Distinctive populations of CD4+T cells associated with vaccine efficacy.

Memory T cells underpin vaccine-induced immunity but are not yet fully understood. To distinguish features of memory cells that confer protective immunity, we used single cell transcriptome analysis to compare antigen-specific CD4+T cells recalled to lungs of mice that received a protective or nonprotective subunit vaccine followed by challenge with a fungal pathogen. We unexpectedly found populations specific to protection that expressed a strong type I interferon response signature, whose distinctive transcriptional signature appeared unconventionally dependent on IFN-γ receptor. We also detected a unique population enriched in protection that highly expressed the gene for the natural killer cell marker NKG7. Lastly, we detected differences in TCR gene use and in Th1- and Th17-skewed responses after protective and nonprotective vaccine, respectively, reflecting heterogeneous Ifng- and Il17a-expressing populations. Our findings highlight key features of transcriptionally diverse and distinctive antigen-specific T cells associated with protective vaccine-induced immunity.

Uncertain, Not Unimportant: Callosal Dysgenesis and Variants of Uncertain Significance in ROBO1.

Congenital anomalies affect 3% to 5% of births and remain the leading cause of infant death in the United States. As whole exome and genome sequencing are increasingly used to diagnose underlying genetic disease, the patient's clinical presentation remains the most important context for interpreting sequencing results, including frequently reported variants of uncertain significance (VUS). Classification of a variant as VUS acknowledges limits on evidence to establish whether a variant can be classified as pathogenic or benign according to the American College of Medical Genetics guidelines. Importantly, the VUS designation reflects limits on the breadth of evidence linking the genetic variant to a disease. However, available evidence, although limited, may be surprisingly relevant in an individual patient's case. Accordingly, a VUS result should be approached neither as nondiagnostic genetic result nor as automatically "uncertain" in its potential to guide clinical decision-making. In this article, we discuss a case of an infant born at 29 weeks 4 days without a corpus callosum, whose whole genome sequencing yielded compound heterozygous variants both classified as VUS in ROBO1, a gene encoding for a receptor involved in a canonical signaling mechanism that guides axons across midline. Approaching the VUS result as potentially pathogenic, we found the infant ultimately had pituitary dysfunction and renal anomalies consistent with other reported ROBO1 variants and basic science literature. Accordingly, we highlight resources for variant interpretation available to clinicians to evaluate VUS results, particularly as they inform the diagnosis of individually rare but collectively common rare diseases.

Hemosuccus Pancreaticus Following Acute Pancreatitis in a 12-years-old Boy Secondary to Pancreatic Pseudoaneurysm Treated With Endovascular Coil Embolization.

Hemosuccus pancreaticus is a very rare cause of upper gastrointestinal bleeding in children. It is defined as bleeding from the pancreatic or peripancreatic vessels into the main pancreatic duct and may be life-threatening. We present the case of a 12-year-old boy with hematemesis and severe anemia that developed following an episode of acute pancreatitis. Upper endoscopy did not reveal a bleeding source. An endoscopic retrograde cholangiopancreatography performed for the evaluation of common bile duct obstruction identified bleeding from the pancreatic duct. Subsequently, the bleeding source, a pseudoaneurysm of the splenic artery, was identified by conventional angiography and occluded with coil embolization. The diagnosis of hemosuccus pancreaticus may be difficult in children due to rare occurrence and the unusual anatomical site; hence, a high index of suspicion is needed in a patient with a history of pancreatitis who presents with intermittent upper gastrointestinal bleeding and normal upper endoscopy.

Pseudomonas poae-Associated Fatal Septic Transfusion Reaction, Peoria, Illinois, USA, 2017.

In the United States, fatal transfusion-transmitted infections from red blood cell units are rare. Although this pattern mostly reflects how inhospitable refrigerated red blood cell units are to contaminant growth, fatalities caused by microorganisms that can grow at storage temperature (4°C), but not in standard clinical blood cultures at 37°C, are probably underestimated. We analyzed a fatal red blood cell transfusion in Peoria, Illinois, USA, that occurred in 2017. Samples from the patient's whole blood and the red blood cell unit remained culture-negative during the investigation, despite direct visualization of gram-negative bacilli within the unit immediately after transfusion. We identified the bacteria as Pseudomonas poae, a nonpathogenic pseudomonad carrying multiple cold-shock domain protein genes, and confirmed its cold tolerance and inability to grow at 37°C. Our work indicates transfusion reaction workups need to include testing for psychrophilic organisms, which could explain the cause of other apparently culture-negative transfusion reactions.

Langerhans Cells Prevent Autoimmunity via Expansion of Keratinocyte Antigen-Specific Regulatory T Cells.

Langerhans cells (LCs) are antigen-presenting cells in the epidermis whose roles in antigen-specific immune regulation remain incompletely understood. Desmoglein 3 (Dsg3) is a keratinocyte cell-cell adhesion molecule critical for epidermal integrity and an autoantigen in the autoimmune blistering disease pemphigus. Although antibody-mediated disease mechanisms in pemphigus are extensively characterized, the T cell aspect of this autoimmune disease still remains poorly understood. Herein, we utilized a mouse model of CD4+ T cell-mediated autoimmunity against Dsg3 to show that acquisition of Dsg3 and subsequent presentation to T cells by LCs depended on the C-type lectin langerin. The lack of LCs led to enhanced autoimmunity with impaired Dsg3-specific regulatory T cell expansion. LCs expressed the IL-2 receptor complex and the disruption of IL-2 signaling in LCs attenuated LC-mediated regulatory T cell expansion in vitro, demonstrating that direct IL-2 signaling shapes LC function. These data establish that LCs mediate peripheral tolerance against an epidermal autoantigen and point to langerin and IL-2 signaling pathways as attractive targets for achieving tolerogenic responses particularly in autoimmune blistering diseases such as pemphigus.

A case of probable trimethoprim-sulfamethoxazole induced circulating antineutrophil cytoplasmic antibody-positive small vessel vasculitis.

Cutaneous leukocytoclastic vasculitis (LCV) can occur as skin-limited disease or as part a systemic vasculitis. Appropriate workup includes the evaluation of antineutrophil cytoplasmic antibodies (ANCAs), with a positive titer raising concern for the associated primary vasculitides including microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA), or eosinophilic granulomatosis with polyangiitis (EGPA). In the absence of systemic findings, however, a drug etiology must also be considered. Tumor necrosis factor (TNF) inhibitors, propylthiouracil, levamisole-adulterated cocaine, hydralazine, and minocycline have been previously documented to induce ANCA-positive vasculitis (APV), which may present with conspicuously high ANCA titers. Herein we report trimethoprim-sulfamethoxazole as another culprit in drug-induced APV. Our case reinforces the need to consider drug etiology for APV and cautions against interpreting positive ANCAs as equivalent to evidence of systemic disease.