Inhibitory IL-10-producing CD4+ T cells are T-bet-dependent and facilitate cytomegalovirus persistence via coexpression of arginase-1.

Inhibitory CD4+ T cells have been linked with suboptimal immune responses against cancer and pathogen chronicity. However, the mechanisms that underpin the development of these regulatory cells, especially in the context of ongoing antigen exposure, have remained obscure. To address this knowledge gap, we undertook a comprehensive functional, phenotypic, and transcriptomic analysis of interleukin (IL)-10-producing CD4+ T cells induced by chronic infection with murine cytomegalovirus (MCMV). We identified these cells as clonally expanded and highly differentiated TH1-like cells that developed in a T-bet-dependent manner and coexpressed arginase-1 (Arg1), which promotes the catalytic breakdown of L-arginine. Mice lacking Arg1-expressing CD4+ T cells exhibited more robust antiviral immunity and were better able to control MCMV. Conditional deletion of T-bet in the CD4+ lineage suppressed the development of these inhibitory cells and also enhanced immune control of MCMV. Collectively, these data elucidated the ontogeny of IL-10-producing CD4+ T cells and revealed a previously unappreciated mechanism of immune regulation, whereby viral persistence was facilitated by the site-specific delivery of Arg1.

Ultrasound-guided tenoscopic decompression of digital sheath synoviocoeles in 10 horses.

OBJECTIVE: To report the diagnostic features and clinical outcome of horses with digital flexor tendon sheath (DFTS) synoviocoeles treated tenoscopically under ultrasonographic guidance. STUDY DESIGN: Retrospective case series. ANIMALS: Client-owned horses (n = 10). METHODS: Medical records were searched for horses with lameness localized to the region of the DFTS and clinical evidence of a fluid-filled mass (synoviocoele) associated with the DFTS. Diagnostic imaging and surgical findings, together with long-term outcome, were reported. RESULTS: Lameness and synoviocoeles were unilateral (5 forelimbs, 5 hindlimbs; 3 lateral and 2 medial in both) and located proximal to the palmar/plantar annular ligament. Synoviocoeles had a firm consistency and focal pain with inability to deflate on non-weight-bearing examination. Intrathecal DFTS anesthesia was positive in 7/8 horses in which it was performed, with the remainder localized to the region of the synoviocoele using perineural and/or intralesional anesthesia. Communication between the DFTS and synoviocoele was suspected ultrasonographically in all cases and confirmed on contrast tenography (6/6). Tenoscopic fenestration of the communication between the DFTS and synoviocoele under ultrasonographic guidance, with treatment of concurrent intrathecal injury (4/10), resolved the lameness in all horses re-evaluated by a veterinarian (9/9) and allowed return to full athletic function in all cases at long-term follow up (median 5 years; range 1.25-9 years). CONCLUSION: Tenoscopic decompression was an effective treatment for DFTS synoviocoeles, which, along with treatment of concurrent intrathecal injury, carried an excellent prognosis and avoided the need for resection via an extrasynovial approach.

A Rare Presentation of Adrenocortical Carcinoma.

An adrenal incidentaloma is a mass found incidentally on radiological imaging performed for other reasons. The prevalence of these incidentalomas increases with age, and they all must be evaluated to determine if they are benign or malignant and if they are functioning or non-functioning. A 71-year-old female presented with sub-acute bilateral lower limb pitting edema and dyspnoea. Imaging showed an 8 cm smoothly defined heterogeneous right adrenal mass and a number of low attenuation lesions throughout the liver. This case report describes a rare presentation of adrenocortical carcinoma due to an adrenal incidentaloma identified on imaging in a patient presenting with bilateral lower limb edema. The laboratory and imaging evaluation of these incidentalomas are also discussed.

Optimal CD8+ T-cell memory formation following subcutaneous cytomegalovirus infection requires virus replication but not early dendritic cell responses.

Cytomegalovirus (CMV) induction of large frequencies of highly functional memory T cells has attracted much interest in the utility of CMV-based vaccine vectors, with exciting preclinical data obtained in models of infectious diseases and cancer. However, pathogenesis of human CMV (HCMV) remains a concern. Attenuated CMV-based vectors, such as replication- or spread-deficient viruses, potentially offer an alternative to fully replicating vectors. However, it is not well understood how CMV attenuation impacts vector immunogenicity, particularly when administered via relevant routes of immunization such as the skin. Herein, we used the murine cytomegalovirus (MCMV) model to investigate the impact of vector attenuation on T-cell memory formation following subcutaneous administration. We found that the spread-deficient virus (ΔgL-MCMV) was impaired in its ability to induce memory CD8+ T cells reactive to some (M38, IE1) but not all (IE3) viral antigens. Impaired-memory T-cell development was associated with a preferential and pronounced loss of polyfunctional (IFN-γ+ TNF-α+ ) T cells and also reduced accumulation of TCF1+ T cells, and was not rescued by increasing the dose of replication-defective MCMV. Finally, whilst vector attenuation reduced dendritic cell (DC) recruitment to skin-draining lymph nodes, systematic depletion of multiple DC subsets during acute subcutaneous MCMV infection had a negligible impact on T-cell memory formation, implying that attenuated responses induced by replication-deficient vectors were likely not a consequence of impaired initial DC activation. Thus, overall, these data imply that the choice of antigen and/or cloning strategy of exogenous antigen in combination with the route of immunization may influence the ability of attenuated CMV vectors to induce robust functional T-cell memory.

IRF5 Promotes Influenza Virus-Induced Inflammatory Responses in Human Induced Pluripotent Stem Cell-Derived Myeloid Cells and Murine Models.

Recognition of influenza A virus (IAV) by the innate immune system triggers pathways that restrict viral replication, activate innate immune cells, and regulate adaptive immunity. However, excessive innate immune activation can exaggerate disease. The pathways promoting excessive activation are incompletely understood, with limited experimental models to investigate the mechanisms driving influenza virus-induced inflammation in humans. Interferon regulatory factor 5 (IRF5) is a transcription factor that plays important roles in the induction of cytokines after viral sensing. In an in vivo model of IAV infection, IRF5 deficiency reduced IAV-driven immune pathology and associated inflammatory cytokine production, specifically reducing cytokine-producing myeloid cell populations in Irf5-/- mice but not impacting type 1 interferon (IFN) production or virus replication. Using cytometry by time of flight (CyTOF), we identified that human lung IRF5 expression was highest in cells of the myeloid lineage. To investigate the role of IRF5 in mediating human inflammatory responses by myeloid cells to IAV, we employed human-induced pluripotent stem cells (hIPSCs) with biallelic mutations in IRF5, demonstrating for the first time that induced pluripotent stem cell-derived dendritic cells (iPS-DCs) with biallelic mutations can be used to investigate the regulation of human virus-induced immune responses. Using this technology, we reveal that IRF5 deficiency in human DCs, or macrophages, corresponded with reduced virus-induced inflammatory cytokine production, with IRF5 acting downstream of Toll-like receptor 7 (TLR7) and, possibly, retinoic acid-inducible gene I (RIG-I) after viral sensing. Thus, IRF5 acts as a regulator of myeloid cell inflammatory cytokine production during IAV infection in mice and humans and drives immune-mediated viral pathogenesis independently of type 1 IFN and virus replication.IMPORTANCE The inflammatory response to influenza A virus (IAV) participates in infection control but contributes to disease severity. After viral detection, intracellular pathways are activated, initiating cytokine production, but these pathways are incompletely understood. We show that interferon regulatory factor 5 (IRF5) mediates IAV-induced inflammation and, in mice, drives pathology. This was independent of antiviral type 1 IFN and virus replication, implying that IRF5 could be specifically targeted to treat influenza virus-induced inflammation. We show for the first time that human iPSC technology can be exploited in genetic studies of virus-induced immune responses. Using this technology, we deleted IRF5 in human myeloid cells. These IRF5-deficient cells exhibited impaired influenza virus-induced cytokine production and revealed that IRF5 acts downstream of Toll-like receptor 7 and possibly retinoic acid-inducible gene I. Our data demonstrate the importance of IRF5 in influenza virus-induced inflammation, suggesting that genetic variation in the IRF5 gene may influence host susceptibility to viral diseases.