Drug metabolite-specific lymphocyte responses in sulfamethoxazole allergic patients with cystic fibrosis

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.

HLA Allele-Restricted Immune-Mediated Adverse Drug Reactions: Framework for Genetic Prediction

Human leukocyte antigen (HLA) is a hallmark genetic marker for the prediction of certain immune-mediated adverse drug reactions (ADRs). Numerous basic and clinical research studies have provided the evidence base to push forward the clinical implementation of HLA testing for the prevention of such ADRs in susceptible patients. This review explores current translational progress in using HLA as a key susceptibility factor for immune ADRs and highlights gaps in our knowledge. Furthermore, relevant findings of HLA-mediated drug-specific T cell activation are covered, focusing on cellular approaches to link genetic associations to drug-HLA binding as a complementary approach to understand disease pathogenesis. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

In-Vitro Approaches to Predict and Study T-Cell Mediated Hypersensitivity to Drugs

Mitigating the risk of drug hypersensitivity reactions is an important facet of a given pharmaceutical, with poor performance in this area of safety often leading to warnings, restrictions and withdrawals. In the last 50 years, efforts to diagnose, manage, and circumvent these obscure, iatrogenic diseases have resulted in the development of assays at all stages of a drugs lifespan. Indeed, this begins with intelligent lead compound selection/design to minimize the existence of deleterious chemical reactivity through exclusion of ominous structural moieties. Preclinical studies then investigate how compounds interact with biological systems, with emphasis placed on modeling immunological/toxicological liabilities. During clinical use, competent and accurate diagnoses are sought to effectively manage patients with such ailments, and pharmacovigilance datasets can be used for stratification of patient populations in order to optimise safety profiles. Herein, an overview of some of the in-vitro approaches to predict intrinsic immunogenicity of drugs and diagnose culprit drugs in allergic patients after exposure is detailed, with current perspectives and opportunities provided.

In vitro diagnosis of delayed-type drug hypersensitivity: mechanistic aspects and unmet needs

Several laboratories use the lymphocyte transformation test for the diagnosis of delayed-type drug hypersensitivity reactions. Recently, the availability of multiple readouts has improved our ability to diagnose reactions. It is important to note that most published studies characterizing the usefulness of diagnostic tests utilize blood samples from well-defined test and control patient groups. The purpose of this article is to briefly summarize the cellular and chemical basis of delayed-type drug hypersensitivity reactions and to review in vitro assays that are available for drug hypersensitivity diagnosis.

Simultaneous analysis of antibiotics in biological samples by ultra high performance liquid chromatography-tandem mass spectrometry

A rapid and reliable multiclass method was developed for the simultaneous analysis of 21 antibiotics (beta-lactams, aminoglycosides, penicillins, cephalosporins, carbapenems or quinolones) in urine, serum, cerebrospinal fluid (CSF) and bronchial aspirations by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). Prior to chromatographic determination, the analytes were extracted from human biological fluids by simple sample treatments, which imply dilution, liquefaction, or protein precipitation. Several chromatographic conditions were optimized in order to obtain a fast separation (<6min for each chromatographic run). MS/MS conditions were evaluated in order to increase selectivity and sensitivity and all compounds were detected in electrospray (ESI) positive ion mode, except clavulanic acid and sulbactam, which were monitored in negative ion mode. The developed method was validated in terms of linearity, selectivity, limits of detection (LODs) and quantification (LOQs), trueness, repeatability and interday precision. The LOQs ranged from 0.01 to 1.00mg/L for urine, serum and CSF. In case of bronchial aspirations, the LOQs were between 0.02 and 0.67mg/kg. In all matrices the recovery results were in the range 70-120% and interday precision was lower than 25%. Finally, the optimized method was applied to the analysis of biological samples from 10 patients in the intensive care unit (ICU) of a hospital located in Almeria (Spain). Several antibiotics (e.g., amoxicillin, tobramycin, levofloxacin, or linezolid) were found in the studied samples, observing that the highest concentrations were obtained in urine samples.

Idiosyncratic adverse drug reactions: current concepts

Idiosyncratic drug reactions are a significant cause of morbidity and mortality for patients; they also markedly increase the uncertainty of drug development. The major targets are skin, liver, and bone marrow. Clinical characteristics suggest that IDRs are immune mediated, and there is substantive evidence that most, but not all, IDRs are caused by chemically reactive species. However, rigorous mechanistic studies are very difficult to perform, especially in the absence of valid animal models. Models to explain how drugs or reactive metabolites interact with the MHC/T-cell receptor complex include the hapten and P-I models, and most recently it was found that abacavir can interact reversibly with MHC to alter the endogenous peptides that are presented to T cells. The discovery of HLA molecules as important risk factors for some IDRs has also significantly contributed to our understanding of these adverse reactions, but it is not yet clear what fraction of IDRs have a strong HLA dependence. In addition, with the exception of abacavir, most patients who have the HLA that confers a higher IDR risk with a specific drug will not have an IDR when treated with that drug. Interindividual differences in T-cell receptors and other factors also presumably play a role in determining which patients will have an IDR. The immune response represents a delicate balance, and immune tolerance may be the dominant response to a drug that can cause IDRs.

Enhanced antigenicity leads to altered immunogenicity in sulfamethoxazole-hypersensitive patients with cystic fibrosis

BACKGROUND

Exposure of patients with cystic fibrosis to sulfonamides is associated with a high incidence of hypersensitivity reactions.

OBJECTIVE

To compare mechanisms of antigen presentation and characterize the phenotype and function of T cells from sulfamethoxazole-hypersensitive patients with and without cystic fibrosis.

METHODS

T cells were cloned from 6 patients and characterized in terms of phenotype and function. Antigen specificity and mechanisms of antigen presentation to specific clones were then explored. Antigen-presenting cell metabolism of sulfamethoxazole was quantified by ELISA. The involvement of metabolism in antigen presentation was evaluated by using enzyme inhibitors.

RESULTS

Enzyme inhibitable sulfamethoxazole-derived protein adducts were detected in antigen-presenting cells from patients with and without cystic fibrosis. A significantly higher quantity of adducts were detected with cells from patients with cystic fibrosis. Over 500 CD4(+) or CD8(+) T-cell clones were generated and shown to proliferate and kill target cells. Three patterns of MHC-restricted reactivity (sulfamethoxazole-responsive, sulfamethoxazole metabolite-responsive, and cross-reactive) were observed with clones from patients without cystic fibrosis. From patients with cystic fibrosis, sulfamethoxazole metabolite-responsive and cross-reactive, but not sulfamethoxazole-responsive, clones were observed. The response of the cross-reactive clones to sulfamethoxazole was dependent on adduct formation and was blocked by glutathione and enzyme inhibitors. Antigen-stimulated clones from patients with cystic fibrosis secreted higher levels of IFN-γ, IL-6, and IL-10, but lower levels of IL-17.

CONCLUSION

Sulfamethoxazole metabolism and protein adduct formation is critical for the stimulation of T cells from patients with cystic fibrosis. T cells from patients with cystic fibrosis secrete high levels of IFN-γ, IL-6, and IL-10.