ImmunoHorizons最新文献

The interleukin-1 receptor (IL-1R) plays an important role in mediating the inflammatory responses against pathogens. However, it is not clear whether a sustained IL-1R signaling following the loss of its endogenous inhibitor, IL-1R antagonist (IL-1RA), could improve mucosal immunity against the murine enteropathogen, Citrobacter rodentium. At basal levels, IL-1RA-deficient (IL1raKO) mice displayed an elevated inflammatory tone as indicated by their higher levels of circulating neutrophils, and the inflammatory marker, lipocalin-2, in both systemic and luminal contents. We reasoned that the heightened inflammatory tone of IL1raKO mice may be beneficial in clearing C. rodentium efficiently, but such was not the case. Oral challenge of C. rodentium (1 × 109 colony-forming units/mouse) resulted in luminal colonization, which peaked at day 7 postinfection, in both wild-type and IL1raKO mice. However, IL1raKO mice displayed a higher C. rodentium burden, and exacerbated colonic inflammation and hyperplasia. The aggravated infection in IL1raKO mice was corroborated using in vivo imaging of mice infected with a bioluminescent strain of C. rodentium. However, IL1raKO mice do not display any defect in their neutrophils with respect to their recruitment to the inflamed gut, generation of neutrophil extracellular traps and reactive oxygen species, or their ability to kill C. rodentium in vitro. In contrast, the macrophages of IL1raKO mice were able to upregulate more inducible nitric oxide synthase and produce more nitrite that wild-type macrophages; however, the former was less effective in mediating killing of C. rodentium in vitro. Together, our results suggest that IL-1RA plays a protective role in combating enteropathogen infection.

Dendritic cells (DCs) and natural killer (NK) cells engage in reciprocal interactions to trigger an efficient innate immune response while governing downstream adaptive immunity. Here, we used an ex vivo autologous human primary immune cell coculture system of DCs and NK cells to examine their impact on naïve CD4+ and CD8+ T cell (CD3+CD45RA+CD197+) activation in response to influenza A viral (IAV) infection. Using multiparameter flow cytometry, we observed that culturing T cells with both DCs and NK cells enhanced CD69 expression on CD4+ and CD8+ T cells, increased CD25 on CD4+ T cells, and promoted CD8+ T cell proliferation, compared with cultures with only NK cells or DCs. When DCs were exposed to the pandemic A/California/07/2009 (H1N1) strain or the A/Victoria/361/2011 (H3N2) strain, subsequent coculture with NK cells reduced the frequency of CD4+CD69+ and CD8+CD69+ naïve T cells. Notably, H3N2, but not H1N1, exposure also reduced CD4+CD25+ T cell frequencies. The IAV-mediated curtailment of T cell activation was dependent on viral replication because exposure to DCs with irradiated the H1N1 strain followed increased the frequency of CD4+CD69+, CD8+CD69+, CD4+CD25+, and CD8+CD25+ T cells, while irradiation of H3N2 increased the frequency of CD4+CD69+, CD8+CD69+ and proliferation of CD4+ and CD8+ T cells. These findings demonstrate that IAV can partially subvert DC-NK cell crosstalk to impair naïve T cell activation in a strain-dependent manner. This knowledge may guide the design of next-generation influenza vaccines to elicit robust cellular immune responses.

The light chain immunoglobulin (IG) genes of inbred mouse strains are poorly documented in current gene databases. We previously showed that IG heavy chain (IGH) loci of wild-derived mouse strains, representing the major mouse subspecies, contained 247 IGH variable (V) sequences not curated in the International ImMunoGeneTics (IMGT) information system database, commonly used for adaptive immune receptor repertoire sequencing (AIRR-seq) analysis. Despite containing levels of polymorphism similar to the IGH locus, the germline gene content and diversity of the light chain loci (kappa, IGK; lambda, IGL) have not been comprehensively cataloged. To explore the extent of germline light chain repertoire diversity across mouse strains commonly used in the biomedical sciences, we performed AIRR-seq analysis and germline gene inference for 18 inbred mouse strains, including 4 wild-derived strains with diverse sub-species origins. We inferred 1582 IGKV and 63 IGLV sequences, representing 459 and 22 unique IGKV and IGLV germline alleles. Of the unique germline IGKV and IGLV sequences, 67.8% and 59%, respectively, were undocumented in IMGT. Across strains we observed germline IGKV sequences shared by three distinct IGK haplotypes and a more conserved IGLV germline repertoire. In addition, joining (J) gene inference indicated a novel IGKJ2 allele shared between PWD/PhJ and MSM/MsJ, a novel IGLJ1 allele for LEWES/EiJ, and a novel IGLJ2 allele for MSM/MsJ. Finally, combined IGHV, IGKV, and IGLV phylogenetic analysis of wild-derived germline sets revealed reduced diversity for light chain sequences compared to the heavy chain, suggesting potential evolutionary differences between heavy and light chain loci.

Neonates have increased vulnerability to life-threatening infections due to the distinct immune landscape. Interleukin (IL)-27 is a key component of this immune profile that we have previously shown to be elevated in both newborn humans and mice. IL-27 continues to increase in the serum and tissues consistent with poor outcomes during gram-negative neonatal bacterial sepsis. Presently, we dissected the IL-27 producer profile at a single-cell level using IL-27p28eGFP reporter mice in our previously established model of neonatal sepsis with luciferase-expressing K1-encapsulated Escherichia coli. Whole animal imaging regionally highlighted the spleen, liver, and lungs as key infection sites by bacterial luminescence. Flow cytometry showed that IL-27 producers increased significantly in the liver with infection and were predominantly F4/80+ and CD11b+ with subpopulations that emerged expressing additional markers. This information paired with single-cell RNA sequencing further identified the most robust populations as monocytes, monocyte-derived cells, and Kupffer cells followed by smaller populations of dendritic cells and neutrophils. The transcriptome demonstrated a diverse range of functionality amongst populations that included differential expression of genes implicated in bactericidal, metabolic, and inflammatory changes. Collectively, the transcriptome of IL-27 producers from the livers of infected animals suggests an uncoordinated mix of inflammatory and suppressive activity that may contribute to immune dysregulation characteristic of sepsis. Together, this work provides previously undescribed insight into the details of IL-27 producers during early-life infection. This further provides essential information needed to support IL-27 as a therapeutic target for neonatal bacterial sepsis.

Immune dysfunction and late mortality from multiorgan failure are hallmarks of severe sepsis. Arginine, a semi-essential amino acid important for protein synthesis, immune response, and circulatory regulation, is deficient in sepsis. However, arginine supplementation in sepsis remains controversial due to the potential to upregulate inducible nitric oxide synthase (iNOS)-mediated excessive nitric oxide (NO) generation in macrophages, leading to vasodilation and hemodynamic catastrophe. Citrulline supplementation has been considered an alternative to replenishing arginine via de novo synthesis, orchestrated by argininosuccinate synthase 1 (ASS1) and argininosuccinate lyase (ASL). However, the functional relevance of the ASS1-ASL pathway in macrophages after endotoxin stimulation is unclear but it is crucial to consider amino acid restoration as a tool for treating sepsis. We demonstrate that lipopolysaccharide (LPS)-mediated iNOS, ASS1, and ASL protein expression and nitric oxide generation were dependent on exogenous arginine in RAW 264.7 macrophages. Exogenous citrulline was not sufficient to restore nitric oxide generation in arginine-free conditions. Despite the induction of iNOS and ASS1 mRNA in arginine-free conditions, exogenous arginine was necessary and citrulline was not sufficient to overcome eIF2-α (elongation initiation factor 2-α)-mediated translational repression of iNOS and ASS1 protein expression. Moreover, exogenous arginine, but not citrulline, selectively modified the inflammatory cytokine and chemokine expression profile of the LPS-activated RAW 264.7 and bone marrow-derived macrophages. Our study highlights the complex, differential regulation of proinflammatory cytokine expression, and NO generation by exogenous arginine in macrophages.

Giardia duodenalis is an intestinal protozoan parasite common in low- and middle-income countries. Infection is often subclinical, even when it is associated with other pathologies like growth stunting in children. Recent longitudinal cohort studies have found Giardia more frequently in patients with milder symptoms and have even suggested that Giardia reduces rotavirus symptom severity. One potential mechanism for limiting disease severity due to other enteropathogens is the promotion of anti-inflammatory responses that limit pathology. Our lab previously showed that Giardia reduces production of interleukin (IL)-12 by dendritic cells stimulated with Toll-like receptor agonists. In this study, we show that Giardia increases the production of the anti-inflammatory cytokine IL-10 by mouse peritoneal macrophages in response to bacterial lipopolysaccharide. This potentiation is specific to IL-10, as no changes were seen in the production of the proinflammatory cytokine tumor necrosis factor ɑ. Moreover, peritoneal macrophages from mice lacking macrophage galactose-binding lectin, a pathogen recognition receptor that has been previously shown to bind N-acetylgalactosamine, failed to increase IL-10 production after stimulation with Giardia and lipopolysaccharide. Giardia's immunoregulation of the IL-10 response may help us understand the parasite's role in reducing diarrheal severity.

Arthritogenic alphaviruses, including chikungunya (CHIKV), Mayaro (MAYV), Ross River (RRV), and O'nyong nyong virus (ONNV), are emerging and reemerging viruses that cause disease characterized by fever, rash, and incapacitating muscle and joint pain and inflammation. Alphavirus infection induces robust immune responses, leading to the upregulation of several cytokines and chemokines, including chemokine C ligand 4 (CCL4). CCL4 is a chemoattractant for immune cells such as T cells, natural killer cells, monocytes/macrophages, and dendritic cells, recruiting these cells to the site of infection, stimulating the release of proinflammatory mediators, and inducing T cell differentiation. CCL4 has been found at high levels in both the acute and chronic phases of chikungunya disease; however, the role of CCL4 in arthritogenic alphavirus disease development remains unexplored. Here, we tested the effect of CCL4 on MAYV infection in mice through antibody neutralization and treatment with recombinant mouse CCL4. We observed no differences in mice depleted of CCL4 or treated with recombinant CCL4 in terms of disease progression such as weight loss and footpad swelling or the development of viremia. CCL4 uses the G protein-coupled receptor C-C chemokine receptor type 5 (CCR5). To determine whether CCR5 deficiency would alter disease outcomes or virus replication in mice, we inoculated CCR5 knockout (CCR5--) mice with MAYV and observed no effect on disease development and immune cell profile of blood and footpads between CCR5-/- and wild type mice. These studies failed to identify a clear role for CCL4 or its receptor CCR5 in MAYV infection.

The efficacy and safety of acalabrutinib, a Bruton tyrosine kinase (BTK) inhibitor, was evaluated in 2 phase 2 studies in hospitalized patients with coronavirus disease 2019 (COVID-19) who received acalabrutinib + best supportive care (BSC) versus BSC alone (Clinicaltrials.gov: NCT04380688 and NCT04346199). The primary endpoint was the percentage of patients alive and free of respiratory failure on day 14 (rest of the world [RoW] study) and day 28 (US study). In the RoW study, 177 patients were randomized (acalabrutinib + BSC: n = 89; BSC: n = 88); in the US study, 62 patients were randomized (acalabrutinib + BSC: n = 31; BSC: n = 31). The percentage of patients who met the primary endpoint was similar in both studies (RoW study: acalabrutinib + BSC: 83.1%, BSC: 90.9%; US study: acalabrutinib + BSC: 80.6%, BSC: 83.9%). No new safety concerns were reported. Overall, no significant clinical benefit of adding acalabrutinib to BSC in patients hospitalized with COVID-19 was observed.

Intracellular adhesion molecule 1 (ICAM-1) is a cell surface glycoprotein that regulates cell-cell interactions, signaling, and immune processes. ICAM-1 expression has been shown to be elevated in many types of infections and inflammatory diseases. Strategies to block ICAM-1 function, including monoclonal anti-ICAM-1 antibodies, have been successful in treating the effects of chronic respiratory, autoimmune, and cardiovascular diseases. Naturally occurring autoantibodies targeting cytokines, endothelial cells, and other host receptors have been identified, and have been found to play a role in immunoregulation in health and disease. In this study, we determined the presence and levels of ICAM-1 autoantibodies across different age groups and disease states. We found that ICAM-1 autoantibody levels increased with age and were lower in individuals with various inflammatory states, suggesting a dynamic role in immune regulation. Using peptide microarrays, we identified high-resolution epitopes targeted by ICAM-1 autoantibodies that overlap with critical functional ICAM-1 binding sites. Finally, we determined that ICAM-1 autoantibodies were enriched for the IgG2 subclass that is critical for the response to bacterial antigens and chronic inflammation. This could indicate that molecular mimicry of bacterial antigens or underlying immune dysregulation could trigger the generation of anti-ICAM-1 antibodies. Understanding the functional implications of ICAM-1 autoantibodies could provide new insights into their contribution to immune homeostasis and their potential impact on inflammatory and autoimmune conditions.

IgE cross-reactivity among peanut allergens is controversial, and allergenicity of peanut allergens other than Arachis hypogaea 2 [Ara h 2] remains to be elucidated. We investigated the origins of peanut IgE cross-reactivity using Western blotting, and allergenicity of peanut allergens employing a passive cutaneous anaphylaxis model. Peanut allergic IgE bound to a large swath of peanut proteins including Ara h 2, Ara h 1, Ara h 3, and Ara h 6. IgE cross-reactivity among peanut allergens could be inhibited by recombinant Ara h 2. Affinity-purified Ara h 2 IgE reconstituted broad IgE binding patterns to Ara h 1, Ara h 3, and Ara h 6 in addition to Ara h 2. Monoclonal human IgE and mouse IgG against peanut allergen component variably bound to other peanut allergen components. Ara h 2 and Ara h 6 could trigger Ara h 2 IgE-mediated peanut allergic reactivity, whereas Ara h 1 and Ara h 3 failed to do so. Ara h 1 IgE was incapable of mediating Ara h 1-triggered allergic reaction. These results revealed that Ara h 2 IgE was the origin of IgE cross-reactivity, and Ara h 2 IgE-mediated peanut allergic reactivity triggered by Ara h 2 and Ara h 6. Ara h 1 and Ara h 3 did not display detectable allergenicity. These results indicated that Ara h 2 IgE appeared to be the "master" responsible for IgE cross-reactivity among peanut allergens and might be the only IgE responsible for allergic reactivity in peanut allergy.