Journal of Experimental Medicine最新文献

Fulminant viral hepatitis (FVH) is a devastating condition caused by hepatotropic viruses such as hepatitis A virus (HAV), hepatitis B virus (HBV), and HSV-1/2. We studied 149 FVH patients (73 males and 76 females, aged 1-76) for blood autoantibodies (auto-Abs) neutralizing type I interferons (IFNs; IFN-α2, -β, -ω). Six of 16 (37.5%) HSV-triggered FVH patients carried such auto-Abs on admission, including three with a previously known autoimmune disease. These patients contrasted with 133 HAV- (n = 46) or HBV-triggered (n = 87) patients, none of whom had such detectable auto-Abs. Odds ratios for HSV-triggered FVH in individuals with auto-Abs ranged from 35.3 (95% CI: 13.0-96.2; P < 10-7) for those neutralizing only 100 pg/ml IFN-α/ω to 1,895 (CI: 448.5-8,002; P < 10-12) for those neutralizing both IFN-α and IFN-ω at 10 ng/ml. Over one third of HSV-triggered FVH cases in this international cohort were due to preexisting auto-Abs. This finding highlights auto-Abs against type I IFNs as a major determinant of HSV-FVH and paves the way for targeted preventive or therapeutic interventions.

Avian influenza A virus (IAV) H5N1 is an emerging threat of human pandemic. We describe a 71-year-old man who died of H5N1 pneumonia in Louisiana and whose blood contained autoantibodies neutralizing type I IFNs (AAN-I-IFNs), including the 12 IFN-α subtypes (1-10 ng/ml) and IFN-ω (100 pg/ml). Causality between these AAN-I-IFN and lethal outcome of avian influenza in this patient is based on (1) our previous report that AA-I-IFN underlie about 5% of cases of critical pneumonia triggered by seasonal influenza viruses in three cohorts, (2) the rarity of this combination of AAN-I-FNs in individuals over 70 years old (<1%), and (3) the rarity of lethal avian influenza among infected individuals (<1%). AAN-I-IFNs underlie a growing number of severe viral diseases, from arboviral encephalitis to viral pneumonia, particularly in the elderly. This case suggests they can also underlie life-threatening avian H5N1 influenza. The presence of AAN-I-IFN may facilitate infection, replication, and adaptation of zoonotic IAVs to humans and, therefore, human-to-human transmission.

Antiretroviral therapy suppresses HIV-1 infection but fails to eliminate a reservoir of intact latent proviruses that reside primarily in CD4+ T cells. The lack of precise understanding of the latent compartment has made it challenging to develop curative strategies for HIV-1 infection. Here we report on the properties of CD4+ T cell clones carrying intact latent proviruses, expanded in vitro from single cells obtained from the reservoir of people living with HIV-1. The latent proviruses in the clones were integrated into ZNF genes, nongenic satellite, and centromeric regions, frequently associated with latency. Despite their descent from single cells, only a fraction of the cells (0.4-14%) expressed relatively low levels of HIV-1 that did not measurably alter host gene transcriptome. Latency-reversing agents (LRAs) variably increased expression, but the effects were modest and clone and LRA specific. The results suggest that pharmacologic and immunologic approaches to clear the reservoir should be optimized to accommodate intra- and inter-clonal diversity.

Modeling complex (patho)physiological processes by sequential targeted mutagenesis in mice is limited by the lack of precision of cellular targeting and complex breeding strategies. We present a new Cre/DreERT2 dual-recombinase germinal center B cell (GCBC)-specific strain, with co-expression of the recombinases from a single allele. This enables highly efficient Cre-mediated FOXO1 knockout in GCBCs in vivo, followed by time-controlled, efficient Dre-mediated FOXO1 re-expression in the same cells, leading to functional rescue of GC compartmentalization and class switch recombination. The present approach can be easily adapted to other cellular contexts.

Immune responses to pathogens lead to the generation of plasma cells through a complex interplay of B cells with their microenvironment in lymphoid organs. To identify new regulators of B cell activation and plasmablast differentiation in the context of the splenic microenvironment, we established an in vivo system for pooled sgRNA CRISPR/Cas9 screens in immunized mice. To improve the infection efficiency of naïve B cells, we generated Cd23-Cre Rosa26LSL-EcoR/+ mice exhibiting increased expression of the ecotropic lentivirus receptor EcoR on naïve B cells. Upon adoptive B cell transfer and immunization of recipient mice, 379 sgRNAs, targeting genes with high expression in plasma cells, were analyzed for their effects on plasmablast generation. Gene hits, encoding 23 positive and 18 negative regulators of B cell activation, plasmablast differentiation, or homeostasis, were uniquely identified in these in vivo screens. Validated genes encoded proteins involved in cell adhesion, signal transduction, protein folding, iron transport, and enzymatic processes. Hence, our in vivo screening system identified novel regulators controlling B cell-mediated immune responses.

Mucosal-associated invariant T (MAIT) cells are predominantly located in barrier tissues where they rapidly respond to pathogens and commensals by recognizing microbial derivatives of riboflavin synthesis. Early-life exposure to these metabolites imprints the abundance of MAIT cells within tissues, so we hypothesized that antibiotic use during this period may abrogate their development. We identified antibiotics that deplete riboflavin-synthesizing commensals and revealed an early period of susceptibility during which antibiotic administration impaired MAIT cell development. The reduction in MAIT cell abundance rendered mice more susceptible to pneumonia, while MAIT cell-deficient mice were unaffected by early-life antibiotics. Concomitant administration of a riboflavin-synthesizing commensal during antibiotic treatment was sufficient to restore MAIT cell development and immunity. Our work demonstrates that transient depletion of riboflavin-synthesizing commensals in early life can adversely affect responses to subsequent infections.

Mapping the causal circuits that shape the phenotypic and functional landscape of immune cells remains a formidable challenge. Recent advances in pooled CRISPR-based screens, coupled with multiplexed single-cell profiling and imaging-based spatial readouts, make this goal increasingly attainable. In this Perspective, we discuss how CRISPR-based genetic screens will fundamentally transform our understanding of immunobiology. We highlight the applications of state-of-the-art, high-throughput pooled perturbation approaches, including emerging methodologies for bulk, single-cell, and spatial CRISPR screens, to advance our understanding of immunity and in vivo biology. Additionally, we summarize new strategies to address the complexity of combinatorial perturbations to uncover genetic interactions and mechanistic drivers of immunity at unprecedented scale and resolution. By integrating CRISPR screening data with experimental insights, we advocate a new framework in immunology research that leverages perturbation-driven regulatory effects and networks to discover new therapeutic targets and establish causal systems biology and immunology for advancing immunological knowledge and therapeutic application.

Gut-associated lymphoid tissues (GALT) represent major sites of adaptive immune priming in the intestine, yet our understanding of human GALT diversity and function remains limited. Here, we used single-cell RNA sequencing, flow cytometry, and confocal laser microscopy to map the fibroblast (FB) landscape of human GALT, including that of Peyer's patches (PP), mucosal isolated lymphoid follicles (M-ILF), and submucosal ILF (SM-ILF). We identify CD24 as a marker that distinguishes GALT from other intestinal FB and demonstrate that CD24+ FB consist of distinct subsets that locate within discrete niches. We show that the composition and transcriptional profile of M-ILF and SM-ILF FB differs with SM-ILF FB appearing more focused at providing T cell support. Finally, we find the transcription profile of PP T zone reticular cells to be altered in Crohn's disease and that cells with a GALT FB-like profile can be detected in other chronic inflammatory diseases. Collectively, our findings provide an important framework for understanding GALT diversity and function.

Tuberculosis (TB) typically causes lung destruction and fibrosis, leading to ∼1.3 million deaths annually. The cellular drivers of human TB immunopathology remain poorly defined. We performed single-cell RNA sequencing and spatial transcriptomics on lung tissues from TB-infected and TB-negative individuals, identifying 30 distinct immune, parenchymal, and stromal cell subsets. Several were linked to TB pathology and corroborated through immunohistochemistry, flow cytometry, and independent human datasets. Fibroblasts were identified as major drivers in both active TB granuloma and TB-diseased lung tissue. In particular, the MMP1+CXCL5+ fibroblast subset, expressing a myofibroblast-like gene signature, was associated with severe disease and higher bacterial burden in nonhuman primate granulomas. Network analyses revealed cross talk between MMP1+CXCL5+ fibroblasts and SPP1+ macrophages within the granuloma cuff, which has been reported in other disease contexts, and may play an important role in TB immunopathology. Our findings highlight previously unappreciated cell populations and potential targets for novel TB therapies.

Mechanical force generated by blood flow stimulates emergence of the first hematopoietic stem cells (HSCs) that populate the blood system. Force drives the transition of HSC precursors from an endothelial to hematopoietic identity, yet the molecular regulation of this fate switch remains poorly understood. We report that shear stress triggers adaptation in mitochondrial composition, ultrastructure, and function, which are essential for hematopoietic fate and engraftment potential. Shear stress remodels mitochondria in hemogenic endothelium by promoting mitochondrial gene transcription and protein synthesis. Laminar flow selectively initiates translation of 5' terminal polypyrimidine (5'TOP) motif-containing transcripts, which commonly encode ribosome and translation machinery. Flow-responsive metabolic reprogramming depends upon mechanistic target of rapamycin (mTOR) activation and is stymied when ribosome activity or mTOR is blocked. Conversely, chemical induction of mTOR mimics the effects of force on mitochondria and blood reconstituting potential and also partially rescues hematopoiesis in heartbeat mutants in utero. These findings identify mechanometabolism as a determinant of hematopoietic fate that could inform engineering of HSCs for disease modeling and treatment.