B*57:01 screening using single nucleotide polymorphism haplotype

WHAT IS KNOWN AND OBJECTIVE

Abacavir (ABC) is a commonly used nucleoside reverse-transcriptase inhibitor with potent antiviral activity against HIV-1. The US Food and Drug Administration and international HIV treatment guidelines recommend HLA-B*57:01 screening before initiating treatment with ABC. The current standard method for HLA-B*57:01 screening is limited by its high-cost, time-consuming and labour-intensive procedure with the requirement of a specialized laboratory. Our study aims to develop a more reliable screening test by selecting rs3093726 as an additional single nucleotide polymorphism (SNP) to combine with rs2395029 for multiplex pyrosequencing development. It offers high-accuracy, cost-effective and rapid detection.

METHODS

Multiplex pyrosequencing was developed for HLA-B*57:01 screening using rs2395029 and rs3093726 as a surrogate marker and tested in 130 Thai subjects in parallel with singleplex pyrosequencing of each SNP and the standard sequence-based method.

RESULTS AND DISCUSSION

Multiplex pyrosequencing showed 100% concordance when compared with both singleplex pyrosequencing and standard sequence-based method. This method showed 100% of negative predictive value (NPV), positive predictive value (PPV), specificity and sensitivity.

WHAT IS NEW AND CONCLUSION

Multiplex pyrosequencing is a powerful tool for HLA-B*57:01 screening using the rs2395029 and rs3093726 haplotype genotyping as surrogate marker for this HLA-B. The assay provides accurate, cost-effective and rapid detection of this haplotype. It can be applied for ABC hypersensitivity screening of the Thai population before initiating treatment with ABC.

Flow cytometry analysis with a new FITC-conjugated monoclonal antibody-3E12 for HLA-B*57:01 rapid screening in prevention of abacavir hypersensitivity in HIV-1-infected patients

BACKGROUND

Rapid screening for the detection of HLA-B*57:01 in the prevention of abacavir hypersensitivity in HIV-1-infected patients is a hallmark for clinical services.

OBJECTIVE

The aim of this work was to analyze the utility of flow cytometry with a new FITC-conjugated B-17 monoclonal antibody (mAb3E12) for HLA-B*57:01 screening in a Spanish cohort of 577 HIV-1+ individuals.

METHODS

Cryopreserved peripheral blood mononuclear cell samples from HIV-1+ individuals were analyzed by flow cytometry with the mAb 3E12 that recognizes both HLA-B*57 and HLA-B*58 alleles (members of the group specificity, HLA-B17). Patients' DNA samples had been previously typed for HLA-B*57:01 with PCR-SSO or PCR-SSP and additional DNA sequencing (EPI Study). The results obtained by flow cytometry were compared with the results obtained by the DNA-PCR techniques.

RESULTS

By flow cytometry, 46 samples (7.97%) were positive for HLA-B17, 530 (91.86%) were negative, and 1 (0.17%) was undetermined. All samples found negative by flow cytometry were negative for HLA-B*57:01 by DNA-PCR. Of the HLA-B17 positive samples, 31 (67.4%) were positive for HLA-B*57:01, 2 (3.25%) were positive for HLA-B*57:03, 11 (26.1%) were positive for HLA-B*58, and 2 (3.25%) were negative for both HLA-B*57 and HLA-B*58 antigens. The undetermined sample was negative for HLA-B*57 and HLA-B*58 alleles by DNA-PCR.

CONCLUSIONS

This study shows that flow cytometry with mAb3E12 is a highly sensitive method (no false negatives) to implement prior to DNA-PCR analysis for rapid screening of HLA-B*57:01. Additional confirmation by molecular HLA typing method would be required in less than 10% of the cohort of HIV-1-infected individuals.

Determination of the high prevalence of Dual/Mixed- or X4-tropism among HIV type 1 CRF01_AE in Hong Kong by genotyping and phenotyping methods

In Hong Kong, the CCR5 antagonist has recently been introduced into salvage therapy for multiclass drug-resistant HIV-1-infected patients. Coreceptor usage must be determined prior to the usage of the CCR5 antagonist, which does not inhibit X4-tropic viruses. This study aimed to determine the tropism prevalence for HIV-1 subtypes B and CRF01_AE in Hong Kong. In addition, a modified promoter-PCR phenotypic assay was used to validate the genotypic tropism prediction on CRF01_AE. One hundred and five subtype B and 98 CRF01_AE antiretroviral-naive patients were recruited for this study. The viral env V3 region isolated from the patients was sequenced and analyzed by Geno2pheno (FPR=5.75% or 10%, Clonal or Clinical), position-specific scoring matrix (WebPSSM, x4r5 subtype B matrix), and the combination of 11/25 and net charge rules. Fifteen concordant and 22 discordant tropism genotyped CRF01_AE samples were further phenotyped by either enhanced sensitivity Trofile assay or an optimized promoter-PCR phenotypic assay. The prevalence of Dual/Mixed- or X4-tropic virus in antiretroviral-naive subtype CRF01_AE was 39.1%, which was significantly higher than subtype B (p<0.05), regardless of the choices of genotypic algorithms. Our phenotypic data proposed that a better genotypic tropism prediction for HIV-1 CRF01_AE would be using both Geno2pheno (FPR=10%, Clonal) and WebPSSM (x4r5 subtype B matrix) algorithms in combination. The sensitivity and specificity for this combination were 88.9% and 89.3%, respectively. The comparatively high prevalence of Dual/Mixed- or X4-tropic virus in CRF01_AE demonstrated the need for special attention to future treatment strategies.

Low incidence of abacavir hypersensitivity reaction among African children initiating antiretroviral therapy

Hypersensitivity reactions are reported in approximately 5% of adults receiving abacavir, but there are few published data in children. Among 1150 African children receiving antiretroviral therapy in a randomized trial, suspected hypersensitivity reactions to abacavir were rare (0.3%; 95% CI, 0.01-0.9). Patients were managed successfully through the provision of clear guidelines and education of clinical staff, children, and their caregivers.

Cost-effectiveness analysis of HLA-B*5701 typing in the prevention of hypersensitivity to abacavir in HIV+ patients in Spain

INTRODUCTION

Approximately 4% to 8% of patients with HIV-1 treated with abacavir present a hypersensitivity reaction (HSR). Various studies have shown a direct association between human leukocyte antigen (HLA)-B*5701 and HSR to abacavir. The objective of this study was to analyze whether systematic HLA-B*5701 testing to prevent HSR in patients treated with abacavir is a cost-effective option for the Spanish National Health System.

METHODS

An analytical decision-making model was constructed as a decision tree model for a simulated cohort of 1000 HIV patients to evaluate whether HLA-B*5701 testing to prevent HSR to abacavir was cost effective compared with not performing the test. The parameters included in the model and the use of healthcare resources should the patient develop HSR were taken from the PREDICT-1 study and the opinion of clinical experts. The principal result obtained was the incremental cost per HSR avoided. The time horizon of the analysis was to 2 months [corrected] . All costs were expressed in 2008 Euros.

RESULTS

The analysis showed that the total direct healthcare costs per patient were €1344 and €1322 with and without HLA-B*5701 testing respectively, and that 36 cases of HSR were prevented per 1000 screened patients. These results yielded a cost per HSR avoided of €630. The sensitivity analysis showed that the results were sensitive to the cost of the test, with an economic saving of €102 or a cost-effectiveness ratio of €4234.

CONCLUSIONS

The model predicts that generalized use of the HLA-B*5701 test before prescribing abacavir in HIV+ patients could represent an economic saving or a limited additional cost for the National Health System which may be counterbalanced by the benefits in terms of a lower incidence of HSR.

HLA-B*5701 screening prior to abacavir prescription: clinical and laboratory aspects

This review focuses on the development of HLA-B*5701 genetic screening as a means of preventing drug hypersensitivity reactions caused by a commonly prescribed antiretroviral drug, abacavir. This strongly predictive genetic association, which in many respects represents a test case for the clinical application of pharmacogenetics, highlights the fine specificity of HLA-restricted immunity, here directed against a drug-specific antigen rather than an allogeneic molecule (as occurs in transplantation) or a pathogenic organism (as in viral infection). However, this example also demonstrates that successful implementation of pharmacogenetic screening requires that a range of criteria be adequately addressed. These include pharmaceutical factors (e.g. lack of alternative treatments with similar or improved cost effectiveness, safety, and efficacy), clinical factors (e.g. accurate diagnosis of the adverse event, in this case provided by clinical diagnostic criteria and adjunctive epicutaneous patch testing), sufficient objective evidence of the test's predictive value and generalizability (in this case provided by the first large-scale randomized trial of a pharmacogenetic test), as well as availability of quality-assured laboratory services that are responsive to the needs of targeted genetic screening. This example is intended to serve as a precedent for other pharmacogenetic screening strategies, particularly those aimed at reducing rates of serious drug hypersensitivity reactions in clinical practice.

Current trends in screening across ethnicities for hypersensitivity to abacavir

Abacavir is a potent nucleoside analog reverse transcriptase inhibitor approved for the treatment of HIV infection. Approximately 5-8% of Caucasian patients receiving abacavir develop a hypersensitivity reaction, characterized by rash, fever and, occasionally, multisystemic involvement. Rechallenge with the drug can be fatal. The discovery of the mechanisms involved in this hypersensitivity reaction and the identification of tools for its prediction are the subject of this review. The most relevant finding is the recognition of a strong association between one specific haplotype at the HLA complex type I, HLA-B*5701, and the abacavir hypersensitivity reaction. The heterogeneity in the prevalence of HLA-B*5701 across distinct ethnicities accounts for differences in the risk of abacavir hypersensitivity reactions in distinct populations.

Are mutations in HIV type-1 reverse transcriptase 245 codon predictive of abacavir hypersensitivity reaction?

Background

HLA-B*5701 is strongly related to abacavir hypersensitivity reactions (HSRs). Polymorphisms at position 245 of HIV type-1 (HIV-1) reverse transcriptase (RT) show an association with HLA-B*5701 suggesting that viral genotyping performed for antiretroviral drug resistance testing could reduce human leukocyte antigen (HLA) screening necessity to prevent abacavir HSR.

Methods

To further test the validity of 245 codon analysis results for predicting HSR, we analysed 1,179 sequences from 752 HIV-1-infected patients.

Results

Mutant amino acid residues in RT 245 were found in 30.6% of sequences. Among 239 patients with multiple longitudinal genotypes, 245 residues varied in 37 (15.5%) from wild type to mutant and/or vice versa. All these changes appeared during antiretroviral treatment. A total of 15 out of 229 (6.5%) abacavir-treated patients developed a clinically confirmed HSR: all carried B subtypes. There was no significant difference in the prevalence of 245 mutants between abacavir-treated patients with HSR (27%) and those without (29%), even after limiting the analysis to subtype B carriers.

Conclusions

The significant intraindividual variability of 245 residues and the lack of their association with clinically confirmed HSR argue against their use as viral genetic markers to exclude patients at risk for HSR.

The HCP5 single-nucleotide polymorphism: a simple screening tool for prediction of hypersensitivity reaction to abacavir

The HLA-B 5701 allele is predictive of hypersensitivity reaction to abacavir, a response herein termed "ABC-HSR." This study of 1,103 individuals infected with human immunodeficiency virus assessed the usefulness of genotyping a HCP5 single-nucleotide polymorphism (SNP), rs2395029, in relation to ABC-HSR. In populations with European ancestry, rs2395029 is in linkage disequilibrium with HLA-B 5701. The HCP5 SNP was present in all 98 HLA-B 5701-positive individuals and was absent in 999 of 1005 HLA-B 5701-negative individuals. rs2395029 was overrepresented in 25 individuals with clinically likely ABC-HSR, compared with its frequency in 175 ABC-tolerant individuals (80% vs. 2%, respectively; P < .0001). Therefore, HCP5 genotyping could serve as a simple screening tool for ABC-HSR, particularly in settings where sequence-based HLA typing is not available.

Recent availability of two novel, fixed formulations of antiretroviral nucleoside analogues: a 12-month prospective, open-label survey of their practical use and therapeutic perspectives in antiretroviral-naive and -experienced patients

The recent introduction of novel, fixed nucleoside-nucleotide reverse transcriptase inhibitor (NRTI) combinations (tenofovir-emtricitabine, and abacavir-lamivudine) expanded the spectrum of available formulations and concurrently increased patients' adherence levels. A prospective survey of the open-label use of these two fixed combinations was performed in 158 patients belonging to our single-center cohort of more than 1,000 HIV-infected subjects enrolled in the last 18 months, and followed for at least 12 months. During the last 18 months, 95 consecutive, evaluable patients (60.1%) received for the first time tenofovir-emtricitabine, or abacavir-lamivudine (63 patients, 39.9%), and were followed for at least 12 months with periodic clinical and laboratory examinations. Among the 53 evaluable patients who were naïve to all antiretrovirals, tenofovir-emtricitabine has been given to 42 subjects (79.2%), mostly associated with efavirenz (26 cases), or different boosted protease inhibitors (16 subjects), whereas abacavir-lamivudine was administered to 11 patients (in 10 cases of 11, together with boosted protease inhibitors). In the remaining 105 patients, tenofovir-emtricitabine or abacavir-lamivudine therapy represented a switch from a prior combination antiretroviral regimen, and was predominantly associated with boosted protease inhibitors (61 patients), versus efavirenz or nevirapine (26 cases), or other drug combinations containing protease inhibitors (the remaining 18 patients). Among the 105 pretreated patients, the prescription of tenofovir-emtricitabine (53 patients) was as frequent as that of abacavir-lamivudine (52 cases), and the therapeutic change was primarily prompted by toxicity or poor tolerability (59 patients), followed by therapeutic failure and viral resistance (46 cases as a whole), and always encompassed a regimen simplification also. Both fixed combinations were well tolerated, and an adherence rate more than 90% was estimated among evaluable patients. From a tolerability point of view, the emtricitabine-tenofovir association was never withdrawn due to untoward events, while only two cases of early abacavir-lamivudine suspension occurred, due to a probable abacavir hypersensitivity reaction. From our preliminary experience, a major role seems to be played by tenofovir-emtricitabine in first-line treatments (preferably among "compact" regimens based on efavirenz), while the proportionally increased abacavir-lamivudine prescription to pretreated patients is mostly attributable to the different genetic barrier of abacavir (which was often associated with boosted protease inhibitors, in this last patient group). The present availability of two more fixed NRTI combinations favored by their single pill, once-daily administration strongly encourages randomized, controlled "head to head" studies in both first-line and experienced patents, in order to better exploit and target their therapeutic potential, and their most effective associations.

Antiretroviral therapy : optimal sequencing of therapy to avoid resistance

In the second decade of highly active antiretroviral therapy, drug regimens offer more potent, less toxic and more durable choices. However, strategies addressing convenient sequential use of active antiretroviral combinations are rarely presented in the literature. Studies have seldom directly addressed this issue, despite it being a matter of daily use in clinical practice. This is, in part, because of the complexity of HIV-1 resistance information as well as the complexity of designing these types of studies. Nevertheless, several principles can effectively assist the planning of antiretroviral drug sequencing. The introduction of tenofovir disoproxil fumarate, abacavir and emtricitabine into current nucleoside backbone options, with each of them selecting for an individual pattern of resistance mutations, now permits sequencing in the context of previously popular thymidine analogues (zidovudine and stavudine). Similarly, newer ritonavir-boosted protease inhibitors could potentially be sequenced in a manner that uses the least cross-resistance prone protease inhibitor at the start of therapy, while leaving the most cross-resistance prone drugs for later, as long as there is rationale to employ such a compound because of its utility against commonly observed drug-resistant forms of HIV-1.

Pharmacogenetic information derived from analysis of HLA alleles

A large amount of pharmacogenetic information has, in particular, accumulated on the association between human leukocyte antigen (HLA) alleles and hypersensitivity to certain drugs. Prospective HLA typing has dramatically reduced the risk of abacavir hypersensitivity because of its strong association with HLA-B*5701. Significant predisposition to nevirapine hypersensitivity has been reported in Caucasian Australians harboring HLA-DRB1*0101 with high CD4+ T-cell counts, and Sardinians and Japanese harboring HLA-Cw8. A strong association between carbamazepine hypersensitivity and HLA-B*1502 has been reported in Han Chinese. Most Han Chinese individuals with allopurinol-induced severe cutaneous adverse reactions are positive for HLA-B*5801. HLA typing can stratify risk of hypersensitivity to certain drugs and allow personalized treatment, although the patients should be monitored closely even if they are negative for HLA alleles associated with hypersensitivity.

Strategies for the optimal sequencing of antiretroviral drugs toward overcoming and preventing drug resistance

Drug regimens now offer more potent, less toxic and more durable choices in the treatment of HIV disease than ever before. This has led to a need to consider the convenient, sequential use of active antiretroviral combinations. Ritonavir-boosted protease inhibitors (PIs) can now be potentially sequenced in a manner that uses the least cross-resistance-prone PI at the start of therapy while leaving the most cross-resistance-prone drug for later, if the latter retains activity against commonly observed drug-resistant forms. Similarly, such new drugs as tenofovir, abacavir and emtricitabine, which make up current nucleoside backbone options, can be potentially sequenced, since each of them selects for an individual pattern of resistance mutations that are generally distinct from those selected by previously popular thymidine analogs such as zidovudine and stavudine.