In Vitro Testing for the Diagnosis of Anticonvulsant Hypersensitivity Syndrome: A Systematic Review

Vesiculopustular drug reaction with eosinophilia and systemic symptoms induced by levetiracetam

Drug reaction with eosinophilia and systemic symptoms (DRESS) is a severe cutaneous adverse reaction characterised by fever, lymphadenopathy, morbilliform rash, haematologic abnormalities, and multiorgan involvement. Herein, we describe a 32-year-old female presenting with a 9-day history of facial oedema, cervical and inguinal lymphadenopathy, and a pruritic rash comprised of vesicles and pustules on her face, trunk, and extremities. Her only medications were valproate, which she had been taking for several years, and levetiracetam, which was initiated 41 days prior to rash onset. On the 16th day of her rash, she was diagnosed with DRESS induced by levetiracetam (Registry of Severe Cutaneous Adverse Reactions: 5). At this point, her absolute eosinophil count was 0.9 × 109 cells/L and aspartate and alanine transaminase levels were 357 and 339 U/L, respectively. Pustules with a morbilliform rash may occur in up to 30% of DRESS cases. In rarer instances, as in our patient, DRESS can present with isolated pustules and vesicles. Similarly, although rare, DRESS can be induced by levetiracetam.

Effects of species of origin and mode of induction of microsomes on carbamazepine-induced cell toxicity

Standardization and validation of in vitro drug metabolism is essential for pre-clinical drug development as well as for in vitro toxicity assays including the lymphocyte toxicity assay (LTA) and the in vitro platelet toxicity assay (iPTA). Use of isolated liver microsomes (MIC) in in vitro testing has been utilized for a long time; however, the effect of species of origin and induction agents on the metabolic capacities of MIC is not adequately evaluated. In this study we investigated the impact of species of origin and induction agent on the capacity of MICs to bioactivate carbamazepine (CBZ) using cytotoxicity as a gross endpoint to measure the levels of cytotoxic metabolites generated by each type of MICs. Jurkat E6.1 cell line was used and MICs from human, rat, mouse, minipig and rabbit origin as well as rat MICs that is either non-induced or induced by phenobarbitone (PHB), dexamethasone (DEXA), 3-methylcholanthrene (3MC), clofibrate (CLOF) and isoniazid (INH) were investigated. MICs from minipig and rat MICs induced with 3MC exhibited the highest capacity to produce cytotoxic metabolites of CBZ. These findings will help optimize and standardize in vitro toxicity assays and provide guidance to pre-clinical investigation of drugs.

Tools for Etiologic Diagnosis of Drug-Induced Allergic Conditions

Drug hypersensitivity reactions are a serious concern in clinical practice because they can be severe and result in lifelong sequelae. An accurate diagnosis and identification of the culprit drug is essential to prevent future reactions as well as for the identification of safe treatment alternatives. Nonetheless, the diagnosis can be challenging. In vivo and in vitro tests can be helpful, although none are conclusive; therefore, the tests are not usually performed in isolation but as part of a diagnostic algorithm. In addition, some in vitro tests are only available in research laboratories, and standardization has not been fully accomplished. Collaborating research is needed to improve drug hypersensitivity reaction diagnosis. In this review, we update the current available in vivo and in vitro tools with their pros and cons and propose an algorithm to integrate them into clinical practice.

Novel insights into molecular and cellular aspects of delayed drug hypersensitivity reactions

INTRODUCTION

Delayed drug hypersensitivity reactions (DDHRs) represent a major health problem. They are unpredictable and can cause life-long disability or even death. The pathophysiology of DDHRs is complicated, multifactorial, and not well understood mainly due to the lack of validated animal models or in vitro systems. The role of the immune system is well demonstrated but its exact pathophysiology still a matter of debate.

AREA COVERED

This review summarizes the current understanding of DDHRs pathophysiology and abridges the available new evidence supporting each hypothesis. A comprehensive literature search for relevant publications was performed using PubMed, Google Scholar, and Medline databases with no date restrictions and focusing on the most recent 10 years.

EXPERT OPINION

Although multiple milestones have been achieved in our understanding of DDHRs pathophysiology as a result of the development of useful experimental models, many questions are yet to be fully answered. A deeper understanding of the mechanistic basis of DDHRs would not only facilitate the development of robust and reliable diagnostic assays for diagnosis, but would also inform therapy by providing specific target(s) for immunomodulation and potentially permit pre-therapeutic risk assessment to pursue the common goal of safe and effective drug therapy.

Drug Hypersensitivity Reactions in Patients with Cystic Fibrosis: Potential Value of the Lymphocyte Toxicity Assay to Assess Risk

BACKGROUND

Cystic fibrosis (CF) is a genetic disease characterized by multi-system dysfunction resulting in recurrent lung infections and progressive pulmonary disease. CF patients are at a higher risk for drug hypersensitivity reactions (DHRs) compared to the general population, which has been attributed to the recurrent need for antibiotics and the inflammation associated with CF disease. In vitro toxicity tests such as the lymphocyte toxicity assay (LTA) offer the potential for risk assessment for DHRs. In the current study, we investigated the utility of the LTA test for diagnosis of DHRs in a cohort of CF patients.

METHOD

Twenty CF patients with suspected DHRs to sulfamethoxazole, penicillins, cephalosporins, meropenem, vancomycin, rifampicin, and tobramycin were recruited to this study and tested using the LTA test along with 20 healthy control volunteers. Demographic data of the patients, including age, sex, and medical history, were obtained. Blood samples were withdrawn from patients and healthy volunteers, and the LTA test was performed on isolated peripheral blood monocytes (PBMCs) from those individuals.

RESULTS

Cells from CF patients with DHRs displayed a significant (p < 0.0001) concentration-dependent enhanced cell death upon incubation with the culprit drug compared to cells from healthy volunteers. The positivity rate of the LTA test was over 80% in patients with a medical history and clinical presentation consistent with DHRs.

CONCLUSION

This study is the first to evaluate the use of the LTA test for diagnosis of DHRs in CF patients. According to our results, the LTA test may be a useful tool for diagnosis and management of DHRs in CF patients. Identifying the culprit drug is essential for optimal healthcare for CF patients in the setting of a suspected DHR. The data also provide evidence that accumulation of toxic reactive metabolites could be an important component in the cascade of events leading to the development of DHRs in CF patients. A larger-scale study is needed to confirm the data.

Bridging the gap between bench and clinic: the importance of understanding the mechanism of iodinated contrast media hypersensitivity

Since the advent of CT, iodinated contract media (ICM) has become one of the most regularly administered intravenous medications in clinical settings. Although considered generally safe, ICM is one of the most common causes of adverse drug reactions in clinical practice, accounting for more than 2 million adverse reactions worldwide. Currently, there are few useful tools to diagnose patient hypersensitivity, with the major limitation being the lack of consensus regarding the mechanisms of hypersensitivity to ICM. While there is an overwhelming abundance of literature pertaining to clinical features including incidence, symptomatology, and risk, few studies have further investigated the underlying mechanisms behind their clinical observations. Of the available literature discussing pathophysiology, most primary studies were completed over 20 years ago, since which the molecular characteristics of ICM have changed. Furthermore, many reviews mentioning pathophysiology fail to adequately emphasize the clinical importance of understanding the molecular pathways involved in hypersensitivity. In this review, we aim to emphasize the clinical relevance of pathophysiology as it relates to the prediction and diagnosis of hypersensitivity reactions to ICM. To this end, we will first briefly characterize hypersensitivity reactions to ICM with respect to epidemiology and clinical presentation. We will then present the existing evidence supporting various proposed mechanisms of hypersensitivity, highlighting the gaps that remain in the mechanistic delineation of both immediate and delayed reactions. Finally, we discuss the possibility of in vitro testing as a way to predict and diagnose hypersensitivity reactions, pending a more complete elucidation of mechanisms.

The role of in vitro testing in pharmacovigilance for ß-lactam-induced serum sickness-like reaction: A pilot study

Background: Current pharmacovigilance (PV) methods for detection of adverse drug reactions (ADRs) fail to capture rare immune-mediated drug hypersensitivity reactions (DHRs) due to their scarcity and the lack of clear diagnostic criteria. Drug-induced serum sickness-like reactions (SSLRs) are rare type of DHRs that occur in susceptible patients 1–3 weeks after exposure to the culprit drug with ß-lactam antibiotics being the most associated drugs. The diagnosis of drug induced SSLR is difficult due to the lack of safe and reliable diagnostic tests for identifying the culprit drug. The lymphocyte toxicity assay (LTA) is an in vitro test used as a diagnostic tool for drug hypersensitivity reactions (DHRs).

Objective: To evaluate the role of the LTA test for diagnosing and capturing SSLR due to ß-lactam antibiotics in a cohort of patients.

Methods: Patients were recruited from patients referred to the Drug Hypersensitivity Clinic at Clinic at London Health Science Centre with suspicion of drug allergy. Twenty patients (10 males and 10 females) were selected to be tested to confirm diagnosis. Demographic data was collected form the patents and blood samples were withdrawn from all patients and from 20 healthy controls. The LTA test was performed on all subjects and data is expressed as percentage increase in cell death compared to control (vehicle without the drug).

Results: In the result of LTA tests performed on samples from the selected 20 patients. There was a significant (p < 0.05) concentration-dependent increase in cell death in cells isolated from patients as compared to cells from healthy controls when incubated with the drug in the presence of phenobarbitone-induced rat liver microsomes.

Conclusion: Giving its safety and good predictive value the LTA test has very strong potential to be a useful diagnostic tool for ß-lactam-induced SSLR. The test procedure is relatively simple and not overly costly. Further studies including other drug classes are needed to evaluate the utility of the LTA test for SSLR due to other drugs.

Model Based Evaluation of Hypersensitivity Adverse Drug Reactions to Antimicrobial Agents in Children

Drug use in children is-in most cases-supported by extrapolation of data generated from clinical trials in adult populations. This puts children at higher risk of developing adverse drug reactions (ADRs) due to "off-label" use of drugs and dosing issues. Major types of ADRs are drug hypersensitivity reactions, an idiosyncratic type of ADRs that are largely unpredictable and can cause high morbidity and mortality in a hard-to-identify specific population of patients. Lack of a complete understanding of the pathophysiology of DHRs and their unpredictive nature make them problematic in clinical practice and in drug development. In addition, ethical and legal obstacles hinder conducting large clinical trials in children, which in turn make children a "therapeutic orphan" where clear clinical guidelines are lacking, and practice is based largely on the personal experience of the clinician, hence making modeling desirable. This brief review summarizes the current knowledge of model-based evaluation of diagnosis and management of drug hypersensitivity reactions (DHRs) to antimicrobial drugs in the pediatric population. Ethical and legal aspects of drug research in children and the effect of different stages of child development and other factors on the risk of DHRs are discussed. The role of animal models, in vitro models and oral provocation test in management of DHRs are examined in the context of the current understanding of the pathophysiology of DHRs. Finally, recent changes in drug development legislations have been put forward to encourage drug developers to conduct trials in children clearly indicate the urgent need for evidence to support drug safety in children and for modeling to guide these clinical trials.

Role of Oxidative Stress in Hypersensitivity Reactions to Sulfonamides

Antimicrobial sulfonamides are important medications. However, their use is associated with major immune-mediated drug hypersensitivity reactions with a rate that ranges from 3% to 4% in the general population. The pathophysiology of sulfa-induced drug hypersensitivity reactions is not well understood, but accumulation of reactive metabolites (sulfamethoxazole [SMX] hydroxylamine [SMX-HA] and SMX N-nitrosamine [SMX-NO]) is thought to be a major factor. These reactive metabolites contribute to the formation of reactive oxygen species (ROS) known to cause cellular damage and induce cell death through apoptosis and necroptosis. ROS can also serve as "danger signals," priming immune cells to mount an immunological reaction. We recruited 26 sulfa-hypersensitive (HS) patients, 19 healthy control subjects, and 6 sulfa-tolerant patients to this study. Peripheral blood monocytes and platelets were isolated from blood samples and analyzed for in vitro cytotoxicity, ROS and carbonyl protein formation, lipid peroxidation, and GSH (glutathione) content after challenge with SMX-HA. When challenged with SMX-HA, cells isolated from sulfa-HS patients exhibited significantly (P ≤ .05) higher cell death, ROS and carbonyl protein formation, and lipid peroxidation. In addition, there was a high correlation between cell death in PBMCs and ROS levels. There was also depletion of GSH and lower GSH/GSSG ratios in peripheral blood mononuclear cells from sulfa-HS patients. The amount of ROS formed was negatively correlated with intracellular GSH content. The data demonstrate a major role for oxidative stress in in vitro cytotoxicity of SMX reactive metabolites and indicate increased vulnerability of cells from sulfa-HS patients to the in vitro challenge.

Recent advances in the understanding of severe cutaneous adverse reactions

Severe cutaneous adverse reactions (SCARs) encompass a heterogeneous group of delayed hypersensitivity reactions, which are most frequently caused by drugs. Our understanding of several aspects of SCAR syndromes has evolved considerably over the last decade. This review explores evolving knowledge of the immunopathogenic mechanisms, pharmacogenomic associations, in vivo and ex vivo diagnostics for causality assessment, and medication cross-reactivity data related to SCAR syndromes. Given the rarity and severity of these diseases, multidisciplinary collaboration through large international, national and/or multicentre networks to collect prospective data on patients with SCAR syndromes should be prioritized. This will further enhance a systematized framework for translating epidemiological, clinical and immunopathogenetic advances into preventive efforts and improved outcomes for patients.

In vitro testing for diagnosis of idiosyncratic adverse drug reactions: Implications for pathophysiology

Idiosyncratic drug reactions (IDRs) represent a major health problem, as they are unpredictable, often severe and can be life threatening. The low incidence of IDRs makes their detection during drug development stages very difficult causing many post-marketing drug withdrawals and black box warnings. The fact that IDRs are always not predictable based on the drug's known pharmacology and have no clear dose-effect relationship with the culprit drug renders diagnosis of IDRs very challenging, if not impossible, without the aid of a reliable diagnostic test. The drug provocation test (DPT) is considered the gold standard for diagnosis of IDRs but it is not always safe to perform on patients. In vitro tests have the advantage of bearing no potential harm to patients. However, available in vitro tests are not commonly used clinically because of lack of validation and their complex and expensive procedures. This review discusses the current role of in vitro diagnostic testing for diagnosis of IDRs and gives a brief account of their technical and mechanistic aspects. Advantages, disadvantages and major challenges that prevent these tests from becoming mainstream diagnostic tools are also discussed here.

Hypersensitivity to antiepileptic drugs

Adverse reactions to antiepileptic drugs (AEDs) may lead to treatment failure, morbidity, and mortality. Drug hypersensitivity reactions (DHRs) are potentially fatal. AED DHRs present with a variety of clinical manifestations. The pathogenesis of AED DHRs has not been fully elucidated. Bioactivation, detoxification, covalent adduct formation, presentation to the immune system, and consequent formation of antibody and T-cell immune effectors have been suggested. This article summarizes the epidemiology, pathogenic mechanisms, risk factors, clinical features, and management of allergic reactions to the aromatic AEDs carbamazepine, phenytoin, and lamotrigine.

New ways to detect adverse drug reactions in pediatrics

Adverse drug reactions (ADRs) complicate at least 5% of all courses of therapy for children. Dealing with an ADR requires a stepwise approach in appreciation of the possibility of an ADR, assessment of whether the adverse event in question is drug-related, assessment of causality, assistance in treating the symptoms of the ADR, and dealing with the aftermath of the event. Several new developments likely will improve the ability to assess, evaluate, treat, and prevent ADRs in children. These developments include tools to evaluate causality, laboratory tests to diagnose ADRs, pharmacogenomic approaches to prevent ADRs, and new insights into treating serious ADRs.

Safety assessment in pediatric studies

It typically takes many years before an association of a drug with a rare, serious adverse reaction is established. As related to pediatric drug use, evidence is even more erratic, as most drugs are used off labels. To enhance child safety, there is an urgent need to develop robust and rapid methods to identify such associations in as timely a manner as possible. In this chapter, several novel methods, both clinically based pharmacoepidemiological approaches and laboratory-based methods, are described.

Antiepileptic drugs and the immune system

Data on the effects of antiepileptic drugs on the immune system are frequently inconsistent and sometimes conflicting because the effects of drugs cannot be separated from those of seizures, first-generation drugs have been most intensively investigated, the patient's genetic background, the mechanism of action and the pharmacokinetic profile of AEDs and the concurrent use of immunosuppressant drugs may act as confounders. Valproate, carbamazepine, phenytoin, vigabatrin, levetiracetam, and diazepam have been found to modulate the immune system activity by affecting humoral and cellular immunity. AEDs are associated with pharmacokinetic interactions (most frequently occurring with carbamazepine, phenytoin, phenobarbital and valproate). Hepatic metabolism is the primary site of interaction for both AEDs and immunotherapies (ACTH, dexamethasone, hydrocortisone, methylprednisolone, cyclophosphamide, methotrexate, rituximab), which entail induction or inhibition of drug effects. However, the clinical importance of these drug interactions is still far from defined. An important adverse effect of the action of AEDs on the immune system is antiepileptic hypersensitivity syndrome (AHS), a life-threatening, idiosyncratic cutaneous reaction to aromatic AEDs resulting in end organ damage. Phenytoin, carbamazepine, phenobarbital, lamotrigine, oxcarbazepine, felbamate, and zonisamide have been implicated. The pathogenic mechanisms of AHS are incompletely understood.

Pathogenesis and Clinical Approaches to Anticonvulsant Hypersensitivity Syndrome: Current State of Knowledge

Anticonvulsant hypersensitivity syndrome (AHS) is a rare, but severe and potentially fatal, adverse reaction that occurs in patients who are treated with commonly used older anticonvulsant drugs (phenytoin, carbamazepine and phenobarbital) and/or with some newer agents (lamotrigine). Paediatric patients are at an increased risk for the development of AHS for the higher incidence of seizure disorder in the first decade of life. Hypersensitivity reactions range from simple maculopapular skin eruptions to a severe life-threatening disorder. AHS is typically associated with the development of skin rash, fever and internal organ dysfunctions. Recent evidence suggests that AHS is the result of a chemotoxic and immunologically-mediated injury, characterized by skin and mucosal bioactivation of antiepileptic drugs and by major histocompatibility complex-dependent clonal expansion of T cells. Early recognition of AHS and withdrawal of anticonvulsant therapy are essential for a successful outcome. In vivo and vitro tests can be helpful for the diagnosis that actually depends essentially on clinical recognition.

Predictive value of the lymphocyte toxicity assay in the diagnosis of drug hypersensitivity syndrome

BACKGROUND

Drug hypersensitivity syndrome (DHS) is a rare but potentially fatal adverse drug reaction that develops in susceptible patients following exposure to certain drugs. Because of the variable clinical picture of DHS and its resemblance to other diseases, the diagnosis of DHS is challenging. The lymphocyte toxicity assay (LTA) is an in vitro test that has been used in the diagnosis of DHS. However, its predictive values are still controversial because of the lack of a 'gold standard' test to measure it against.

OBJECTIVES

To determine the sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of the LTA in the diagnosis of DHS due to different classes of drugs, based on systemic re-exposure as a gold standard, and to evaluate the current clinical utility of the LTA in clinical practice.

METHODS

Potential participants were identified from their medical records and contacted to obtain their consent to participate in the study. One hundred forty-seven patients were recruited and interviewed by telephone to identify events of re-exposure and their consequences. These data were used to determine true positive, false positive, true negative, and false negative results of the test, which were then used to estimate the predictive value of the test.

RESULTS

We identified 26 re-exposure events in 22 patients: 4 were true positives, 17 were true negatives, 1 was a false positive, and 4 were false negatives, as determined by systemic re-exposure. Although the number of identified re-exposures limited the ability to calculate the predictive values, our data provide an estimate of the clinical value of the test for the diagnosis of DHS. The data also highlight the effect of the type of drug involved in the reaction on the predictive value of the test.

CONCLUSION

The LTA is potentially a valuable diagnostic tool for DHS; however, its sensitivity, specificity, NPV, and PPV seem to vary according to the drug involved in the reaction.

Drug Induced Hypersensitivity and the HLA Complex

Drug-induced hypersensitivity reactions are of major concern and present a burden for national healthcare systems due to their often severe nature, high rate of hospital admissions and high mortality. They manifest with a wide range of symptoms and signs, and can be initiated by a wide range of structurally diverse chemical compounds. The pathophysiological mechanisms underlying hypersensitivity reactions are not well understood, but it is thought that they are immune mediated. MHC region on Chromosome 6 contains many genes with immune function. Classical MHC molecules are highly polymorphic cell surface glycoproteins whose function is to present peptide antigens to T cells. In addition to conferring protection from some diseases, HLA alleles are also associated with an increased risk of other diseases, including drug-induced hypersensitivity. Pharmacogenetic approach to predict the risk of drug-induced hypersensitivity has been established for several drugs. We will discuss the progress of hypersensitivity pharmacogenetics over the last few years and focus on current efforts of the international community to develop consortia which aim to standardize disease phenotypes and to identify affected individuals through international collaborations. In addition, we will discuss the clinical utility of HLA typing as predictive or diagnostic testing for drug-induced hypersensitivity.