High sensitivity of human leukocyte antigen-b*5701 as a marker for immunologically confirmed abacavir hypersensitivity in white and black patients

Variation within the non-coding genome influences genetic and epigenetic regulation of the human leukocyte antigen genes

Variation within the non-coding genome may influence the regulation and expression of important genes involved in immune control such as the human leukocyte antigen (HLA) system. Class I and Class II HLA molecules are essential for peptide presentation which is required for T lymphocyte activation. Single nucleotide polymorphisms within non-coding regions of HLA Class I and Class II genes may influence the expression of these genes by affecting the binding of transcription factors and chromatin modeling molecules. Furthermore, an interplay between genetic and epigenetic factors may also influence HLA expression. Epigenetic factors such as DNA methylation and non-coding RNA, regulate gene expression without changing the DNA sequence. However, genetic variation may promote or allow genes to escape regulation by epigenetic factors, resulting in altered expression. The HLA system is central to most diseases, therefore, understanding the role of genetics and epigenetics on HLA regulation will tremendously impact healthcare. The knowledge gained from these studies may lead to novel and cost-effective diagnostic approaches and therapeutic interventions. This review discusses the role of non-coding variants on HLA regulation. Furthermore, we discuss the interplay between genetic and epigenetic factors on the regulation of HLA by evaluating literature based on polymorphisms within DNA methylation and miRNA regulatory sites within class I and Class II HLA genes. We also provide insight into the importance of the HLA non-coding genome on disease, discuss ethnic-specific differences across the HLA region and provide guidelines for future HLA studies.

Stevens-Johnson syndrome and toxic epidermal necrolysis: Updates in pathophysiology and management

ABSTRACT

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are life-threatening conditions characterized by extensive detachment of the epidermis and mucous membranes. These severe disorders carry a high mortality rate, and their pathogenesis remains largely unclear. Furthermore, optimal therapeutic strategies for SJS/TEN remain a subject of ongoing debate. Early diagnosis of SJS/TEN is challenging, and reliable biomarkers for diagnosis or severity prediction have not been firmly established. Certain drugs, such as carbamazepine and allopurinol, have shown a strong association with specific human leukocyte antigen (HLA) types. Recently, the potential benefits of HLA screening prior to administering these drugs to reduce the incidence of SJS/TEN have been explored. Epidermal cell death in SJS/TEN lesions is caused by extensive apoptosis, primarily through the Fas-FasL and perforin/granzyme pathways. Our findings suggest that necroptosis, a form of programmed necrosis, also contributes to epidermal cell death. Annexin A1, released from monocytes, interacts with the formyl peptide receptor 1 to induce necroptosis. Several biomarkers, such as CC chemokine ligand (CCL)-27, interleukin-15, galectin-7, receptor-interacting protein kinases 3 (RIP3), and lipocalin-2, have been identified for diagnostic and prognostic purposes in SJS/TEN. Supportive care is recommended for treating SJS/TEN, but the efficacy of various therapeutic options-including systemic corticosteroids, intravenous immunoglobulin, cyclosporine, and tumor necrosis factor-α antagonists-remains controversial. Recent studies have investigated the potential benefits of tumor necrosis factor-α antagonists. In this review, we discuss recent advances in the understanding and management of SJS/TEN.

Delayed Skin Testing for Systemic Medications: Helpful or Not?

Cutaneous adverse drug reactions collectively are delayed drug reactions such as morbilliform drug eruption and severe cutaneous adverse reactions (SCARs). Morbilliform drug eruption may wane over time, be the result of drug viral interactions, and be amenable to slow reintroduction or rechallenge, whereas SCARs are HLA class I restricted, T-cell-mediated reactions that demonstrate durable immunity and warrant lifelong avoidance. SCARs such as drug reaction with eosinophilia and systemic symptoms, Stevens-Johnson syndrome and toxic epidermal necrolysis, acute generalized exanthematous pustulosis, and generalized bullous fixed drug eruption often occur in the setting of multiple drugs dosed together. Collectively, they lead to significant morbidity, mortality, and drug safety concerns that could severely limit future treatment options. Currently, no single or combination of diagnostic tests for SCARs such as ex vivo or in vitro testing, in vivo (skin) testing, or other adjunctive tests such as HLA typing have 100% negative predictive value. In this "Controversies in Allergy Review" article, we review the current literature on delayed skin testing (patch and delayed prick/intradermal test) and critically assess the evidence base of its utility across different drugs and clinical phenotypes of delayed hypersensitivity reactions.

Human leukocyte antigen HLA-B*57:01 status in HIV-1 patients developing hypersensitivity reactions in Benin: a pilot study

BACKGROUND

Antiretroviral drugs in people living with HIV-1 (PLHIV-1) often trigger side effects which may lead to discontinuation or failure of treatment. Human Leukocyte Antigen B*57:01 (HLA-B*57:01) allele is known to predict hypersensitivity reactions to Abacavir. Very few data are available on the prevalence of HLA-B*57:01 allele in PLHIV-1 in African countries. This study aimed to screen for HLA-B*57:01 allele in PLHIV-1 in Benin.

METHODS

This pilot study was carried out on one hundred ten PLHIV-1 enrolled in two health facilities in Benin. Socio-demographic and clinical data were collected. Biological data were determined and HLA-B*57:01 allele was genotyped, using Single Specific Primer-Polymerase Chain Reaction in blood samples.

RESULTS

70% of participants were female. PLHIV-1 were under TDF + 3TC + DTG (47.2%) or TDF + 3TC + EFV (57.3%). Their median age was 41 [36-48.75] years and the average CD4 + T cell count was 249 [130-381.25] cells/µl. The average viral load in treatment failure PLHIV-1 was 4.7 [3.9-5.2] Log10. At the inclusion date, twenty-nine (26.4%) PLHIV-1 under TDF + 3TC + EFV have developed hypersensitivity reactions. None of 110 patients had shown HLA-B*5701 allele.

CONCLUSION

Our study revealed that HLA-B*57:01 allele was very rare in PLHIV-1 in Benin, suggesting that its screening before starting the Abacavir regimen did not seem necessary.

Severe cutaneous adverse reactions

Severe cutaneous adverse reactions (SCARs), which include Stevens-Johnson syndrome and toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms (also known as drug-induced hypersensitivity syndrome), acute generalized exanthematous pustulosis, and generalized bullous fixed drug eruption, are life-threatening conditions. The pathogenesis of SCARs involves T cell receptors recognizing drug antigens presented by human leukocyte antigens, triggering the activation of distinct T cell subsets. These cells interact with keratinocytes and various immune cells, orchestrating cutaneous lesions and systemic manifestations. Genetic predisposition, impaired drug metabolism, viral reactivation or infections, and heterologous immunity influence SCAR development and clinical presentation. Specific genetic associations with distinct SCAR phenotypes have been identified, leading to the implementation of genetic screening before prescription in various countries to prevent SCARs. Whilst systemic corticosteroids and conventional immunomodulators have been the primary therapeutic agents, evolving strategies, including biologics and small molecules targeting tumour necrosis factor, different cytokines, or Janus kinase signalling pathways, signify a shift towards a precision management paradigm that considers individual clinical presentations.

HLA-B*57:01-dependent intracellular stress in keratinocytes triggers dermal hypersensitivity reactions to abacavir

Specific human leukocyte antigen (HLA) polymorphisms combined with certain drug administration strongly correlate with skin eruption. Abacavir hypersensitivity (AHS), which is strongly associated with HLA-B*57:01, is one of the most representative examples. Conventionally, HLA transmits immunological signals via interactions with T cell receptors on the cell surface. This study focused on HLA-mediated intracellular reactions in keratinocytes that might determine the onset of skin immunotoxicity by drug treatments. Abacavir exposure resulted in keratinocytes expressing HLA-B*57:01 exhibiting endoplasmic reticulum (ER) stress responses, such as immediate calcium release into the cytosol and enhanced HSP70 expression. In contrast, keratinocytes expressing HLA-B*57:03 (closely related to HLA-B*57:01) did not show these changes. This indicated that HLA-B*57:01 has a specific intracellular response to abacavir in keratinocytes in the absence of lymphocytes. Furthermore, abacavir exposure in HLA-B*57:01-expressing keratinocytes elevated the expression of cytokines/chemokines such as interferon-γ, interleukin-1β, and CCL27, and induced T lymphoblast migration. These effects were suppressed by ER stress relief using 4-phenylbutyrate (4-PB). HLA-B*57:01-transgenic mice also exhibited ER stress in epidermal areas following abacavir administration, and abacavir-induced skin toxicity was attenuated by the administration of 4-PB. Moreover, abacavir bound to HLA-B*57:01 within cells and its exposure led to HLA-B*57:01 protein aggregation and interaction with molecular chaperones in the ER of keratinocytes. Our results underscore the importance of HLA-mediated intracellular stress responses in understanding the onset of HLA-B*57:01-mediated AHS. We provide the possibility that the intracellular behavior of HLA is crucial for determining the onset of drug eruptions.

Changing patterns in the epidemiology of drug allergy

Drug allergy (DA) remains a complex and unaddressed problem worldwide that often deprives patients of optimal medication choices and places them at risk for life-threatening reactions. Underdiagnosis and overdiagnosis are common and due to the lack of standardized definitions and biomarkers. The true burden of DA is unknown, and recent efforts in data gathering through electronic medical records are starting to provide emerging patterns around the world. Ten percent of the general population engaged in health care claim to have a DA, and the most common label is penicillin allergy. Up to 20% of emergency room visits for anaphylaxis are due to DA and 15%-20% of hospitalized patients report DA. It is estimated that DA will increase based on the availability and use of new and targeted antibiotics, vaccines, chemotherapies, biologicals, and small molecules, which are aimed at improving patient's options and quality of life. Global and regional variations in the prevalence of diseases such as human immunodeficiency virus and mycobacterial diseases, and the drugs used to treat these infections have an impact on DA. The aim of this review is to provide an update on the global impact of DA by presenting emerging data on drug epidemiology in adult and pediatric populations.

Elucidating the Mechanisms Underlying Interindividual Differences in the Onset of Adverse Drug Reactions

Idiosyncratic drug toxicities (IDTs) pose a significant challenge; they are marked by life-threatening adverse reactions that emerge aftermarket release and are influenced by intricate genetic and environmental variations. Recent genome-wide association studies have highlighted a strong correlation between specific human leukocyte antigen (HLA) polymorphisms and IDT onset. This review provides an overview of current research on HLA-mediated drug toxicities. In the last six years, HLA-transgenic (Tg) mice have been instrumental in advancing our understanding of these underlying mechanisms, uncovering systemic immune reactions that replicate human drug-induced immune stimulation. Additionally, the potential role of immune tolerance in shaping individual differences in adverse effects highlights its relevance to the interplay between HLA polymorphisms and IDTs. Although HLA-Tg mice offer valuable insights into systemic immune reactions, further exploration is essential to decipher the intricate interactions that lead to organ-specific adverse effects, especially in organs such as the skin or liver. Navigating the intricate interplay of HLA, which may potentially trigger intracellular immune responses, this review emphasizes the need for a holistic approach that integrates findings from both animal models and molecular/cellular investigations. The overarching goal is to enhance our comprehensive understanding of HLA-mediated IDTs and identify factors shaping individual variations in drug reactions. This review aims to facilitate the development of strategies to prevent severe adverse effects, address existing knowledge gaps, and provide guidance for future research initiatives in the field of HLA-mediated IDTs.

Pharmacogenomics and adverse effects of anti-infective drugs in children

Children, as a special group, have their own peculiarities in terms of individualized medication use compared to adults. Adverse drug reactions have been an important issue that needs to be addressed in the hope of safe medication use in children, and the occurrence of adverse drug reactions is partly due to genetic factors. Anti-infective drugs are widely used in children, and they have always been an important cause of the occurrence of adverse reactions in children. Pharmacogenomic technologies are becoming increasingly sophisticated, and there are now many guidelines describing the pharmacogenomics of anti-infective drugs. However, data from paediatric-based studies are scarce. This review provides a systematic review of the pharmacogenomics of anti-infective drugs recommended for gene-guided use in CPIC guidelines by exploring the relationship between pharmacogenetic frequencies and the incidence of adverse reactions, which will help inform future studies of individualized medication use in children.

Prevalence of the HLA-B*5701 Allele and Abacavir Hypersensitivity in Saudi HIV Patients: A Multicenter Study

Introduction Human immunodeficiency virus (HIV) incidence and prevalence are increasing in Saudi Arabia, with a total prevalence of 12,000 in 2020. Treatment of HIV patients includes multiple regimens that may involve abacavir (ABC), which is a potent drug for treating HIV and can be used as a single or combined pill. Unfortunately, its use was limited by the known associated hypersensitivity reaction (HSR). A worldwide literature review over the past decades reported that the incidence of ABC-related HSR is 5-8%. Methods The study was a cross-sectional multicentric study involving five governmental hospitals in Saudi Arabia and included all HIV patients who were following in these centers. Results Out of 3082 patients, 1293 were tested for HLA-B*5701. The prevalence for ABC-HSR is 1.59%, with variability among the five hospitals, with the highest in King Fahad Hospital in Hafuf (KFH-H) at 4.00% and the lowest in Dammam Medical Complex (DMC) at 0.49%. In previous studies, HLA-B*5701 associated with ABC-HSR varied among different ethnic groups. Our study showed that two patients developed ABC-HSR clinically while they were both negative for HLA-B*5701. Conclusion The fact that patients with negative genetic testing are still at risk of developing ABC-HSR makes continuing screening for HLA-B*5701 status essential, as the consequences of missing such a life-threatening HSR could be detrimental.

Drug-induced altered self-presentation increases tumor immunogenicity

Anti-human immunodeficiency virus (HIV) drug abacavir (ABC) binds to the specific allele of human leukocyte antigen (HLA-B*57:01) and activates CD8+ T cells by presenting altered abnormal peptides. Here, we examined the effect of ABC-induced altered self-presentation by HLA-B*57:01 on immunogenicity of cancer cells and CD8+ T-cell-dependent anti-tumor immunity. We established human-mouse chimeric HLA-B*57:01-expressing tumor cell lines (B16F10 and 3LL) and tested the anti-tumor effect of ABC in vivo. ABC treatment inhibited the growth of HLA-B*57:01-expressing tumors by a CD8+ T-cell-dependent mechanism. ABC treatment induced CXCR3-dependent infiltration of CD8+ T cells into HLA-B*57:01-expressing tumors, and activated those tumor-infiltrating CD8+ T cells to proliferate and secrete IFN-γ. The activation of CD8+ T cells using drug-induced altered self-presentation may be a new strategy to increase tumor immunogenicity and improve the efficacy of immunotherapy.

HLA-B*57:01 typing in a Malaysian cohort: implications of abacavir hypersensitivity in people living with HIV

Background: Abacavir (ABC) in combination with other antiretroviral drugs, is used to treat people living with HIV (PLWH). However, it is linked to a fatal hypersensitivity reaction in susceptible individuals, and is strongly associated with the HLA-B*57:01 allele. Materials & methods: A total of 152 patients, 50 PLWH and 102 HIV-1 negative patients, were assessed for the HLA-B*57:01 allele through a sequence-specific primer PCR. Results: All PLWH tested negative for the HLA-B*57:01 allele, but two HIV-negative patients were found to have HLA-B*57, with one of them expressing the HLA-B*57:01 allele. Conclusion: Given the low prevalence of this risk allele in the population, testing for the presence of HLA-B*57:01 in PLWH may not provide significant benefit for the reported population.

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.

Advances in understanding of the pathogenesis and therapeutic implications of drug reaction with eosinophilia and systemic symptoms: an updated review

Drug reaction with eosinophilia and systemic symptoms or drug-induced hypersensitivity syndrome (DRESS/DIHS) is one type of severe cutaneous adverse reaction (SCAR). It is featured by fever, widespread skin lesions, protracted clinical course, internal organ involvement, and possibly long-term autoimmune sequelae. The presence of high-risk human leukocyte antigen (HLA) alleles, hypersensitivity reaction after culprit drug ingestion, and human herpesvirus reactivation may all contribute to its complex clinical manifestations. Some recent studies focusing on the roles of involved cytokines/chemokines and T cells co-signaling pathways in DRESS/DIHS were conducted. In addition, some predictors of disease severity and prognosis were also reported. In this review, we provided an update on the current understanding of the pathogenesis, potential biomarkers, and the relevant therapeutic rationales of DRESS/DIHS.

HLA-B*57:01/Carbamazepine-10,11-Epoxide Association Triggers Upregulation of the NFκB and JAK/STAT Pathways

Measure of drug-mediated immune reactions that are dependent on the patient's genotype determine individual medication protocols. Despite extensive clinical trials prior to the license of a specific drug, certain patient-specific immune reactions cannot be reliably predicted. The need for acknowledgement of the actual proteomic state for selected individuals under drug administration becomes obvious. The well-established association between certain HLA molecules and drugs or their metabolites has been analyzed in recent years, yet the polymorphic nature of HLA makes a broad prediction unfeasible. Dependent on the patient's genotype, carbamazepine (CBZ) hypersensitivities can cause diverse disease symptoms as maculopapular exanthema, drug reaction with eosinophilia and systemic symptoms or the more severe diseases Stevens-Johnson-Syndrome or toxic epidermal necrolysis. Not only the association between HLA-B*15:02 or HLA-A*31:01 but also between HLA-B*57:01 and CBZ administration could be demonstrated. This study aimed to illuminate the mechanism of HLA-B*57:01-mediated CBZ hypersensitivity by full proteome analysis. The main CBZ metabolite EPX introduced drastic proteomic alterations as the induction of inflammatory processes through the upstream kinase ERBB2 and the upregulation of NFκB and JAK/STAT pathway implying a pro-apoptotic, pro-necrotic shift in the cellular response. Anti-inflammatory pathways and associated effector proteins were downregulated. This disequilibrium of pro- and anti-inflammatory processes clearly explain fatal immune reactions following CBZ administration.

Updates on the immunopathology and genomics of severe cutaneous adverse drug reactions

Severe cutaneous adverse reactions (SCARs) such as Stevens-Johnson syndrome, toxic epidermal necrolysis (SJS/TEN), and drug reaction with eosinophilia and systemic symptoms (DRESS)/drug-induced hypersensitivity syndrome (DIHS) cause significant morbidity and mortality and impede new drug development. HLA class I associations with SJS/TEN and drug reaction with eosinophilia and systemic symptoms/drug-induced hypersensitivity syndrome have aided preventive efforts and provided insights into immunopathogenesis. In SJS/TEN, HLA class I-restricted oligoclonal CD8+ T-cell responses occur at the tissue level. However, specific HLA risk allele(s) and antigens driving this response have not been identified for most drugs. HLA risk alleles also have incomplete positive and negative predictive values, making truly comprehensive screening currently challenging. Although, there have been key paradigm shifts in knowledge regarding drug hypersensitivity, there are still many open and unanswered questions about SCAR immunopathogenesis, as well as genetic and environmental risk. In addition to understanding the cellular and molecular basis of SCAR at the single-cell level, identification of the MHC-restricted drug-reactive self- or viral peptides driving the hypersensitivity reaction will also be critical to advancing premarketing strategies to predict risk at an individual and drug level. This will also enable identification of biologic markers for earlier diagnosis and accurate prognosis, as well as drug causality and targeted therapeutics.

Utility and Safety of Skin Tests in Drug Reaction With Eosinophilia and Systemic Symptoms (DRESS): A Systematic Review

BACKGROUND

Determination of culprit drug in drug reaction with eosinophilia and systemic symptoms (DRESS) is crucial. Skin tests have been used, although it remains unclear how sensitive these are.

OBJECTIVE

To determine the value of skin tests in the assessment of drug causality in DRESS.

METHODS

A systematic literature search was conducted for publications from 1996 onward of skin tests (skin prick test = SPT, patch test = PT, intradermal test = IDT) performed in clearly defined DRESS cases. Outcomes of testing, drug culpability assessments, and challenge test data were extracted.

RESULTS

A total of 17 articles met inclusion criteria. In 290 patients with DRESS, patch testing was most frequent (PT = 97.2% [n = 282], IDT = 12.4% [n = 36], SPT = 3.1% [n = 9]). Positive results were noted in 58.4% (n = 160 of 282) of PTs, 66.5% of IDTs, and 25% of SPTs. When confidence of drug causality was high (n = 73 of 194), testing did not correlate well with clinical suspicion: PTs, 37.6%; IDTs, 36.5%. Direct comparison of skin testing with provocation testing (n = 12) showed 83.3% correlation. Positive IDT results were reported in 8 negative PT cases.

CONCLUSIONS

Skin tests, particularly PTs and IDTs, have been reported as tools for diagnosis of causal drugs in DRESS. Heterogeneity in methodology, results analysis, and reporting of cohorts make meta-analysis to determine sensitivity and specificity of published literature impossible and highlight weaknesses in the field. We propose that international collaboration is essential to harmonize the methodology and reporting measures from hypersensitivity testing studies in larger cohorts.

Integrating pharmacogenomics into clinical trials of hearing disorders

In 2019, the U.S. Food and Drug Administration issued guidance to increase the efficiency of drug development and support precision medicine, including tailoring treatments to those patients who will benefit based on genetic variation even in the absence of a documented mechanism of action. Although multiple advancements have been made in the field of pharmacogenetics (PGx) for other disease conditions, there are no approved PGx guidelines in the treatment of hearing disorders. In studies of noise-induced hearing loss (NIHL), some progress has been made in the last several years associating genomic loci with susceptibility to noise damage. However, the power of such studies is limited as the underlying physiological responses may vary considerably among the patient populations. Here, we have summarized previous animal studies to argue that NIHL subtyping is a promising strategy to increase the granularity of audiological assessments. By coupling this enhanced phenotyping capability with genetic association studies, we suggest that drug efficacy will be better predicted, increasing the likelihood of success in clinical trials when populations are stratified based on genetic variation or designed with multidrug combinations to reach a broader segment of individuals suffering or at risk from NIHL.

HLA pharmacogenetic markers of drug hypersensitivity from the perspective of the populations of the Greater Middle East

Specific HLA associations with drug hypersensitivity may vary between geographic regions and ethnic groups. There are little to no data related to HLA-drug hypersensitivity on populations who reside in the Greater Middle East (GME), a vast region spanning from Morocco in the west to Pakistan in the east. In this review, the authors intended to summarize the significant HLA alleles associated with hypersensitive drug reactions induced by different drugs, as have been found in different populations, and to summarize the prevalence of these alleles in the specific and diverse populations of the GME. For example, HLA-B*57:01 allele prevalence, associated with abacavir-induced hypersensitivity, ranges from 1% to 3%, and HLA-DPB1*03:01 prevalence, associated with aspirin-induced asthma, ranges from 10% to 14% in the GME population. Studying pharmacogenomic associations in the ethnic groups of the GME may allow the discovery of new associations, confirm ones found with a low evidence rate and enable cost-effectiveness analysis of allele screening before drug use.

Weak complex formation of adverse drug reaction-associated HLAB57, B58, and B15 molecules

The combination of certain human leukocyte antigen (HLA) polymorphisms with administration of certain drugs shows a strong correlation with developing drug hypersensitivity. Examples of typical combinations are HLA-B*57:01 with abacavir and HLA-B*15:02 with carbamazepine. However, despite belonging to the same serotype, HLA-B*57:03 and HLA-B*15:01 are not associated with drug hypersensitivity. Recent studies have shown that several HLA polymorphisms are associated with multiple drugs rather than a single drug, all resulting in drug hypersensitivity. In this study, we compared the molecular structures and intracellular localization of HLA-B*57:01, HLA-B*58:01, and HLA-B*15:02, which pose risks for developing drug hypersensitivity, as well as HLA-B*57:03 and HLA-B*15:01 that do not present such risks. We found that HLA molecules posing risks have a low affinity for the subunit β₂-microglobulin; notably, the weak hydrogen bond formed via Gln96 of the HLA molecule contributes to this behavior. We also clarified that these HLA molecules are easily accumulated in the endoplasmic reticulum, exhibiting a low expression on the cell surface. Considering that these hypersensitivity risk-associated HLA molecules form complexes with β₂-microglobulin and peptides in the endoplasmic reticulum, we assumed that their low complex formation ability in the endoplasmic reticulum facilitates the interaction with multiple drugs.

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

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

Drug Reaction with Eosinophilia and Systemic Symptoms (DReSS)/Drug-Induced Hypersensitivity Syndrome (DiHS)-Readdressing the DReSS

Drug reaction with eosinophilia and systemic symptoms (DReSS), also known as drug-induced hypersensitivity syndrome (DiHS), is a severe, systemic, T cell mediated drug reaction with combinations of cutaneous, hematologic, and internal organ involvement. Pathogenesis of DReSS is multi-factorial, involving drug-exposure, genetic predisposition through specific human leukocyte antigen (HLA) alleles and metabolism defects, viral reactivation, and immune dysregulation. Clinical features of this condition are delayed, stepwise, and heterogenous, making this syndrome challenging to recognize and diagnose. Two sets of validated diagnostic criteria exist that can be employed to diagnose DReSS/DiHS. Methods to improve early recognition of DReSS and predict disease severity has been a recent area of research focus. In vitro and in vivo tests can be employed to confirm the diagnosis and help identify culprit drugs. The mainstay treatment of DReSS is prompt withdrawal of the culprit drug, supportive treatment, and immunosuppression depending on the severity of disease. We present a comprehensive review on the most recent research and literature on DReSS, with emphasis on pathogenesis, clinical features, diagnosis, confirmatory testing modalities, and treatment. Additionally, this summary aims to highlight the differing viewpoints on this severe disease and broaden our perspective on the condition known as DReSS.

Evolution of HLA-B Pharmacogenomics and the Importance of PGx Data Integration in Health Care System: A 10 Years Retrospective Study in Thailand

Background: The HLA-B is the most polymorphic gene, play a crucial role in drug-induced hypersensitivity reactions. There is a lot of evidence associating several risk alleles to life-threatening adverse drug reactions, and a few of them have been approved as valid biomarkers for predicting life-threatening hypersensitivity reactions.

Objectives: The objective of this present study is to present the progression of HLA-B pharmacogenomics (PGx) testing in the Thai population during a 10‐year period, from 2011 to 2020.

Methods: This was a retrospective observational cohort study conducted at the Faculty of Medicine Ramathibodi Hospital. Overall, 13,985 eligible patients who were tested for HLA-B risk alleles between periods of 2011–2020 at the study site were included in this study.

Results: The HLA PGx testing has been increasing year by year tremendously, 94 HLA-B testing was done in 2011; this has been raised to 2,880 in 2020. Carbamazepine (n = 4,069, 33%), allopurinol (n = 4,675, 38%), and abacavir (n = 3,246, 26%) were the most common drugs for which the HLA-B genotyping was performed. HLA-B*13:01, HLA-B*15:02 and HLA-B*58:01 are highly frequent, HLA-B*51:01 and HLA-B*57:01 are moderately frequent alleles that are being associated with drug induced hypersensitivity. HLA-B*59:01 and HLA-B*38:01 theses alleles are rare but has been reported with drug induced toxicity. Most of the samples were from state hospital (50%), 36% from private clinical laboratories and 14% from private hospitals.

Conclusion: According to this study, HLA-B PGx testing is increasing substantially in Thailand year after year. The advancement of research in this field, increased physician awareness of PGx, and government and insurance scheme reimbursement assistance could all be factors. Incorporating PGx data, along with other clinical and non-clinical data, into clinical decision support systems (CDS) and national formularies, on the other hand, would assist prescribers in prioritizing therapy for their patients. This will also aid in the prediction and prevention of serious adverse drug reactions.

Proteomic Profiling and T Cell Receptor Usage of Abacavir Susceptible Subjects

Type B adverse drug reactions (ADRs) represent a significant threat as their occurrence arises unpredictable and despite proper application of the drug. The severe immune reaction Abacavir Hypersensitivity Syndrome (AHS) that arises in HIV⁺ patients treated with the antiretroviral drug Abacavir (ABC) strongly correlates to the presence of the human leukocyte antigen (HLA) genotype HLA-B*57:01 and discriminates HLA-B*57:01⁺ HIV⁺ patients from ABC treatment. However, not all HLA-B*57:01⁺ HIV⁺ patients are affected by AHS, implying the involvement of further patient-specific factors in the development of AHS. The establishment of a reliable assay to classify HLA-B*57:01 carriers as ABC sensitive or ABC tolerant allowed to investigate the T cell receptor (TCR) Vβ chain repertoire of effector cells and revealed Vβ6 and Vβ24 as potential public TCRs in ABC sensitive HLA-B*57:01 carriers. Furthermore, distinct effects of ABC on the cellular proteome of ABC sensitive and tolerant volunteers were observed and suggest enhanced activation and maturation of dentritic cells (DC) in ABC sensitive volunteers. Analysis of ABC-naïve cellular proteomes identified the T cell immune regulator 1 (TCIRG1) as a potential prognostic biomarker for ABC susceptibility and the involvement of significantly upregulated proteins, particularly in peptide processing, antigen presentation, interferon (IFN), and cytokine regulation.

Abacavir inhibits but does not cause self-reactivity to HLA-B*57:01-restricted EBV specific T cell receptors

Pre-existing pathogen-specific memory T cell responses can contribute to multiple adverse outcomes including autoimmunity and drug hypersensitivity. How the specificity of the T cell receptor (TCR) is subverted or seconded in many of these diseases remains unclear. Here, we apply abacavir hypersensitivity (AHS) as a model to address this question because the disease is linked to memory T cell responses and the HLA risk allele, HLA-B*57:01, and the initiating insult, abacavir, are known. To investigate the role of pathogen-specific TCR specificity in mediating AHS we performed a genome-wide screen for HLA-B*57:01 restricted T cell responses to Epstein-Barr virus (EBV), one of the most prevalent human pathogens. T cell epitope mapping revealed HLA-B*57:01 restricted responses to 17 EBV open reading frames and identified an epitope encoded by EBNA3C. Using these data, we cloned the dominant TCR for EBNA3C and a previously defined epitope within EBNA3B. TCR specificity to each epitope was confirmed, however, cloned TCRs did not cross-react with abacavir plus self-peptide. Nevertheless, abacavir inhibited TCR interactions with their cognate ligands, demonstrating that TCR specificity may be subverted by a drug molecule. These results provide an experimental road map for future studies addressing the heterologous immune responses of TCRs including T cell mediated adverse drug reactions.

A Comprehensive Review of HLA and Severe Cutaneous Adverse Drug Reactions: Implication for Clinical Pharmacogenomics and Precision Medicine

Human leukocyte antigen (HLA) encoded by the HLA gene is an important modulator for immune responses and drug hypersensitivity reactions as well. Genetic polymorphisms of HLA vary widely at population level and are responsible for developing severe cutaneous adverse drug reactions (SCARs) such as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug reaction with eosinophilia and systemic symptoms (DRESS), maculopapular exanthema (MPE). The associations of different HLA alleles with the risk of drug induced SJS/TEN, DRESS and MPE are strongly supportive for clinical considerations. Prescribing guidelines generated by different national and international working groups for translation of HLA pharmacogenetics into clinical practice are underway and functional in many countries, including Thailand. Cutting edge genomic technologies may accelerate wider adoption of HLA screening in routine clinical settings. There are great opportunities and several challenges as well for effective implementation of HLA genotyping globally in routine clinical practice for the prevention of drug induced SCARs substantially, enforcing precision medicine initiatives.

The PD1 inhibitory pathway and mature dendritic cells contribute to abacavir hypersensitivity in human leukocyte antigen transgenic PD1 knockout mice

Based on recent genome-wide association studies, abacavir-induced hypersensitivity is highly associated with human leukocyte antigen (HLA)-B*57:01 allele. However, the underlying mechanism of this occurrence is unclear. To investigate the underlying mechanism, we developed HLA-B*57:01 transgenic mice and found that application of abacavir could cause CD8 T cell activation with elevation in PD1 expression; however, severe skin hypersensitivity was not observed. To eliminate the immunosuppressive effect of PD1, HLA-B*57:01 transgenic/PD1 knockout (01Tg/PD1) mice were generated by mating HLA-B*57:01 transgenic mice and PD1 knockout mice. Thereafter, 01Tg/PD1 mice were treated with abacavir. Similar to the above results, severe skin hypersensitivity was not observed. Therefore, we treated 01Tg/PD1 mice with an anti-CD4 antibody to deplete CD4 T cells, followed by abacavir topically and orally. Severe abacavir-induced skin hypersensitivity was observed in 01Tg/PD1 mice after depletion of CD4 T cells, in addition to significant CD8 T cell activation and dendritic cell maturation. Taken together, we succeeded in reproducing severe skin hypersensitivity in a mouse model. And we found that through the combined depletion of PD1 and CD4 T cells, CD8 T cells could be activated and could proceed to clonal proliferation, which is promoted by mature dendritic cells, thereby eventually inducing severe skin hypersensitivity.

Regulation of the immune tolerance system determines the susceptibility to HLA-mediated abacavir-induced skin toxicity

Idiosyncratic drug toxicity (IDT) associated with specific human leukocyte antigen (HLA) allotype is a rare and unpredictable life-threatening adverse drug reaction for which prospective mechanistic studies in humans are difficult. Here, we show the importance of immune tolerance for IDT onset and determine whether it is susceptible to a common IDT, HLA-B*57:01-mediated abacavir (ABC)-induced hypersensitivity (AHS), using CD4⁺ T cell-depleted programmed death-1 receptor (PD-1)-deficient HLA-B*57:01 transgenic mice (B*57:01-Tg/PD-1^−/−). Although AHS is not observed in B*57:01-Tg mice, ABC treatment increases the proportion of cytokine- and cytolytic granule-secreting effector memory CD8⁺ T cells in CD4⁺ T cell-depleted B*57:01-Tg/PD-1^−/− mice, thereby inducing skin toxicity with CD8⁺ T cell infiltration, mimicking AHS. Our results demonstrate that individual differences in the immune tolerance system, including PD-1^highCD8⁺ T cells and regulatory CD4⁺ T cells, may affect the susceptibility of humans to HLA-mediated IDT in humans.

Using a transgenic mouse model that recapitulates abacavir hypersensitivity syndrome, an idiosyncratic adverse drug reaction, Susukida et al show that individual differences in the immune tolerance system affect the susceptibility to idiosyncratic drug toxicity.

Influence of HLA-B*5701 on 20 year survival rate among patients living with HIV

BACKGROUND

The life expectancy of people living with HIV (PLWH) remains shorter than that of the general population, despite significant improvement in the recent years. Mortality in HIV-infected individuals may be associated with a higher viral load at of diagnosis, a lower CD4 count, or clinical variables such as sex or route of transmission. This article investigated the role of the HLA-B*5701 varian on mortality among PLWH.

METHODS

Material for the analysis consist of the data of 2,393 patients for whom the HLA-B*57 variant was known. Those patients were followed under the care of the Infectious Diseases Hospital in Warsaw (n = 1555) and the Clinic of Acquired Immunodeficiency of the Pomeranian Medical University in Szczecin (n = 838). Factors such as age, gender, date of HIV diagnosis, route of transmission, date of death, baseline HIV viral load and baseline CD4 counts, were collected, and end-point cross-sectional analyses were marked at 60, 120, 180 and 240 month of observation.

RESULTS

HLA-B*5701 allele was found in 133 (5.5%) analyzed cases. Median age was notably higher for HLA-B*5701 positive patients [32.7 (28.3-41.3) vs. 31.6 (26.8-38.3)years p = 0.02]. HLA-B*5701 was associated with lower baseline viral load [4.21 (3.5-4.8) vs. 4.79 (4.2-5.3)log copies/ml p<0.001] and higher CD4count [448 (294.5-662) vs. 352 (176-514) cells/μl p<0.001]. There were no association between HLA-B*5701 and survival for any given end-point. Higher mortality was associated to male gender, intravenous drug users, lower CD4 count at baseline and higher baseline viral load.

CONCLUSIONS

In our study, the presence of HLA-B*5701 allel was not associated with mortality rate of HIV infected patients, irrespective of being associated with both higher baseline CD4 + cell count and lower baseline HIV viral load.

[Importance of HLA in Determining Individual Differences in the Onset of Adverse Drug Reactions]

Individuals vary in their susceptibility to adverse reactions to medications, some of which can be potentially life-threatening. Idiosyncratic drug toxicity (IDT) has been shown to be strongly associated to specific polymorphisms in genes encoding human leukocyte antigens (HLAs) by recent genome-wide association studies. However, the pathogenic mechanisms governing such reactions remain unclarified, at least in part because of a lack of suitable experimental animal models to assess IDT. This review describes our work on the specific allele/drug combination of HLA-B*57:01 and abacavir, an antiretroviral drug targeting the human immunodeficiency virus. As abacavir is known to trigger an HLA-dependent immune response, we engineered a transgenic mouse model-HLA-Tg-by partially substituting the mouse HLA sequence for the corresponding human sequence. Local abacavir exposure was found to trigger a significant immune response in an HLA-dependent manner, and oral administration induced liver injury partially via concurrent activation of the innate immune system. Additionally, we developed a technique for evaluating structural alterations in HLA complexes resulting from drug exposure based on phage display to ensure specificity. Further scrutiny of the mechanism(s) underlying drug-induced immune reactions using the HLA-Tg model, as well as enhanced methods for predicting adverse event incidence, are anticipated to help resolve issues surrounding HLA-associated drug hypersensitivity.

Translational Pharmacogenomics: Discovery, Evidence Synthesis and Delivery of Race-Conscious Medicine

Response to medications, the principal treatment modality for acute and chronic diseases, is highly variable, with 40-70% of patients exhibiting lack of efficacy or adverse drug reactions. With ~ 15-30% of this variability explained by genetic variants, pharmacogenomics has become a valuable tool in our armamentarium for optimizing treatments and is poised to play an increasing role in clinical care. This review presents the progress made toward elucidating genetic underpinnings of drug response including discovery of race/ancestry-specific pharmacogenetic variants and discusses the current evidence and evidence framework for actionability. The review is framed in the context of changing demographics and evolving views related to race and ancestry. Finally, it highlights the vital role played by cohort studies in elucidating genetic differences in drug response across race and ancestry and the informal collaborations that have enabled the field to bridge the "bench to bedside" translational gap.

Immunogenetic determinants of heterosexual HIV-1 transmission: key findings and lessons from two distinct African cohorts

Immunogenetic studies in the past three decades have uncovered a broad range of human genetic factors that seem to influence heterosexual HIV-1 transmission in one way or another. In our own work that jointly evaluated both genetic and nongenetic factors in two African cohorts of cohabiting, HIV-1-discordant couples (donor and recipient pairs) at risk of transmission during quarterly follow-up intervals, relatively consistent findings have been seen with three loci (IL19, HLA-A, and HLA-B), although the effect size (i.e., odds ratio or hazards ratio) of each specific variant was quite modest. These studies offered two critical lessons that should benefit future research on sexually transmitted infections. First, in donor partners, immunogenetic factors (e.g., HLA-B*57 and HLA-A*36:01) that operate directly through HIV-1 viral load or indirectly through genital coinfections are equally important. Second, thousands of single-nucleotide polymorphisms previously recognized as "causal" factors for human autoimmune disorders did not appear to make much difference, which is somewhat puzzling as these variants are predicted or known to influence the expression of many immune response genes. Replicating these observations in additional cohorts is no longer feasible as the field has shifted its focus to early diagnosis, universal treatment, and active management of comorbidities.

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

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

Genomic Risk Factors Driving Immune-Mediated Delayed Drug Hypersensitivity Reactions

Adverse drug reactions (ADRs) remain associated with significant mortality. Delayed hypersensitivity reactions (DHRs) that occur greater than 6 h following drug administration are T-cell mediated with many severe DHRs now associated with human leukocyte antigen (HLA) risk alleles, opening pathways for clinical prediction and prevention. However, incomplete negative predictive value (NPV), low positive predictive value (PPV), and a large number needed to test (NNT) to prevent one case have practically prevented large-scale and cost-effective screening implementation. Additional factors outside of HLA contributing to risk of severe T-cell-mediated DHRs include variation in drug metabolism, T-cell receptor (TCR) specificity, and, most recently, HLA-presented immunopeptidome-processing efficiencies via endoplasmic reticulum aminopeptidase (ERAP). Active research continues toward identification of other highly polymorphic factors likely to impose risk. These include those previously associated with T-cell-mediated HLA-associated infectious or auto-immune disease such as Killer cell immunoglobulin-like receptors (KIR), epistatically linked with HLA class I to regulate NK- and T-cell-mediated cytotoxic degranulation, and co-inhibitory signaling pathways for which therapeutic blockade in cancer immunotherapy is now associated with an increased incidence of DHRs. As such, the field now recognizes that susceptibility is not simply a static product of genetics but that individuals may experience dynamic risk, skewed toward immune activation through therapeutic interventions and epigenetic modifications driven by ecological exposures. This review provides an updated overview of current and proposed genetic factors thought to predispose risk for severe T-cell-mediated DHRs.

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.

Abacavir adverse reactions related with HLA-B*57: 01 haplotype in a large cohort of patients infected with HIV

OBJECTIVE

Carriage of human leukocyte antigen (HLA)-B*57:01 allele increases the risk of abacavir hypersensitivity reaction. Therefore, since 2008 HIV treatment guidelines recommend HLA-B*57:01 screening before abacavir administration, greatly reducing hypersensitivity reaction rate. However, clinically suspected abacavir-related hypersensitivity reactions are described in allele non-carriers. Major aim of this study was to evaluate the relationship between HLA-B*57:01 pattern and abacavir-related hypersensitivity reaction, focusing on hypersensitivity reaction prevalence in allele non-carriers.

METHODS

We included all outpatients aged >18 years old with HIV infection and known HLA-B*57:01 pattern, followed at our Department from January 2000 until December 2017. Patients were divided according to HLA-B*57:01 pattern and first antiretroviral treatment prescribed (containing or not abacavir) as follows: HLA-B*57:01 allele carriers treated with abacavir and HLA-B*57:01 allele non-carriers treated with abacavir. We considered all adverse events reported during first abacavir administration, differentiating between confirmed hypersensitivity reactions and non-hypersensitivity reactions, according to abacavir hypersensitivity reaction definition included in the abacavir EU Summary of Product Characteristics and the US Prescribing Information.

RESULTS

A total of 3144 patients had a known HLA-B*57:01 pattern. About 5.4% of them showed allele polymorphism; Caucasian ethnicity was the most represented. In this cohort, 1801 patients were treated with a first abacavir-containing regimen (98.2% of them was represented by allele non-carriers). 191 out of 1801 patients discontinued abacavir because of toxicity/intolerance; among them 107 described adverse events fulfilled the criteria of confirmed abacavir hypersensitivity reaction (22/32 allele-positive patients and 85/1769 allele-negative patients). After having experienced a confirmed abacavir hypersensitivity reaction, abacavir was re-administered to eight HLA-B*57:01 negative patients. Seven of them re-experienced a syndrome consistent with hypersensitivity reaction, finally leading to drug discontinuation. Overall, no fatal reactions were described.

CONCLUSION

Not all abacavir-related side effects occur as a result of classic HLA-B*57:01-mediated hypersensitivity reaction, as they can develop irrespective of HLA-B*57:01 status. Clinical vigilance must be an essential part of the management of individuals starting abacavir, at any time during treatment. In a 'real-life' setting, clinical diagnosis of suspected abacavir hypersensitivity reaction in allele non-carriers remains crucial for further clinical decision making.

Beneficial and Adverse Effects of cART Affect Neurocognitive Function in HIV-1 Infection: Balancing Viral Suppression against Neuronal Stress and Injury

HIV-associated neurocognitive disorders (HAND) persist despite the successful introduction of combination antiretroviral therapy (cART). While insufficient concentration of certain antiretrovirals (ARV) may lead to incomplete viral suppression in the brain, many ARVs are found to cause neuropsychiatric adverse effects, indicating their penetration into the central nervous system (CNS). Several lines of evidence suggest shared critical roles of oxidative and endoplasmic reticulum stress, compromised neuronal energy homeostasis, and autophagy in the promotion of neuronal dysfunction associated with both HIV-1 infection and long-term cART or ARV use. As the lifespans of HIV patients are increased, unique challenges have surfaced. Longer lives convey prolonged exposure of the CNS to viral toxins, neurotoxic ARVs, polypharmacy with prescribed or illicit drug use, and age-related diseases. All of these factors can contribute to increased risks for the development of neuropsychiatric conditions and cognitive impairment, which can significantly impact patient well-being, cART adherence, and overall health outcome. Strategies to increase the penetration of cART into the brain to lower viral toxicity may detrimentally increase ARV neurotoxicity and neuropsychiatric adverse effects. As clinicians attempt to control peripheral viremia in an aging population of HIV-infected patients, they must navigate an increasingly complex myriad of comorbidities, pharmacogenetics, drug-drug interactions, and psychiatric and cognitive dysfunction. Here we review in comparison to the neuropathological effects of HIV-1 the available information on neuropsychiatric adverse effects and neurotoxicity of clinically used ARV and cART. It appears altogether that future cART aiming at controlling HIV-1 in the CNS and preventing HAND will require an intricate balancing act of suppressing viral replication while minimizing neurotoxicity, impairment of neurocognition, and neuropsychiatric adverse effects. Graphical abstract Schematic summary of the effects exerted on the brain and neurocognitive function by HIV-1 infection, comorbidities, psychostimulatory, illicit drugs, therapeutic drugs, such as antiretrovirals, the resulting polypharmacy and aging, as well as the potential interactions of all these factors.

Beyond Metabolism: Role of the Immune System in Hepatic Toxicity

The liver is primarily thought of as a metabolic organ; however, the liver is also an important mediator of immunological functions. Key perspectives on this emerging topic were presented in a symposium at the 2018 annual meeting of the American College of Toxicology entitled "Beyond metabolism: Role of the immune system in hepatic toxicity." Viral hepatitis is an important disease of the liver for which insufficient preventive vaccines exist. Host immune responses inadequately clear these viruses and often potentiate immunological inflammation that damages the liver. In addition, the liver is a key innate immune organ against bacterial infection. Hepatocytes and immune cells cooperatively control systemic and local bacterial infections. Conversely, bacterial infection can activate multiple types of immune cells and pathways to cause hepatocyte damage and liver injury. Finally, the immune system and specifically cytokines and drugs can interact in idiosyncratic drug-induced liver injury. This rare disease can result in a disease spectrum that ranges from mild to acute liver failure. The immune system plays a role in this disease spectrum.

Drug Reaction with Eosinophilia and Systemic Symptoms: A Complex Interplay between Drug, T Cells, and Herpesviridae

Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome, also known as drug induced hypersensitivity (DiHS) syndrome is a severe delayed hypersensitivity reaction with potentially fatal consequences. Whilst recognised as T cell-mediated, our understanding of the immunopathogenesis of this syndrome remains incomplete. Here, we discuss models of DRESS, including the role of human leukocyte antigen (HLA) and how observations derived from new molecular techniques adopted in key studies have informed our mechanism-based understanding of the central role of Herpesviridae reactivation and heterologous immunity in these disorders.

S3 Guidelines: Epicutaneous patch testing with contact allergens and drugs - Short version, Part 2

Epicutaneous patch testing is the diagnostic standard for the detection of allergic contact dermatitis. The present guidelines are aimed at residents and board-certified physicians in the fields of dermatology and allergology as well as other medical specialties involved in establishing the indication for patch testing and its execution in patients with contact dermatitis and other forms of delayed-type hypersensitivity. The target audience also includes other health care providers and insurance funds. Based on a systematic literature search and a formal consensus process (S3), the guidelines were developed by dermatologists in collaboration with pediatricians, occupational medicine physicians, nursing staff as well as patient representatives. The systematic methodological approach and appraisal of evidence upon which the recommendations are based are outlined in a separate method report that also contains evidence tables. The guidelines address general aspects of patch testing as well as medicolegal issues. The recommendations given relate to topics such as the indication for patch testing, informed patient consent, as well as the choice of test substances, test chambers and test site, duration of exposure, reading times and interpretation of test reactions. Furthermore, recommendations are provided with respect to endogenous and exogenous factors, specific patient groups (children, pregnant women, immunosuppressed individuals) as well as possible risks and adverse events associated with patch testing using contact allergens.