Identification of drug-specific public TCR driving severe cutaneous adverse reactions

A comprehensive update on the human leukocyte antigen and idiosyncratic adverse drug reactions

INTRODUCTION

Idiosyncratic adverse drug reactions (IADRs) or drug hypersensitivity reactions (DHRs) represent a major health problem because they are unpredictable and can be severe with potential life-long or even lethal consequences. Their pathophysiology is not clear but thought to be immune mediated, supported by the significant statistical association of these reactions with specific alleles of the human leukocyte antigen (HLA) gene.

AREA COVERED

This comprehensive update review summarizes the currently available evidence on the role of HLA gene locus in IADRs and discusses the present understanding of the pathophysiology of IADRs. We searched the available literature in PubMed and Google Scholar with no date restriction for publications on HLA and adverse drug reactions. Findings are summarized and discussed in the context of the currently available evidence.

EXPERT OPINION

The role of the immune system in IADRs and the role of pharmacogenetic testing in this field is evident. HLA genetic testing is very promising in the management of these reactions. Many obstacles seem to prevent pharmacogenetic testing to meet its full potential including cost and health care providers' education. Further work in needed to provide more evidence and allow widespread use of pharmacogenetic testing in the clinical practice.

Class I HLA Alleles Are Associated With an Increased Risk of Osimertinib-Induced Hypersensitivity

BACKGROUND

Osimertinib, a third-generation epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI), shows superior lung cancer treatment efficacy. However, osimertinib-induced severe hypersensitivity, including Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN), is frequently observed in Asian populations and hinders cancer treatment.

OBJECTIVE

We investigated the genetic HLA predisposition and immune pathomechanism of osimertinib-induced hypersensitivity.

METHODS

We enrolled 17 patients with osimertinib-induced delayed hypersensitivity (seven with severe SJS/TEN and 10 with mild maculopapular exanthema), 98 osimertinib-tolerant subjects, and 2,123 general population controls. We performed HLA genotyping, drug-induced lymphocyte activation test, and surface plasmon resonance assay.

RESULTS

HLA-B∗51:02 was present in 83.3% of osimertinib-induced SJS/TEN patients but in only 3.3% of the general population controls (P = 2.8 × 10-7; corrected P = 6.9 × 10-6; odds ratio [OR] = 146), and 0% of osimertinib-tolerant controls (P = 6.5 × 10-8; corrected P = 1.6 × 10-6; OR = 707). The association of HLA-B∗51:01 and HLA-A∗24:02 with osimertinib-induced maculopapular exanthema patients, rather than with osimertinib-tolerant subjects (P = .002, OR = 15.7 for HLA-B∗51:01; and P = .003, OR = 9.5 for HLA-A∗24:02), was identified as a phenotype-specific association. Granulysin, the SJS/TEN-specific cytotoxic protein, was significantly higher in plasma of SJS/TEN patients (39.8 ± 4.5 ng/mL; P < .001) and in in vitro lymphocyte activation test (sensitivity = 83.3%; P < .01) compared with tolerant controls. Patients with osimertinib-induced hypersensitivity appeared to tolerate alternative EGFR-TKIs. Surface plasmon resonance results also confirmed that HLA-B∗51:02 protein has a higher binding affinity for osimertinib and lower or no affinity for other EGFR-TKIs.

CONCLUSIONS

HLA-B∗51:02 frequently occurs in Asian populations and is strongly associated with osimertinib-induced SJS/TEN. Our findings suggest HLA-B∗51:02 screening as a preemptive test to reduce osimertinib-induced severe hypersensitivity.

Delayed drug hypersensitivity reactions: How p-i transforms pharmacology into immunology

Delayed drug hypersensitivity reactions (dDHRs) are iatrogenic diseases, which are mostly due to non-covalent interactions of a drug with the immune receptors HLA and/or TCR causing T-cell activation. This is also known as pharmacological interaction with immune receptors or p-i. P-i activation differs from classical antigen-driven immune reactions: a) drug binding induces structural changes in TCR-HLA proteins which make them look like allo-like TCR-HLA-complexes, able to elicit allo-like stimulations of T cells with cytotoxicity and IFNγ production, notably without the involvement of innate immunity; b) drug binding to TCR and/or HLA can increase the affinity of TCR-HLA interactions, which may affect signaling and IL-5 production by CD4+ T cells, and thus contribute to eosinophilia commonly found in dDHRs or induce oligoclonal T cell expansions; c) Both, antigen and p-i stimulations can induce eosinophil- or neutrophil-rich inflammations; but these stimulations should be distinguished as their underlying mechanism and development differ; and d) p-i stimulation can - like graft versus host reactions - result in long-lasting T-cell activations, which can lead to viremia, occasional autoimmunity, or a new syndrome characterized by multiple drug hypersensitivity (MDH). In summary, dDHRs are not allergic reactions but represent peculiar T-cell activations, similar to allo-like stimulations. Understanding and considering the p-i mechanism is needed for preventive measures and optimal treatments of dDHR. In addition, it may help to understand TCR signaling, alloreactivity, and may even open a new way of specific immune stimulations.

Exploring recent advances in drugs severe cutaneous adverse reactions immunopathology

Severe cutaneous adverse reactions to drugs (SCARs) are rare but life-threatening delayed allergies. While they primarily affect the skin, they can also affect internal organs. Accordingly, they present with diverse clinical symptoms that vary not only between SCARs subtypes but also among patients. Despite the availability of topical and systemic treatments, these only address the symptoms and not the cause. To develop more effective therapies, it is necessary to elucidate the complexity of the pathophysiology of SCARs in relation to their severity. In line with the new type IV hypersensitivity reactions nomenclature proposed by the European Academy of Allergy and Clinical Immunology (EAACI), this review highlights the current insights into the intricate immune mechanisms engaged, the interplay between the culprit drug and genetic predisposition in drug presentation mechanisms, but also how external factors, such as viruses, are implicated in SCARs. Their relevance to the development of targeted medicine is also discussed.

Immune checkpoint inhibitor-induced severe epidermal necrolysis mediated by macrophage-derived CXCL10 and abated by TNF blockade

Immune checkpoint inhibitors (ICI) represent new anticancer agents and have been used worldwide. However, ICI can potentially induce life-threatening severe cutaneous adverse reaction (SCAR), such as Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN), hindering continuous ICI therapy. We examine 6 cohorts including 25 ICI-induced SJS/TEN patients and conduct single-cell RNA sequencing (scRNA-seq) analysis, which shows overexpression of macrophage-derived CXCL10 that recruits CXCR3+ cytotoxic T lymphocytes (CTL) in blister cells from ICI-SJS/TEN skin lesions. ScRNA expression profiles and ex vivo blocking studies further identify TNF signaling as a pathway responsible for macrophage-derived CXCL10 and CTL activation. Based on the trajectory analysis, ICI-activated T cells from whole blood are proposed to serve as the initial cells involved in inflammation, that lead to monocytes differentiating into macrophages and increasing their susceptibility to migrate to the lesion sites. Compared with systemic corticosteroids treatment, ICI-induced SJS/TEN patients treated with biologic TNF blockade showed a significantly rapid recovery and no recurrence of SCAR with continuous ICI therapy. Our findings identify that macrophage-eliciting CTL contribute to the pathogenesis of ICI-induced epidermal necrolysis and provide potential therapeutic targets for the management and prevention of SCAR induced by ICI therapy.

Pomalidomide in patients with multiple myeloma: potential impact on the reconstitution of a functional T-cell immunity

BACKGROUND

Pomalidomide, a third-generation oral immunomodulatory drug, exhibits efficacy in patients with relapsed multiple myeloma or those refractory to bortezomib and lenalidomide (RRMM).

METHODS

In this clinical context, we employed flow cytometry and CDR3 spectratyping to monitor the dynamics of the T-cell repertoire during Pomalidomide treatment, aiming to investigate its potential to reverse the immunological abnormalities characteristic of RRMM.

RESULTS

By flow cytometry at baseline we found a significant decrease in CD4 + frequency in MM patients, while CD8 + frequency were significantly higher in patients when compared to controls. Most T cell populations remained stable across all time points, except for CD4 + frequency, which notably decreased from t1 to subsequent assessments. Our investigation revealed as most relevant finding the notable increase in CD4 + expansions and the growing prevalence of patients manifesting these expansions. This pattern is even more evident in patients receiving their treatment until t3 and therefore still responding to treatment with Pomalidomide. We also conducted a comparison of spectratyping data before and after treatment, substantially demonstrating a relatively stable pattern throughout the course of Pomalidomide treatment.

CONCLUSIONS

These observations imply that Pomalidomide treatment influences the T-cell repertoire, particularly in the CD4 + subpopulation during the later stages of treatment, raising speculation about the potential involvement of these lymphocyte expansions in mechanisms related to antitumor immunity.

HLA-B*35:01-mediated activation of emodin-specific T cells contributes to Polygonum multiflorum thunb. -induced liver injury in mice

ETHNOPHARMACOLOGICAL RELEVANCE

HLA-B*35:01 has been identified as a risk allele for Polygonum multiflorum Thunb.-induced liver injury (PMLI). However, the immune mechanism underlying HLA-B*35:01-mediated PMLI remains unknown.

AIM OF THE STUDY

To characterize the immune mechanism of HLA-B*35:01-mediated PMLI.

MATERIALS AND METHODS

Components of P. multiflorum (PM) bound to the HLA-B*35:01 molecule was screened by immunoaffinity chromatography. Both wild-type mice and HLA-B*35:01 transgenic (TG) mice were treated with emodin. The levels of transaminases, histological changes and T-cell response were assessed. Splenocytes from emodin-treated mice were isolated and cultured in vitro. Phenotypes and functions of T cells were characterized upon drug restimulation using flow cytometry or ELISA. Emodin-pulsed antigen-presenting cells (APCs) or glutaraldehyde-fixed APCs were co-cultured with splenocytes from emodin-treated transgenic mice to detect their effect on T-cell activation.

RESULTS

Emodin, the main component of PM, could non-covalently bind to the HLA-B*35:01-peptide complexes. TG mice were more sensitive to emodin-induced immune hepatic injury, as manifested by elevated aminotransferase levels, infiltration of inflammatory cells, increased percentage of CD8+T cells and release of effector molecules in the liver. However, these effects were not observed in wild-type mice. An increase in percentage of T cells and the levels of interferon-γ, granzyme B, and perforin was detected in emodin-restimulated splenocytes from TG mice. Anti-HLA-I antibodies inhibited the secretion of these effector molecules induced by emodin. Mechanistically, emodin-pulsed APCs failed to stimulate T cells, while fixed APCs in the presence of emodin could elicit the secretion of T cell effector molecules.

CONCLUSION

The HLA-B*35:01-mediated CD8+ T cell reaction to emodin through the P-I mechanism may contribute to P. multiflorum-induced liver injury.

Selective HLA Class II Allele-Restricted Activation of Atabecestat Metabolite-Specific Human T-Cells

Elevations in hepatic enzymes were detected in several trial patients exposed to the Alzheimer's drug atabecestat, which resulted in termination of the drug development program. Characterization of hepatic T-lymphocyte infiltrates and diaminothiazine (DIAT) metabolite-responsive, human leukocyte antigen (HLA)-DR-restricted, CD4+ T-lymphocytes in the blood of patients confirmed an immune pathogenesis. Patients with immune-mediated liver injury expressed a restricted panel of HLA-DRB1 alleles including HLA-DRB1*12:01, HLA-DRB1*13:02, and HLA-DRB1*15:01. Thus, the objectives of this study were to (i) generate DIAT-responsive T-cell clones from HLA-genotyped drug-naive donors, (ii) characterize pathways of DIAT-specific T-cell activation, and (iii) assess HLA allele restriction of the DIAT-specific T-cell response. Sixteen drug-naive donors expressing the HLA-DR molecules outlined above were recruited, and T-cell clones were generated. Cellular phenotype, function, and HLA-allele restriction were assessed using culture assays. Peptides displayed by HLA class II molecules in the presence and absence of atabecestat were analyzed by mass spectrometry. Several DIAT-responsive CD4+ clones, displaying no reactivity toward the parent drug, were successfully generated from donors expressing HLA-DRB1*12:01, HLA-DRB1*13:02, and HLA-DRB1*15:01 but not from other donors expressing other HLA-DRB1 alleles. T-cell clones were activated following direct binding of DIAT to HLA-DR proteins expressed on the surface of antigen presenting cells. DIAT binding did not alter the HLA-DRB1 peptide binding repertoire, indicative of a binding interaction with the HLA-associated peptide rather than with the HLA protein itself. DIAT-specific T-cell responses displayed HLA-DRB1*12:01, HLA-DRB1*13:02, and HLA-DRB1*15:01 restriction. These data demonstrate that DIAT displays a degree of selectivity toward HLA protein and associated peptides, with expression of certain alleles increasing and that of others decreasing, the likelihood that a drug-specific T-cell response develops.

Multiomic single-cell sequencing defines tissue-specific responses in Stevens-Johnson syndrome and toxic epidermal necrolysis

Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) is a rare but life-threatening cutaneous drug reaction mediated by human leukocyte antigen (HLA) class I-restricted CD8+ T cells. For unbiased assessment of cellular immunopathogenesis, here we perform single-cell (sc) transcriptome, surface proteome, and T cell receptor (TCR) sequencing on unaffected skin, affected skin, and blister fluid from 15 SJS/TEN patients. From 109,888 cells, we identify 15 scRNA-defined subsets. Keratinocytes express markers indicating HLA class I-restricted antigen presentation and appear to trigger the proliferation of and killing by cytotoxic CD8+ tissue-resident T cells that express granulysin, granzyme B, perforin, LAG3, CD27, and LINC01871, and signal through the PKM, MIF, TGFβ, and JAK-STAT pathways. In affected tissue, cytotoxic CD8+ T cells express private expanded and unexpanded TCRαβ that are absent or unexpanded in unaffected skin, and mixed populations of macrophages and fibroblasts express pro-inflammatory markers or those favoring repair. This data identifies putative cytotoxic TCRs and therapeutic targets.

Stevens-Johnson syndrome and toxic epidermal necrolysis: Updates in pathophysiology and management

ABSTRACT

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are life-threatening conditions characterized by extensive detachment of the epidermis and mucous membranes. These severe disorders carry a high mortality rate, and their pathogenesis remains largely unclear. Furthermore, optimal therapeutic strategies for SJS/TEN remain a subject of ongoing debate. Early diagnosis of SJS/TEN is challenging, and reliable biomarkers for diagnosis or severity prediction have not been firmly established. Certain drugs, such as carbamazepine and allopurinol, have shown a strong association with specific human leukocyte antigen (HLA) types. Recently, the potential benefits of HLA screening prior to administering these drugs to reduce the incidence of SJS/TEN have been explored. Epidermal cell death in SJS/TEN lesions is caused by extensive apoptosis, primarily through the Fas-Fas ligand (FasL) and perforin/granzyme pathways. Our findings suggest that necroptosis, a form of programmed necrosis, also contributes to epidermal cell death. Annexin A1, released from monocytes, interacts with the formyl peptide receptor 1 to induce necroptosis. Several biomarkers, such as CC chemokine ligand (CCL)-27, interleukin-15, galectin-7, receptor-interacting protein kinases 3 (RIP3), and lipocalin-2, have been identified for diagnostic and prognostic purposes in SJS/TEN. Supportive care is recommended for treating SJS/TEN, but the efficacy of various therapeutic options-including systemic corticosteroids, intravenous immunoglobulin, cyclosporine, and tumor necrosis factor-α antagonists-remains controversial. Recent studies have investigated the potential benefits of tumor necrosis factor-α antagonists. In this review, we discuss recent advances in the understanding and management of SJS/TEN.

Defining the activity of pro-reparative extracellular vesicles in wound healing based on miRNA payloads and cell type-specific lineage mapping

Small extracellular vesicles (EVs) are released by cells and deliver biologically active payloads to coordinate the response of multiple cell types in cutaneous wound healing. Here we used a cutaneous injury model as a donor of pro-reparative EVs to treat recipient diabetic obese mice, a model of impaired wound healing. We established a functional screen for microRNAs (miRNAs) that increased the pro-reparative activity of EVs and identified a down-regulation of miR-425-5p in EVs in vivo and in vitro associated with the regulation of adiponectin. We tested a cell type-specific reporter of a tetraspanin CD9 fusion with GFP to lineage map the release of EVs from macrophages in the wound bed, based on the expression of miR-425-5p in macrophage-derived EVs and the abundance of macrophages in EV donor sites. Analysis of different promoters demonstrated that EV release under the control of a macrophage-specific promoter was most abundant and that these EVs were internalized by dermal fibroblasts. These findings suggested that pro-reparative EVs deliver miRNAs, such as miR-425-5p, that stimulate the expression of adiponectin that has insulin-sensitizing properties. We propose that EVs promote intercellular signaling between cell layers in the skin to resolve inflammation, induce proliferation of basal keratinocytes, and accelerate wound closure.

Systemic and skin-limited delayed-type drug hypersensitivity reactions associate with distinct resident and recruited T cell subsets

Delayed-type drug hypersensitivity reactions are major causes of morbidity and mortality. The origin, phenotype, and function of pathogenic T cells across the spectrum of severity require investigation. We leveraged recent technical advancements to study skin-resident memory T cells (TRMs) versus recruited T cell subsets in the pathogenesis of severe systemic forms of disease, Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) and drug reaction with eosinophilia and systemic symptoms (DRESS), and skin-limited disease, morbilliform drug eruption (MDE). Microscopy, bulk transcriptional profiling, and single-cell RNA-sequencing (scRNA-Seq) plus cellular indexing of transcriptomes and epitopes by sequencing (CITE-Seq) plus T cell receptor sequencing (TCR-Seq) supported clonal expansion and recruitment of cytotoxic CD8+ T cells from circulation into skin along with expanded and nonexpanded cytotoxic CD8+ skin TRM in SJS/TEN. Comparatively, MDE displayed a cytotoxic T cell profile in skin without appreciable expansion and recruitment of cytotoxic CD8+ T cells from circulation, implicating TRMs as potential protagonists in skin-limited disease. Mechanistic interrogation in patients unable to recruit T cells from circulation into skin and in a parallel mouse model supported that skin TRMs were sufficient to mediate MDE. Concomitantly, SJS/TEN displayed a reduced Treg signature compared with MDE. DRESS demonstrated recruitment of cytotoxic CD8+ T cells into skin as in SJS/TEN, yet a pro-Treg signature as in MDE. These findings have important implications for fundamental skin immunology and clinical care.

Drug hypersensitivity reactions: review of the state of the science for prediction and diagnosis

Drug hypersensitivity reactions (DHRs) are a type of adverse drug reaction that can occur with different classes of drugs and affect multiple organ systems and patient populations. DHRs can be classified as allergic or non-allergic based on the cellular mechanisms involved. Whereas nonallergic reactions rely mainly on the innate immune system, allergic reactions involve the generation of an adaptive immune response. Consequently, drug allergies are DHRs for which an immunological mechanism, with antibody and/or T cell, is demonstrated. Despite decades of research, methods to predict the potential for a new chemical entity to cause DHRs or to correctly attribute DHRs to a specific mechanism and a specific molecule are not well-established. This review will focus on allergic reactions induced by systemically administered low-molecular weight drugs with an emphasis on drug- and patient-specific factors that could influence the development of DHRs. Strategies for predicting and diagnosing DHRs, including potential tools based on the current state of the science, will also be discussed.

Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis: Analysis of the Russian Database of Spontaneous Reports

(1) Background: Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are extremely severe cutaneous adverse drug reactions which are relatively rare in routine clinical practice. An analysis of a national pharmacovigilance database may be the most effective method of obtaining information on SJS and TEN. (2) Methods: Design-a retrospective descriptive pharmacoepidemiologic study of spontaneous reports (SRs) with data on SJS and TEN retrieved from the Russian National Pharmacovigilance database for the period from 1 April 2019 to 31 December 2023. Descriptive statistics was used to assess the demographic data of patients and the structure of suspected drugs. (3) Results: A total of 170 SRs on SJS and TEN were identified, of which 32.9% were SJS and 67.1%-TEN. In total, 30% were pediatric SRs, 21.2%-SRs of the elderly. There were 12 lethal cases, and all cases were TEN. The leading culprit drugs were anti-infectives for systemic use and nervous system agents. The top 10 involved drugs are as follows: lamotrigine (23.5%), ibuprofen (12.9%), ceftriaxone (8.8%), amoxicillin and amoxicillin with beta-lactam inhibitors (8.8%), paracetamol (7.6%), carbamazepine (5.9%), azithromycin (4.1%), valproic acid (4.1%), omeprazole (3.5%), and levetiracetam (3.5%). (4) Conclusions: Our study was the first study in Russia aimed at the assessment of the structure of the drugs involved in SJS and TEN on the national level.

Human Leukocyte Antigens and Sulfamethoxazole/Cotrimoxazole-Induced Severe Cutaneous Adverse Reactions: A Systematic Review and Meta-Analysis

Importance

Sulfamethoxazole (SMX) and cotrimoxazole (CTX), a fixed-dose combination of SMX and trimethoprim in a 5:1 ratio, are antibacterial sulfonamides commonly used for treating various diseases. A substantial prevalence of severe cutaneous adverse reactions (SCARs) following the administration of these drugs has been reported. However, the association between human leukocyte antigen (HLA) genotypes and SMX/CTX-induced SCARs has remained unclear.

Objective

To investigate the association between HLA genotypes and SMX/CTX-induced SCARs.

Data sources

A comprehensive search was conducted in CENTRAL (Cochrane Library), MEDLINE, and Embase from inception to January 17, 2023.

Study Selection

Case-control studies that recruited patients who had experienced SCARs following SMX or CTX were included, and HLA alleles were analyzed.

Data Extraction and Synthesis

Two independent authors extracted data on study characteristics and outcome data. The Meta-analysis of Observational Studies in Epidemiology (MOOSE) reporting guideline and the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guidelines were followed. The Newcastle-Ottawa Scale for case-control studies was used to assess study quality. Odds ratios (ORs) were calculated using a random-effects model for meta-analysis.

Main Outcomes and Measures

The prespecified outcome was the OR comparing SMX/CTX-induced SCARs with healthy or SMX/CTX-tolerant controls based on different HLA alleles.

Results

Six studies involving 322 patients with SCAR were included, including 236 patients with Stevens-Johnson syndrome/toxic epidermal necrolysis, 86 with drug reaction with eosinophilia and systemic symptoms, 8448 healthy controls, and 229 tolerant controls. Significant associations were found in HLA-A*11:01 (OR, 2.10; 95% CI, 1.11-4.00), HLA-B*13:01 (OR, 5.96; 95% CI, 1.58-22.56), HLA-B*15:02 (OR, 2.23; 95% CI, 1.20-4.14), HLA-B*38:02 (OR, 3.47; 95% CI, 1.42-8.48), and HLA-C*08:01 (OR, 2.63; 95% CI, 1.07-6.44) compared with tolerant controls. In the Stevens-Johnson syndrome/toxic epidermal necrolysis subgroup, significant associations were found in HLA-B*15:02 (OR, 3.01; 95% CI, 1.56-5.80) and HLA-B*38:02 (OR, 5.13; 95% CI, 1.96-13.47). In the drug reaction with eosinophilia and systemic symptoms subgroup, significant associations were found in HLA-A*68:01 (OR, 12.86; 95% CI, 1.09-151.34), HLA-B*13:01 (OR, 23.09; 95% CI, 3.31-161.00), HLA-B*39:01 (OR, 4.56; 95% CI, 1.31-15.82).

Conclusions and Relevance

The results of this systematic review and meta-analysis suggest that multiple HLA alleles (HLA-A*11:01, HLA-B*13:01, HLA-B*15:02, HLA-B*38:02, and HLA-C*0801) are associated with SMX/CTX-induced SCARs.

Drug-induced hypersensitivity syndrome/drug reaction with eosinophilia and systemic symptoms. Part I. Epidemiology, pathogenesis, clinicopathological features, and prognosis

Drug-induced hypersensitivity syndrome (DiHS), also known as drug reaction with eosinophilia and systemic symptoms (DRESS), is a severe cutaneous adverse reaction (SCAR) characterized by an exanthem, fever, and hematologic and visceral organ involvement. Anticonvulsants, antibiotics, and allopurinol are the most common triggers. The pathogenesis involves a complex interplay between drugs, viruses, and the immune system primarily mediated by T-cells. DiHS/DRESS typically presents with a morbilliform eruption 2-6 weeks after drug exposure, and is associated with significant morbidity, mortality, and risk of relapse. Long-term sequelae primarily relate to organ dysfunction and autoimmune diseases. Part I of this continuing medical education activity on DiHS/DRESS provides an update on epidemiology, novel insights into pathogenesis, and a description of clinicopathological features and prognosis.

Severe cutaneous adverse reactions

Severe cutaneous adverse reactions (SCARs), which include Stevens-Johnson syndrome and toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms (also known as drug-induced hypersensitivity syndrome), acute generalized exanthematous pustulosis, and generalized bullous fixed drug eruption, are life-threatening conditions. The pathogenesis of SCARs involves T cell receptors recognizing drug antigens presented by human leukocyte antigens, triggering the activation of distinct T cell subsets. These cells interact with keratinocytes and various immune cells, orchestrating cutaneous lesions and systemic manifestations. Genetic predisposition, impaired drug metabolism, viral reactivation or infections, and heterologous immunity influence SCAR development and clinical presentation. Specific genetic associations with distinct SCAR phenotypes have been identified, leading to the implementation of genetic screening before prescription in various countries to prevent SCARs. Whilst systemic corticosteroids and conventional immunomodulators have been the primary therapeutic agents, evolving strategies, including biologics and small molecules targeting tumour necrosis factor, different cytokines, or Janus kinase signalling pathways, signify a shift towards a precision management paradigm that considers individual clinical presentations.

Knowledge mapping and global trends of drug hypersensitivity from 2013 to 2023: A bibliometric analysis

BACKGROUND

Drug hypersensitivity is a major global public health issue with a significant increase in prevalence in populations. Here, we provide a deep insight into the frontier hotspot and future direction in the field of drug hypersensitivity.

METHODS

A knowledge map is portrayed based on publications related to drug hypersensitivity from Web of Science Core Collection using CiteSpace. Co-occurrence relationships of countries, institutes, authors, journals, references, and keywords are constructed. According to the co-occurrence relationships, hotspots and future trends are overviewed.

RESULTS

The United States ranked first in the world and China with the second highest publications was the only developing country. Torres, Mayorga, and Blanca were highly productive authors. Harvard University was the institution with the most research publications. Keywords co-occurrence analysis suggested applications in emerging causes, potential mechanisms, and clinical diagnosis as the research hotspots and development frontiers.

CONCLUSION

Research on drug hypersensitivity is in a rapid development stage and an emerging trend in reports of anaphylaxis to polyethylene glycols is identified. Developing algorithms for understanding the standardization process of culprit drugs, clinical manifestations, and diagnostic methods will be the focus of future direction. In addition, a better understanding of the mechanisms to culprit drugs with immunological precise phenotypic definitions and high-throughput platforms is needed.

HLA-B*57:01-dependent intracellular stress in keratinocytes triggers dermal hypersensitivity reactions to abacavir

Specific human leukocyte antigen (HLA) polymorphisms combined with certain drug administration strongly correlate with skin eruption. Abacavir hypersensitivity (AHS), which is strongly associated with HLA-B*57:01, is one of the most representative examples. Conventionally, HLA transmits immunological signals via interactions with T cell receptors on the cell surface. This study focused on HLA-mediated intracellular reactions in keratinocytes that might determine the onset of skin immunotoxicity by drug treatments. Abacavir exposure resulted in keratinocytes expressing HLA-B*57:01 exhibiting endoplasmic reticulum (ER) stress responses, such as immediate calcium release into the cytosol and enhanced HSP70 expression. In contrast, keratinocytes expressing HLA-B*57:03 (closely related to HLA-B*57:01) did not show these changes. This indicated that HLA-B*57:01 has a specific intracellular response to abacavir in keratinocytes in the absence of lymphocytes. Furthermore, abacavir exposure in HLA-B*57:01-expressing keratinocytes elevated the expression of cytokines/chemokines such as interferon-γ, interleukin-1β, and CCL27, and induced T lymphoblast migration. These effects were suppressed by ER stress relief using 4-phenylbutyrate (4-PB). HLA-B*57:01-transgenic mice also exhibited ER stress in epidermal areas following abacavir administration, and abacavir-induced skin toxicity was attenuated by the administration of 4-PB. Moreover, abacavir bound to HLA-B*57:01 within cells and its exposure led to HLA-B*57:01 protein aggregation and interaction with molecular chaperones in the ER of keratinocytes. Our results underscore the importance of HLA-mediated intracellular stress responses in understanding the onset of HLA-B*57:01-mediated AHS. We provide the possibility that the intracellular behavior of HLA is crucial for determining the onset of drug eruptions.

Multiomic single-cell sequencing defines tissue-specific responses in Stevens-Johnson Syndrome and Toxic epidermal necrolysis

Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) is a rare but life-threatening cutaneous drug reaction mediated by human leukocyte antigen (HLA) class I-restricted CD8+ T-cells. To obtain an unbiased assessment of SJS/TEN cellular immunopathogenesis, we performed single-cell (sc) transcriptome, surface proteome, and TCR sequencing on unaffected skin, affected skin, and blister fluid from 17 SJS/TEN patients. From 119,784 total cells, we identified 16 scRNA-defined subsets, confirmed by subset-defining surface protein expression. Keratinocytes upregulated HLA and IFN-response genes in the affected skin. Cytotoxic CD8+ T-cell subpopulations of expanded and unexpanded TCRαβ clonotypes were shared in affected skin and blister fluid but absent or unexpanded in SJS/TEN unaffected skin. SJS/TEN blister fluid is a rich reservoir of oligoclonal CD8+ T-cells with an effector phenotype driving SJS/TEN pathogenesis. This multiomic database will act as the basis to define antigen-reactivity, HLA restriction, and signatures of drug-antigen-reactive T-cell clonotypes at a tissue level.

Elucidating the Mechanisms Underlying Interindividual Differences in the Onset of Adverse Drug Reactions

Idiosyncratic drug toxicities (IDTs) pose a significant challenge; they are marked by life-threatening adverse reactions that emerge aftermarket release and are influenced by intricate genetic and environmental variations. Recent genome-wide association studies have highlighted a strong correlation between specific human leukocyte antigen (HLA) polymorphisms and IDT onset. This review provides an overview of current research on HLA-mediated drug toxicities. In the last six years, HLA-transgenic (Tg) mice have been instrumental in advancing our understanding of these underlying mechanisms, uncovering systemic immune reactions that replicate human drug-induced immune stimulation. Additionally, the potential role of immune tolerance in shaping individual differences in adverse effects highlights its relevance to the interplay between HLA polymorphisms and IDTs. Although HLA-Tg mice offer valuable insights into systemic immune reactions, further exploration is essential to decipher the intricate interactions that lead to organ-specific adverse effects, especially in organs such as the skin or liver. Navigating the intricate interplay of HLA, which may potentially trigger intracellular immune responses, this review emphasizes the need for a holistic approach that integrates findings from both animal models and molecular/cellular investigations. The overarching goal is to enhance our comprehensive understanding of HLA-mediated IDTs and identify factors shaping individual variations in drug reactions. This review aims to facilitate the development of strategies to prevent severe adverse effects, address existing knowledge gaps, and provide guidance for future research initiatives in the field of HLA-mediated IDTs.

Personalized neoantigen-based T cell therapy triggers cytotoxic lymphocytes expressing polyclonal TCR against metastatic ovarian cancer

Neoantigen-reactive cytotoxic T lymphocytes play a vital role in precise cancer cell elimination. In this study, we demonstrate the effectiveness of personalized neoantigen-based T cell therapy in inducing tumor regression in two patients suffering from heavily-burdened metastatic ovarian cancer. Our approach involved the development of a robust pipeline for ex vivo expansion of neoantigen-reactive T lymphocytes. Neoantigen peptides were designed and synthesized based on the somatic mutations of the tumors and their predicted HLA binding affinities. These peptides were then presented to T lymphocytes through co-culture with neoantigen-loaded dendritic cells for ex vivo expansion. Subsequent to cell therapy, both patients exhibited significant reductions in tumor marker levels and experienced substantial tumor regression. One patient achieved repeated cancer regression through infusions of T cell products generated from newly identified neoantigens. Transcriptomic analyses revealed a remarkable increase in neoantigen-reactive cytotoxic lymphocytes in the peripheral blood of the patients following cell therapy. These cytotoxic T lymphocytes expressed polyclonal T cell receptors (TCR) against neoantigens, along with abundant cytotoxic proteins and pro-inflammatory cytokines. The efficacy of neoantigen targeting was significantly associated with the immunogenicity and TCR polyclonality. Notably, the neoantigen-specific TCR clonotypes persisted in the peripheral blood after cell therapy. Our findings indicate that personalized neoantigen-based T cell therapy triggers cytotoxic lymphocytes expressing polyclonal TCR against ovarian cancer, suggesting its promising potential in cancer immunotherapy.

Impact of Pharmacogenomics in Clinical Practice

Polymorphisms of genes encoding drug metabolizing enzymes and transporters can significantly modify pharmacokinetics, and this can be associated with significant differences in drug efficacy, safety, and tolerability. Moreover, genetic variants of some components of the immune system can explain clinically relevant drug-related adverse events. However, the implementation of drug dose individualization based on pharmacogenomics remains scarce. In this narrative review, the impact of genetic variations on the disposition, safety, and tolerability of the most commonly prescribed drugs is reported. Moreover, reasons for poor implementation of pharmacogenomics in everyday clinical settings are discussed. The literature analysis showed that knowledge of how genetic variations can modify the effectiveness, safety, and tolerability of a drug can lead to the adjustment of usually recommended drug dosages, improve effectiveness, and reduce drug-related adverse events. Despite some efforts to introduce pharmacogenomics in clinical practice, presently very few centers routinely use genetic tests as a guide for drug prescription. The education of health care professionals seems critical to keep pace with the rapidly evolving field of pharmacogenomics. Moreover, multimodal algorithms that incorporate both clinical and genetic factors in drug prescribing could significantly help in this regard. Obviously, further studies which definitively establish which genetic variations play a role in conditioning drug effectiveness and safety are needed. Many problems must be solved, but the advantages for human health fully justify all the efforts.

The allopurinol metabolite, oxypurinol, drives oligoclonal expansions of drug-reactive T cells in resolved hypersensitivity cases and drug-naïve healthy donors

Allopurinol (ALP) is a successful drug used in the treatment of gout. However, this drug has been implicated in hypersensitivity reactions that can cause severe to life-threatening reactions such as Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). Individuals who carry the human leukocyte antigen (HLA)-B*58:01 allotype are at higher risk of experiencing a hypersensitivity reaction (odds ratios ranging from 5.62 to 580.3 for mild to severe reactions, respectively). In addition to the parent drug, the metabolite oxypurinol (OXP) is implicated in triggering T cell-mediated immunopathology via a labile interaction with HLA-B*58:01. To date, there has been limited information regarding the T-cell receptor (TCR) repertoire usage of reactive T cells in patients with ALP-induced SJS or TEN and, in particular, there are no reports examining paired αβTCRs. Here, using in vitro drug-treated PBMCs isolated from both resolved ALP-induced SJS/TEN cases and drug-naïve healthy donors, we show that OXP is the driver of CD8+ T cell-mediated responses and that drug-exposed memory T cells can exhibit a proinflammatory immunophenotype similar to T cells described during active disease. Furthermore, this response supported the pharmacological interaction with immune receptors (p-i) concept by showcasing (i) the labile metabolite interaction with peptide/HLA complexes, (ii) immunogenic complex formation at the cell surface, and (iii) lack of requirement for antigen processing to elicit drug-induced T cell responsiveness. Examination of paired OXP-induced αβTCR repertoires highlighted an oligoclonal and private clonotypic profile in both resolved ALP-induced SJS/TEN cases and drug-naïve healthy donors.

Updates in SJS/TEN: collaboration, innovation, and community

Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (SJS/TEN) is a predominantly drug-induced disease, with a mortality rate of 15-20%, that engages the expertise of multiple disciplines: dermatology, allergy, immunology, clinical pharmacology, burn surgery, ophthalmology, urogynecology, and psychiatry. SJS/TEN has an incidence of 1-5/million persons per year in the United States, with even higher rates globally. One of the challenges of SJS/TEN has been developing the research infrastructure and coordination to answer questions capable of transforming clinical care and leading to improved patient outcomes. SJS/TEN 2021, the third research meeting of its kind, was held as a virtual meeting on August 28-29, 2021. The meeting brought together 428 international scientists, in addition to a community of 140 SJS/TEN survivors and family members. The goal of the meeting was to brainstorm strategies to support the continued growth of an international SJS/TEN research network, bridging science and the community. The community workshop section of the meeting focused on eight primary themes: mental health, eye care, SJS/TEN in children, non-drug induced SJS/TEN, long-term health complications, new advances in mechanisms and basic science, managing long-term scarring, considerations for skin of color, and COVID-19 vaccines. The meeting featured several important updates and identified areas of unmet research and clinical need that will be highlighted in this white paper.

Drug hypersensitivity and eosinophilia: The decisive role of p-i stimulation

Eosinophilia is a common finding in drug hypersensitivity reactions (DHR). Its cause is unclear, as neither antigen/allergen-driven inflammation nor clonal expansion is involved. Most delayed-DHRs are due to p-i (pharmacologic interaction of drugs with immune receptors). These are off-target activities of drugs with immune receptors that result in various types of T-cell stimulation, some of which involve excessive IL-5 production. Functional and phenotypic studies of T-cell clones and their TCR-transfected hybridoma cell lines revealed that some p-i-induced drug stimulations occur without CD4/ CD8 co-receptor engagement. The CD4/CD8 co-receptors link Lck (lymphocyte-specific protein tyrosine kinase) and LAT (linker for activation of T cells) to the TCR. Alteration of Lck or LAT can result in a TCR signalosome with enhanced IL-5 production. Thus, if a more affine TCR-[drug/peptide/HLA] interaction allows bypassing the CD4 co-receptor, a modified Lck/LAT activation may lead to a TCR signalosome with elevated IL-5 production. This "IL-5-TCR-signalosome" hypothesis could also explain eosinophilia in superantigen or allo-stimulation (graft-versus-host disease), in which evasion of CD4/CD8 co-receptors has also been described. It may open new therapeutic possibilities in certain eosinophilic diseases by directly targeting the IL-5-TCR signalosome.

An association study of HLA with levofloxacin-induced severe cutaneous adverse drug reactions in Han Chinese

Levofloxacin-induced severe cutaneous adverse drug reactions (LEV-SCARs) remain unexplored. An association study of human leukocyte antigen (HLA) alleles with LEV-SCARs among 12 patients, 806 healthy subjects, and 100 levofloxacin-tolerant individuals was performed. The carrier frequencies of HLA-B∗13:01 (odds ratio [OR]: 4.50; 95% confidence interval [CI]: 1.15-17.65; p = 0.043), HLA-B∗13:02 (OR: 6.14; 95% CI: 1.73-21.76; p = 0.0072), and serotype B13 (OR: 17.73; 95% CI: 3.61-86.95; p = 4.85 × 10-5) in patients with LEV-SCARs were significantly higher than those of levofloxacin-tolerant individuals. Molecular docking analysis suggested that levofloxacin formed more stable binding models with HLA-B∗13:01 and HLA-B∗13:02 than with non-risk HLA-B∗46:01. Mass spectrometry revealed that nonapeptides bound to HLA-B∗13:02 shifted at several positions after exposure to levofloxacin. Prospective screening for serotype B13 (sensitivity: 83%, specificity: 78%) and alternative drug treatment for carriers may significantly decrease the incidence of LEV-SCARs.

Associations of T-Cell Receptor Repertoire Diversity with L-Asparaginase Allergy in Childhood Acute Lymphoblastic Leukemia

Asparaginase is a critical component of therapy for childhood acute lymphoblastic leukemia (ALL), but it is commonly associated with allergy, which results in morbidity and poorer outcomes. The underlying basis of this allergy is undoubtedly immune-mediated, but the exact components of T-cell immunity have yet to be characterized. We performed longitudinal TCR sequencing of 180 bone marrow samples from 67 children with B-ALL treated as part of the Ma-Spore-ALL-2010 trial, and we evaluated the associations of TCR profile with asparaginase hypersensitivity, with functional validation of asparaginase activity in a separate cohort of 113 children. We found that a more diverse and dynamically changing TCR repertoire was associated with increased risk of clinical hypersensitivity and decreased L-asp activity. Allergic patients had a higher proportion of infrequent clonotypes, as well as a significantly lower degree of shared clonotypes amongst the cohort. Allergic patients also had significantly higher longitudinal variability of clonotypes across timepoints, where a higher dissimilarity between diagnosis and week 5 represented an 8.1-fold increased risk of an allergic event. After an allergy had occurred, there was shaping and convergence of the TCR repertoire towards a common antigen. Understanding the immunological basis of T-cell responses in allergy lays the groundwork for developing predictive biomarkers or strategies to mediate this common toxicity in childhood ALL.

TCR_Explore: A novel webtool for T cell receptor repertoire analysis

T cells expressing either alpha-beta or gamma-delta T cell receptors (TCR) are critical sentinels of the adaptive immune system, with receptor diversity being essential for protective immunity against a broad array of pathogens and agents. Programs available to profile TCR clonotypic signatures can be limiting for users with no coding expertise. Current analytical pipelines can be inefficient due to manual processing steps, open to data entry errors and have multiple analytical tools with unique inputs that require coding expertise. Here we present a bespoke webtool designed for users irrespective of coding expertise, coined 'TCR_Explore', enabling analysis either derived via Sanger sequencing or next generation sequencing (NGS) platforms. Further, TCR_Explore incorporates automated quality control steps for Sanger sequencing. The creation of flexible and publication ready figures are enabled for different sequencing platforms following universal conversion to the TCR_Explore file format. TCR_Explore will enhance a user's capacity to undertake in-depth TCR repertoire analysis of both new and pre-existing datasets for identification of T cell clonotypes associated with health and disease. The web application is located at https://tcr-explore.erc.monash.edu for users to interactively explore TCR repertoire datasets.

Updates on the immunopathology and genomics of severe cutaneous adverse drug reactions

Severe cutaneous adverse reactions (SCARs) such as Stevens-Johnson syndrome, toxic epidermal necrolysis (SJS/TEN), and drug reaction with eosinophilia and systemic symptoms (DRESS)/drug-induced hypersensitivity syndrome (DIHS) cause significant morbidity and mortality and impede new drug development. HLA class I associations with SJS/TEN and drug reaction with eosinophilia and systemic symptoms/drug-induced hypersensitivity syndrome have aided preventive efforts and provided insights into immunopathogenesis. In SJS/TEN, HLA class I-restricted oligoclonal CD8+ T-cell responses occur at the tissue level. However, specific HLA risk allele(s) and antigens driving this response have not been identified for most drugs. HLA risk alleles also have incomplete positive and negative predictive values, making truly comprehensive screening currently challenging. Although, there have been key paradigm shifts in knowledge regarding drug hypersensitivity, there are still many open and unanswered questions about SCAR immunopathogenesis, as well as genetic and environmental risk. In addition to understanding the cellular and molecular basis of SCAR at the single-cell level, identification of the MHC-restricted drug-reactive self- or viral peptides driving the hypersensitivity reaction will also be critical to advancing premarketing strategies to predict risk at an individual and drug level. This will also enable identification of biologic markers for earlier diagnosis and accurate prognosis, as well as drug causality and targeted therapeutics.

The use of non-functional clonotypes as a natural calibrator for quantitative bias correction in adaptive immune receptor repertoire profiling

High-throughput sequencing of adaptive immune receptor repertoires is a valuable tool for receiving insights in adaptive immunity studies. Several powerful TCR/BCR repertoire reconstruction and analysis methods have been developed in the past decade. However, detecting and correcting the discrepancy between real and experimentally observed lymphocyte clone frequencies are still challenging. Here, we discovered a hallmark anomaly in the ratio between read count and clone count-based frequencies of non-functional clonotypes in multiplex PCR-based immune repertoires. Calculating this anomaly, we formulated a quantitative measure of V- and J-genes frequency bias driven by multiplex PCR during library preparation called Over Amplification Rate (OAR). Based on the OAR concept, we developed an original software for multiplex PCR-specific bias evaluation and correction named iROAR: immune Repertoire Over Amplification Removal (https://github.com/smiranast/iROAR). The iROAR algorithm was successfully tested on previously published TCR repertoires obtained using both 5' RACE (Rapid Amplification of cDNA Ends)-based and multiplex PCR-based approaches and compared with a biological spike-in-based method for PCR bias evaluation. The developed approach can increase the accuracy and consistency of repertoires reconstructed by different methods making them more applicable for comparative analysis.

Delayed Drug Hypersensitivity Reactions: Molecular Recognition, Genetic Susceptibility, and Immune Mediators

Drug hypersensitivity reactions are classified into immediate and delayed types, according to the onset time. In contrast to the immediate type, delayed drug hypersensitivity mainly involves T lymphocyte recognition of the drug antigens and cell activation. The clinical presentations of such hypersensitivity are various and range from mild reactions (e.g., maculopapular exanthema (MPE) and fixed drug eruption (FDE)), to drug-induced liver injury (DILI) and severe cutaneous adverse reactions (SCARs) (e.g., Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug reaction with eosinophilia and systemic symptoms (DRESS), and acute generalized exanthematous pustulosis (AGEP)). The common culprits of delayed drug hypersensitivity include anti-epileptics, antibiotics, anti-gout agents, anti-viral drugs, etc. Delayed drug hypersensitivity is proposed to be initiated by different models of molecular recognition, composed of drug/metabolite antigen and endogenous peptide, HLA presentation, and T cell receptor (TCR) interaction. Increasing the genetic variants of HLA loci and drug metabolic enzymes has been identified to be responsible for delayed drug hypersensitivity. Furthermore, preferential TCR clonotypes, and the activation of cytotoxic proteins/cytokines/chemokines, are also involved in the pathogenesis of delayed drug hypersensitivity. This review provides a summary of the current understanding of the molecular recognition, genetic susceptibility, and immune mediators of delayed drug hypersensitivity.

Advances in the Understanding of Drug Hypersensitivity: 2012 Through 2022

Over the last decade there have been key advances in understanding mechanisms, risk, and consequences of both true immunological drug hypersensitivity and unverified drug allergy labels that have changed clinical practice. This has been facilitated by the widespread adoption of electronic health records (EHRs). The vast majority of EHR drug allergy labels are unverified and cause significant morbidity from unnecessary avoidance of optimal drug therapy. There has also been significant movement in our understanding of mechanisms of drug hypersensitivity that, in addition to advancing our understanding of the pathogenesis of immediate and delayed reactions, have guided preventive efforts, diagnostic procedures, and clinical management. More widespread adoption, including scale-up of "allergy" delabeling and appropriate management, specifically for antibiotics, opiates, radiocontrast, chemotherapeutics, biologics, and nonsteroidal anti-inflammatory medications, will be necessary to improve patient outcomes over the next decade. This will require further engagement and collaboration between primary care health care providers, allergists, and other specialists.

Pathology of drug hypersensitivity reactions and mechanisms of immune tolerance

Immune-mediated type IV adverse drug reactions are idiosyncratic in nature, generally not related to the primary or secondary pharmacology of the drug. Due to their complex nature and rarity, these iatrogenic reactions are seldom predicted or encountered during preclinical/early clinical development stages, and often precipitate upon exposure to wider populations (i.e. phase III onwards). They confer a burden on the healthcare sector in both a clinical and financial sense presenting a severe impediment to the drug discovery and development process. Research over the past 50 years has improved our understanding of these reactions markedly as both in vitro and in vivo studies have placed the role of the immune system, in particular; drug-responsive T cells, firmly in the spotlight as the mediators of these reactions. Indeed, the role of different populations of T cells in adverse events and the interaction of drug molecules with HLA proteins expressed on the surface of antigen-presenting cells is of considerable interest. Herein, this review examines the pathways of immune-mediated adverse events including the various T cell subtypes implicated and the mechanisms of T cell activation. Additionally, we address the enigma of immunological tolerance and explore the role tolerance plays in determination of susceptibility to such adverse events even in individuals carrying immunogenic liabilities.

Associations of HLA-A and HLA-B with vancomycin-induced drug reaction with eosinophilia and systemic symptoms in the Han-Chinese population

Vancomycin is a commonly used antibiotic; however, it can cause life-threatening severe cutaneous adverse reactions, such as drug reaction with eosinophilia and systemic symptoms (DRESS). A previous study has reported a strong association between HLA-A*32:01 and vancomycin-induced DRESS in European ethnicity. Herein, we aim to investigate the genetic predisposition of vancomycin-induced DRESS in the Han-Chinese population. In this study, we enrolled a total of 26 patients with vancomycin-induced DRESS, 1,616 general population controls, and 51 subjects tolerant to vancomycin. In vitro granulysin-based lymphocyte activation tests (LAT) were conducted among 6 vancomycin-induced DRESS patients who were concomitantly receiving other medicines. HLA-A and HLA-B genotypes were determined by sequencing-based typing. Our results found that vancomycin-induced DRESS was associated with HLA-A*32:01 [odds ratio (OR) = 7.8, 95% confidence interval (CI) = 1.7-35.8; p-value = 0.035], HLA-B*07:05 (OR = 32.3, 95% CI = 2.8-367.7; p-value = 0.047), HLA-B*40:06 (OR = 4.7, 95% CI = 1.3-16.1; p-value = 0.036) and HLA-B*67:01 (OR = 44.8, 95% CI = 7.2-280.4; p-value = 0.002) when comparing the vancomycin-induced DRESS patients with the general population controls. LAT results showed that granulysin significantly increased in the vancomycin-induced DRESS patients upon vancomycin stimulation (4.7 ± 3.7 fold increased), but not upon other co-medicines. This study identified that, in addition to HLA-A*32:01, HLA-B*07:05, HLA-B*40:06, and HLA-B*67:01 were also genetic markers for vancomycin-induced DRESS in the Han-Chinese population. Associations of ethnic variances in HLA with vancomycin-DRESS were observed.

Profiling genes encoding the adaptive immune receptor repertoire with gAIRR Suite

Adaptive immune receptor repertoire (AIRR) is encoded by T cell receptor (TR) and immunoglobulin (IG) genes. Profiling these germline genes encoding AIRR (abbreviated as gAIRR) is important in understanding adaptive immune responses but is challenging due to the high genetic complexity. Our gAIRR Suite comprises three modules. gAIRR-seq, a probe capture-based targeted sequencing pipeline, profiles gAIRR from individual DNA samples. gAIRR-call and gAIRR-annotate call alleles from gAIRR-seq reads and annotate whole-genome assemblies, respectively. We gAIRR-seqed TRV and TRJ of seven Genome in a Bottle (GIAB) DNA samples with 100% accuracy and discovered novel alleles. We also gAIRR-seqed and gAIRR-called the TR and IG genes of a subject from both the peripheral blood mononuclear cells (PBMC) and oral mucosal cells. The calling results from these two cell types have a high concordance (99% for all known gAIRR alleles). We gAIRR-annotated 36 genomes to unearth 325 novel TRV alleles and 29 novel TRJ alleles. We could further profile the flanking sequences, including the recombination signal sequence (RSS). We validated two structural variants for HG002 and uncovered substantial differences of gAIRR genes in references GRCh37 and GRCh38. gAIRR Suite serves as a resource to sequence, analyze, and validate germline TR and IG genes to study various immune-related phenotypes.

Functional and structural characteristics of HLA-B*13:01-mediated specific T cells reaction in dapsone-induced drug hypersensitivity

BACKGROUND

Severe cutaneous adverse drug reactions (SCARs) are a group of serious clinical conditions caused by immune reaction to certain drugs. The allelic variance of human leukocyte antigens of HLA-B*13:01 has been strongly associated with hypersensitivities induced by dapsone (DDS). T-cell receptor mediated activation of cytotoxic T lymphocytes (CTLs) has also been suggested to play an essential role in pathogenesis of SCARs. However, HLA-B*13:01-DDS-TCR immune synapse that plays role in drug-induced hypersensitivity syndrome (DIHS) associated T cells activation remains uncharacterized.

METHODS

To investigate the molecular mechanisms for HLA-B*13:01 in the pathogenesis of Dapsone-induced drug hypersensitivity (DDS-DIHS), we performed crystallization and expanded drug-specific CTLs to analyze the pathological role of DDS-DIHS.

RESULTS

Results showed the crystal structure of HLA-B*13:01-beta-2-microglobulin (β2M) complex at 1.5 Å resolution and performed mutation assays demonstrating that I118 or I119, and R121 of HLA-B*13:01 were the key residues that mediate the binding of DDS. Subsequent single-cell TCR and RNA sequencing indicated that TCRs composed of paired TRAV12-3/TRBV28 clonotype with shared CDR3 region specifically recognize HLA-B*13:01-DDS complex to trigger inflammatory cytokines associated with DDS-DIHS.

CONCLUSION

Our study identified the novel p-i-HLA/TCR as the model of interaction between HLA-B*13:01, DDS and the clonotype-specific TCR in DDS-DIHS.

Pathology of T-cell-mediated drug hypersensitivity reactions and impact of tolerance mechanisms on patient susceptibility

PURPOSE OF REVIEW

T-cell-mediated drug hypersensitivity is responsible for significant morbidity and mortality, and represents a substantial clinical concern. The purpose of this article is to focus on T-cell reactions and discuss recent advances in disease pathogenesis by exploring the impact of tolerance mechanisms in determining susceptibility in genetically predisposed patients.

RECENT FINDINGS

Certain drugs preferentially activate pathogenic T cells that have defined pathways of effector function. Thus, a critical question is what extenuating factors influence the direction of immune activation. A large effort has been given towards identifying phenotypic (e.g., infection) or genotypic (e.g., human leukocyte antigen) associations which predispose individuals to drug hypersensitivity. However, many individuals expressing known risk factors safely tolerate drug administration. Thus, mechanistic insight is needed to determine what confers this tolerance. Herein, we discuss recent clinical/mechanistic findings which indicate that the direction in which the immune system is driven relies upon a complex interplay between co-stimulatory/co-regulatory pathways which themselves depend upon environmental inputs from the innate immune system.

SUMMARY

It is becoming increasingly apparent that tolerance mechanisms impact on susceptibility to drug hypersensitivity. As the field moves forward it will be interesting to discover whether active tolerance is the primary response to drug exposure, with genetic factors such as HLA acting as a sliding scale, influencing the degree of regulation required to prevent clinical reactions in patients.

Practical Implementation of Genetics: New Concepts in Immunogenomics to Predict, Prevent, and Diagnose Drug Hypersensitivity

Delayed drug hypersensitivities are CD8⁺ T cell-mediated reactions associated with up to 50% mortality. Human leukocyte antigen (HLA) alleles are known to predispose disease and are specific to drug, reaction, and patient ethnicity. Pretreatment screening is recommended for a handful of the strongest associations to identify and prevent drug use in high-risk patients. However, an incomplete predictive value implicates other HLA-imposed risk factors, and low carriage of many identified HLA-risk alleles combined with the high cost of sequence-based typing has limited economic viability for similar recommendation of screening across drugs and health care systems. For mitigation, an expanding armory of low-cost polymerase chain reaction-based screens is being developed, and HLA-imposed risk factors are being discovered. These include (1) polymorphic variants of metabolic and endoplasmic reticulum aminopeptidase enzymes toward multiallelic screening with increased predictivity; (2) regulation by immune checkpoint inhibitors, enabling detolerized animal models of human disease; and (3) immunodominant T cell receptors (TCR) on clonally expanded CD8⁺ T cells. For the latter, HLA risk-restricted TCR provides immunogenomic strategies and samples from a single patient to identify novel HLA-risk associations in underserved minority populations, tissue-relevant effector biomarkers toward earlier diagnosis and treatment, and HLA-TCR-presented immunogenic structures to aid future drug development.

Advances in Our Understanding of the Interaction of Drugs with T-cells: Implications for the Discovery of Biomarkers in Severe Cutaneous Drug Reactions

Drugs can activate different cells of the immune system and initiate an immune response that can lead to life-threatening diseases collectively known as severe cutaneous adverse reactions (SCARs). Antibiotics, anticonvulsants, and antiretrovirals are involved in the development of SCARs by the activation of αβ naïve T-cells. However, other subsets of lymphocytes known as nonconventional T-cells with a limited T-cell receptor repertoire and innate and adaptative functions also recognize drugs and drug-like molecules, but their role in the pathogenesis of SCARs has only just begun to be explored. Despite 30 years of advances in our understanding of the mechanisms in which drugs interact with T-cells and the pathways for tissue injury seen during T-cell activation, at present, the development of useful clinical biomarkers for SCARs or predictive preclinical in vitro assays that could identify immunogenic moieties during drug discovery is an unmet goal. Therefore, the present review focuses on (i) advances in the understanding of the pathogenesis of SCARs reactions, (ii) a description of the interaction of drugs with conventional and nonconventional T-cells, and (iii) the current state of soluble blood circulating biomarker candidates for SCARs.

Idiosyncratic Drug Reactions: A 35-Year Chemical Research in Toxicology Perspective

When Larry Marnett founded Chemical Research in Toxicology, the study of idiosyncratic drug reactions (IDRs) was in its infancy. There was evidence that IDRs involve chemically reactive metabolites, and many of the papers in Chemical Research in Toxicology investigated the bioactivation of drugs. However, it became clear that not all drugs that form reactive metabolites are associated with a high risk of IDRs, and some drugs that do not appear to form reactive metabolites do cause IDRs. Some of the early Chemical Research in Toxicology papers investigated involvement of the adaptive immune system in the mechanism of IDRs, and HLA associations provided strong evidence for an immune mechanism of IDRs. This led to the question of how reactive metabolites might induce an immune response. The classic hapten hypothesis provided an obvious explanation, but a new hypothesis the danger hypothesis, added another dimension. Although there are common features to IDRs, it is becoming increasingly clear that there are also many differences in the mechanisms caused by different drugs. Other pharmacological effects of drugs may also play a role in the mechanism, and that is obviously true of IDRs caused by biological agents. The requirement for specific HLA and T-cell receptors is presumably the major factor that makes IDRs idiosyncratic. However, an innate immune response is required to prime the adaptive immune response. In contrast to the adaptive immune response, the innate immune response is unlikely to be idiosyncratic, and studies of the innate immune response to drugs may provide a much more accurate way to screen drugs for their potential to cause IDRs. For essential drugs that are known to cause IDRs, it may be possible to markedly decrease risk by a slow dose titration to induce immune tolerance. Significant progress has been made in the study of IDRs, but there is still a long way to go.

An Updated Review of Genetic Associations With Severe Adverse Drug Reactions: Translation and Implementation of Pharmacogenomic Testing in Clinical Practice

Adverse drug reactions (ADR) remain the major problems in healthcare. Most severe ADR are unpredictable, dose-independent and termed as type B idiosyncratic reactions. Recent pharmacogenomic studies have demonstrated the strong associations between severe ADR and genetic markers, including specific HLA alleles (e.g., HLA-B*15:02/HLA-B*57:01/HLA-A*31:01 for carbamazepine-induced severe cutaneous adverse drug reactions [SCAR], HLA-B*58:01 for allopurinol-SCAR, HLA-B*57:01 for abacavir-hypersensitivity, HLA-B*13:01 for dapsone/co-trimoxazole-induced SCAR, and HLA-A*33:01 for terbinafine-induced liver injury), drug metabolism enzymes (such as CYP2C9*3 for phenytoin-induced SCAR and missense variant of TPMT/NUDT15 for thiopurine-induced leukopenia), drug transporters (e.g., SLCO1B1 polymorphism for statin-induced myopathy), and T cell receptors (Sulfanilamide binding into the CDR3/Vα of the TCR 1.3). This mini review article aims to summarize the current knowledge of pharmacogenomics of severe ADR, and the potentially clinical use of these genetic markers for avoidance of ADR.

Advances in the Pathomechanisms of Delayed Drug Hypersensitivity

Delayed drug hypersensitivity continues to contribute to major clinical problems worldwide. The clinical presentations of delayed drug hypersensitivity are diverse, ranging from mild skin rashes to life-threatening systemic reactions. The pathomechanism of delayed drug hypersensitivity involves human leukocyte antigens (HLA) presentation of drugs/metabolites to T cell receptors (TCR), resulting in T-cell activation. The pathogenesis of delayed drug hypersensitivity also has reactivation of the virus, and activation of many immune mediators. In this review, we discuss the immune pathogenesis, molecular interactions of HLA/drugs/TCR, and downstream signaling of cytotoxic proteins/cytokines/chemokines, as well as disease prevention and management for delayed drug hypersensitivity.

Advances and highlights in T and B cell responses to drug antigens

The immunological mechanisms involved in drug hypersensitivity reactions (DHRs) are complex, and despite important advances, multiple aspects remain poorly understood. These not fully known aspects are mainly related to the factors that drive towards either a tolerant or a hypersensitivity response and specifically regarding the role of B and T cells. In this review, we focus on recent findings on this knowledge area within the last 2 years. We highlight new evidences of covalent and non-covalent interactions of drug antigen with proteins, as well as the very first characterization of naturally processed flucloxacillin-haptenated human leukocyte antigen (HLA) ligands. Moreover, we have analysed new insights into the identification of risk factors associated with the development of DHRs, such as the role of oxidative metabolism of drugs in the activation of the immune system and the discovery of new associations between DHRs and HLA variants. Finally, evidence of IgG-mediated anaphylaxis in humans and the involvement of specific subpopulations of effector cells associated with different clinical entities are also topics explored in this review. All these recent findings are relevant for the underlying pathology mechanisms and advance the field towards a more precise diagnosis, management and treatment approach for DHRs.

Proteomic Profiling and T Cell Receptor Usage of Abacavir Susceptible Subjects

Type B adverse drug reactions (ADRs) represent a significant threat as their occurrence arises unpredictable and despite proper application of the drug. The severe immune reaction Abacavir Hypersensitivity Syndrome (AHS) that arises in HIV⁺ patients treated with the antiretroviral drug Abacavir (ABC) strongly correlates to the presence of the human leukocyte antigen (HLA) genotype HLA-B*57:01 and discriminates HLA-B*57:01⁺ HIV⁺ patients from ABC treatment. However, not all HLA-B*57:01⁺ HIV⁺ patients are affected by AHS, implying the involvement of further patient-specific factors in the development of AHS. The establishment of a reliable assay to classify HLA-B*57:01 carriers as ABC sensitive or ABC tolerant allowed to investigate the T cell receptor (TCR) Vβ chain repertoire of effector cells and revealed Vβ6 and Vβ24 as potential public TCRs in ABC sensitive HLA-B*57:01 carriers. Furthermore, distinct effects of ABC on the cellular proteome of ABC sensitive and tolerant volunteers were observed and suggest enhanced activation and maturation of dentritic cells (DC) in ABC sensitive volunteers. Analysis of ABC-naïve cellular proteomes identified the T cell immune regulator 1 (TCIRG1) as a potential prognostic biomarker for ABC susceptibility and the involvement of significantly upregulated proteins, particularly in peptide processing, antigen presentation, interferon (IFN), and cytokine regulation.

Risk Assessment in Drug Hypersensitivity: Detecting Small Molecules Which Outsmart the Immune System

Drug hypersensitivity (DH) reactions are clinically unusual because the underlying immune stimulations are not antigen-driven, but due to non-covalent drug-protein binding. The drugs may bind to immune receptors like HLA or TCR which elicits a strong T cell reaction (p-i concept), the binding may enhance the affinity of antibodies (enhanced affinity model), or drug binding may occur on soluble proteins which imitate a true antigen (fake antigen model). These novel models of DH could have a major impact on how to perform risk assessments in drug development. Herein, we discuss the difficulties of detecting such non-covalent, labile and reversible, but immunologically relevant drug-protein interactions early on in drug development. The enormous diversity of the immune system, varying interactions, and heterogeneous functional consequences make it to a challenging task. We propose that a realistic approach to detect clinically relevant non-covalent drug interactions for a new drug could be based on a combination of in vitro cell culture assays (using a panel of HLA typed donor cells) and functional analyses, supplemented by structural analysis (computational data) of the reactive cells/molecules. When drug-reactive cells/molecules with functional impact are detected in these risk assessments, a close clinical monitoring of the drug may reveal the true incidence of DH, as suppressing but also enhancing factors occurring in vivo can influence the clinical manifestation of a DH.

Longitudinal High-Throughput Sequencing of the T-Cell Receptor Repertoire Reveals Dynamic Change and Prognostic Significance of Peripheral Blood TCR Diversity in Metastatic Colorectal Cancer During Chemotherapy

Colorectal cancer (CRC) is a major cause of cancer mortality and morbidity. Despite advances in chemotherapy and targeted therapy, unsustainable clinical benefit was noted due to recurrence and therapy resistance. The immune status of the cancer patient may affect the effectiveness of disease treatments. The dynamic change in the T-cell receptor (TCR) repertoire might be a clinical parameter for monitoring treatment responses. In this study, we aimed to determine the characteristics and clinical significance of the TCR repertoire in patients with unresectable metastatic colorectal cancer (mCRC). Herein, we comprehensively profile 103 peripheral blood samples from 20 healthy controls and 16 CRC patients with a follow-up of 98 to 452 days to identify hypervariable rearrangements of the TCRα and TCRβ repertoires using high-throughput sequencing. We found that TCRα repertoires, TCRβ repertoires, and CDR3 clonotypes were altered in mCRC patients compared with healthy controls. The diversity of TCR repertoires and CDR3 clonotypes decreased in most mCRC patients after therapy. Furthermore, compared with baseline TCR diversity, patients whose TCR diversity dropped considerably during therapy had better treatment responses, including lower CEA and CA19-9 levels and smaller tumor sizes. TCR baseline diversity was also significantly associated with partial response (PR) status (odds ratio: 5.29, p = 0.04). In conclusion, the present study demonstrated the association between dynamic changes in TCR diversity during chemotherapy and clinical outcomes as well as the potential utility of the TCR repertoire in predicting the prognosis of cancer treatment.