Emergence of circulating monomyeloid precursors predicts reactivation of human herpesvirus-6 in drug-induced hypersensitivity syndrome

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.

Current Perspective Regarding the Immunopathogenesis of Drug-Induced Hypersensitivity Syndrome/Drug Reaction with Eosinophilia and Systemic Symptoms (DIHS/DRESS)

Drug-induced hypersensitivity syndrome/drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS) is a severe type of adverse drug eruption associated with multiorgan involvement and the reactivation of human herpesvirus 6, which arises after prolonged exposure to certain drugs. Typically, two waves of disease activity occur during the course of DIHS/DRESS; however, some patients experience multiple waves of exacerbation and remission of the disease. Severe complications, some of which are related to cytomegalovirus reactivation, can be fatal. DIHS/DRESS is distinct from other drug reactions, as it involves herpes virus reactivation and can lead to the subsequent development of autoimmune diseases. The association between herpesviruses and DIHS/DRESS is now well established, and DIHS/DRESS is considered to arise as a result of complex interactions between several herpesviruses and comprehensive immune responses, including drug-specific immune responses and antiviral immune responses, each of which may be mediated by distinct types of immune cells. It appears that both CD4 and CD8 T cells are involved in the pathogenesis of DIHS/DRESS but play distinct roles. CD4 T cells mainly initiate drug allergies in response to drug antigens, and then herpesvirus-specific CD8 T cells that target virus-infected cells emerge, resulting in tissue damage. Regulatory T-cell dynamics are also suggested to contribute to the diverse symptoms of DIHS/DRESS. However, the pathomechanisms of this complex disease remain largely unknown. In particular, how viral infections contribute to the pathogenesis of DIHS/DRESS and why autoimmune sequelae arise in DIHS/DRESS are yet to be elucidated. This review describes the clinical features of DIHS/DRESS, including the associated complications and sequelae, and discusses recent advances in our understanding of the immunopathogenic mechanisms of DIHS/DRESS.

Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS): An Interplay among Drugs, Viruses, and Immune System

Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is a severe multiorgan hypersensitivity reaction mostly caused by a limited number of eliciting drugs in patients with a genetic predisposition. Patients with DRESS syndrome present with characteristic but variable clinical and pathological features. Reactivation of human herpesviruses (HHV), especially HHV-6, is the hallmark of the disease. Anti-viral immune responses intertwined with drug hypersensitivity make the disease more complicated and protracted. In recent years, emerging studies have outlined the disease more clearly, though several important questions remain unresolved. In this review, we provide an overview of DRESS syndrome, including clinical presentations, histopathological features, pathomechanisms, and treatments.

Skin recruitment of monomyeloid precursors involves human herpesvirus-6 reactivation in drug allergy

BACKGROUND

In drug-induced hypersensitivity syndrome (DIHS), latent human herpesvirus (HHV)-6 is frequently reactivated in association with flaring of symptoms such as fever and hepatitis. We recently demonstrated an emergence of monomyeloid precursors expressing HHV-6 antigen in the circulation during this clinical course.

METHODS

To clarify the mechanism of HHV-6 reactivation, we immunologically investigated peripheral blood mononuclear cells (PBMCs), skin-infiltrating cells, and lymphocytes expanded from skin lesions of patients with DIHS.

RESULTS

The circulating monomyeloid precursors in the patients with DIHS were mostly CD11b(+) CD13(+) CD14(-) CD16(high) and showed substantial expression of skin-associated molecules, such as CCR4. CD13(+) CD14(-) cells were also found in the DIHS skin lesions, suggesting skin recruitment of this cell population. We detected high levels of high-mobility group box (HMGB)-1 in blood and skin lesions in the active phase of patients with DIHS and showed that recombinant HMGB-1 had functional chemoattractant activity for monocytes/monomyeloid precursors in vitro. HHV-6 infection of the skin-resident CD4(+) T cells was confirmed by the presence of its genome and antigen. This infection was likely to be mediated by monomyeloid precursors recruited to the skin, because normal CD4(+) T cells gained HHV-6 antigen after in vitro coculture with highly virus-loaded monomyeloid precursors from the patients.

CONCLUSIONS

Our results suggest that monomyeloid precursors harboring HHV-6 are navigated by HMGB-1 released from damaged skin and probably cause HHV-6 transmission to skin-infiltrating CD4(+) T cells, which is an indispensable event for HHV-6 replication. These findings implicate the skin as a cryptic and primary site for initiating HHV-6 reactivation.

Human herpesviruses 6, 7, and 8 from a dermatologic perspective

Human herpesviruses (HHVs) have frequently been suspected as etiologic agents or cofactors in cutaneous disease. However, clearly established associations are rare. Investigations into an etiologic association between HHVs and cutaneous disease are complicated by the ubiquity and nearly universal prevalence of some herpesviruses. This article summarizes the associations between cutaneous disease and HHV-6, HHV-7, and HHV-8. In addition to a personal library of references, the PubMed database of biomedical literature was searched using the following Medical Subject Heading terms: HHV-6, HHV-7, and HHV-8, each in conjunction with cutaneous manifestations, virology, epidemiology, dermatopathology, and therapeutics, between 1998 and March 2011. Free-text searches with known or suspected disease associations were added for broader coverage. The results have been summarized to provide a practical review for the physician likely to encounter cutaneous diseases.

Recent progress of elucidating the mechanisms of drug hypersensitivity

Recent technical approaches to investigating drug hypersensitivity have provided a great deal of information to solve the mechanisms that remain poorly understood. First, immunological investigations and in silico analysis have revealed that a novel interaction between T cells and antigen-presenting cells, namely the pharmacological interaction concept, is involved in drug recognition and the hapten theory. Second, progress in immunology has provided a new concept of CD4+ T cell subsets. Th17 cells have proven to be a critical player in acute generalized exanthematous pustulosis. Our recent findings suggest that this subset might contribute to the pathogenesis of Stevens-Johnson syndrome/toxic epidermal necrolysis. Third, alarmins, molecules associated with innate immunity, are also associated with exaggeration and the persistence of severe drug hypersensitivity. The latest innovative techniques are providing a new landscape to examine drug hypersensitivity.

The innate immune system in delayed cutaneous allergic reactions to medications

PURPOSE OF REVIEW

Innate immune responses are attracting increasing interest from researchers in the field of drug allergy. This review discusses recent advances in the understanding of several innate immune components in delayed cutaneous hypersensitivity reactions to medications, with special attention on severe reactions.

RECENT FINDINGS

The mechanism of activation of dendritic cells in response to drugs is being unravelled. Activated monocytes and macrophages have been found in affected skin of bullous diseases. Increased gene expression of monomyeloid cell products including several 'alarmins' or endogenous damage-associated molecular patterns has been described in Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN). Natural killer (NK) cells from patients respond to drugs in vitro. In-vivo, NK cells may contribute to severe diseases through the secretion of effector molecules such as granulysin. The innate receptor CD94/NKG2C is expressed by NK cells and cytotoxic T lymphocytes in SJS/TEN and triggers degranulation in response to human leukocyte antigen-E-expressing keratinocytes. T cells with innate activities have been detected in patients during severe acute reactions.

SUMMARY

Humoral and cellular components of the innate immune response have been identified in association with delayed drug hypersensitivity reactions. Their participation in certain diseases may explain the variability of phenotypes in hypersensitivity reactions to medications.