Drug hypersensitivity in HIV

Tolvaptan safety in autosomal-dominant polycystic kidney disease; a focus on idiosyncratic drug-induced liver injury liabilities

Tolvaptan is a vasopressin V2 receptor antagonist which has proven to be an effective and mostly well-tolerated agent for the treatment of autosomal-dominant polycystic kidney disease. However, its administration is associated with rare but serious idiosyncratic liver injury, which has warranted a black box warning on the drug labels and frequent monitoring of liver blood tests in the clinic. This review outlines mechanistic investigations that have been conducted to date and constructs a working narrative as an explanation for the idiosyncratic drug-induced liver injury (IDILI) events that have occurred thus far. Potential risk factors which may contribute to individual susceptibility to DILI reactions are addressed, and key areas for future investigative/clinical development are highlighted.

Risk factors for drug hypersensitivity reactions in children

Drug hypersensitivity reactions are common in children. Risk factors predisposing to IgE-mediated drug allergies and delayed drug reactions are a matter of debate. Gender, age, previous reactions to the same drug or to another drug, reduced drug metabolism, chronic diseases, polypharmacy, drug doses are linked with the onset of hypersensitivity reactions in some children. Novel advances in genetic polymorphisms can rapidly change the approach to the prevention of reactions since gene testing can be a useful screening test for severe cutaneous adverse reactions. Viral infections may act as cofactors in susceptible individuals. Polypharmacy, high doses, repeated doses and parental route of administration are also risk factors. Clinicians should take into account risk factors to allow the risk-benefit balance to be maintained.

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.

Trimethoprim/sulfamethoxazole desensitization in an HIV-positive patient with previous Stevens-Johnson syndrome; a failed study

Drug-induced Stevens-Johnson syndrome (SJS) is a rare but life-threatening hypersensitivity reaction. Drug desensitization might be considered in drug-allergic patients with no therapeutic alternative. A 29-year-old man with a recent diagnosis of HIV and HBV (CD4 count: 4 cells/mm3) who has been receiving Trimethoprim/sulfamethoxazole (TMP/SMX) for Pneumocystis pneumonia (PCP) prophylaxis was admitted at Imam Khomeini hospital complex affiliated to Tehran University of Medical Sciences, with the diagnosis of SJS due to TMP/SMX. After 45 days of supportive care, the patient was a candidate for TMP/SMX desensitization due to our region's unavailability of alternative agents. A 9-day desensitization protocol was used, but the patient complained about diarrhea with severe pain in the rectal mucosa, and macules developed over his lips again on the third day. As a result, the desensitization process immediately stopped, and after the signs and symptoms were resolved, the patient was discharged with Clindamycin tablet 600 mg TDS. Unfortunately, two weeks after discharge, the patient experienced acute kidney injury (AKI) and expired after two dialysis sessions.

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.

Pathology of drug hypersensitivity reactions and mechanisms of immune tolerance

Immune-mediated type IV adverse drug reactions are idiosyncratic in nature, generally not related to the primary or secondary pharmacology of the drug. Due to their complex nature and rarity, these iatrogenic reactions are seldom predicted or encountered during preclinical/early clinical development stages, and often precipitate upon exposure to wider populations (i.e. phase III onwards). They confer a burden on the healthcare sector in both a clinical and financial sense presenting a severe impediment to the drug discovery and development process. Research over the past 50 years has improved our understanding of these reactions markedly as both in vitro and in vivo studies have placed the role of the immune system, in particular; drug-responsive T cells, firmly in the spotlight as the mediators of these reactions. Indeed, the role of different populations of T cells in adverse events and the interaction of drug molecules with HLA proteins expressed on the surface of antigen-presenting cells is of considerable interest. Herein, this review examines the pathways of immune-mediated adverse events including the various T cell subtypes implicated and the mechanisms of T cell activation. Additionally, we address the enigma of immunological tolerance and explore the role tolerance plays in determination of susceptibility to such adverse events even in individuals carrying immunogenic liabilities.

Advances in Our Understanding of the Interaction of Drugs with T-cells: Implications for the Discovery of Biomarkers in Severe Cutaneous Drug Reactions

Drugs can activate different cells of the immune system and initiate an immune response that can lead to life-threatening diseases collectively known as severe cutaneous adverse reactions (SCARs). Antibiotics, anticonvulsants, and antiretrovirals are involved in the development of SCARs by the activation of αβ naïve T-cells. However, other subsets of lymphocytes known as nonconventional T-cells with a limited T-cell receptor repertoire and innate and adaptative functions also recognize drugs and drug-like molecules, but their role in the pathogenesis of SCARs has only just begun to be explored. Despite 30 years of advances in our understanding of the mechanisms in which drugs interact with T-cells and the pathways for tissue injury seen during T-cell activation, at present, the development of useful clinical biomarkers for SCARs or predictive preclinical in vitro assays that could identify immunogenic moieties during drug discovery is an unmet goal. Therefore, the present review focuses on (i) advances in the understanding of the pathogenesis of SCARs reactions, (ii) a description of the interaction of drugs with conventional and nonconventional T-cells, and (iii) the current state of soluble blood circulating biomarker candidates for SCARs.

The association of CD4 lymphocyte count with drug hypersensitivity reaction to highly active antiretroviral therapy, trimethoprim sulfamethoxazole, and antitubercular agents in human immunodeficiency virus patients

Background

The introduction of highly active antiretroviral therapy (HAART) and antibiotic regimens for the treatment of human immunodeficiency virus (HIV) and its concomitant opportunistic infections, respectively, significantly improve the morbidity and mortality of the infected patients. However, these drugs commonly cause drug hypersensitivity reactions (DHRs) in patients with acquired immunodeficiency syndrome. The reason proposed are multifactorial, which includes immune hyperactivation, changes in drug metabolism, patient cytokine profiles, oxidative stress, genetic predisposition, and the principal target in HIV patients, the CD4+ lymphocytes.

Objective

This study determined the association of CD4 count and DHRs to first-line HAART, trimethoprim sulfamethoxazole, and antitubercular agents among HIV patients.

Methods

This is a retrospective analytical study. Review of charts were done. The demographic and clinical profile used a descriptive statistics such as mean and standard deviation for quantitative data and frequency and percent for categorical data. Chi-square and Fisher exact tests were used to measure the degree of the relationship of CD4 count and DHRs.

Results

A total of 337 eligible patients were included. There was a 25% incidence of hypersensitivity reactions. However, the prevalence of DHRs across the different CD4 groups was not statistically significant (p = 0.167). Likewise, the study found no significant association between the CD4 count and DHRs to first-line HAART, trimethoprim sulfamethoxazole, and antitubercular agents (p = 0.311). The most common DHR was morbilliform rash, and nevirapine was the most reported antiretroviral drug causing DHR.

Conclusion

There was no association in the CD4 count and DHRs to first-line HAART, trimethoprim sulfamethoxazole, and antitubercular agents. Hence, regardless of the baseline CD4 lymphocyte count, the physician should be vigilant in monitoring hypersensitivity reactions. Patient education on common DHRs is very important upon diagnosis of HIV and/or initiation of treatment.

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.

AIDS in the Heartland-Hemophilia Was the Harbinger of Things to Come

ABSTRACT

The history of the AIDS epidemic in the United States has focused largely on the experience in coastal cities where the syndrome was first recognized among gay men. In Cleveland and in many other heartland cities, early recognition of this syndrome was primarily among men with hemophilia who were at risk because of exposure to HIV during treatment with lyophilized antihemophilic factor concentrates that were pooled from plasmas of thousands of donors. Disease and subclinical immune deficiency in these men and in other populations drove recognition that AIDS was due to a blood-borne and sexually transmissible agent. As the AIDS epidemic expanded, heartland cities mobilized their staff and resources to meet the needs of a growing epidemic that ultimately affected the entire nation.

Stevens Johnson syndrome: A review of a vision and life-threatening mucocutaneous disease including histopathology with updates on pathogenesis and genetic risk factors

BACKGROUND

The Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) spectrum of diseases are devastating blistering disorders involving mucosal surfaces with ocular sequelae that manifest particularly profound long-term morbidity. Advances in deoxyribonucleic acid (DNA) sequencing, genome-wide association studies, and both molecular and pharmacogenetics have helped clarify genetic susceptibility and characterize the iatrogenic risk of SJS for a given patient.

METHODS

A review of peer reviewed publications featured on PubMed pertaining to the clinical, pathologic, pharmacogenetic and molecular genetic features of SJS/TEN was conducted. Propose: To provide an in-depth clinicopathologic description of the ocular, ocular adnexal, and cutaneous findings in SJS/TEN, summarize pathogenesis and related conditions, and provide an update on the molecular genetic modifications that contribute to the phenotypic variations and genetic susceptibilities of SJS.

CONCLUSIONS

HLA subtyping and other genetic testing may eventually be valuable in the appropriate context to prevent the debilitating ocular sequelae of SJS, particularly as it relates to medication use.

The diagnosis of hypersensitivity to antibiotics is rarely confirmed by allergy work-up in cystic fibrosis patients

Cystic fibrosis (CF) patients receive many antibiotic treatments for recurrent respiratory infections and frequently report antibiotic hypersensitivity reactions (HSRs). In this retrospective study, medical records of CF patients were reviewed to clarify the clinical features, the culprit antibiotics, and the prevalence of antibiotic HSRs in the CF population. From 601 CF patients, 95 suspected antibiotic HSRs occurred in 60 patients (prevalence of 10.0%). β-Lactams were the most common inducers, but cotrimoxazole was also frequently involved. Seventy-six of 95 suspected HSRs were assessed by allergy workup including skin tests (43/76 reactions) and/or drug reintroduction as a full course of the culprit antibiotic (73 of 76 reactions). From the 43 suspected HSRs that were skin-tested, only three had positive skin tests and were not subjected to drug readministration. All the other 73 suspected HSRs received a full course of the culprit antibiotic: HSR symptoms recurred in 10 of 73 cases and therefore were considered as confirmed antibiotic HSRs; for the remaining 63 suspected HSRs that did not relapse after drug readministration, the diagnosis of antibiotic HSRs was excluded. In summary, 13 of 76 suspected HSRs were confirmed as antibiotic HSRs. The prevalence of suspected and confirmed antibiotic HSRs in CF patients appears similar to that reported in the general population. Of note, most of the antibiotic suspected HSRs are not confirmed after allergology workup. A complete allergy workup appears therefore crucial to make a correct diagnosis and to avoid unnecessary contraindication of major antibiotics.

HIV, drugs and the kidney

Human immunodeficiency virus (HIV) affects over 36 million people worldwide. Antiretroviral therapy (ART) is expanding and improving HIV viral suppression, resulting in increasing exposure to drugs and drug interactions. Polypharmacy is a common complication as people are living longer on ART, increasing the risk of drug toxicities. Polypharmacy is related not only to ART exposure and medication for opportunistic infections, but also to treatment of chronic lifestyle diseases. Acute kidney injury (AKI) is frequent in HIV and is commonly the result of sepsis, dehydration and drug toxicities. Furthermore, HIV itself increases the risk of chronic kidney disease (CKD). Drug treatment is often complicated in people living with HIV because of a greater incidence of AKI and/or CKD compared to the HIV-negative population. Impaired renal function affects drug interactions, drug toxicities and importantly drug dosing, requiring dose adjustment. This review discusses ART and its nephrotoxic effects, including drug–drug interactions. It aims to guide the clinician on dose adjustment in the setting of renal impairment and dialysis, for the commonly used drugs in patients with HIV.

Immunotherapy against Systemic Fungal Infections Based on Monoclonal Antibodies

The increasing incidence in systemic fungal infections in humans has increased focus for the development of fungal vaccines and use of monoclonal antibodies. Invasive mycoses are generally difficult to treat, as most occur in vulnerable individuals, with compromised innate and adaptive immune responses. Mortality rates in the setting of our current antifungal drugs remain excessively high. Moreover, systemic mycoses require prolonged durations of antifungal treatment and side effects frequently occur, particularly drug-induced liver and/or kidney injury. The use of monoclonal antibodies with or without concomitant administration of antifungal drugs emerges as a potentially efficient treatment modality to improve outcomes and reduce chemotherapy toxicities. In this review, we focus on the use of monoclonal antibodies with experimental evidence on the reduction of fungal burden and prolongation of survival in in vivo disease models. Presently, there are no licensed monoclonal antibodies for use in the treatment of systemic mycoses, although the potential of such a vaccine is very high as indicated by the substantial promising results from several experimental models.

The challenge of de-labeling penicillin allergy

BACKGROUND

Even though 8%-25% of most populations studied globally are labeled as penicillin allergic, most diagnoses of penicillin allergy are made in childhood and relate to events that are either not allergic in nature, are low risk for immediate hypersensitivity, or are a potential true allergy that has waned over time. Penicillin allergy labels directly impact antimicrobial stewardship by leading to use of less effective and broader spectrum antimicrobials and are associated with antimicrobial resistance. They may also delay appropriate antimicrobial therapy and lead to increased risk of specific adverse healthcare outcomes. Operationalizing penicillin allergy de-labeling into a new arm of antimicrobial stewardship programs (ASPs) has become an increasing global focus.

METHODS

We performed an evidence-based narrative review of the literature of penicillin allergy label carriage, the adverse effects of penicillin allergy labels, and current approaches and barriers to penicillin allergy de-labeling. Over the period 1928-2018 in Pubmed and Medline, search terms used included "penicillin allergy" or "penicillin hypersensitivity" alone or in combination with "adverse events," "testing," "evaluation," "effects," "label," "de-labeling," "prick or epicutaneous," and "intradermal" skin testing, "oral challenge or provocation," "cross-reactivity," and "antimicrobial stewardship".

RESULTS

Penicillin allergy labels are highly prevalent, largely inaccurate and their carriage may lead to unnecessary treatment and inferior outcomes with alternative agents as well as adverse public health outcomes such as antibiotic resistance.

CONCLUSIONS

Operationalizing penicillin allergy de-labeling as an aspect of ASP has become an increasing global focus. There is a need for validated approaches that optimally combine the use of history and ingestion challenge with or without proceeding formal skin testing to tackle penicillin allergy efficiently within complex healthcare systems. At the same time, there is great promise for penicillin allergy evaluation and de-labeling as an individual and public health strategy to reduce adverse healthcare outcomes, improve antimicrobial stewardship, and decrease healthcare costs.

T-Cell Activation by Low Molecular Weight Drugs and Factors That Influence Susceptibility to Drug Hypersensitivity

Drug hypersensitivity reactions adversely affect treatment outcome, increase the length of patients' hospitalization, and limit the prescription options available to physicians. In addition, late stage drug attrition and the withdrawal of licensed drugs cost the pharmaceutical industry billions of dollars. This significantly increases the overall cost of drug development and by extension the price of licensed drugs. Drug hypersensitivity reactions are characterized by a delayed onset, and reactions tend to be more serious upon re-exposure. The role of drug-specific T-cells in the pathogenesis of drug hypersensitivity reactions and definition of the nature of the binding interaction of drugs with HLA and T-cell receptors continues to be the focus of intensive research, primarily because susceptibility is associated with expression of one or a small number of HLA alleles. This review critically examines the mechanisms of T-cell activation by drugs. Specific examples of drugs that activate T-cells via the hapten, the pharmacological interaction with immune receptors and the altered self-peptide repertoire pathways, are discussed. Furthermore, the impacts of drug metabolism, drug-protein adduct formation, and immune regulation on the development of drug antigen-responsive T-cells are highlighted. The knowledge gained from understanding the pathways of T-cell activation and susceptibility factors for drug hypersensitivity will provide the building blocks for the development of predictive in vitro assays that will prevent or help to minimize the incidence of these reactions in clinic.

The life-threatening eruption in HIV and immunosuppression

Immunosuppressed patients frequently have skin diseases of mild to moderate intensity. Diagnosis as well as treatment should be performed early to avoid important complications for these patients. Skin eruptions are among these problems. Life-threatening eruptions in HIV and other types of immunosuppression range from acute retroviral syndrome to drug eruptions; immune reconstitution inflammatory syndrome; infection by virus, protozoan, bacteria, or fungi; inflammatory and immune dermatoses; and neoplasia. All of these are discussed in this group of patients.

Drug hypersensitivity in HIV infection

PURPOSE OF REVIEW

Immune-mediated adverse drug reactions (IM-ADRs) are many times more common in HIV-infected patients. Usual offending drugs include antiretroviral and antiinfectives, but the burden of specific drug IM-ADRs is population-specific; changing as new and fixed dose combinations enter the market, and drug-resistance patterns demand. This review considers recent literature on epidemiology, mechanisms, clinical management and prevention of IM-ADRs amongst persons living with HIV/AIDS.

RECENT FINDINGS

Epidemiological studies continue to describe high rates of delayed hypersensitivity to known offenders, as well as similar reactions in preexposure prophylaxis. IM-ADRs to oral and injectable integrase strand transfer inhibitors are reported with expanding use. The clinical spectrum and management of IM-ADRs occurring in HIV-infected populations is similar to uninfected; with exceptions such as a recently described severe delayed efavirenz DILI with high mortality. Furthermore, the context can be unique, such as the lower than expected mortality in a Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) cohort from a HIV/TB high burden setting. Programmatic data showing the near complete elimination of Abacavir drug hypersensitivity syndrome following implementation of HLA-B57:01 screening is a stellar example of how prevention is possible with mechanistic insight.

SUMMARY

IM-ADRs remain a challenge in persons living with HIV. The complexities posed by polypharmacy, overlapping drug toxicities, drug interactions, overlap of IM-ADRs with other diseases, limited alternative drugs, and vulnerable patients with advanced immunosuppression with high mortality, necessitate increased use of drug provocation testing, treat-through and desensitization strategies. There is an urgent need for improved diagnostics and predictive biomarkers for prevention, or to guide treat-through, rechallenge and desensitization approaches.

Discovery of Selective Toxoplasma gondii Dihydrofolate Reductase Inhibitors for the Treatment of Toxoplasmosis

A safer treatment for toxoplasmosis would be achieved by improving the selectivity and potency of dihydrofolate reductase (DHFR) inhibitors, such as pyrimethamine (1), for Toxoplasma gondii DHFR ( TgDHFR) relative to human DHFR ( hDHFR). We previously reported on the identification of meta-biphenyl analog 2, designed by in silico modeling of key differences in the binding pocket between TgDHFR and hDHFR. Compound 2 improves TgDHFR selectivity 6.6-fold and potency 16-fold relative to 1. Here, we report on the optimization and structure-activity relationships of this arylpiperazine series leading to the discovery of 5-(4-(3-(2-methoxypyrimidin-5-yl)phenyl)piperazin-1-yl)pyrimidine-2,4-diamine 3. Compound 3 has a TgDHFR IC₅₀ of 1.57 ± 0.11 nM and a hDHFR to TgDHFR selectivity ratio of 196, making it 89-fold more potent and 16-fold more selective than 1. Compound 3 was highly effective in control of acute infection by highly virulent strains of T. gondii in the murine model, and it possesses the best combination of selectivity, potency, and prerequisite drug-like properties to advance into IND-enabling, preclinical development.

Antibiotic Allergy in Pediatrics

The overlabeling of pediatric antibiotic allergy represents a huge burden in society. Given that up to 10% of the US population is labeled as penicillin allergic, it can be estimated that at least 5 million children in this country are labeled with penicillin allergy. We now understand that most of the cutaneous symptoms that are interpreted as drug allergy are likely viral induced or due to a drug-virus interaction, and they usually do not represent a long-lasting, drug-specific, adaptive immune response to the antibiotic that a child received. Because most antibiotic allergy labels acquired in childhood are carried into adulthood, the overlabeling of antibiotic allergy is a liability that leads to unnecessary long-term health care risks, costs, and antibiotic resistance. Fortunately, awareness of this growing burden is increasing and leading to more emphasis on antibiotic allergy delabeling strategies in the adult population. There is growing literature that is used to support the safe and efficacious use of tools such as skin testing and drug challenge to evaluate and manage children with antibiotic allergy labels. In addition, there is an increasing understanding of antibiotic reactivity within classes and side-chain reactions. In summary, a better overall understanding of the current tools available for the diagnosis and management of adverse drug reactions is likely to change how pediatric primary care providers evaluate and treat patients with such diagnoses and prevent the unnecessary avoidance of antibiotics, particularly penicillins.

Structural Elements Recognized by Abacavir-Induced T Cells

Adverse drug reactions are one of the leading causes of morbidity and mortality in health care worldwide. Human leukocyte antigen (HLA) alleles have been strongly associated with drug hypersensitivities, and the causative drugs have been shown to stimulate specific T cells at the sites of autoimmune destruction. The structural elements recognized by drug-specific T cell receptors (TCRs) in vivo are poorly defined. Drug-stimulated T cells express TCRs specific for peptide/HLA complexes, but the characteristics of peptides (sequence, or endogenous or exogenous origin) presented in the context of small molecule drugs are not well studied. Using HLA-B*57:01 mediated hypersensitivity to abacavir as a model system, this study examines structural similarities of HLA presented peptides recognized by drug-specific TCRs. Using the crystal structure of HLA-B*57:01 complexed with abacavir and an immunogenic self peptide, VTTDIQVKV SPT5a 976-984, peptide side chains exhibiting flexibility and solvent exposure were identified as potential drug-specific T cell recognition motifs. Viral sequences with structural motifs similar to the immunogenic self peptide were identified. Abacavir-specific T cell clones were used to determine if virus peptides presented in the context of abacavir stimulate T cell responsiveness. An abacavir-specific T cell clone was stimulated by VTQQAQVRL, corresponding to HSV1/2 230-238, in the context of HLA-B*57:01. These data suggest the T cell polyclonal response to abacavir consists of multiple subsets, including T cells that recognize self peptide/HLA-B*57:01 complexes and crossreact with viral peptide/HLA-B*57:01 complexes due to similarity in TCR contact residues.

Drug reaction with eosinophilia and systemic symptoms related to antiretroviral treatment in human immunodeficiency virus patients

BACKGROUND

The drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is a life-threatening condition caused by different medications. The objective of this study was to analyze DRESS cases related to antiretroviral therapy in human immunodeficiency virus (HIV) patients.

MATERIALS AND METHODS

Systematic review of DRESS suspected cases in HIV patients associated to antiretrovirals published between January 1998 and April 2017. The registry of the severe cutaneous adverse reactions score was used to classify each report as a "definitive," "probable," "possible," or "no" DRESS case. Clinical characteristics, management, and outcomes were evaluated.

RESULTS

Thirty-five case reports were analyzed involving 5 antiretrovirals: Abacavir in 10 (28.6%) cases, efavirenz in 6 (17.1%), nevirapine in 12 (34.3%), raltegravir in 6 (17.1%), and tenofovir in 1 (2.9%). Mean age of the patients was 40 ± 13 years, 65% of which were male. A total of 57.1% reports were classified as having a "definitive-probable" DRESS case. Management was based on withdrawal of the causal antiretroviral and corticosteroids in 68.6% of the cases. None of the patients died. Treatment with nevirapine or raltegravir, the longer onset of symptoms and the presence of lymphadenopathy, eosinophilia, liver involvement, and a longer time for clinical resolution were more frequent among "definitive-probable" DRESS cases.

CONCLUSIONS

A DRESS syndrome has to be suspected in HIV patients with lymphadenopathy, eosinophilia, and liver involvement developing weeks after the initiation of nevirapine or raltegravir. Suspension of the causal antiretroviral and in most cases treatment with corticosteroids allowed adequate clinical control.

Adverse Drug Reactions Causing Admission to Medical Wards: A Cross-Sectional Survey at 4 Hospitals in South Africa

Limited data exist on the burden of serious adverse drug reactions (ADRs) in sub-Saharan Africa, which has high HIV and tuberculosis prevalence. We determined the proportion of adult admissions attributable to ADRs at 4 hospitals in South Africa. We characterized drugs implicated in, risk factors for, and the preventability of ADR-related admissions.We prospectively followed patients admitted to 4 hospitals' medical wards over sequential 30-day periods in 2013 and identified suspected ADRs with the aid of a trigger tool. A multidisciplinary team performed causality, preventability, and severity assessment using published criteria. We categorized an admission as ADR-related if the ADR was the primary reason for admission.There were 1951 admissions involving 1904 patients: median age was 50 years (interquartile range 34-65), 1057 of 1904 (56%) were female, 559 of 1904 (29%) were HIV-infected, and 183 of 1904 (10%) were on antituberculosis therapy (ATT). There were 164 of 1951 (8.4%) ADR-related admissions. After adjustment for age and ATT, ADR-related admission was independently associated (P ≤ 0.02) with female sex (adjusted odds ratio [aOR] 1.51, 95% confidence interval [95% CI] 1.06-2.14), increasing drug count (aOR 1.14 per additional drug, 95% CI 1.09-1.20), increasing comorbidity score (aOR 1.23 per additional point, 95% CI 1.07-1.41), and use of antiretroviral therapy (ART) if HIV-infected (aOR 1.92 compared with HIV-negative/unknown, 95% CI 1.17-3.14). The most common ADRs were renal impairment, hypoglycemia, liver injury, and hemorrhage. Tenofovir disoproxil fumarate, insulin, rifampicin, and warfarin were most commonly implicated, respectively, in these 4 ADRs. ART, ATT, and/or co-trimoxazole were implicated in 56 of 164 (34%) ADR-related admissions. Seventy-three of 164 (45%) ADRs were assessed as preventable.In our survey, approximately 1 in 12 admissions was because of an ADR. The range of ADRs and implicated drugs reflect South Africa's high HIV and tuberculosis burden. Identification and management of these ADRs should be considered in HIV and tuberculosis care and treatment programs and should be emphasized in health care worker training programmes.

Antiviral drug allergy

Antiviral drugs used to treat HIV and hepatitis C are common causes of delayed drug hypersensitivities for which many of the more severe reactions have been recently shown to be immunogenetically mediated such as abacavir hypersensitivity where HLA-B(∗)57:01 is now used routinely as a screening test to exclude patients carrying this allele from abacavir prescription. Most antiviral drug allergies consist of mild to moderate delayed rash without other serious features (eg, fever, mucosal involvement, blistering rash, organ impairment. In these cases treatment can be continued with careful observation and symptomatic management and the discontinuation rate is low.

Pathological and protective immunity to Pneumocystis infection

Pneumocystis jirovecii is a common opportunistic infection in the HIV-positive population and is re-emerging as a growing clinical concern in the HIV-negative immunosuppressed population. Newer targeted immunosuppressive therapies and the discovery of rare genetic mutations have furthered our understanding of the immunity required to clear Pneumocystis infection. The immune system can also mount a pathologic response against Pneumocystis following removal of immunosuppression and result in severe damage to the host lung. The current review will examine the most recent epidemiologic studies about the incidence of Pneumocystis in the HIV-positive and HIV-negative populations in the developing and developed world and will detail methods of diagnosis for Pneumocystis pneumonia. Finally, this review aims to summarize the known mediators of immunity to Pneumocystis and detail the pathologic immune response leading to Pneumocystis-related immune reconstitution inflammatory syndrome.

Skin rash induced by ritonavir-boosted darunavir is common, but generally tolerable in an observational setting

Ritonavir-boosted darunavir (DRV/r) is a protease inhibitor widely used in the treatment of HIV-1 infection. However, skin rash is a well-known adverse event of DRV, and limited data are available from observational settings. This observational study examined the characteristics of DRV-induced skin rash in treatment-naïve patients who commenced once-daily DRV/r-containing antiretroviral therapy (ART). Of the 292 study patients, DRV rashes developed in 31 (11%) patients with a median latency of 10 days (developing from 7 to 14 days in 93%) from initiation of ART. DRV skin rash was generally mild, as only one patient (3%) had grade 3 rash whereas 24 (77%) patients had grade 2 and 6 (19%) patients had grade 1. Only two patients (7%) discontinued DRV/r due to skin rash, and the other continued DRV/r and their rashes disappeared completely without any complications. Interestingly, DRV rash occurred more frequently to patients with less advanced HIV-1 infection than those with advanced infection. The incidence of DRV rash was not significantly different between patients with and without history of sulfonamide allergy (p = 0.201). Furthermore, when we exclude patients without history of sulfonamide use and only examine patients with sulfonamide use (n = 145), the result was similar (p = 0.548). In conclusion, DRV rashes were frequently observed but the prognosis was benign. Most patients tolerated DRV rashes with use of oral steroid or antihistamine without discontinuation of DRV. To date, there is no clear clinical evidence to suggest that DRV should be avoided in patients with history of sulfonamide allergy.

Effect of antiretroviral drugs on the DNA damage in mice

In order to investigate the effects of two non-nucleoside reverse transcriptase inhibitors (NNRTIs) on the DNA damage in vivo, nevirapine (NVP; 3.3 mg/kg), efavirenz (EFV; 10 mg/kg) or saline were administered orally. Acute effects were analyzed 24 h after the administration of a single NNRTI dose, and subchronic effects 24 h after the last dose. Peripheral blood, brain, heart and liver samples were subjected to genotoxicity analyses and polychromatic erythrocytes from the bone marrow to micronucleus test. The micronucleus test did not reveal any significant differences between animals from the acute or subchronic groups. Comet assay showed that acute and subchronic NNRTI treatment did not cause any significant DNA damage in heart, liver or peripheral blood cells. However, increased damage indexes and frequencies were observed in the brain of mice, subchronically treated with EFV. This result suggests for the first time that this drug might induce genotoxicity in the brain.

Stevens-Johnson syndrome / toxic epidermal necrolysis: an Asia-Pacific perspective

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are severe cutaneous adverse reactions (SCAR) to drugs which are associated with significant morbidity and mortality. High risk drugs in Asia are similar to those reported worldwide. Human leukocyte antigen (HLA)-related risk alleles for carbamazepine and allopurinol SCAR are unique to Asians. Although prognostic scoring systems like the SCORTEN have been used for more than a decade, pitfalls and caveats need to be recognized, in particular in patients with multiple medical co-morbidities and systemic features in SJS/TEN. In centres without a tertiary Burns Centre, SJS/TEN patients can still be managed successfully in general and dermatology wards with well-executed supportive/nursing care. Controversy remains regarding the effectiveness of immunomodulation in reducing SJS/TEN morbidity, mortality and hastening re-epithelialization. Despite paucity of robust evidence, intravenous immunoglobulins and ciclosporin remain the most commonly used modalities worldwide. Acute and long-term ocular effects are an important source of morbidity for which emerging ophthalmic therapies appear promising. Quality of life issues have now become an important outcome in patients with SJS/TEN as they often impact survivors' future attitudes towards pharmacotherapy. Even though pharmacogenetic testing for high-risk drugs appears to be the panacea for preventing carbamazepine- and allopurinol-induced SJS/TEN in ethnic Asians, many issues remain before health regulators in our region can conclusively determine whether testing should be made mandatory or highly recommended as standard of care.

The Pharmacogenomic HLA Biomarker Associated to Adverse Abacavir Reactions: Comparative Analysis of Different Genotyping Methods

Many pharmacogenomic biomarkers (PGBM) were identified and translated into clinical practice, affecting the usage of drugs via label updates. In this context, abacavir is one of the most brilliant examples of pharmacogenetic studies translated into clinical practice. Pharmacogenetic studies have revealed that abacavir HSRs are highly associated with the major histocompatibility complex class I. Large studies established the effectiveness of prospective HLA-B*57:01 screening to prevent HSRs to abacavir. Accordingly to these results the abacavir label has been modified: the European Medicines Agency (EMA) and the FDA recommend/suggested that the administration of abacavir must be preceded by a specific genotyping test. The HLA locus is extremely polymorphic, exhibiting many closely related alleles, making it difficult to discriminate HLA-B*57:01 from other related alleles, and a number of different molecular techniques have been developed recently to detect the presence of HLA-B*57:01. In this review, we provide a summary of the available techniques used by laboratories to genotype HLA-B*57:01, outlining the scientific and pharmacoeconomics pros and cons.

Use of patch testing for the diagnosis of abacavir-related hypersensitivity reaction in HIV patients

BACKGROUND

The use of antiretroviral drug abacavir (ABC) has been often associated with cutaneous hypersensitivity reactions, the majority being severe.

OBJECTIVE

The present study discusses the issues of patch testing associated with pharmacogenetic screening in light of the development of abacavir hypersensitivity reactions (HSRs).

METHODS

The present authors classified 100 patients into three groups: 20 patients (group A) had experienced a hypersensitivity reaction when treated with highly active antiretroviral therapy (HAART) including ABC; 60 HIV-positive patients (group B) were receiving HAART scheme including ABC; 20 HIV-negative patients acted as control group (group C). Patients of group A and B were patch tested with ABC as such, then with an ABC extract diluted to 1 and 10% in petrolatum. Group C patients underwent patches with petrolatum only. A biopsy of the lesion was performed in those patients who showed a positive skin reaction. All patients had been tested for HLA-B5701.

RESULTS

A correlation between positive ABC-patch testing and HLA-B5701 was found in 50% of patients enrolled in group A, while in group B and C, all patients tested negative for both genetic marker and ABC-patch testing. Histopathology findings confirmed a vigorous CD4+ and CD8+ cellular response that is compatible with HSR.

CONCLUSIONS

Patch testing is a safe and sensitive method that can be used for to confirm or exclude any correlation between abacavir and hypersensitivity skin reactions in patients who have been previously treated with abacavir during HAART. Correlation between patch test, immunohistochimical, and genetic tests results shows that genetic testing increases the possibility to identify patients with a true reaction.

Individualization of antiretroviral therapy

Antiretroviral therapy (ART) has evolved considerably over the last three decades. From the early days of monotherapy with high toxicities and pill burdens, through to larger pill burdens and more potent combination therapies, and finally, from 2005 and beyond where we now have the choice of low pill burdens and once-daily therapies. More convenient and less toxic regimens are also becoming available, even in resource-poor settings. An understanding of the individual variation in response to ART, both efficacy and toxicity, has evolved over this time. The strong association of the major histocompatibility class I allele HLA-B*5701 and abacavir hypersensitivity, and its translation and use in routine HIV clinical practice as a predictive marker with 100% negative predictive value, has been a success story and a notable example of the challenges and triumphs in bringing pharmacogenetics to the clinic. In real clinical practice, however, it is going to be the exception rather than the rule that individual biomarkers will definitively guide patient therapy. The need for individualized approaches to ART has been further increased by the importance of non-AIDS comorbidities in HIV clinical practice. In the future, the ideal utilization of the individualized approach to ART will likely consist of a combined approach using a combination of knowledge of drug, virus, and host (pharmacogenetic and pharmacoecologic [factors in the individual’s environment that may be dynamic over time]) information to guide the truly personalized prescription. This review will focus on our knowledge of the pharmacogenetics of the efficacy and toxicity of currently available antiretroviral agents and the current and potential utility of such information and approaches in present and future HIV clinical care.

HIV: practical implications for the practicing allergist-immunologist

OBJECTIVES

To review the effects of human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS) on allergic diseases and discuss the clinical, pathophysiologic, diagnostic, and therapeutic challenges unique to HIV-infected patients receiving highly active antiretroviral therapy (HAART).

DATA SOURCES

The MEDLINE and OVID databases were searched to identify pertinent articles using the following keywords: HIV, AIDS, IgE, allergic rhinitis, adverse drug reaction, asthma, chronic obstructive pulmonary disease, food allergy, and immunization. References from the chosen articles were also examined.

STUDY SELECTION

Articles were selected based on their relevance to the subject matter and currency.

RESULTS

Human immunodeficiency virus infection causes immunologic alterations that ultimately lead to cell-mediated immune deficiency. In addition, the immune dysfunction caused by HIV also increases the likelihood of developing allergic and other immune-mediated diseases in many patients. HAART is associated with reconstitution of immune system function. While offering protection against infection, immune reconstitution also can provoke immunopathologic conditions. Patients infected with HIV show an increased prevalence of allergic rhinitis, adverse drug reactions, and noninfectious pulmonary complications. The pathophysiology of HIV infection is associated with unique clinical, diagnostic, and therapeutic considerations when treating allergic diseases in HIV-infected patients.

CONCLUSIONS

With the use of HAART and the subsequent decrease in infectious complications, HIV-infected patients now live longer and experience common chronic diseases. Evaluation of HIV-infected patients with rhinitis, asthma, and adverse drug reactions may become more frequent as HAART continues to extend the life expectancy of patients living with HIV. Understanding the interactions between HIV and these conditions can facilitate a knowledgeable approach to treating an HIV-infected patient.

Epidemiology and risk factors for drug allergy

The aim of this review was to describe the current evidence-based knowledge of the epidemiology, prevalence, incidence, risk factors and genetic associations of drug allergy. Articles published between 1966 and 2010 were identified in MEDLINE using the key words adult, adverse drug reaction reporting systems, age factors, anaphylactoid, anaphylaxis, anaesthetics, antibiotics, child, drug allergy, drug eruptions, ethnic groups, hypersensitivity, neuromuscular depolarizing agents, neuromuscular nondepolarizing agents, sex factors, Stevens Johnson syndrome and toxic epidermal necrolysis. Additional studies were identified from article reference lists. Relevant, peer-reviewed original research articles, case series and reviews were considered for review. Current epidemiological studies on adverse drug reactions (ADRs) have used different definitions for ADR-related terminology, often do not differentiate immunologically and non-immunologically mediated drug hypersensitivity, study different study populations (different ethnicities, inpatients or outpatients, adults or children), utilize different methodologies (spontaneous vs. non-spontaneous reporting, cohort vs. case-control studies), different methods of assessing drug imputability and different methods of data analyses. Potentially life-threatening severe cutaneous adverse reactions (SCAR) are associated with a high risk of morbidity and mortality. HLA associations for SCAR associated with allopurinol, carbamazepine and abacavir have been reported with the potential for clinical use in screening prior to prescription. Identification of risk factors for drug allergy and appropriate genetic screening of at-risk ethnic groups may improve the outcomes of drug-specific SCAR. Research and collaboration are necessary for the generation of clinically-relevant, translational pharmacoepidemiological and pharmacogenomic knowledge, and success of health outcomes research and policies on drug allergies.

Aciclovir desensitisation and rechallenge

A 29-year-old patient with HIV developed a facial angioedema hypersensitivity reaction to aciclovir when treated for acute retinal necrosis secondary to a herpes virus infection. She developed a similar reaction to famciclovir. Successful rapid desensitisation with oral aciclovir was performed and she became tolerant to aciclovir. She successfully completed 28 months of continuous treatment with no further reactions. However, 28 months later she experienced blurred vision and resumed taking oral aciclovir without a preceding desensitisation regimen. No allergic reaction occurred.

Practical management of antibiotic allergy in adults

This review looks at the main issues around immediate hypersensitivity and the role and limitations of testing. The majority of literature on antibiotic hypersensitivity relates to β-lactam antibiotics, mainly because of the heavy usage of this class of drugs. Concerns around cross-reactivity always worry clinicians, particularly in the emergency situation. Reasonable data now exist in relation to β-lactam antibiotics and derivatives, which enable appropriate risk management to be undertaken. The available literature for other classes of antibiotics is also discussed.

Case report: anaphylactic reaction to guaifenesin

Adverse drug reactions lead to a significant number of hospital admissions each year and thus contribute to the overall financial burden of health care. Some of these drug reactions are allergic responses. As the overall predictability of allergic responses to drugs remains low, efforts to improve our understanding of the processes underlying these responses continue as we strive toward the ultimate goal of primary prevention. Allergic reactions range from mild pruritic to severe systemic anaphylactic responses. We report a case of a young healthy man who developed an anaphylactic reaction to an over-the-counter expectorant. A skin test showed that the patient had an immunoglobulin E-mediated allergic response to guaifenesin, one of the components of commonly available cough medications. Our review of published literature showed that this is the first report of a severe allergic response to guaifenesin.

Prediction of severe adverse drug reactions using pharmacogenetic biomarkers

Severe adverse drug reactions (ADRs) are a major issue for drug therapy because they can cause serious disorders and be life-threatening. Many severe ADRs appear to be idiosyncratic and unpredictable. Genetic factors may underlie susceptibility to severe ADRs, and identification of predisposing genotypes may improve drug therapy by facilitating prescreening of carriers for specific genetic biomarkers. In this review, we clarify the current status of ADRs in Japan from open ADR data sources. Then, we introduce recent progress in the field of pharmacogenetic biomarkers for severe cutaneous ADRs, liver injury, and statin-induced myopathy. Key challenges for discovery of predictable risk alleles for these severe ADRs are also discussed.