Infiltration of cytotoxic T cells in drug-induced cutaneous eruptions

One-month daily and three-month weekly rifapentine plus isoniazid are comparable in completion rate and safety for latent tuberculosis infection in non-HIV Population: a randomized controlled trial

OBJECTIVES

The weekly rifapentine plus isoniazid for 3 months (3HP) improves completion rate of latent tuberculosis infection treatment, but flu-like symptoms are common. The novel 1HP regimen, involving daily rifapentine plus isoniazid for 28 days, has demonstrated low toxicity in HIV-infected populations. We aimed to investigate whether 1HP has a lower incidence rate of systemic drug reaction (SDR) compared with 3HP during treatment in non-HIV populations.

METHODS

This randomized, multicentre trial compared the completion rate and risks of SDRs of 1HP and 3HP in aged ≥13 years non-HIV subjects with latent tuberculosis infection between September 2019 and September 2023 (ClinicalTrials.gov: NCT04094012). We also investigated associations between SDRs and plasma levels of drugs and their metabolites.

RESULTS

A total of 251 and 239 individuals were randomly assigned to 1HP and 3HP groups, respectively, with completion rates of 82.9% (208/251) and 84.5% (202/239), respectively. Among them, 12.7% (32/251) and 10.9% (26/239) of 1HP and 3HP groups experienced SDRs, respectively (p 0.522), predominantly urticaria in 1HP group (59.4% [19/32]) and flu-like syndrome in 3HP group (80.8% [21/26]). Among participants experiencing SDRs, 43.8% (14/32) and 34.6% (9/26) in 1HP and 3HP groups, respectively, completed treatment (p 0.470). Cutaneous reactions were more common in 1HP than 3HP group (32.7% [82/251] vs. 13.0% [31/239], p < 0.001). In 1HP group, urticaria was associated with a higher plasma desacetyl-rifapentine level (ug/mL) at both 2 (median [interquartile range]: 36.06 [17.46-50.79] vs. 22.94 [14.67-31.65], p 0.018) and 6 hours (26.13 [15.80-53.06] vs. 29.83 [18.13-34.01], p 0.047) after dosing.

DISCUSSION

In non-HIV population, the incidence rate of SDR under 1HP is not lower than 3HP. Notably, urticaria, rather than flu-like syndrome, was the predominant SDR associated 1HP. The findings of this study underscore the feasibility of 1HP regimen in non-HIV populations with a high-completion rate exceeding 80%.

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.

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.

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.

HIV-Associated Immune Dysregulation in the Skin: A Crucible for Exaggerated Inflammation and Hypersensitivity

Skin diseases are hallmarks of progressive HIV-related immunosuppression, with severe noninfectious inflammatory and hypersensitivity conditions as common as opportunistic infections. Conditions such as papular pruritic eruption are AIDS defining, whereas delayed immune-mediated adverse reactions, mostly cutaneous, occur up to 100-fold more during HIV infection. The skin, constantly in contact with the external environment, has a complex immunity. A dense, tightly junctioned barrier with basal keratinocytes and epidermal Langerhans cells with antimicrobial, innate-activating, and antigen-presenting functions form the frontline. Resident dermal dendritic, mast, macrophage, and innate lymphoid cells play pivotal roles in directing and polarizing appropriate adaptive immune responses and directing effector immune cell trafficking. Sustained viral replication leads to progressive declines in CD4 T cells, whereas Langerhans and dermal dendritic cells serve as viral reservoirs and points of first viral contact in the mucosa. Cutaneous cytokine responses and diminished lymphoid populations create a crucible for exaggerated inflammation and hypersensitivity. However, beyond histopathological description, these manifestations are poorly characterized. This review details normal skin immunology, changes associated with progressive HIV-related immunosuppression, and the characteristic conditions of immune dysregulation increased with HIV. We highlight the main research gaps and several novel tissue-directed strategies to define mechanisms that will provide targeted approaches to prevention or treatment.

Viral infections and drug hypersensitivity

Virus infections and T-cell-mediated drug hypersensitivity reactions (DHR) can influence each other. In most instances, systemic virus infections appear first. They may prime the reactivity to drugs in two ways: First, by virus-induced second signals: certain drugs like β-lactam antibiotics are haptens and covalently bind to various soluble and tissue proteins, thereby forming novel antigens. Under homeostatic conditions, these neo-antigens do not induce an immune reaction, probably because co-stimulation is missing. During a virus infection, the hapten-modified peptides are presented in an immune-stimulatory environment with co-stimulation. A drug-specific immune reaction may develop and manifest as exanthema. Second, by increased pharmacological interactions with immune receptors (p-i): drugs tend to bind to proteins and may even bind to immune receptors. Without viral infections, this low affine binding may be insufficient to elicit T-cell activation. During a viral infection, immune receptors are more abundantly expressed and allow more interactions to occur. This increases the overall avidity of p-i reactions and may even be sufficient for T-cell activation and symptoms. There is a situation where the virus-DHR sequence of events is inversed: in drug reaction with eosinophilia and systemic symptoms (DRESS), a severe DHR can precede reactivation and viremia of various herpes viruses. One could explain this phenomenon by the massive p-i mediated immune stimulation during acute DRESS, which coincidentally activates many herpes virus-specific T cells. Through p-i stimulation, they develop a cytotoxic activity by killing herpes peptide-expressing cells and releasing herpes viruses. These concepts could explain the often transient nature of DHR occurring during viral infections and the often asymptomatic herpes-virus viraemia after DRESS.

Compound-honeysuckle-induced drug eruption with special manifestations: A case report

BACKGROUND

The clinical manifestations of drug eruption are complex and diverse, which can lead to missed diagnosis or misdiagnosis. The clinical manifestations of drug eruption caused by compound honeysuckle have not been reported.

CASE SUMMARY

A 20-year-old man was admitted to our department of dermatology due to erythema and papules on the chest and abdomen with pruritus for 3 d. The next day after taking compound honeysuckle granules, the patient suddenly developed a rash and intense itching on his chest and abdomen. Physical examination revealed diffuse red needle-cap size macules and papules with well-defined borders on the chest and abdomen, and discoloration after finger pressure. No abnormality was observed in other areas of the skin. Back skin scratch was positive. White blood cells, eosinophil count and eosinophil ratio were higher than normal. Histopathological examination of the skin lesions on the left abdomen revealed intercellular edema, blurred focal basal cell layers, and focal lymphocyte infiltration in the superficial dermis and perivascular areas. Immunohistochemistry showed CD3⁺_, CD4⁺ and CD8⁺ T lymphocytes. The diagnosis was drug eruption with special manifestations induced by compound honeysuckle. The skin lesions completely subsided without pruritus after 2 wk of antihistamine and hormone therapy. Follow-up for > 1 mo showed no recurrence.

CONCLUSION

Chinese patent medicine compound honeysuckle granules can induce allergic reaction and rare skin damage.

The Activation Pattern of Drug-Reacting T Cells Has an Impact on the Clinical Picture of Hypersensitivity Reactions

Rationale

β-lactam antibiotics cause drug hypersensitivity reactions (DHR) with various clinical pictures from minor affections like maculopapular exanthema (MPE) and urticaria to severe cutaneous adverse reactions and anaphylaxis. Currently, two different reactivity patterns have been shown to initiate an immune reaction by activating T cells—the hapten concept and the pharmacological interaction with immune receptor (p–i) concept.

Objectives

In this study, the relationship between the reactivity pattern of drug-reacting T cells of drug allergic patients and their clinical picture has been investigated.

Findings

Drug-reacting T-cell clones (TCCs) were isolated from patients hypersensitive to β-lactams. Analysis of their reactivity pattern revealed an exclusive use of the hapten mechanism for patients with immediate reactions and for patients of MPE. In patients suffering from drug reactions with eosinophils and systemic symptoms, a severe DHR, analysis of isolated drug-reacting TCC identified the p–i concept as the unique mechanism for T-cell activation.

Conclusions

The results show a shift from hapten pattern in mild allergic reactions to p–i pattern in severe life-threatening allergic reactions. They strongly argue against the current preclinical risk evaluation of new drugs based on the ability to form haptens.

Mechanisms of Immunotoxicity: Stressors and Evaluators

The immune system defends the body against certain tumor cells and against foreign agents such as fungi, parasites, bacteria, and viruses. One of its main roles is to distinguish endogenous components from non-self-components. An unproperly functioning immune system is prone to primary immune deficiencies caused by either primary immune deficiencies such as genetic defects or secondary immune deficiencies such as physical, chemical, and in some instances, psychological stressors. In the manuscript, we will provide a brief overview of the immune system and immunotoxicology. We will also describe the biochemical mechanisms of immunotoxicants and how to evaluate immunotoxicity.

Characterization of T-Cell Responses to SMX and SMX-NO in Co-Trimoxazole Hypersensitivity Patients Expressing HLA-B*13:01

HLA-B*13:01-positive patients in Thailand can develop frequent co-trimoxazole hypersensitivity reactions. This study aimed to characterize drug-specific T cells from three co-trimoxazole hypersensitive patients presenting with either Stevens-Johnson syndrome or drug reaction with eosinophilia and systemic symptoms. Two of the patients carried the HLA allele of interest, namely HLA-B*13:01. Sulfamethoxazole and nitroso sulfamethoxazole specific T cell clones were generated from T cell lines of co-trimoxazole hypersensitive HLA-B*13:01-positive patients. Clones were characterized for antigen specificity and cross-reactivity with structurally related compounds by measuring proliferation and cytokine release. Surface marker expression was characterized via flow cytometry. Mechanistic studies were conducted to assess pathways of T cell activation in response to antigen stimulation. Peripheral blood mononuclear cells from all patients were stimulated to proliferate and secrete IFN-γ with nitroso sulfamethoxazole. All sulfamethoxazole and nitroso sulfamethoxazole specific T cell clones expressed the CD4+ phenotype and strongly secreted IL-13 as well as IFN-γ, granzyme B and IL-22. No secretion of IL-17 was observed. A number of nitroso sulfamethoxazole-specific clones cross-reacted with nitroso dapsone but not sulfamethoxazole whereas sulfamethoxazole specific clones cross-reacted with nitroso sulfamethoxazole only. The nitroso sulfamethoxazole specific clones were activated in both antigen processing-dependent and -independent manner, while sulfamethoxazole activated T cell responses via direct HLA binding. Furthermore, activation of nitroso sulfamethoxazole-specific, but not sulfamethoxazole-specific, clones was blocked with glutathione. Sulfamethoxazole and nitroso sulfamethoxazole specific T cell clones from hypersensitive patients were CD4+ which suggests that HLA-B*13:01 is not directly involved in the iatrogenic disease observed in co-trimoxazole hypersensitivity patients.

Treating Through Drug-Associated Exanthems in Drug Allergy Management: Current Evidence and Clinical Aspects

In the setting of an acute cutaneous adverse drug reaction there is increasing interest in selected phenotypes and hosts to continue drug therapy, especially in settings in which there are limited therapeutic options. This concept of "treating through," defined as the continued use of a drug in the setting of, in particular maculopapular exanthema, potentially avoids unnecessary drug discontinuation. A review of the recent literature, historical viewpoints, and expert opinion are provided within to form recommendations and algorithms for a "treating-through" approach.

The complexity of T cell-mediated penicillin hypersensitivity reactions

Penicillin refers to a group of beta-lactam antibiotics that are the first-line treatment for a range of infections. However, they also possess the ability to form novel antigens, or neoantigens, through haptenation of proteins and can stimulate a range of immune-mediated adverse reactions-collectively known as drug hypersensitivity reactions (DHRs). IgE-mediated reactions towards these neoantigens are well studied; however, IgE-independent reactions are less well understood. These reactions usually manifest in a delayed manner as different forms of cutaneous eruptions or liver injury consistent with priming of an immune response. Ex vivo studies have confirmed the infiltration of T cells into the site of inflammation, and the subsets of T cells involved appear dependent on the nature of the reaction. Here, we review the evidence that has led to our current understanding of these immune-mediated reactions, discussing the nature of the lesional T cells, the characterization of drug-responsive T cells isolated from patient blood, and the potential mechanisms by which penicillins enter the antigen processing and presentation pathway to stimulate these deleterious responses. Thus, we highlight the need for a more comprehensive understanding of the underlying genetic and molecular basis of penicillin-induced DHRs.

Genome-wide Study Identifies Association between HLA-B∗55:01 and Self-Reported Penicillin Allergy

Hypersensitivity reactions to drugs are often unpredictable and can be life threatening, underscoring a need for understanding their underlying mechanisms and risk factors. The extent to which germline genetic variation influences the risk of commonly reported drug allergies such as penicillin allergy remains largely unknown. We extracted data from the electronic health records of more than 600,000 participants from the UK, Estonian, and Vanderbilt University Medical Center's BioVU biobanks to study the role of genetic variation in the occurrence of self-reported penicillin hypersensitivity reactions. We used imputed SNP to HLA typing data from these cohorts to further fine map the human leukocyte antigen (HLA) association and replicated our results in 23andMe's research cohort involving a total of 1.12 million individuals. Genome-wide meta-analysis of penicillin allergy revealed two loci, including one located in the HLA region on chromosome 6. This signal was further fine-mapped to the HLA-B∗55:01 allele (OR 1.41 95% CI 1.33-1.49, p value 2.04 × 10-31) and confirmed by independent replication in 23andMe's research cohort (OR 1.30 95% CI 1.25-1.34, p value 1.00 × 10-47). The lead SNP was also associated with lower lymphocyte counts and in silico follow-up suggests a potential effect on T-lymphocytes at HLA-B∗55:01. We also observed a significant hit in PTPN22 and the GWAS results correlated with the genetics of rheumatoid arthritis and psoriasis. We present robust evidence for the role of an allele of the major histocompatibility complex (MHC) I gene HLA-B in the occurrence of penicillin allergy.

T Cell Assessment in Allergic Drug Reactions during the Acute Phase According to the Time of Occurrence

Allergic drug reactions can be classified as immediate, accelerated or delayed. This classification usually correlates with the mechanism involved: immediate reactions are IgE mediated and delayed reactions are T cell dependent. We analyzed lymphocyte involvement in patients with these reactions by determining cell subpopulations, activation state and skin homing receptor expression (CLA) in blood and skin. Patients with immediate, accelerated and delayed reactions were evaluated during the acute phase and after resolution. Controls taking drugs were included. Phenotypic immunofluorescence analysis was done by flow cytometry in peripheral blood, and by immunohistochemistry in skin for delayed reactions. Forty-six patients were included, 17 with immediate reactions, 10 accelerated and 19 delayed. At the acute phase CLA was significantly increased in delayed reactions and HLA-DR in all three types of reaction. In the severest delayed reactions, Steven-Johnson/Lyell syndromes, the CD4 subsets were increased in peripheral blood and skin compared to maculopapular exanthemas and urticaria and HLA-DR when compared with urticaria. In maculopapular exanthemas CLA was significantly increased in peripheral blood and skin compared to urticaria and the severe reactions. We found that T-cells are implicated, besides delayed reactions, in immediate and accelerated reactions. In delayed reactions there is a parallelism between results found in skin and peripheral blood with a higher participation of CD4+ cells the more severe the reaction.

Carbamazepine-Mediated Adverse Drug Reactions: CBZ-10,11-epoxide but Not Carbamazepine Induces the Alteration of Peptides Presented by HLA-B∗15:02

Among patients treated with the anticonvulsive and psychotropic drug carbamazepine (CBZ), approximately 10% develop severe and life-threatening adverse drug reactions. These immunological conditions are resolved upon withdrawal of the medicament, suggesting that the drug does not manifest in the body in long term. The HLA allele B∗15:02 has been described to be a genomic biomarker for CBZ-mediated immune reactions. It is not well understood if the immune reactions are triggered by the original drug or by its metabolite carbamazepine-10,11-epoxide (EPX) and how the interaction between the drug and the distinct HLA molecule occurs. Genetically engineered human B-lymphoblastoid cells expressing soluble HLA-B∗15:02 molecules were treated with the drug or its metabolite. Functional pHLA complexes were purified; peptides were eluted and sequenced. Applying mass spectrometric analysis, CBZ and EPX were monitored by analyzing the heavy chain and peptide fractions separately for the presence of the drug. This method enabled the detection of the drug in a biological situation post-pHLA assembly. Both drugs were bound to the HLA-B∗15:02 heavy chain; however, solely EPX altered the peptide-binding motif of B∗15:02-restricted peptides. This observation could be explained through structural insight; EPX binds to the peptide-binding region and alters the biochemical features of the F pocket and thus the peptide motif. Understanding the nature of immunogenic interactions between CBZ and EPX with the HLA immune complex will guide towards effective and safe medications.

[Pathogenic Mechanism and Diagnostic Testing for Drug Allergies]

　Three stages of the pathogenic mechanism of drug allergies can be considered: antigen formation, immune reaction and inflammation/disorder reaction. Drugs are thought to form 4 types of antigens: drug only, polymers, drug-carrier conjugates, and metabolite-carrier complexes. Antigens are recognized by B cell receptors and T cell receptors. Helper T cells (Th) are differentiated into four subsets, namely, Th1, Th2, Th17 and regulatory T cells (Treg). Th1 produces interleukin (IL)-2 and interferon (IFN)-γ, and activates macrophages and cytotoxic T cells (Tc). Macrophages induce type IV allergies, and Tc lead to serious type IV allergies. On the other hand, Th2 produces IL-4, IL-5, and IL-6, etc., and activates B cells. B cells produce IgE antibodies, and the IgE antibody affects mast cells and induces type I allergies. Activated eosinophil leads to the chronic state of type I allergy. Diagnostic testing for allergenic drugs is necessary for patients with drug allergies. Because in vivo diagnostic tests for allergenic drugs are associated with a risk and burden to the patient, in vitro allergy tests are recommended to identify allergenic drugs. In allergy tests performed in vitro, cytological tests are more effective than serological tests, and the leukocyte migration test (LMT) presently has the highest efficacy. An LMT-chamber is better than LMT-agarose in terms of usability and sensitivity, and it can detect about 80% of allergenic drugs.

Cytomegalovirus-Specific T Cells Isolated by IFN-γ Secretion Assay Do Not Induce Significant Graft-Versus-Host Reactions In Vitro

BACKGROUND

Graft-versus-host (GvH) disease (GvHD) remains a serious concern for patients undergoing antiviral cellular therapy. Despite the major improvements in cellular immunotherapy, the immunogenicity of virus-specific T cells has not yet been fully defined. This present study aims to examine how cytomegalovirus (CMV)-specific cytotoxic T lymphocytes (CTLs) respond to allogeneic antigen stimulation and whether they give rise to GvHD target tissue damage.

METHODS

Cytomegalovirus-specific CTLs were isolated by the IFN-γ secretion assay (gamma-catch) from healthy seropositive volunteers and expanded in vitro. The levels of intracellular IFN-γ, cytotoxic activity, IFN-γ and granzyme B secretion, and CD25 expression were measured using flow cytometry (fluorescence-activated cell sorting). The ability of CMV-CTLs to induce GvHD target tissue damage was evaluated using the human in vitro skin explant assay (skin explant assay).

RESULTS

Cytomegalovirus-specific CTLs responded specifically to CMV-phosphoprotein 65 stimulation by secreting IFN-γ and killing virus peptide loaded autologous phytohemagglutinin (PHA) blasts. Compared with unselected peripheral blood mononuclear cells, CMV-CTLs induced significantly less severe cutaneous GvH tissue damage. This observation coincided with low levels of CD25 expression, as well as IFN-γ and granzyme B secretion after allogeneic antigen stimulation in both the mixed lymphocyte reaction and in the skin explant assay.

CONCLUSIONS

Cytomegalovirus-specific CTLs isolated by the IFN-γ secretion assay from HLA-unmatched healthy donors exhibited a high level of anti-CMV potency without inducing significant cutaneous GvH tissue damage in vitro. This finding provides novel evidence supporting the safe use of in vitro expanded CMV-CTLs as an antiviral therapy in transplant patients with refractory CMV infections.

Adverse Medication Reactions

Cutaneous adverse drug reactions (ADRs) are among the most frequent adverse reactions in patients receiving drug therapy. They have a broad spectrum of clinical manifestations, are caused by various drugs, and result from different pathophysiological mechanisms. Hence, their diagnosis and management is challenging.

Severe cutaneous ADRs comprise a group of diseases with major morbidity and mortality, reaching 30 % mortality rate in cases of Toxic Epidermal Necrolysis.

This chapter covers the terminology, epidemiology, pathogenesis and classification of cutaneous ADR, describes the severe cutaneous ADRs and the clinical and laboratory approach to the patient with cutaneous ADR and presents the translation of laboratory-based discoveries on the genetic predisposition and pathogenesis of cutaneous ADRs to clinical management guidelines.

A Case of Dasatinib-Induced Hemorrhagic Colitis Diagnosed by the Lymphocyte Transformation Test in a Chronic Myeloid Leukemia Patient

Dasatinib is an effective treatment option for patients diagnosed with Philadelphia chromosome positive chronic myeloid leukemia and who are non-responsive or intolerant to imatinib treatment. Dasatinib, however, is associated with various adverse effects and on rare occasions, may cause hemorrhagic colitis. We report the case of a 68-year-old male patient with dasatinib-induced hemorrhagic colitis, the first such case in Korea. Endoscopic biopsy of the transverse colon demonstrated non-specific inflammatory changes only. Cessation of dasatinib led to the resolution of symptoms, while reintroduction of the therapy led to the recurrence of his bloody diarrhea. To clarify the association between dasatinib and hemorrhagic colitis, the lymphocyte transformation test (LTT) was performed. The LTT result sustained a relatively high proliferation activity in the affected patient compared with almost no proliferation activity in normal control.

Eosinophilic esophagitis is characterized by a non-IgE-mediated food hypersensitivity

Eosinophilic esophagitis (EoE) is a chronic disease characterized clinically by symptoms of esophageal dysfunction and histologically by eosinophil-predominant inflammation. EoE is frequently associated with concomitant atopic diseases and immunoglobulin E (IgE) sensitization to food allergens in children as well as to aeroallergens and cross-reactive plant allergen components in adults. Patients with EoE respond well to elemental and empirical food elimination diets. Recent research has, however, indicated that the pathogenesis of EoE is distinct from IgE-mediated food allergy. In this review, we discuss the individual roles of epithelial barrier defects, dysregulated innate and adaptive immune responses, and of microbiota in the pathogenesis of EoE. Although food has been recognized as a trigger factor of EoE, the mechanism by which it initiates or facilitates eosinophilic inflammation appears to be largely independent of IgE and needs to be further investigated. Understanding the pathogenic role of food in EoE is a prerequisite for the development of specific diagnostic tools and targeted therapeutic procedures.

Adverse drug reactions and organ damage: The skin

Cutaneous adverse drug reactions are frequent, affecting 2-3% of hospitalized patients and in one twentieth of them are potentially life-threatening. Almost any pharmacologic agent can induce skin reactions, and certain drug classes, such as non-steroidal anti-inflammatory drugs, antibiotics and antiepileptics, have drug eruption rates ranging from 1% to 5%. Cutaneous drug reactions recognize several different pathomechanisms: some skin manifestations are immune-mediated like allergic reactions while others are the result of non immunological causes such as cumulative toxicity, photosensitivity, interaction with other drugs or different metabolic pathways. Cutaneous adverse drug reactions can be classified into two groups: common non-severe and rare life-threatening adverse drug reactions. Non-severe reactions are often exanthematous or urticarial whereas life-threatening reactions typically present with skin detachment or necrosis of large areas of the body and mucous membrane involvement, as in the Stevens-Johnson syndrome or toxic epidermal necrolysis. Clinicians should carefully evaluate the signs and symptoms of all cutaneous adverse drug reactions thought to be due to drugs and immediately discontinue drugs that are not essential. Short cycles of systemic corticosteroids in combination with antihistamines may be necessary for widespread exanthematous rashes, while more aggressive corticosteroid regimens or intravenous immunoglobulins associated with supportive treatment should be used for patients with Stevens-Johnson syndrome or toxic epidermal necrolysis.

Allopurinol hypersensitivity: investigating the cause and minimizing the risk

Allopurinol is the most commonly prescribed urate-lowering therapy for the management of gout. Serious adverse reactions associated with allopurinol, while rare, are feared owing to the high mortality. Such reactions can manifest as a rash combined with eosinophilia, leukocytosis, fever, hepatitis and progressive kidney failure. Risk factors for allopurinol-related severe adverse reactions include the recent introduction of allopurinol, the presence of the HLA-B(*)58:01 allele, and factors that influence the drug concentration. The interactions between allopurinol, its metabolite, oxypurinol, and T cells have been studied, and evidence exists that the presence of the HLA-B(*)58:01 allele and a high concentration of oxypurinol function synergistically to increase the number of potentially immunogenic-peptide-oxypurinol-HLA-B(*)58:01 complexes on the cell surface, thereby increasing the risk of T-cell sensitization and a subsequent adverse reaction. This Review will discuss the above issues and place this in the clinical context of reducing the risk of serious adverse reactions.

Drug-induced skin reactions: a pathologist viewpoint

Cutaneous drug reactions are common adverse effects that occur in about 2-3% of the hospitalized patients. They have both immunologic and non-immunologic underlying mechanisms. These reactions are clinically and histologically similar to dermatoses. Their significant clinical indicators include: history of drug intake, atypical clinical features and improvement after cessation of the offending drugs. Their diagnostic histological clues include the presence of mixed histological patterns, apoptotic keratinocytes, eosinophils (dermis and epidermis), papillary dermal edema and extravasations of erythrocytes. However, no single clinical or histological feature is specific of drug eruptions. This work attempts to classify the histomorphologic reactions to various drugs in defined categories for assistance in morphologic diagnosis.

[Delayed-type cutaneous drug reactions. Pathogenesis, clinical features and histology]

BACKGROUND

Cutaneous reactions to drugs can be subdivided in different ways. In addition to the standard classification according to the etiopathogenesis there are also classifications based predominantly on morphological criteria. The majority of drug-related cutaneous adverse reactions are immunological reactions which are collectively classified under the term hypersensitivity. These reactions are based on drug-specific immunoglobulin E (IgE) or cell-mediated mechanisms, not on the mechanism of action of the drug and are unpredictable. Delayed type reactions to drugs are forms of type IV T-cell mediated hypersensitivity. A prerequisite is a stable association of a pharmaceutical substance with a protein so that hapten-protein conjugates can be produced. The most common clinical symptom is maculopapular (morbilliform) drug-related exanthema. This article also examines lichen planus like drug reaction and drug-induced (hematogenic) allergic contact dermatitis in more detail.

DIAGNOSTICS

The diagnostics are never trivial but also include the differentiation from viral exanthema and initial phases of severe cutaneous adverse reactions, such as toxic epidermal necrolysis. In addition to the morphological classification, the final diagnosis encompasses the interpretation of histopathological alterations in the skin biopsy, analysis of patient medication history, laboratory results and inclusion of data from the literature. Patch tests can also have additional diagnostic benefits. In vitro tests which involve the cellular incubation of the drug responsible should be reserved for specialized laboratories. A prerequisite for successful treatment is immediate termination of the drug responsible.

THERAPY AND PROGNOSIS

Therapy is symptomatic with topical and also short-term systemic steroids and antihistamines. The prognosis is very good.

Role of dermatology in pharmacogenomics: drug-induced skin injury

Different individuals may respond diversely to the same drug, in terms of efficacy and toxicity. Adverse drug reactions cause about 6% of all hospital admissions and account for up to 9% of hospitalization costs. Drug-induced skin injury (DISI) is the most common presentation of adverse drug reactions, ranging from maculopapular eruptions to severe adverse cutaneous drug reactions (SCARs) with mortality of up to 40%. Specific genetic polymorphisms confer susceptibility to different types of DISI. Identifying patients genetically at risk for SCARs is one of the goals of pharmacogenomics. In this article, the aspects of clinical dermatology relevant to the pharmacogenetics of DISI are reviewed. Many SCARs are now preventable, with consequent reduction of morbidity, mortality and healthcare costs.

Cellular in vitro diagnosis of adverse drug reactions

Adverse drug reactions can manifest clinically in a variety of ways. Whilst the majority can be explained by dose-dependent side effects, there is group of unpredictable immunological or non-immunological intolerances that represent a particular diagnostic challenge. Skin tests are frequently negative, whilst challenge tests are time-consuming and often hazardous. Against this backdrop, cellular in vitro tests play a particularly important role in the identification of the causative drug. Whilst basophil tests can be used in the case of immunoglobulin E (IgE)- as well as non-IgE-mediated hypersensitivity reactions, T-cellular test methods assist in the diagnosis of drug eruptions. The reliability of individual tests can be affected by a variety of parameters, such as the pathomechanism underlying the drug reaction, the causative medication, or the point in time of testing. Not only is a sound knowledge of the basic principles of the individual assays an essential prerequisite for correctly indicating and interpreting this test method, but also an awareness of these additional factors.

T cells infiltrate the liver and kill hepatocytes in HLA-B(∗)57:01-associated floxacillin-induced liver injury

Drug-induced liver injury is a major safety issue. It can cause severe disease and is a common cause of the withdrawal of drugs from the pharmaceutical market. Recent studies have identified the HLA-B(∗)57:01 allele as a risk factor for floxacillin (FLUX)-induced liver injury and have suggested a role for cytotoxic CD8(+) T cells in the pathomechanism of liver injury caused by FLUX. This study aimed to confirm the importance of FLUX-reacting cytotoxic lymphocytes in the pathomechanism of liver injury and to dissect the involved mechanisms of cytotoxicity. IHC staining of a liver biopsy from a patient with FLUX-induced liver injury revealed periportal inflammation and the infiltration of cytotoxic CD3(+) CD8(+) lymphocytes into the liver. The infiltration of cytotoxic lymphocytes into the liver of a patient with FLUX-induced liver injury demonstrates the importance of FLUX-reacting T cells in the underlying pathomechanism. Cytotoxicity of FLUX-reacting T cells from 10 HLA-B(∗)57:01(+) healthy donors toward autologous target cells and HLA-B(∗)57:01-transduced hepatocytes was analyzed in vitro. Cytotoxicity of FLUX-reacting T cells was concentration dependent and required concentrations in the range of peak serum levels after FLUX administration. Killing of target cells was mediated by different cytotoxic mechanisms. Our findings emphasize the role of the adaptive immune system and especially of activated drug-reacting T cells in human leukocyte antigen-associated, drug-induced liver injury.

Sorafenib induces delayed-onset cutaneous hypersensitivity: a case series

Sorafenib is an oral multikinase inhibitor with clinical activity against hepatocellular carcinoma (HCC) and renal cell carcinoma. Administration of sorafenib carries a variety of adverse cutaneous reactions. Common adverse effects induced by sorafenib include hand-foot skin reactions, facial erythema, splinter subungual hemorrhage, and alopecia. Although erythema multiforme (EM) related to sorafenib has been reported, delayed-type cutaneous hypersensitivity reactions are rare in patients treated with sorafenib and there has been no case of Stevens-Johnson syndrome (SJS) reported so far. We recently experienced 3 cases of delayed-type cutaneous hypersensitivity related to administration of sorafenib. The first case was a 47-year female had targetoid erythematous rashes on her arms 12 days after starting sorafenib for HCC. The rashes spread from the arms to the trunk rapidly except for the hands and feet, and erosive lesions developed in the oral mucosa and lips. She was diagnosed as SJS. The second case was an 81-year-old male had maculopapular eruptions with multiple targetoid lesions on the trunk, arms, and legs 10 days after starting sorafenib for his HCC. There was no evidence of mucosal involvement. He was diagnosed with EM. The last one was a 20-year-old female developed generalized maculopapular eruptions in the whole body 10 days after starting sorafenib for the treatment of HCC. All 3 patients completely recovered after discontinuation of sorafenib.

T cell responses to drugs and drug metabolites

Understanding the chemical mechanisms by which drugs and drug metabolites interact with cells of the immune system is pivotal to our knowledge of drug hypersensitivity as a whole.In this chapter, we will discuss the currently accepted mechanisms where there is scientific and clinical evidence to support the ways in which drugs and their metabolites interact with T cells. We will also discuss bioanalytical platforms, such as mass spectrometry, and in vitro test assays such as the lymphocyte transformation test that can be used to study drug hypersensitivity; the combination of such techniques can be used to relate the chemistry of drug antigen formation to immune function. Ab initio T cell priming assays are also discussed with respect to predicting the potential of a drug to cause hypersensitivity reactions in humans in relation to the chemistry of the drug and its ability to form haptens, antigens and immunogens in patients.

Cutaneous infiltrates of acute myelogenous leukemia simulating inflammatory dermatoses

Some cases of specific cutaneous manifestations of acute myelogenous leukemia (AML) may mimic inflammatory dermatoses both clinically and histopathologically, presenting with an inconspicuous maculopapular eruption and with only sparse dermal infiltrates. The authors studied the histopathological and immunohistochemical features of 17 biopsies from 16 patients (11 men and 5 women, age range 15-85 years) presenting with minimal skin infiltrates as the first manifestation of AML or as first sign of recurrence after complete remission of the disease. In all cases, the diagnosis of leukemia has been confirmed by bone marrow examination. Two of these cases had been sent to one of us for second expert consultation. Patients presented with generalized, exanthematic maculopapular eruptions, sometimes with a hemorrhagic note, that were mostly interpreted clinically as drug reactions. Histopathologically, the lesions showed sparse, superficial, and mid-dermal infiltrates with minimal perivascular and periadnexal accentuation. Infiltrating cells consisted mostly of neoplastic monocytoid elements with only few reactive lymphocytes and histiocytes. Immunohistochemical stainings revealed in the majority of cases positivity for CD68 (14 of 16 patients), naphthol chloroacetate esterase (NaSDCl) (7 of 10 patients), and myeloperoxidase (6 of 9 patients). Other markers tested were positive only in a minority of cases. These cases represent a pitfall both in the clinical and in the histopathological diagnosis of cutaneous AML. Accurate morphologic and phenotypic correlation together with a high index of suspicion allows a precise diagnosis in these unconventional cases.

Synergistic effect between amoxicillin and TLR ligands on dendritic cells from amoxicillin-delayed allergic patients

Amoxicillin, a low-molecular-weight compound, is able to interact with dendritic cells inducing semi-maturation in vitro. Specific antigens and TLR ligands can synergistically interact with dendritic cells (DC), leading to complete maturation and more efficient T-cell stimulation. The aim of the study was to evaluate the synergistic effect of amoxicillin and the TLR2, 4 and 7/8 agonists (PAM, LPS and R848, respectively) in TLR expression, DC maturation and specific T-cell response in patients with delayed-type hypersensitivity (DTH) reactions to amoxicillin. Monocyte-derived DC from 15 patients with DTH to amoxicillin and 15 controls were cultured with amoxicillin in the presence or absence of TLR2, 4 and 7/8 agonists (PAM, LPS and R848, respectively). We studied TLR1-9 gene expression by RT-qPCR, and DC maturation, lymphocyte proliferation and cytokine production by flow cytometry. DC from both patients and controls expressed all TLRs except TLR9. The amoxicillin plus TLR2/4 or TLR7/8 ligands showed significant differences, mainly in patients: AX+PAM+LPS induced a decrease in TLR2 and AX+R848 in TLR2, 4, 7 and 8 mRNA levels. AX+PAM+LPS significantly increased the percentage of maturation in patients (75%) vs. controls (40%) (p=0.036) and T-cell proliferation (80.7% vs. 27.3% of cases; p=0.001). Moreover, the combinations AX+PAM+LPS and AX+R848 produced a significant increase in IL-12p70 during both DC maturation and T-cell proliferation. These results indicate that in amoxicillin-induced maculopapular exanthema, the presence of different TLR agonists could be critical for the induction of the innate and adaptive immune responses and this should be taken into account when evaluating allergic reactions to these drugs.

The p-i Concept: Pharmacological Interaction of Drugs With Immune Receptors

The immune response in drug hypersensitivity is normally explained by the hapten hypothesis. It postulates that drugs with a molecular weight of less than 1000 D are too small to cause an immune response per se. However, if a chemically reactive drug or drug metabolite binds covalently to a protein and thus forms a so-called hapten-carrier complex, this modified protein can induce an immune response. This concept has recently been supplemented by the p-i concept (or pharmacological interaction with immune receptors), which postulates that some drugs that lack hapten characteristics can bind directly and reversibly (noncovalently) to immune receptors and thereby stimulate the cells. For example, a certain drug may bind to a particular T-cell receptor, and this binding suffices to stimulate the T cell to secrete cytokines, to proliferate, and to exert cytotoxicity. The p-i concept has major implications for our understanding of drug interaction with the specific immune system and for drug hypersensitivity reactions. It is based on extensive investigations of T-cell clones reacting with the drug and recently of hybridoma cells transfected with the drug-specific T-cell receptor for antigen (TCR). It is a highly specific interaction dependent on the expression of a TCR into which the drug can bind with sufficient affinity to cause signaling. Small modification of the drug structure may already abrogate reactivity. Stimulation of T cells occurs within minutes as revealed by rapid Ca influx after drug addition to drug-specific T-cell clones or hybridoma cells, thus, before metabolism and processing can occur. As the immune system can only react in an immunologic way, the symptoms arising after drug stimulation of immune receptors imitate an immune response after recognition of a peptide antigen, although it is actually a pharmacological stimulation of some T cells via their TCRs. Clinically, the p-i concept could explain the sometimes rapid appearance of symptoms without previous sensitizations and the sometimes chaotic immune reaction of drug hypersensitivity with participation of different immune mechanisms while normal immune reactions to antigens are highly coordinated. Nevertheless, because the reactions lead to expansion of drug-reactive cells, many features such as skin test reactivity and stronger reactivity upon reexposure are identical to real immune reactions.

Educational case series: Mechanisms of drug allergy

Once administered, a drug can activate the immune system by various mechanisms and lead to a large range of clinical manifestations closely related to the type of immune reaction elicited. Administration of the drug can classically result in an immunoglobulin E (IgE)-type sensitization, but can also result in more complex activation of the immune system potentially resulting in severe syndromes, such as the drug-induced hypersensitivity syndrome (DIHS). Although there has been a major increase in our knowledge over the last years, the exact mechanisms of drug allergy are not well understood for most clinical manifestations. A complex interaction between individual characteristics, environmental factors, and the drug itself is usually responsible for adverse reactions to drugs. In this educational review series, we described three cases of drug allergy: first, a child with a typical IgE-mediated drug allergy, second, a child with a non-immediate reaction to penicillin, and in the third patient, we will discuss the drug-induced hypersensitivity syndrome, which is rare but potentially fatal. These cases are correlated to the immune mechanism potentially involved.

Delayed drug hypersensitivity: models of T-cell stimulation

Drug-induced hypersensitivity reactions can cause a variety of serious diseases by involving drug-specific T-cells. Many of these reactions have been explained by the hapten concept, which postulates that small chemical compounds need to bind covalently to proteins to be recognized by the immune system. Due to their chemical reactivity, haptens stimulate the innate immunity by binding covalently to endogenous proteins and form so called hapten-carrier complexes, which are antigenic and induce T-cell responses. In recent years, a new concept has been developed since drug-induced hypersensitivity reactions were also observed with chemically unreactive drugs. This concept implies direct and reversible interactions of the drug between T-cell receptors (TCR) and major histocompatability complex (MHC) molecules. Therefore it was termed pharmacological interactions with immune receptors (p-i concept). Early observations on drug reacting T-cell clones (TCC) let believe that drugs bind first to the T-cell receptor since HLA molecules could be exchanged without affecting the drug reactivity. However, MHC molecules were always required for full activation of TCC. According to its strong HLA-B*5701 association, recent data on abacavir suggest that a drug could first bind to the peptide binding groove of the MHC molecule. The thereby modified HLA molecule can then be recognized by specific T-cells. Consequently, two types of reactions based on the p-i mechanism may occur: on the one hand, drugs might preferentially bind directly to the TCR, whereas in defined cases with strong HLA association, drugs might bind directly to the MHC molecule.

Involvement of the immune system in idiosyncratic drug reactions

There is strong evidence that most idiosyncratic drug reactions (IDRs) are immune-mediated and are caused by reactive metabolites of a drug rather than by the drug itself. Several hypotheses have been proposed by which a drug could induce an immune response. The major hypotheses are the hapten hypothesis and the danger hypothesis; however, the characteristics and spectrum of IDRs are different with different drugs, and this likely reflects mechanistic differences; therefore, no one hypothesis is likely to explain all IDRs. Some IDRs appear to involve epigenetic effects, direct activation of antigen-presenting cells, or disturbing the normal balance of the immune system. It has been suggested that many cases of idiosyncratic liver injury are not immune-mediated, and other mechanisms such as mitochondrial injury may be involved. It is essential that any hypothesis be consistent with the clinical characteristics of the IDR. Although the characteristics of most idiosyncratic liver injury do not suggest that mitochondria are the major target, it is quite possible that milder mitochondrial injury could stimulate an immune-mediated reaction. The observation that IDRs can vary widely among different drugs and different patients is most easily explained by an immune mechanism in which the target of the immune response is different.