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Memory CD4 T cells are critical to human immunity, yet it is unclear whether viral inflammation during memory formation has long-term consequences. Here, we compared transcriptional and epigenetic landscapes of Spike (S)–specific memory CD4 T cells in 24 individuals whose first exposure to S was via SARS-CoV-2 infection or mRNA vaccination. Nearly 2 years after memory formation, S-specific CD4 T cells established by infection remained enriched for transcripts related to cytotoxicity and for interferon-stimulated genes, likely because of a chromatin accessibility landscape altered by inflammation. Moreover, S-specific CD4 T cells primed by infection had reduced proliferative capacity in vitro relative to vaccine-primed cells. Furthermore, the transcriptional state of S-specific memory CD4 T cells was minimally altered by booster immunization and/or breakthrough infection. Thus, infection-associated inflammation durably imprints CD4 T cell memory, which affects the function of these cells and may have consequences for long-term immunity. Editor's summary: It is unclear whether the memory CD4 T cells generated via mRNA vaccination and via SARS-CoV-2 infection are comparable in terms of frequency and function. Gray-Gaillard et al. performed single-cell analysis of spike protein (S)–specific memory CD4 T cells taken from a longitudinal sample of individuals variously vaccinated against SARS-CoV-2 or naturally infected with the virus. Infection-primed S-specific memory CD4 T cells exhibited a durable transcriptional and epigenetic signature of inflammation, a cytotoxic profile, and a proliferative disadvantage compared with vaccine-primed memory CD4 T cells. Breakthrough infections did not generally alter the transcriptional profile of vaccine-primed memory T cells, although re-exposure to antigen accompanied by high levels of inflammation could alter the transcriptional profiles of these cells in a clonotype-specific manner. —Seth Thomas Scanlon [ABSTRACT FROM AUTHOR]

Objective: The objective for this study was to evaluate the effects of short chain fatty acids (SCFAs) on arthritic bone remodeling. Methods: We treated a recently described preclinical murine model of psoriatic arthritis (PsA), R26STAT3Cstopfl/fl CD4Cre mice, with SCFA‐supplemented water. We also performed in vitro osteoclast differentiation assays in the presence of serum‐level SCFAs to evaluate the direct impact of these microbial metabolites on maturation and function of osteoclasts. We further characterized the molecular mechanism of SCFAs by transcriptional analysis. Results: The osteoporosis condition in R26STAT3Cstopfl/fl CD4Cre animals is attributed primarily to robust osteoclast differentiation driven by an expansion of osteoclast progenitor cells (OCPs), accompanied by impaired osteoblast development. We show that SCFA supplementation can rescue the osteoporosis phenotype in this model of PsA. Our in vitro experiments revealed an inhibitory effect of the SCFAs on osteoclast differentiation, even at very low serum concentrations. This suppression of osteoclast differentiation enabled SCFAs to impede osteoporosis development in R26STAT3Cstopfl/fl CD4Cre mice. Further interrogation revealed that bone marrow–derived OCPs from diseased mice expressed a higher level of SCFA receptors than those of control mice and that the progenitor cells in the bone marrow of SCFA‐treated mice presented a modified transcriptomic landscape, suggesting a direct impact of SCFAs on bone marrow progenitors in the context of osteoporosis. Conclusion: We demonstrated how gut microbiota‐derived SCFAs can regulate distal pathology (ie, osteoporosis) and identified a potential therapeutic option for restoring bone density in rheumatic disease, further highlighting the critical role of the gut–bone axis in these disorders. [ABSTRACT FROM AUTHOR]

A central challenge for improving autoimmune therapy is preventing inflammatory pathology without inducing generalized immunosuppression. T helper 17 ([T.sub.H]17) cells, characterized by their production of interleukin-17, have emerged as important and broad mediators of autoimmunity. Here we show that the small molecule halofuginone (HF) selectively inhibits mouse and human [T.sub.H]17 differentiation by activating a cytoprotective signaling pathway, the amino acid starvation response (AAR). Inhibition of [T.sub.H]17 differentiation by HF is rescued by the addition of excess amino acids and is mimicked by AAR activation after selective amino acid depletion. HF also induces the AAR in vivo and protects mice from [T.sub.H]17-associated experimental autoimmune encephalomyelitis. These results indicate that the AAR pathway is a potent and selective regulator of inflammatory T cell differentiation in vivo.

Germinal centers (GCs) represent the main sites for the generation of high-affinity, class-switched antibodies during T cell-dependent antibody responses. To study gene function specifically in GC B cells, we generated C[gamma]1-cre mice in which the expression of Cre recombinase is induced by transcription of the Ig [gamma]1 constant region gene segment (C[gamma]1). In these mice, Cre-mediated recombination at the fas, Ig[beta], IgH, and Rosa26 loci occurred in GC B cells as early as 4 days after immunization with T cell-dependent antigens and involved >85% of GC B cells at the peak of the GC reaction. Less than 2% of Ig[M.sup.+] B cells showed Cre-mediated recombination. These cells carried few lg somatic mutations, expressed germ-line C[gamma]1- and activation-induced cytidine deaminase-specific transcripts and likely include GC B cell founders and/or plasma cell precursors. Cre-mediated recombination involved most IgG1, but also a fraction of IgG3-, IgG2a-, IgG2b-, and IgA-expressing GC and post-GC B cells. This result indicates that a GC B cell can transcribe more than one downstream CH gene before undergoing class switch recombination. The efficient induction of Cre expression in GC B cells makes the C[gamma]1-cre allele a powerful tool for the genetic analysis of these cells, as well as, in combination with a suitable marker for Cre-mediated recombination, the tracking of class-switched memory B and plasma cells in vivo. To expedite the genetic analysis of GC B cells, we have established C[gamma]1-cre [F.sub.1] embryonic stem cells, allowing further rounds of gene targeting and the cloning of compound mutants by tetraploid embryo complementation. class switch recombination | Cre recombinase | memory B | plasma cells

The use of coronavirus disease 2019 (COVID-19) vaccines will play the major role in helping to end the pandemic that has killed millions worldwide. COVID-19 vaccines have resulted in robust humoral responses and protective efficacy in human trials, but efficacy trials excluded individuals with a prior diagnosis of COVID-19. As a result, little is known about how immune responses induced by mRNA vaccines differ in individuals who recovered from COVID-19. Here, we evaluated longitudinal immune responses to two-dose BNT162b2 mRNA vaccination in 15 adults who had experienced COVID-19, compared to 21 adults who did not have prior COVID-19. Consistent with prior studies of mRNA vaccines, we observed robust cytotoxic CD8+ T cell responses in both cohorts after the second dose. Furthermore, SARS-CoV-2–naive individuals had progressive increases in humoral and antigen-specific antibody-secreting cell (ASC) responses after each dose of vaccine, whereas SARS-CoV-2–experienced individuals demonstrated strong humoral and antigen-specific ASC responses to the first dose but these responses were not further enhanced after the second dose of the vaccine at the time points studied. Together, these data highlight the relevance of immunological history for understanding vaccine immune responses and may have implications for personalizing mRNA vaccination regimens used to prevent COVID-19, including for the deployment of booster shots. The impact of prior immunity: Prior infection with SARS-CoV-2 elicits antibodies and T cell responses that influence subsequent responses to vaccines. Here, Samanovic et al. evaluated adaptive immune responses in individuals who received two doses of the BNT162b2 COVID-19 vaccine with or without prior confirmed SARS-CoV-2 infection. The authors found that humoral and cellular immune responses were elicited in both cohorts. Individuals who were vaccinated after prior infection exhibited increased humoral immunity after the first dose of vaccine that was stable after the second dose. Together, these findings show that immunological history may be important for vaccine and booster regimens. [ABSTRACT FROM AUTHOR]

B lymphocytes play a central role in host immune defense. B cell receptor (BCR) signaling regulates survival, proliferation, and differentiation of B lymphocytes. Signaling through the BCR signalosome is a multi‐component cascade that is tightly regulated and is important in the coordination of B cell differentiation and function. At different stages of development, B cells that have BCRs recognizing self are eliminated to prevent autoimmunity. microRNAs (miRNAs) are small single‐stranded non‐coding RNAs that contribute to post‐transcriptional regulation of gene expression and have been shown to orchestrate cell fate decisions through the regulation of lineage‐specific transcriptional profiles. Studies have identified miRNAs to be crucial for B cell development in the bone marrow and their subsequent population of the peripheral immune system. In this review, we focus on the role of miRNAs in the regulation of BCR signaling as it pertains to B lymphocyte development and function. In particular, we discuss the most recent studies describing the role of miRNAs in the regulation of both early B cell development and peripheral B cell responses and examine the ways by which miRNAs regulate signal downstream of B cell antigen receptor to prevent aberrant activation and autoimmunity. [ABSTRACT FROM AUTHOR]

Objective: To investigate the humoral and cellular immune response to messenger RNA (mRNA) COVID-19 vaccines in patients with immune-mediated inflammatory diseases (IMIDs) on immunomodulatory treatment.Methods: Established patients at New York University Langone Health with IMID (n=51) receiving the BNT162b2 mRNA vaccination were assessed at baseline and after second immunisation. Healthy subjects served as controls (n=26). IgG antibody responses to the spike protein were analysed for humoral response. Cellular immune response to SARS-CoV-2 was further analysed using high-parameter spectral flow cytometry. A second independent, validation cohort of controls (n=182) and patients with IMID (n=31) from Erlangen, Germany, were also analysed for humoral immune response.Results: Although healthy subjects (n=208) and patients with IMID on biologic treatments (mostly on tumour necrosis factor blockers, n=37) demonstrate robust antibody responses (over 90%), those patients with IMID on background methotrexate (n=45) achieve an adequate response in only 62.2% of cases. Similarly, patients with IMID on methotrexate do not demonstrate an increase in CD8+ T-cell activation after vaccination.Conclusions: In two independent cohorts of patients with IMID, methotrexate, a widely used immunomodulator for the treatment of several IMIDs, adversely affected humoral and cellular immune response to COVID-19 mRNA vaccines. Although precise cut-offs for immunogenicity that correlate with vaccine efficacy are yet to be established, our findings suggest that different strategies may need to be explored in patients with IMID taking methotrexate to increase the chances of immunisation efficacy against SARS-CoV-2 as has been demonstrated for augmenting immunogenicity to other viral vaccines. [ABSTRACT FROM AUTHOR]

Spondyloarthritis (SpA) is a group of chronic, immune-mediated, inflammatory diseases affecting the bone, synovium, and enthesis. Microbiome, the community of microorganisms that has co-evolved with human hosts, plays a pivotal role in human health and disease. This invisible "essential organ" supplies the host with a myriad of chemicals and molecules. In turn, microbial metabolites can serve as messengers for microbes to communicate with each other and in the cross-talk with host cells. Gut dysbiosis in SpA is associated with altered microbial metabolites, and an accumulated body of research has contributed to the understanding that changes in intestinal microbiota can modulate disease pathogenesis. We review the novel findings from human and animal studies to provide an overview of the contribution of individual microbial metabolites and antigens to SpA. [ABSTRACT FROM AUTHOR]

Rationale: Workers' exposure to metalworking fluid (MWF) has been associated with respiratory disease.Objectives: As part of a public health investigation of a manufacturing facility, we performed a cross-sectional study using paired environmental and human sampling to evaluate the cross-pollination of microbes between the environment and the host and possible effects on lung pathology present among workers.Methods: Workplace environmental microbiota were evaluated in air and MWF samples. Human microbiota were evaluated in lung tissue samples from workers with respiratory symptoms found to have lymphocytic bronchiolitis and alveolar ductitis with B-cell follicles and emphysema, in lung tissue samples from control subjects, and in skin, nasal, and oral samples from 302 workers from different areas of the facility. In vitro effects of MWF exposure on murine B cells were assessed.Measurements and Main Results: An increased similarity of microbial composition was found between MWF samples and lung tissue samples of case workers compared with control subjects. Among workers in different locations within the facility, those that worked in the machine shop area had skin, nasal, and oral microbiota more closely related to the microbiota present in the MWF samples. Lung samples from four index cases and skin and nasal samples from workers in the machine shop area were enriched with Pseudomonas, the dominant taxa in MWF. Exposure to used MWF stimulated murine B-cell proliferation in vitro, a hallmark cell subtype found in the pathology of index cases.Conclusions: Evaluation of a manufacturing facility with a cluster of workers with respiratory disease supports cross-pollination of microbes from MWF to humans and suggests the potential for exposure to these microbes to be a health hazard. [ABSTRACT FROM AUTHOR]

and its toxins have been linked to disease progression and mortality in advanced stages of cutaneous T-cell lymphoma (CTCL). CD8+ T cells play a crucial role in anti-cancer responses and high CD8+ T cell numbers in tumor lesions are associated with a favorable prognosis in CTCL. Here, we show that CD8+ T cells from both healthy donors and Sézary syndrome patients are highly susceptible to cell death induced by Staphylococcal alpha-toxin, whereas malignant T cells are not. Importantly, alpha-toxin almost completely blocks cytotoxic killing of CTCL tumor cells by peptide-specific CD8+ T cells, leading to their escape from induced cell death and continued proliferation. These findings suggest that alpha-toxin may favor the persistence of malignant CTCL cells in vivo by inhibiting CD8+ T cell cytotoxicity. Thus, we propose a novel mechanism by which colonization with Staphylococcus aureus may contribute to cancer immune evasion and disease progression in CTCL. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus is implicated in disease progression in cutaneous T-cell lymphoma (CTCL). Here, we demonstrate that malignant T cell lines derived from CTCL patients as well as primary malignant CD4+ T cells from Sézary syndrome patients are considerably more resistant to alpha-toxin-induced cell death than their non-malignant counterparts. Thus, in a subset of Sézary syndrome patients the ratio between malignant and non-malignant CD4+ T cells increases significantly following exposure to alpha-toxin. Whereas toxin-induced cell death is ADAM10 dependent in healthy CD4+ T cells, resistance to alpha-toxin in malignant T cells involves both downregulation of ADAM10 as well as other resistance mechanisms. In conclusion, we provide first evidence that Staphylococcus aureus derived alpha-toxin can tilt the balance between malignant and non-malignant CD4+ T cells in CTCL patients. Consequently, alpha-toxin may promote disease progression through positive selection of malignant CD4+ T cells, identifying alpha-toxin as a putative drug target in CTCL. [ABSTRACT FROM AUTHOR]

Objective: Intestinal microbiota are associated with the development of inflammatory arthritis. The aim of this study was to dissect intestinal mucosal immune responses in the preclinical phase of arthritis and determine whether the presence of Th17 cells, beyond involvement of the cytokine interleukin‐17 (IL‐17), is required for arthritis development, and whether the involvement of Th17 cells in arthritis depends on the composition of the host microbiota. Methods: Mucosal T cell production of IL‐17, interferon‐γ, tumor necrosis factor α (TNFα), IL‐22, and granulocyte–macrophage colony‐stimulating factor (GM‐CSF) was analyzed by flow cytometry and Luminex assay before arthritis onset in mice immunized to develop collagen‐induced arthritis (CIA). Pathogenic features of arthritis in mice with CIA and mice with antigen‐induced arthritis were compared between Th17 cell–deficient (CD4‐Cre+Rorcflox/flox) and Th17 cell–sufficient (CD4‐Cre−Rorcflox/flox) mice. In addition, the impact of intestinal microbiota on the Th17 cell dependence of CIA was assessed. Results: Lamina propria CD4 T cells were activated before the onset of arthritis in mice with CIA, with marked up‐regulation of several cytokines, including IL‐17A, TNFα, and GM‐CSF. CD4‐Cre+Rorcflox/flox mice showed a specific reduction in intestinal mucosal levels of Th17 cells and partially reduced levels of IL‐17–producing CD8 T cells. However, total levels of IL‐17A, mostly produced by γδ T cells and neutrophils, were unaffected. The severity of arthritis was significantly reduced in Th17 cell–deficient mice, suggesting that Th17 cells have additional, IL‐17A–independent roles in inflammatory arthritis. Accordingly, antigen‐stimulated T cells from Th17 cell–deficient mice produced less IL‐17A, IL‐17F, and GM‐CSF. Importantly, the dependence of CIA on the involvement of Th17 cells was mitigated in the presence of an alternative microbiome. Conclusion: These data from murine models suggest that activation of mucosal immunity precedes the development of arthritis, and also that Th17 cells have a microbiota‐dependent role in arthritis. Therefore, a microbiome‐guided stratification of patients might improve the efficacy of Th17‐targeted therapies. [ABSTRACT FROM AUTHOR]

Objective: To introduce a novel preclinical animal model of psoriatic arthritis (PsA) in R26Stat3Cstopfl/fl CD4Cre mice, and to investigate the role of Th17 cytokines in the disease pathogenesis. Methods: We characterized a novel murine model of Th17‐driven cutaneous and synovio‐entheseal disease directed by T cell–specific expression of a hyperactive Stat3 allele. By crossing R26Stat3Cstopfl/fl CD4Cre mice onto an interleukin‐22 (IL‐22)–knockout background or treating the mice with a neutralizing antibody against IL‐17, we interrogated how these Th17 cytokines could contribute to the pathogenesis of PsA. Results: R26Stat3Cstopfl/fl CD4Cre mice developed acanthosis, hyperkeratosis, and parakeratosis of the skin, as well as enthesitis/tendinitis and periarticular bone erosion in different joints, accompanied by osteopenia. T cell–specific expression of a hyperactive Stat3C allele was found to drive the augmented Th17 response in these animals. Careful characterization of the mouse bone marrow revealed an increase in osteoclast progenitor (OCP) and RANKL‐producing cells, which contributed to the osteopenia phenotype observed in the mutant animals. Abrogation of the Th17 cytokines IL‐17 or IL‐22 improved both the skin and bone phenotype in R26Stat3Cstopfl/fl CD4Cre mice, revealing a central role of Th17 cells in the regulation of OCP and RANKL expression on stromal cells. Conclusion: Perturbation of the IL‐23/Th17 axis instigates Th17‐mediated inflammation in R26Stat3Cstopfl/fl CD4Cre mice, leading to cutaneous and synovio‐entheseal inflammation and bone pathologic features highly reminiscent of human PsA. Both IL‐17A and IL‐22 produced by Th17 cells appear to play critical roles in promoting the cutaneous and musculoskeletal inflammation that characterizes PsA. [ABSTRACT FROM AUTHOR]