Potent neutralizing human monoclonal antibodies protect from inhalational Rift Valley fever virus.

Rift Valley fever (RVF) is an emerging arboviral disease affecting both humans and livestock. In humans, RVF displays a spectrum of clinical manifestations, including encephalitis. To date, there are no FDA-approved vaccines or therapeutics for human use, although several are in pre-clinical development. Few small animal models of RVF encephalitis exist, further complicating countermeasure assessment. Human mAbs RVFV-140, RVFV-268 and RVFV-379 are recombinant potently neutralizing antibodies that prevent infection by binding the RVFV surface glycoproteins. Previous studies showed that both RVFV-268 and RVFV-140 improve survival in a lethal mouse model of disease, and RVFV-268 has prevented vertical transmission in a pregnant rat model of infection. Despite these successes, evaluation of mAbs in the context of brain disease has been limited. This is the first study to assess neutralizing antibodies for prevention of RVF neurologic disease using a rat model. Administration of RVFV-140, RVFV-268, or RVFV-379 twenty-four hours prior to aerosol exposure to the virulent ZH501 strain of RVFV results in substantially enhanced survival and lack of neurological signs of disease. These results using a stringent and highly lethal aerosol infection model supports the potential use of human mAbs to prevent the development of RVF encephalitis.

NKT cells promote Th1 immune bias to dengue virus that governs long term protective antibody dynamics.

NKT cells are innate-like T cells, recruited to the skin during viral infection, yet their contributions to long-term immune memory to viruses are unclear. We identified granzyme K, a product made by cytotoxic cells including NKT cells, is linked to induction of Th1-associated antibodies during primary dengue virus (DENV) infection in humans. We examined the role of NKT cells in vivo using DENV-infected mice lacking CD1d-dependent (CD1ddep) NKT cells. In CD1d-KO mice, Th1-polarized immunity and infection resolution were impaired, which was dependent on intrinsic NKT cell production of IFN-γ, since it was restored by adoptive transfer of WT but not IFN-γ-KO NKT cells. Furthermore, NKT cell deficiency triggered immune bias, resulting in higher levels of Th2-associated IgG1 than Th1-associated IgG2a, which failed to protect against a homologous DENV re-challenge and promoted antibody-dependent enhanced disease during secondary heterologous infections. Similarly, Th2-immunity, typified by a higher IgG4:IgG3 ratio, was associated with worsened human disease severity during secondary infections. Thus, CD1ddep NKT cells establish Th1 polarity during the early innate response to DENV, which promotes infection resolution, memory formation and long-term protection from secondary homologous and heterologous infections. These observations illustrate how early innate immune responses during primary infections can influence secondary infection outcomes.

Human gut microbiota-reactive DP8a regulatory T cells prevent acute graft-versus-host disease in a CD73-dependent manner.

Graft-versus-host disease (GvHD) is a life-threatening complication frequently occurring following allogeneic hematopoietic stem cell transplantation (allo-HSCT). Since gut microbiota and regulatory T cells (Tregs) are believed to play roles in GvHD prevention, we investigated whether DP8a Tregs, which we have previously described to harbor a TCR-specificity for the gut commensal Faecalibacterium prausnitzii, could protect against GvHD, thereby linking microbiota and its effect on GvHD. We observed a decrease in CD73+ DP8α Treg frequency in allo-HSCT patients at 1-month post-transplantation, which was associated with aGvHD development at 1-month post-transplantation, as compared to aGvHD-free patients, without being correlated to hematological disease's relapse. Importantly, CD73 activity was shown to be critical for DP8αTreg suppressive function. Moreover, the frequency of host-reactive DP8α Tregs was also lower in aGvHD patients, as compared to aGvHD-free patients, which could embody a protective mechanism responsible for the maintenance of these cell subset in GvHD-free patients. We also showed that human DP8α Tregs protected mice against xeno-GvHD through limiting deleterious inflammation and preserving gut integrity. Altogether, these results demonstrated that human DP8α Tregs mediate aGvHD prevention in a CD73-dependent manner, likely through host-reactivity, advocating for the use of these cells for the development of innovative therapeutic strategies to preclude aGvHD-related inflammation.

Calcineurin is an adaptor required for assembly of the TCR signaling complex.

The serine/threonine phosphatase calcineurin is a component of the T cell receptor (TCR) signalosome, where it promotes T cell activation by dephosphorylating LckS59. Using small interfering RNA (siRNA)-mediated knockdown and CRISPR-Cas9-targeted genetic disruption of the calcineurin A chain α and ß isoforms, we find that calcineurin also functions as an adaptor in TCR-signaled human T cells. Unlike inhibition of its phosphatase activity, in the absence of calcineurin A, TCR signaling results in attenuated actin rearrangement, markedly reduced TCR-Lck microcluster formation and recruitment of the adaptor RhoH, and diminished phosphorylation of critical targets downstream of Lck such as TCRζ and ZAP-70. Reconstitution of deficient T cells with either calcineurin Aα or Aß restores TCR microcluster formation and signaling, as does reconstitution with a phosphatase-inactive Aα chain. These results assign a non-enzymatic adaptor function to calcineurin in the formation and stabilization of a functional TCR signaling complex.

Protocol for analyzing arginase I expression in tumor-associated myeloid-derived suppressor cells from murine colon cancer using flow cytometry.

Arginase1 (ARG1) is a metabolic enzyme that is highly expressed in tumor-associated myeloid-derived suppressor cells (MDSCs) and causes the dysfunction of tumor-reactive T cells. Here, we present a protocol for detecting ARG1 expression in tumor MDSCs from a murine model of colon cancer using flow cytometry. We describe steps for tumor tissue processing, antibody staining, and data acquisition. We then detail procedures for identifying MDSC subsets and detecting ARG1 expression using a precise gating strategy. For complete details on the use and execution of this protocol, please refer to Zhang et al.1.

Isolation, expansion, and adoptive transfer of human ILC2s for the treatment of mice bearing liquid and solid tumors.

Type 2 innate lymphoid cells (ILC2s) are crucial in regulating immune responses and various physiological processes, including tissue repair, metabolic homeostasis, inflammation, and cancer surveillance. Here, we present a protocol that outlines the isolation, expansion, and adoptive transfer of human ILC2s from peripheral blood mononuclear cells for an in vivo lineage tracking experiment in a mouse model. Additionally, we detail the steps involved in the adoptive transfer of human ILC2s to recipient mice bearing human liquid or solid tumors. For complete details on the use and execution of this protocol, please refer to Li et al.1.

Protocol for analyzing TRAIL- and Fas-induced signaling complexes by immunoprecipitation from human cells.

Engagement of TRAIL or Fas death receptors can trigger the assembly of cytoplasmic caspase-8/FADD/RIPK1 (FADDosome) signaling complexes that promote nuclear factor κB (NF-κB) activation. Here, we present a protocol for immunoprecipitation of TRAIL- or Fas-induced FADDosomes from human cell lines. We describe steps for stimulating human cells with TRAIL or Fas ligand, followed by preparation of membrane death receptor-associated, as well as cytoplasmic FADDosome, signaling complexes. This protocol has application in the analysis of death receptor-induced signaling complex formation. For complete details on the use and execution of this protocol, please refer to Davidovich et al.1.

Immune-regulating effect of oxytocin and its association with the hypothalamic-pituitary axes.

Oxytocin can regulate immunological activity directly or indirectly; however, immunological functions and mechanisms of oxytocin actions under chronic stress like cesarean delivery (CD) are poorly understood. Our study found that abnormal oxytocin production and secretion in CD rats caused atrophy of thymic tissues. Neurotoxin kainic acid microinjected into the dorsolateral supraoptic nucleus in male rats selectively reduced hypothalamic oxytocin levels, increased corticotrophin-releasing hormone and plasma interleukin-1ß while reducing plasma oxytocin, thyroxine and testosterone levels and causing atrophy of immune tissues. Thus, plasma oxytocin is essential for immunological homeostasis, which involves oxytocin facilitation of thyroid hormone and sex steroid secretion.

Characterisation of delayed severity flares in patients with HLA-B27-associated anterior uveitis.

BACKGROUND/AIMS: To explore and characterise the clinical phenotype of acute anterior uveitis flares with delayed severity in patients with human leucocyte antigen B27 (HLA-B27)-associated anterior uveitis. METHODS: Retrospective chart review of patients with HLA-B27-associated anterior uveitis. Demographic and clinical data were recorded, as well as the clinical characteristics of acute anterior uveitis flares. A flare was considered to have delayed severity if any of the following criteria were met within 3-21 days of symptomatic onset: a two-step increase in anterior chamber inflammation on consecutive exams; a new development of hypopyon or fibrinoid aqueous reaction on consecutive examinations or a significant worsening of symptoms. RESULTS: A total of 371 patient charts were identified, of which 137 were included. 321 acute anterior uveitis flares were documented, with 36 (11.2%) meeting the criteria for a delayed severity flare. The average time from symptomatic onset was 10.2 days, and patients presented with an average anterior chamber cell grade of 3.5 in delayed severity flares compared with 1.6 in non-delayed severity flares. No significant difference in frequency of delayed severity presentation was noted based on the presence or absence of systemically associated rheumatological disease, papillitis on initial presentation and retinal vasculitis on initial presentation. The frequency of topical steroid therapy after symptomatic onset was not significantly different between the two flare phenotypes. CONCLUSIONS: Our study presents the novel characterisation of a delayed severity phenotype of HLA-B27-associated acute anterior uveitis flares.

Subcutaneous granuloma annulare: a systematic review of a rare and underdiagnosed disease.

Subcutaneous granuloma annulare (SGA) is a rare clinicopathologic subtype of granuloma annulare characterized by the presence of subcutaneous nodules. There are no present reviews synthesizing the clinical features and treatment modalities in SGA. We conducted a systematic review following PRISMA guidelines [CRD42022344672] on all peer-reviewed English-language studies that reported one or more cases of SGA. A total of 97 studies, comprising 26 case series and 71 case reports with 324 patients, were included for analysis. Most cases were predominantly pediatric, with 78.9% of the cases identified being age 16 or lower and a median age of diagnosis of 6. There was no overall gender predisposition. Although over two-thirds of patients did not have any comorbidities, diabetes mellitus was the most common comorbidity present in 4% of cases. The most common feature of SGA was nodules, which were present in 99.6% of patients. Pain or tenderness was reported in 15.4%, and erythema of overlying skin in 11.0% of cases. Surgical excision was performed in 96/141 (68.1%) patients. Among the 27/141 (18.0%) patients who were conservatively managed, 87.0% spontaneously improved, including 60.0% who completely self-resolved. Topical and intralesional steroids were used in 3.40% and 1.85% of patients, respectively, resulting in complete or partial resolution in 54.6% and 100%. Among patients who were followed up, 83/324 (25.6%) patients experienced recurrence after a median duration of 26 weeks. SGA is predominantly a pediatric disease that frequently occurs on the limbs and the head. Juxta-articular lesions are more commonly observed in adults than in children. Surgical excision is common and effective in most patients. Spontaneous improvement occurs in most untreated cases, and intralesional steroids but not topical steroids may be beneficial for non-resolving cases and to reduce time to resolution.

PTEN acts as a crucial inflammatory checkpoint controlling TLR9/IL-6 axis in B cells.

Phosphatase and tensin homolog (PTEN) is vital for B cell development, acting as a key negative regulator in the PI3K signaling pathway. We used CD23-cre to generate PTEN-conditional knockout mice (CD23-cKO) to examine the impact of PTEN mutation on peripheral B cells. Unlike mb1-cre-mediated PTEN deletion in early B cells, CD23-cKO mutants exhibited systemic inflammation with increased IL-6 production in mature B cells upon CpG stimulation. Inflammatory B cells in CD23-cKO mice showed elevated phosphatidylinositol 3-phosphate [PI(3)P] levels and increased TLR9 endosomal localization. Pharmacological inhibition of PI(3)P synthesis markedly reduced TLR9-mediated IL-6. Single-cell RNA-sequencing (RNA-seq) revealed altered endocytosis, BANK1, and NF-κB1 expression in PTEN-deficient B cells. Ectopic B cell receptor (BCR) expression on non-inflammatory mb1-cKO B cells restored BANK1 and NF-κB1 expression, enhancing TLR9-mediated IL-6 production. Our study highlights PTEN as a crucial inflammatory checkpoint, regulating TLR9/IL-6 axis by fine-tuning PI(3)P homeostasis. Additionally, BCR downregulation prevents the differentiation of inflammatory B cells in PTEN deficiency.

Endogenously produced itaconate negatively regulates innate-driven cytokine production and drives global ubiquitination in human macrophages.

A wide variety of electrophilic derivatives of itaconate, the Kreb's cycle-derived metabolite, are immunomodulatory, yet these derivatives have overlapping and sometimes contradictory activities. Therefore, we generated a genetic system to interrogate the immunomodulatory functions of endogenously produced itaconate in human macrophages. Endogenous itaconate is driven by multiple innate signals restraining inflammatory cytokine production. Endogenous itaconate directly targets cysteine 13 in IRAK4 (disrupting IRAK4 autophosphorylation and activation), drives the degradation of nuclear factor κB, and modulates global ubiquitination patterns. As a result, cells unable to make itaconate overproduce inflammatory cytokines such as tumor necrosis factor alpha (TNFα), interleukin-6 (IL-6), and IL-1ß in response to these innate activators. In contrast, the production of interferon (IFN)ß, downstream of LPS, requires the production of itaconate. These data demonstrate that itaconate is a critical arbiter of inflammatory cytokine production downstream of multiple innate signaling pathways, laying the groundwork for the development of itaconate mimetics for the treatment of autoimmunity.

Protocol to identify and isolate rare murine tumor-resident dendritic cell populations for low-input transcriptomic profiling.

Conventional type 1 dendritic cells (cDC1s) are critical for innate sensing of cancer, yet they are scarce in the tumor microenvironment (TME). Here, we present a protocol to identify and isolate cDC1 subsets from murine implantable tumors for subsequent transcriptomic profiling using a flow sorting-based strategy. We describe steps for cell culture of mouse tumors, tumoral growth, dissociation and isolation of tumoral cells, extracellular staining, and cell sorting. We then detail procedures for RNA isolation, mRNA library preparation, and sequencing. For complete details on the use and execution of this protocol, please refer to Papadas et al.1.

Protocol for analysis of single-cell sequencing data by Seqtometry.

Seqtometry (sequencing-to-measurement) is an analytical platform for single-cell analysis based on direct profiling of gene expression and accessibility achieved by advanced scoring with gene signatures. Here, we present a protocol for single-cell RNA sequencing (scRNA-seq) and single-cell assay for transposase-accessible chromatin using sequencing (scATAC-seq) analysis using Seqtometry. We describe steps for preprocessing, imputation, scoring, and plotting, with extensions to large datasets and integration of multiple datasets. This protocol yields results in the form of biologically interpretable dimensions for direct identification and comprehensive characterization of specific cells. For complete details on the use and execution of this protocol, please refer to Kousnetsov et al.1.

The immunology of B-1 cells: from development to aging.

B-1 cells have intricate biology, with distinct function, phenotype and developmental origin from conventional B cells. They generate a B cell receptor with conserved germline characteristics and biased V(D)J recombination, allowing this innate-like lymphocyte to spontaneously produce self-reactive natural antibodies (NAbs) and become activated by immune stimuli in a T cell-independent manner. NAbs were suggested as "rheostats" for the chronic diseases in advanced age. In fact, age-dependent loss of function of NAbs has been associated with clinically-relevant diseases in the elderly, such as atherosclerosis and neurodegenerative disorders. Here, we analyzed comprehensively the ontogeny, phenotypic characteristics, functional properties and emerging roles of B-1 cells and NAbs in health and disease. Additionally, after navigating through the complexities of B-1 cell biology from development to aging, therapeutic opportunities in the field are discussed.

Immunity against conserved epitopes dominates after two consecutive exposures to SARS-CoV-2 Omicron BA.1.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exposure histories become increasingly complex through original and variant-adapted vaccines and infections with viral variants. Upon exposure to the highly altered Omicron spike glycoprotein, pre-immunized individuals predominantly mount recall responses of Wuhan-Hu-1 (wild-type)-imprinted memory B (BMEM) cells mostly targeting conserved non-neutralizing epitopes, leading to diminished Omicron neutralization. We investigated the impact of imprinting in individuals double/triple vaccinated with a wild-type-strain-based mRNA vaccine who, thereafter, had two consecutive exposures to Omicron BA.1 spike (breakthrough infection followed by BA.1-adapted vaccine). We found that depletion of conserved epitope-recognizing antibodies using a wild-type spike bait results in strongly diminished BA.1 neutralization. Furthermore, spike-specific BMEM cells recognizing conserved epitopes are much more prevalent than BA.1-specific BMEM cells. Our observations suggest that imprinted BMEM cell recall responses limit the induction of strain-specific responses even after two consecutive BA.1 spike exposures. Vaccine adaptation strategies need to consider that prior SARS-CoV-2 infections and vaccinations may cause persistent immune imprinting.

Resistance against the development of diethylnitrosamine-induced hepatocellular carcinoma in female C3H mice: an experimental model.

Histopathological features of hepatocellular carcinoma (HCC) induced by diethylnitrosamine (DEN) in mice display strong similarities with those seen in humans, including the higher tumor prevalence in males than in females. Previous studies have demonstrated that continual production of the pro-inflammatory IL-6 by Kupffer cells is involved in the initiation and progression of DEN-induced HCC and that estrogen-mediated reduction of IL-6 secretion would decrease its incidence in females. Given the predominant utilization of male mice in hepatic carcinogenesis research, the objective of this study was to examine histopathological and immunological parameters in the DEN-induced liver carcinogenesis model in female C3H mice. We observed a significant prevalence of hepatocellular hyperplasias and adenomas alongside a minimal infiltration of inflammatory cells and a scarcity of senescent areas in females. Further, a low expression of immunosuppression markers is observed in females - such as neutrophil/lymphocyte ratio, PD-1 expression in CD8 T cells, and PD-L1 in myeloid cells - compared to males. Comparative studies between susceptible and resistant hosts to chemical carcinogenesis may help to unveil novel therapeutic strategies against cancer.

B cell academy of the gut: an update on gut associated germinal centre B cell dynamics.

BACKGROUND: The gut is an environment in which the immune system closely interacts with a vast number of foreign antigens, both inert such as food and alive, from the viral, bacterial, fungal and protozoal microbiota. Within this environment, germinal centres, which are microanatomical structures where B cells affinity-mature, are chronically present and active. MAIN BODY: The functional mechanism by which gut-associated germinal centres contribute to gut homeostasis is not well understood. Additionally, the role of T cells in class switching to immunoglobulin A and the importance of B cell affinity maturation in homeostasis remains elusive. Here, we provide a brief overview of the dynamics of gut-associated germinal centres, T cell dependency in Immunoglobulin A class switching, and the current state of research regarding the role of B cell selection in germinal centres in the gut under steady-state conditions in gnotobiotic mouse models and complex microbiota, as well as in response to immunization and microbial colonization. Furthermore, we briefly link those processes to immune system maturation and relevant diseases. CONCLUSION: B cell response at mucosal surfaces consists of a delicate interplay of many dynamic factors, including the microbiota and continuous B cell influx. The rapid turnover within gut-associated germinal centres and potential influences of an early-life window of immune system imprinting complicate B cell dynamics in the gut.