Severe Delayed Drug Reactions: Role of Genetics and Viral Infections

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.

Prior antibiotics and risk of subsequent Herpes zoster: A population-based case control study

Background

The effect of antibiotics on the human microbiome is now well established, but their indirect effect on the related immune response is less clear. The possible association of Herpes zoster, which involves a reactivation of a previous varicella zoster virus infection, with prior antibiotic exposure might indicate a potential link with the immune response.

Methods

A case-control study was carried out using a clinical database, the UK’s Clinical Practice Research Datalink. A total of 163,754 patients with varicella zoster virus infection and 331,559 age/sex matched controls were identified and their antibiotic exposure over the previous 10 years, and longer when data permitted, was identified. Conditional logistic regression was used to identify the association between antibiotic exposure and subsequent infection in terms of volume and timing.

Results

The study found an association of antibiotic prescription and subsequent risk of varicella zoster virus infection (adjusted odds ratio of 1.50; 95%CIs: 1.42–1.58). The strongest association was with a first antibiotic over 10 years ago (aOR: 1.92; 95%CIs: 1.88–1.96) which was particularly pronounced in the younger age group of 18 to 50 (aOR 2.77; 95%CIs: 1.95–3.92).

Conclusions

By finding an association between prior antibiotics and Herpes zoster this study has shown that antibiotics may be involved in the reactivation of the varicella zoster virus. That effect, moreover, may be relatively long term. This indirect effect of antibiotics on viruses, possibly mediated through their effect on the microbiome and immune system, merits further study.

Drug-Induced Hypersensitivity Syndrome (DIHS)/Drug Reaction With Eosinophilia and Systemic Symptoms (DRESS): Clinical Features and Pathogenesis

Drug-induced hypersensitivity syndrome/drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS) is one example of a severe delayed T-cell-mediated adverse drug reaction. DIHS/DRESS presents with fever, widespread rash and facial edema, organ involvement, and hematological abnormalities, including eosinophilia and atypical lymphocytosis. DIHS/DRESS is associated with relapse 2 to 4 weeks after acute symptoms, often coinciding with reactivation of prevalent chronic persistent human herpesviruses such as human herpesvirus 6, EBV, and cytomegalovirus. The mortality of DIHS/DRESS is up to 10% and often related to unrecognized myocarditis and cytomegalovirus complications, with longer-term consequences that contribute to morbidity including autoimmune diseases such as thyroiditis. It is essential that all potential drug causes, including all new drugs introduced within the 8 weeks preceding onset of DIHS/DRESS symptoms, are identified. All potential drug culprits, as well as drugs that are closely related structurally to the culprit drug, should be avoided in the future. Systemic corticosteroids have remained the mainstay for the treatment of DIHS/DRESS with internal organ involvement. Steroid-sparing agents, such as cyclosporine, mycophenolate mofetil, and monthly intravenous immune globulin, have been successfully used for treatment, and careful follow-up for cytomegalovirus reactivation is recommended. Strong associations between HLA class I alleles and DIHS/DRESS predisposition include HLA-B∗13:01 and dapsone, HLA-B∗58:01 and allopurinol, and HLA-B∗32:01 and vancomycin. These have opened a pathway for prevention, risk stratification, and earlier diagnosis. Single-cell sequencing and other studies of immunopathogenesis promise to identify targeted treatment approaches.

An atypical presentation of toxic epidermal necrolysis without mucosal involvement

Toxic epidermal necrolysis (TEN) is a severe adverse cutaneous drug reaction with ubiquitous involvement of mucosa. Drugs are identified as the main etiology in most cases. Cutaneous involvement in TEN occurs in the form of widespread painful erythematous macules, targetoid lesions, full-thickness or focal epidermal necrosis, whereas mucosal involvement involves oral, genital, and ocular mucous membranes along with preceding prodromal flu-like symptoms. Atypical presentations include involvement of only mucosa without involvement of skin. We report a rare case of TEN without any mucosal involvement.

Skin Resident Memory T Cells May Play Critical Role in Delayed-Type Drug Hypersensitivity Reactions

Delayed-type drug hypersensitivity reactions (dtDHR) are immune-mediated reactions with skin and visceral manifestations ranging from mild to severe. Clinical care is negatively impacted by a limited understanding of disease pathogenesis. Though T cells are believed to orchestrate disease, the type of T cell and the location and mechanism of T cell activation remain unknown. Resident memory T cells (T_RM) are a unique T cell population potentially well situated to act as key mediators in disease pathogenesis, but significant obstacles to defining, identifying, and testing T_RM in dtDHR preclude definitive conclusions at this time. Deeper mechanistic interrogation to address these unanswered questions is necessary, as involvement of T_RM in disease has significant implications for prediction, diagnosis, and treatment of disease.

Delabeling Delayed Drug Hypersensitivity: How Far Can You Safely Go?

Delayed immune-mediated adverse drug reactions (IM-ADRs) are defined as reactions occurring more than 6 hours after dosing. They include heterogeneous clinical phenotypes that are typically T-cell-mediated reactions with distinct mechanisms across a wide spectrum of severity from benign exanthems through to life-threatening cutaneous or organ-specific diseases. For mild reactions such as benign exanthem, considerations for delabeling are similar to immediate reactions and may include a graded or single-dose drug challenge with or without preceding skin or patch testing. Evaluation of challenging cases such as the patient who is on multiple drugs at the time a severe delayed IM-ADR occurs should prioritize clinical ascertainment of the most likely phenotype and implicated drug(s). Although not widely available and validated, procedures such as patch testing, delayed intradermal skin testing, and laboratory-based functional drug assays or genetic (human leukocyte antigen) testing may provide valuable information to further help risk stratify patients and identify the likely implicated and/or cross-reactive drug(s). The decision to use a drug challenge as a diagnostic or delabeling tool in a patient with a severe delayed IM-ADR should weigh the risk-benefit ratio, balancing the severity and priority for the treatment of the underlying, and the availability of alternative efficacious and safe treatments.

Idiosyncratic Drug-Induced Liver Injury: Mechanistic and Clinical Challenges

Idiosyncratic drug-induced liver injury (IDILI) remains a significant problem for patients and drug development. The idiosyncratic nature of IDILI makes mechanistic studies difficult, and little is known of its pathogenesis for certain. Circumstantial evidence suggests that most, but not all, IDILI is caused by reactive metabolites of drugs that are bioactivated by cytochromes P450 and other enzymes in the liver. Additionally, there is overwhelming evidence that most IDILI is mediated by the adaptive immune system; one example being the association of IDILI caused by specific drugs with specific human leukocyte antigen (HLA) haplotypes, and this may in part explain the idiosyncratic nature of these reactions. The T cell receptor repertoire likely also contributes to the idiosyncratic nature. Although most of the liver injury is likely mediated by the adaptive immune system, specifically cytotoxic CD8+ T cells, adaptive immune activation first requires an innate immune response to activate antigen presenting cells and produce cytokines required for T cell proliferation. This innate response is likely caused by either a reactive metabolite or some form of cell stress that is clinically silent but not idiosyncratic. If this is true it would make it possible to study the early steps in the immune response that in some patients can lead to IDILI. Other hypotheses have been proposed, such as mitochondrial injury, inhibition of the bile salt export pump, unfolded protein response, and oxidative stress although, in most cases, it is likely that they are also involved in the initiation of an immune response rather than representing a completely separate mechanism. Using the clinical manifestations of liver injury from a number of examples of IDILI-associated drugs, this review aims to summarize and illustrate these mechanistic hypotheses.

Drug hypersensitivity in children: a retrospective analysis of 101 pharmacovigilance reports

Our objective was to describe and discuss management of recent cases of drug hypersensitivity in children reported in a pharmacovigilance center. Two pediatric allergy units conducted a collaborative retrospective analysis of 101 adverse drug reactions reported to a regional pharmacovigilance center between January 2016 and July 2019. Time lapse between hypersensitivity reaction onset and allergy consultation varied from 1 month to 12 years. Sixty-two patients (61.4%) presented with immediate reactions, 11 (10.9%) with non-immediate reactions, and 28 (27.7%) had reactions impossible to classify through medical interview. Overall, 92 children (91%) were explored for simultaneously administered drugs. All 113 prick tests were negative, and 2 were uncertain. Among 108 intradermal tests, 2 were positive to penicillin and to an iodinated contrast medium, 105 were negative, and 1 was uncertain. Overall, 129 drug provocation tests were proposed. Nine provocation tests among 80 were positive (11.25%): 6 to penicillin, 1 to sulfonamide antibiotics, and 2 to non-steroidal anti-inflammatory drugs; the remaining 71 were negative. No severe reaction was observed during these tests. Finally, drug allergy was only retained in 11 reported cases (10.9%).Conclusion: These pharmacovigilance reports show the difficulty in defining drug allergy in children only by anamnesis, and that explorations, particularly provocation tests, should take place at a reasonable time lapse after drug hypersensitivity reaction onset. What is Known: • True drug allergy is rarely observed in children. • Absence of full workup leads to falsely labeling children as "allergic." What is New: • Short time lapse between hypersensitivity onset and consultation improves classification of pediatric allergy. • Timely allergy consultations are essential, and tests are useful to confirm or exclude pediatric allergy.

Updates and Insights in the Diagnosis and Management of DRESS Syndrome

PURPOSE OF REVIEW

To provide updates on recent advances in the diagnosis and management of drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome.

RECENT FINDINGS

The number of identified HLA allele associations with DRESS continues to grow. There is increasing evidence indicating viral infection, reactivation, and cross-reactivity may play key roles in disease. Translational work illuminated JAK/STAT activation in recalcitrant disease. There is expanding recognition of rapid-onset DRESS resulting from specific drugs.

SUMMARY

DRESS is a severe form of adverse drug reaction with potential for significant morbidity and mortality. Recent research advances may improve clinical care. HLA screening can now be performed to prevent disease in susceptible patients and may help identify culprit drugs in the near future. Viral testing should be performed on every patient, and if positive, patients potentially treated with antiviral therapy. JAK inhibitors may be an effective treatment option for DRESS. Early onset of disease relative to drug exposure should not exclude the diagnosis of DRESS.

Mechanisms of Severe Cutaneous Adverse Reactions: Recent Advances

Cutaneous adverse drug reactions are unpredictable and include various different skin conditions of varying degrees of severity. The most concerning are usually referred to as severe cutaneous adverse reactions (SCARs) and include acute generalized exanthematous pustulosis (AGEP), drug reaction with eosinophilia and systemic symptoms (DRESS), also known as drug-induced hypersensitivity syndrome (DiHS) or hypersensitivity syndrome (HSS), Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). All are delayed type IV hypersensitivity reactions in which a T-cell-mediated drug-specific immune response is responsible for causing the disease. Nonetheless, specific T-cell subpopulations develop in response to certain environmental conditions and produce cytokines that orchestrate the various phenotypes. Cytotoxic T lymphocytes (CTLs), T-helper type 1 (Th1), Th2, Th17, and regulatory T cells (Treg), among other T-cell subpopulations, participate in the development of SCAR phenotypes. Cell subpopulations belonging to the innate immune system, comprising natural killer cells, innate lymphoid cells, monocytes, macrophages and dendritic cells, can also participate in shaping specific immune responses in various clinical conditions. Additionally, tissue-resident cells, including keratinocytes, can contribute to epidermal damage by secreting chemokines that attract pro-inflammatory immunocytes. The final phenotypes in each clinical entity result from the complex interactions between a variety of cell lineages, their products, soluble mediators and genetic and environmental factors. Although the pathophysiology of these reactions is not fully understood, intensive research in recent years has led to major progress in our understanding of the contribution of certain cell types and soluble mediators to the variability of SCAR phenotypes.

Hypersensitivity Reactions: An Everyday Occurrence in Pediatric Allergy Clinics

The explanation of hypersensitivity reactions has long relied on the classification of Gell and Coombs, originally proposed in the 1960s. However, their concepts were predated by other authors by at least 50 years. A 21st century pediatric allergy clinic provides multiple examples of these basic concepts on a daily basis. We review classic and less classic examples of the original criteria, highlight where current disease pathophysiology does not always fit the original model, and provide updated language for common and uncommon immunologically driven hypersensitivity diseases.

Understanding Idiosyncratic Toxicity: Lessons Learned from Drug-Induced Liver Injury

Idiosyncratic adverse drug reactions (IADRs) encompass a diverse group of toxicities that can vary by drug and patient. The complex and unpredictable nature of IADRs combined with the fact that they are rare makes them particularly difficult to predict, diagnose, and treat. Common clinical characteristics, the identification of human leukocyte antigen risk alleles, and drug-induced proliferation of lymphocytes isolated from patients support a role for the adaptive immune system in the pathogenesis of IADRs. Significant evidence also suggests a requirement for direct, drug-induced stress, neoantigen formation, and stimulation of an innate response, which can be influenced by properties intrinsic to both the drug and the patient. This Perspective will provide an overview of the clinical profile, mechanisms, and risk factors underlying IADRs as well as new approaches to study these reactions, focusing on idiosyncratic drug-induced liver injury.

An Update on the Immunological, Metabolic and Genetic Mechanisms in Drug Hypersensitivity Reactions

Drug hypersensitivity reactions (DHRs) represent a major burden on the healthcare system since their diagnostic and management are complex. As they can be influenced by individual genetic background, it is conceivable that the identification of variants in genes potentially involved could be used in genetic testing for the prevention of adverse effects during drug administration. Most genetic studies on severe DHRs have documented HLA alleles as risk factors and some mechanistic models support these associations, which try to shed light on the interaction between drugs and the immune system during lymphocyte presentation. In this sense, drugs are small molecules that behave as haptens, and currently three hypotheses try to explain how they interact with the immune system to induce DHRs: the hapten hypothesis, the direct pharmacological interaction of drugs with immune receptors hypothesis (p-i concept), and the altered self-peptide repertoire hypothesis. The interaction will depend on the nature of the drug and its reactivity, the metabolites generated and the specific HLA alleles. However, there is still a need of a better understanding of the different aspects related to the immunological mechanism, the drug determinants that are finally presented as well as the genetic factors for increasing the risk of suffering DHRs. Most available information on the predictive capacity of genetic testing refers to abacavir hypersensitivity and anticonvulsants-induced severe cutaneous reactions. Better understanding of the underlying mechanisms of DHRs will help us to identify the drugs likely to induce DHRs and to manage patients at risk.

Adverse Drug Reactions Across the Age Continuum: Epidemiology, Diagnostic Challenges, Prevention, and Treatments

Adverse drug reactions (ADRs) are common and important complications of drug therapy for children. The risk for ADRs changes over childhood, as do the nature and types of ADRs. Importantly, the risk and nature of ADRs in children are markedly different from those of adults, and adult data cannot be relied on to guide safe drug therapy in children. There are groups of children, notably those with complex and chronic diseases, who are at substantial risk for ADRs. The evaluation of an undesired effect during therapy is ideally accomplished by an organized approach that is a skill that clinicians who care for children-especially those children at high risk for ADRs must have. Additionally, clinicians as well as drug regulatory agencies and industry need to be both vigilant and astute as well as aware that ADRs in children are often different in nature and frequency from those in adults. The increasing use of pharmacogenomics to guide drug dosing and the increasing number of biological agents will provide new sets of challenges to clinicians over the next decade.

Adaptive immune cells in calcific aortic valve disease

Calcific aortic valve disease (CAVD) is highly prevalent and has no pharmaceutical treatment. Surgical replacement of the aortic valve has proved effective in advanced disease but is costly, time limited, and in many cases not optimal for elderly patients. This has driven an increasing interest in noninvasive therapies for patients with CAVD. Adaptive immune cell signaling in the aortic valve has shown potential as a target for such a therapy. Up to 15% of cells in the healthy aortic valve are hematopoietic in origin, and these cells, which include macrophages, T lymphocytes, and B lymphocytes, are increased further in calcified specimens. Additionally, cytokine signaling has been shown to play a causative role in aortic valve calcification both in vitro and in vivo. This review summarizes the physiological presence of hematopoietic cells in the valve, innate and adaptive immune cell infiltration in disease states, and the cytokine signaling pathways that play a significant role in CAVD pathophysiology and may prove to be pharmaceutical targets for this disease in the near future.

Clinical features, outcomes and treatment in children with drug induced Stevens-Johnson syndrome and toxic epidermal necrolysis

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), which can be considered a late-onset allergic reaction, can cause serious long-term sequelae. SJS/TEN are considered a spectrum of life-threatening adverse drug reactions. They have the same clinical manifestations and the only difference is in the extent of epidermal detachment. These conditions are associated with high mortality, although incidence of SJS/TEN is rare in children. SJS/TEN is an adverse drug reaction influenced by genes that involve pharmacokinetics, pharmacodynamics and immune response. Infective agents are additional influencing factors. Anticonvulsants and antibiotics, and especially sulphonamides and non-steroidal anti-inflammatory drugs, are among the drugs that were predominantly suspected of triggering SJS/TEN. No evidence-based standardized treatment guidelines for SJS or TEN are currently available. The usual treatment is mainly founded on the withdrawal of the suspected causative agent and supportive therapy. In pediatric patients, the specific therapeutic strategies are controversial and comprise systemic corticosteroids and the use of intravenous immunoglobulin (IVIG). More recently, new therapeutic approaches have been used, such as immunosuppressive therapies, including cyclosporine and TNF-α inhibitors. (www.actabiomedica.it)

Antibiotic allergy

Antibiotics are the commonest cause of life-threatening immune-mediated drug reactions that are considered off-target, including anaphylaxis, and organ-specific and severe cutaneous adverse reactions. However, many antibiotic reactions documented as allergies were unknown or not remembered by the patient, cutaneous reactions unrelated to drug hypersensitivity, drug-infection interactions, or drug intolerances. Although such reactions pose negligible risk to patients, they currently represent a global threat to public health. Antibiotic allergy labels result in displacement of first-line therapies for antibiotic prophylaxis and treatment. A penicillin allergy label, in particular, is associated with increased use of broad-spectrum and non-β-lactam antibiotics, which results in increased adverse events and antibiotic resistance. Most patients labelled as allergic to penicillins are not allergic when appropriately stratified for risk, tested, and re-challenged. Given the public health importance of penicillin allergy, this Review provides a global update on antibiotic allergy epidemiology, classification, mechanisms, and management.

Cephalosporin Allergy: Current Understanding and Future Challenges

Cephalosporins are commonly used antibiotics both in hospitalized patients and in outpatients. Hypersensitivity reactions to cephalosporins are becoming increasingly common with a wide range of immunopathologic mechanisms. Cephalosporins are one of the leading causes for perioperative anaphylaxis and severe cutaneous adverse reactions. Patients allergic to cephalosporins tend to tolerate cephalosporins with disparate R1 side chains but may react to other beta-lactams with common R1 side chains. Skin testing for cephalosporins has not been well validated but appears to have a good negative predictive value for cephalosporins with disparate R1 side chains. In vitro tests including basophil activation tests have lower sensitivity when compared with skin testing. Rapid drug desensitization procedures are safe and effective and have been used successfully for immediate and some nonimmediate cephalosporin reactions. Many gaps in knowledge still exist regarding cephalosporin hypersensitivity.

[Three keys to the appropriate choice of oral antibiotic treatment in the respiratory tract infections]

Exacerbation of chronic obstructive pulmonary disease and community-acquired pneumonia are the most frequent infections of the lower respiratory tract in daily clinical practice. Antibiotic selection is a crucial component in its treatment and, in most cases, it is performed empirically. Scientific societies make therapeutic recommendations based on scientific evidence and / or expert recommendations that are of great help to clinicians. Beta-lactams, fluoroquinolones and macrolides are the most commonly used drugs for oral administration. From a practical point of view, there are three keys to the appropriate choice of oral antibiotic treatment, which are the effectiveness, safety and the ecological impact on the patient's microbiota, including the development of resistance, which will be assessed in depth in this review.

Controversies in drug allergy: Testing for delayed reactions

Controversies exist with regard to in vivo approaches to delayed immunologically mediated adverse drug reactions, such as exanthem (maculopapular eruption), drug reaction with eosinophilia and systemic symptoms, acute generalized exanthematous pustulosis, Stevens-Johnson syndrome/toxic epidermal necrolysis, and fixed drug eruptions. In particular, widespread differences exist between regions and practice on the availability and use of intradermal and patch testing, the standard drug concentrations used, the use of additional drugs in intradermal and patch testing to help determine cross-reactivity, the timing of testing in relation to the occurrence of the adverse drug reaction, the use of testing in specific phenotypes, and the use of oral challenge in conjunction with delayed intradermal and patch testing to ascertain drug tolerance. It was noted that there have been advances in the science of delayed T cell-mediated reactions that have shed light on immunopathogenesis and provided a mechanism of preprescription screening in the case of HLA-B*57:01 and abacavir hypersensitivity and HLA-B*15:02 and carbamazepine Stevens-Johnson syndrome/toxic epidermal necrolysis in Southeast Asian subjects. Future directions should include the collaboration of large international networks to develop and standardize in vivo diagnostic approaches, such as skin testing and patch testing, combined with ex vivo and in vitro laboratory approaches.

Applications of Immunopharmacogenomics: Predicting, Preventing, and Understanding Immune-Mediated Adverse Drug Reactions

Adverse drug reactions (ADRs) are a significant health care burden. Immune-mediated adverse drug reactions (IM-ADRs) are responsible for one-fifth of ADRs but contribute a disproportionately high amount of that burden due to their severity. Variation in human leukocyte antigen ( HLA) genes has emerged as a potential preprescription screening strategy for the prevention of previously unpredictable IM-ADRs. Immunopharmacogenomics combines the disciplines of immunogenomics and pharmacogenomics and focuses on the effects of immune-specific variation on drug disposition and IM-ADRs. In this review, we present the latest evidence for HLA associations with IM-ADRs, ongoing research into biological mechanisms of IM-ADRs, and the translation of clinical actionable biomarkers for IM-ADRs, with a focus on T cell-mediated ADRs.

NEW STRATEGIES TO PREDICT AND PREVENT SERIOUS IMMUNOLOGICALLY MEDIATED ADVERSE DRUG REACTIONS

Preventive efforts for serious immunologically mediated adverse drug reactions (IM-ADRs) have been fueled by discovery of strong class I human leukocyte antigen (HLA) associations; however, the low positive predictive value of HLA for IM-ADRs has limited translation. Studies were undertaken to explain why most patients carrying an HLA risk allele do not develop IM-ADR on exposure to the risk drug. Tissue-specific approaches defined the T-cell receptor (TCR) repertoire and phenotype of the pathogenic T cells found in the skin and blister fluid of IM-ADRs. Dominant CD8+ T cell clonotypes representing >50% of total TCRαβ sequences among CD8+ CD137+ T cells were identified in tissue to identify the pathogenic activated T cells. Identification of the specific molecular and cellular signatures of the antigen-driven pathogenic T cells will facilitate more specific mechanisms to determine the small percentage of individuals carrying an HLA risk allele who are likely to develop an IM-ADR before drug exposure.