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The dynamics of innate and adaptive immunity to infection in infants remain obscure. Here, we used a multi-omics approach to perform a longitudinal analysis of immunity to SARS-CoV-2 infection in infants and young children in the first weeks and months of life by analyzing blood samples collected before, during, and after infection with Omicron and Non-Omicron variants. Infection stimulated robust antibody titers that, unlike in adults, were stably maintained for >300 days. Antigen-specific memory B cell (MCB) responses were durable for 150 days but waned thereafter. Somatic hypermutation of V-genes in MCB accumulated progressively over 9 months. The innate response was characterized by upregulation of activation markers on blood innate cells, and a plasma cytokine profile distinct from that seen in adults, with no inflammatory cytokines, but an early and transient accumulation of chemokines (CXCL10, IL8, IL-18R1, CSF-1, CX3CL1), and type I IFN. The latter was strongly correlated with viral load, and expression of interferon-stimulated genes (ISGs) in myeloid cells measured by single-cell transcriptomics. Consistent with this, single-cell ATAC-seq revealed enhanced accessibility of chromatic loci targeted by interferon regulatory factors (IRFs) and reduced accessibility of AP-1 targeted loci, as well as traces of epigenetic imprinting in monocytes, during convalescence. Together, these data provide the first snapshot of immunity to infection during the initial weeks and months of life.

All fifteen patients with HLA-A*32:01 restricted vancomycin-induced DRESS, showed negative ex vivo responses to dalbavancin however two showed cross-reactivity to teicoplanin and telavancin. Adjunctive diagnostic testing should be considered to detect potential cross-reactivity amongst glycopeptides.

Background Vancomycin is a prevalent cause of the severe hypersensitivity syndrome drug reaction with eosinophilia and systemic symptoms (DRESS), which leads to significant morbidity and mortality and commonly occurs in the setting of combination antibiotic therapy, affecting future treatment choices. Variations in HLA class I in particular have been associated with serious T cell–mediated adverse drug reactions, which has led to preventive screening strategies for some drugs. Objective We sought to determine whether variation in the HLA region is associated with vancomycin-induced DRESS. Methods Probable vancomycin-induced DRESS cases were matched 1:2 with tolerant control subjects based on sex, race, and age by using BioVU, Vanderbilt's deidentified electronic health record database. Associations between DRESS and carriage of HLA class I and II alleles were assessed by means of conditional logistic regression. An extended sample set from BioVU was used to conduct a time-to-event analysis of those exposed to vancomycin with and without the identified HLA risk allele. Results Twenty-three subjects met the inclusion criteria for vancomycin-associated DRESS. Nineteen (82.6%) of 23 cases carried HLA-A*32:01 compared with 0 (0%) of 46 of the matched vancomycin-tolerant control subjects (P = 1 × 10−8) and 6.3% of the BioVU population (n = 54,249, P = 2 × 10−16). Time-to-event analysis of DRESS development during vancomycin treatment among the HLA-A*32:01–positive group indicated that 19.2% had DRESS and did so within 4 weeks. Conclusions HLA-A*32:01 is strongly associated with vancomycin-induced DRESS in a population of predominantly European ancestry. HLA-A*32:01 testing could improve antibiotic safety, help implicate vancomycin as the causal drug, and preserve future treatment options with coadministered antibiotics.

The majority of immune-mediated adverse drug reactions (IM-ADRs) involve the skin, and many have additional systemic features. Severe cutaneous adverse drug reactions (SCAR) are an uncommon, potentially life-threatening and challenging sub-group of IM-ADRs with diverse clinical phenotypes, mechanisms and offending drugs. T-cell mediated immunopathology is central to these severe delayed reactions, but effector cells and cytokines differ by clinical phenotype. Strong HLA-gene associations have been elucidated for specific drug-SCAR IM-ADRs such as Stevens-Johnson Syndrome/toxic epidermal necrolysis (SJS/TEN); although the mechanisms by which carriage of a specific HLA allele is necessary but not sufficient for the development of many IM-ADRs is still being defined. SCAR management is complicated by substantial short and long-term morbidity/ mortality and the potential need to treat ongoing co-morbid disease with related medications. Multidisciplinary specialist teams at experienced units should care for patients. In the setting of SCAR, patient outcomes as well as preventive,diagnostic, treatment and management approaches are often not generalizable, but rather context specific, driven by population HLA-genetics, the pharmacology and genetic risk factors of the implicated drug, severity of underlying co-morbid disease necessitating ongoing treatments, and cost considerations. In this review, we update the basic and clinical science of SCAR diagnosis and management.

Capsule Summary. Single-cell responses in HLA-B*57:01 abacavir patch test positive skin remote to the acute hypersensitivity reaction demonstrate polyclonal T-cell activation and proliferation characterized by a transcriptional and cellular response consistent with memory responses to altered peptides.

Human leukocyte antigen (HLA) alleles have been implicated as risk factors for immune-mediated adverse drug reactions. The authors recently reported a strong association between HLA-A*32:01 and vancomycin-induced drug reaction with eosinophilia and systemic symptoms. Identification of individuals with the risk allele before or shortly after the initiation of vancomycin therapy is of great clinical importance to prevent morbidity and mortality, and improve drug safety and antibiotic treatment options. A prerequisite to the success of pharmacogenetic screening tests is the development of simple, robust, cost-effective single HLA allele test that can be implemented in routine diagnostic laboratories. In this study, the authors developed a simple, real-time allele-specific PCR for typing the HLA-A*32:01 allele. Four-hundred and fifty-eight DNA samples including 30 HLA-A*32:01–positive samples were typed by allele-specific PCR. Compared with American Society for Histocompatibility and Immunogenetics–accredited, sequence-based, high-resolution, full-allelic HLA typing, this assay demonstrates 100% accuracy, 100% sensitivity (95% CI, 88.43% to 100%), and 100% specificity (95% CI, 99.14% to 100%). The lowest limit of detection of this assay using PowerUp SYBR Green is 10 ng of template DNA. The assay demonstrates a sensitivity and specificity to differentiate the HLA-A*32:01 allele from closely related non–HLA-A*32 alleles and may be used in clinical settings to identify individuals with the risk allele before or during the course of vancomycin therapy.

Purpose of review: Antimicrobials are a leading cause of severe T cell-mediated adverse drug reactions (ADRs). The purpose of this review is to address the current understanding of antimicrobial cross-reactivity and the ready availability of and evidence for in-vitro, in-vivo, and ex-vivo diagnostics for T cell-mediated ADRs. Recent findings: Recent literature has evaluated the efficacy of traditional antibiotic allergy management, including patch testing, skin prick testing, intradermal testing, and oral challenge. Although patch and intradermal testing are specific for the diagnosis of immune-mediated ADRs, they suffer from drug-specific limitations in sensitivity. The use of ex-vivo diagnostics, especially enzyme-linked immunospot, has been highlighted as a promising new approach to assigning causality. Knowledge of true rates of antimicrobial cross-reactivity aids empirical antibiotic choice in the setting of previous immune-mediated ADRs. Summary: In an era of increasing antimicrobial resistance and use of broad-spectrum antimicrobial therapy, ensuring patients are assigned the correct ‘allergy label’ is essential. Re-exposure to implicated antimicrobials, especially in the setting of severe adverse cutaneous reaction, is associated with significant morbidity and mortality. The process through which an antibiotic label gets assigned, acted on and maintained is still imprecise. Predicting T cell-mediated ADRs via personalized approaches, including human leukocyte antigen-typing, may pave future pathways to safer antimicrobial prescribing guidelines.

The role of tumor heterogeneity in regulating disease progression is poorly understood. We hypothesized that interactions between subpopulations of cancer cells can affect the progression of tumors selecting for a more aggressive phenotype. We developed an in vivo assay based on the immortalized nontumorigenic breast cell line MCF10A and its Ras-transformed derivatives AT1 (mildly tumorigenic) and CA1d (highly tumorigenic). CA1d cells outcompeted MCF10A, forming invasive tumors. AT1 grafts were approximately 1% the size of CA1d tumors when initiated using identical cell numbers. In contrast, CA1d/AT1 mixed tumors were larger than tumors composed of AT1 alone (100-fold) or CA1d (3-fold), suggesting cooperation in tumor growth. One of the mechanisms whereby CA1d and AT1 were found to cooperate was by modulation of TGF-α and TGF-β signaling. Both of these molecules were sufficient to induce changes in AT1 proliferative potential in vitro. Reisolation of AT1 tumor-derived (AT1-TD) cells from these mixed tumors revealed that AT1-TD cells grew in vivo, forming tumors as large as tumorigenic CA1d cells. Cooperation between subpopulations of cancer epithelium is an understudied mechanism of tumor growth and invasion that may have implications on tumor resistance to current therapies.—Franco, O. E., Tyson, D. R., Konvinse, K. C., Udyavar, A. R., Estrada, L., Quaranta, V., Crawford, S. E., Hayward, S. W. Altered TGF-α/β signaling drives cooperation between breast cancer cell populations.

We used the FilmArray meningitis/encephalitis panel for evaluation of sepsis in febrile neonates. We detected human herpesvirus 6, a virus we did not routinely test for previously, in the cerebrospinal fluid of 7 neonates. In all 7 cases, detection of the virus did not warrant antiviral treatment.

Adverse drug reactions (ADRs) are a significant health care burden. Immune-mediated adverse drug reactions (IM-ADRs) are responsible for one-fifth of ADRs but contribute a disproportionately high amount of that burden due to their severity. Variation in human leukocyte antigen ( HLA) genes has emerged as a potential preprescription screening strategy for the prevention of previously unpredictable IM-ADRs. Immunopharmacogenomics combines the disciplines of immunogenomics and pharmacogenomics and focuses on the effects of immune-specific variation on drug disposition and IM-ADRs. In this review, we present the latest evidence for HLA associations with IM-ADRs, ongoing research into biological mechanisms of IM-ADRs, and the translation of clinical actionable biomarkers for IM-ADRs, with a focus on T cell–mediated ADRs.

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.

Immune-mediated adverse drug reactions (IM-ADRs) occur because of off-target interactions of medications with immune receptors and result in disproportionately high patient morbidity, mortality, and cost to drug delivery, development, and healthcare systems. IM-ADRs of greatest clinical relevance include Type I IgE-mediated anaphylaxis and delayed (Type IV) T cell–mediated pathologies across a spectrum of severity from benign exanthems to severe systemic, single-organ, and cutaneous pathologies such as drug reaction and eosinophilia and systemic symptoms, drug-induced liver disease, and Stevens-Johnson syndrome and toxic epidermal necrolysis. More recent discoveries of strong associations between human leukocyte antigen (HLA) genes and drug-specific T cell–mediated syndromes have not only provided pretreatment screening strategies for some drugs, but have also furthered our understanding of the immunopathogenesis of IM-ADR. Fundamental questions remain regarding the immunopathogenesis of T cell–mediated adverse drug reactions, including why, in most cases, only a small proportion of persons who carry a risk HLA gene will develop hypersensitivity to drug, why the clinical presentation of these syndromes varies widely, and how T cell immune responses are maintained for many years following drug exposure and resolution of clinical disease. In this chapter, we will review what is known about the immunopathogenesis of T cell–mediated adverse drug reactions with focus on drug- and syndrome-specific examples, how epidemiologic and mechanistic insights have been translated into clinical tests to prevent these syndromes, and future directions for basic science and clinical discovery in this field.

Background For severe cutaneous adverse reactions (SCARs) associated with multiple antibiotics dosed concurrently, clinical causality is challenging and diagnostic approaches are limited, leading to constricted future antibiotic choices. Objective To examine the combined utility of in vivo and ex vivo diagnostic approaches at assigning drug causality in a cohort of patients with antibiotic-associated (AA)-SCARs. Methods Patients with AA-SCARs were prospectively recruited between April 2015 and February 2017. In vivo testing (patch testing or delayed intradermal testing) was performed to the implicated antibiotic(s) at the highest nonirritating concentration and read at 24 hours through 1 week. Ex vivo testing used patient peripheral blood mononuclear cells (PBMCs) stimulated with a range of pharmacologically relevant concentrations of implicated antibiotics to measure dose-dependent IFN-γ release from CD4+ and CD8+ T cells via an enzyme-linked immunoSpot assay. Results In 19 patients with AA-SCARs, combined in vivo and ex vivo testing assigned antibiotic causality in 15 (79%) patients. Ten patients (53%) with AA-SCARs were positive on IFN-γ release enzyme-linked immunoSpot assay, with an overall reported sensitivity of 52% (95% CI, 29-76) and specificity of 100% (95% CI, 79-100), with improved sensitivity noted in acute (within 1 day to 6 weeks after SCAR onset) testing (75%) and in patients with higher phenotypic scores (59%). There was increased use of narrow-spectrum beta-lactams and antibiotics from within the implicated class following testing in patients with a positive ex vivo or in vivo test result. Conclusions We demonstrate the potential utility of combined in vivo and ex vivo testing in patients with AA-SCARs to assign drug causality with high specificity.

Rationale Striking class I HLA risk associations and CD8+ T cell dependency have been described for both Stevens-Johnson Syndrome/toxic epidermal necrolysis (SJS/TEN) and abacavir hypersensitivity (AHS). However, distinct clinical phenotypes and positive predictive values (55% for HLA-B*57:01 restricted AHS and 97%) in blister fluid and skin. In contrast, for AHS, abacavir responsive CD8+ T cells with shared TCR clonotypes were isolated from the peripheral blood and positive patch tests that were polyclonal. Conclusions Single cell approaches that define the signatures of drug-specific T cells in the skin and peripheral blood highlight mechanistic differences between HLA class I restricted drug hypersensitivity syndromes and will help drive the development of targeted therapeutics and screening approaches.

Recent observations indicate prostatic diseases are comorbidities of systemic metabolic dysfunction. These discoveries revealed fundamental questions regarding the nature of prostate metabolism. We previously showed that prostate-specific ablation of PPARγ in mice resulted in tumorigenesis and active autophagy. Here, we demonstrate control of overlapping and distinct aspects of prostate epithelial metabolism by ectopic expression of individual PPARγ isoforms in PPARγ knockout prostate epithelial cells. Expression and activation of either PPARγ 1 or 2 reduced de novo lipogenesis and oxidative stress and mediated a switch from glucose to fatty acid oxidation through regulation of genes including Pdk4, Fabp4, Lpl, Acot1 and Cd36. Differential effects of PPARγ isoforms included decreased basal cell differentiation, Scd1 expression and triglyceride fatty acid desaturation and increased tumorigenicity by PPARγ1. In contrast, PPARγ2 expression significantly increased basal cell differentiation, Scd1 expression and AR expression and responsiveness. Finally, in confirmation of in vitro data, a PPARγ agonist versus high-fat diet (HFD) regimen in vivo confirmed that PPARγ agonization increased prostatic differentiation markers, whereas HFD downregulated PPARγ-regulated genes and decreased prostate differentiation. These data provide a rationale for pursuing a fundamental metabolic understanding of changes to glucose and fatty acid metabolism in benign and malignant prostatic diseases associated with systemic metabolic stress.