BHLHE40 Regulates Myeloid Cell Polarization through IL-10-Dependent and -Independent Mechanisms

Better understanding of the host responses to Mycobacterium tuberculosis infections is required to prevent tuberculosis and develop new therapeutic interventions. The host transcription factor BHLHE40 is essential for controlling M. tuberculosis infection, in part by repressing Il10 expression, where excess IL-10 contributes to the early susceptibility of Bhlhe40-/- mice to M. tuberculosis infection. Deletion of Bhlhe40 in lung macrophages and dendritic cells is sufficient to increase the susceptibility of mice to M. tuberculosis infection, but how BHLHE40 impacts macrophage and dendritic cell responses to M. tuberculosis is unknown. In this study, we report that BHLHE40 is required in myeloid cells exposed to GM-CSF, an abundant cytokine in the lung, to promote the expression of genes associated with a proinflammatory state and better control of M. tuberculosis infection. Loss of Bhlhe40 expression in murine bone marrow-derived myeloid cells cultured in the presence of GM-CSF results in lower levels of proinflammatory associated signaling molecules IL-1β, IL-6, IL-12, TNF-α, inducible NO synthase, IL-2, KC, and RANTES, as well as higher levels of the anti-inflammatory-associated molecules MCP-1 and IL-10 following exposure to heat-killed M. tuberculosis. Deletion of Il10 in Bhlhe40-/- myeloid cells restored some, but not all, proinflammatory signals, demonstrating that BHLHE40 promotes proinflammatory responses via both IL-10-dependent and -independent mechanisms. In addition, we show that macrophages and neutrophils within the lungs of M. tuberculosis-infected Bhlhe40-/- mice exhibit defects in inducible NO synthase production compared with infected wild-type mice, supporting that BHLHE40 promotes proinflammatory responses in innate immune cells, which may contribute to the essential role for BHLHE40 during M. tuberculosis infection in vivo.

BHLHE40 Mediates Cross-Talk between Pathogenic TH17 Cells and Myeloid Cells during Experimental Autoimmune Encephalomyelitis

TH17 cells are implicated in the pathogenesis of multiple sclerosis and experimental autoimmune encephalomyelitis (EAE). We previously reported that the transcription factor basic helix-loop-helix family member e40 (BHLHE40) marks cytokine-producing pathogenic TH cells during EAE, and that its expression in T cells is required for clinical disease. In this study, using dual reporter mice, we show BHLHE40 expression within TH1/17 and ex-TH17 cells following EAE induction. Il17a-Cre-mediated deletion of BHLHE40 in TH cells led to less severe EAE with reduced TH cell cytokine production. Characterization of the leukocytes in the CNS during EAE by single-cell RNA sequencing identified differences in the infiltrating myeloid cells when BHLHE40 was present or absent in TH17 cells. Our studies highlight the importance of BHLHE40 in promoting TH17 cell encephalitogenicity and instructing myeloid cell responses during active EAE.

The ZFP36 family of RNA binding proteins regulates homeostatic and autoreactive T cell responses

RNA binding proteins are important regulators of T cell activation, proliferation, and cytokine production. The zinc finger protein 36 (ZFP36) family genes (Zfp36, Zfp36l1, and Zfp36l2) encode RNA binding proteins that promote the degradation of transcripts containing AU-rich elements. Numerous studies have demonstrated both individual and shared functions of the ZFP36 family in immune cells, but their collective function in T cells remains unclear. Here, we found a redundant and critical role for the ZFP36 proteins in regulating T cell quiescence. T cell-specific deletion of all three ZFP36 family members in mice resulted in early lethality, immune cell activation, and multiorgan pathology characterized by inflammation of the eyes, central nervous system, kidneys, and liver. Mice with T cell-specific deletion of any two Zfp36 genes were protected from this spontaneous syndrome. Triply deficient T cells overproduced proinflammatory cytokines, including IFN-γ, TNF, and GM-CSF, due to increased mRNA stability of these transcripts. Unexpectedly, T cell-specific deletion of both Zfp36l1 and Zfp36l2 rendered mice resistant to experimental autoimmune encephalomyelitits due to failed priming of antigen-specific CD4⁺ T cells. ZFP36L1 and ZFP36L2 double-deficient CD4⁺ T cells had poor proliferation during in vitro T helper cell polarization. Thus, the ZFP36 family redundantly regulates T cell quiescence at homeostasis, but ZFP36L1 and ZFP36L2 are specifically required for antigen-specific T cell clonal expansion.

Antigen-guided depletion of anti-HLA antibody-producing cells by HLA-Fc fusion proteins

Platelet transfusion and transplantation of allogeneic stem cells and solid organs are life-saving therapies. Unwanted alloantibodies to nonself human leukocyte antigens (HLAs) on donor cells increase the immunological barrier to these therapies and are important causes of platelet transfusion refractoriness and graft rejection. Although the specificities of anti-HLA antibodies can be determined at the allelic level, traditional treatments for antibody-mediated rejection nonselectively suppress humoral immunity and are not universally successful. We designed HLA-Fc fusion proteins with a bivalent targeting module derived from extracellular domains of HLA and an Fc effector module from mouse IgG2a. We found that HLA-Fc with A2 (A2Fc) and B7 (B7Fc) antigens lowered HLA-A2- and HLA-B7-specific reactivities, respectively, in sera from HLA-sensitized patients. A2Fc and B7Fc bound to B-cell hybridomas bearing surface immunoglobulins with cognate specificities and triggered antigen-specific and Fc-dependent cytotoxicity in vitro. In immunodeficient mice carrying HLA-A2-specific hybridoma cells, A2Fc treatment lowered circulating anti-HLA-A2 levels, abolished the outgrowth of hybridoma cells, and prolonged survival compared with control groups. In an in vivo anti-HLA-A2-mediated platelet transfusion refractoriness model, A2Fc treatment mitigated refractoriness. These results support HLA-Fc being a novel strategy for antigen-specific humoral suppression to improve transfusion and transplantation outcomes. With the long-term goal of targeting HLA-specific memory B cells for desensitization, further studies of HLA-Fc's efficacy in immune-competent animal models are warranted.

The ZFP36 family of RNA-binding proteins regulate homeostatic and autoreactive T cell responses

The zinc finger 36 (ZFP36) family of RNA-binding proteins, consisting of ZFP36, ZFP36L1, and ZFP36L2, is known to negatively regulate mRNA stability and/or inhibit translation of many transcripts, including cytokines. While there are reports of all three family members regulating T cell cytokine production, delineating the functions of these genes is challenging due to spontaneous phenotypes upon global deletion of single genes and potential redundancy in their functions. To overcome this, we generated Cd4-Cre+ Zfp36fl/fl Zfp36l1fl/fl Zfp36l2fl/fl mice. Only upon triple deletion, but not individual or paired deletions, do mice spontaneously develop an inflammatory disease characterized by early lethality, hypercytokinemia, and immune cell infiltration into some peripheral organs, including the central nervous system. As SNPs in human ZFP36L1 and ZFP36L2 have been linked to susceptibility for multiple sclerosis, we tested ZFP36 family member individual and paired T cell-deficient mice in experimental autoimmune encephalomyelitis (EAE). To our surprise, Cd4-Cre+ Zfp36l1fl/fl Zfp36l2fl/fl mice were markedly protected from EAE clinical disease, while no change in disease severity was seen with any deletion strains involving Zfp36. There was a severe impairment in generating antigen-specific CD4+ T cells in Cd4-Cre+ Zfp36l1fl/fl Zfp36l2fl/fl mice during EAE priming. Our findings demonstrate a novel redundancy of the ZFP family members in regulating T cell homeostasis and a shared role for ZFP36L1 and ZFP36L2 to promote clonal expansion. Understanding the individual and shared functions of the ZFP36 family members may lead to opportunities to target them to suppress T cell-driven autoimmunity.

M.E.C. supported by the National Science Foundation Graduate Research Fellowship program (DGE-1745038) and by grant 5T32AI007163 from the NIAID. B.T.E. supported by the NIAID (R01 AI113118).

A-46 Deconstructing Competitiveness: The Effect of Age on Athlete’s Desire to Succeed, Win, and Achieve Goals

Objective

Our previous research indicated that athletes scoring high in competitiveness were less likely to report sports-related concussion symptoms and withdraw from the game. The present study examined whether athletes’ desire to succeed (competitiveness motive), win (win orientation), and achieve personal goals (goal orientation) were related to the age of players.

Method

Participants included 161 athletes, ages 14–32 (M = 17.6 years; 33.2% female), recruited from a mid-sized Canadian city participating in low (rowing), moderate (soccer) and high (hockey, rugby, football) contact sports. Confirmatory factor analysis was first used to evaluate the structure of the Sports Orientation Questionnaire. Then, using SEM, athletes’ competitiveness, goal orientation, and win orientation were predicted by age.

Results

High internal consistency was obtained within each factor (.84–.93). The model demonstrated suboptimal fit for this sample (CFI = .84; χ2f/df ratio = 2.02; RMSEA = .087; 90% CI: .077–.097). All factors were significantly related to age, indicating that athletes’ desire to succeed (competitiveness motive; β = .18, p = .009), achieve personal goals (goal orientation; β = .26, p = .007), and win (win orientation; β = .30, p = .000) increases with age.

Conclusion

The small positive association between age and competitiveness, win, and goal orientation indicates that older athletes are more competitive than younger athletes. Given that competitiveness predicts athletes’ intention to report a concussion, clinicians and coaches should pay particular attention to senior athletes who demonstrate high levels of general competitiveness and who are driven by the desire to win and achieve personal goals. Therefore, interventions targeting the barriers to reporting concussions should evaluate subco.

Impacting cost and appropriateness of stress ulcer prophylaxis at a university medical center

OBJECTIVE

To determine the appropriateness and medication cost of stress ulcer prophylaxis before and after a targeted educational intervention.

DESIGN

In the preintervention cohort (phase 1), 264 patients were evaluated over 2 months, using stress ulcer prophylaxis guidelines developed by a comprehensive literature search. Targeted educational programs were subsequently used to inform trauma housestaff on appropriate usage of stress ulcer prophylaxis medications with emphasis on using sucralfate. The postintervention cohort (phase 2) involved concurrent evaluation of 279 patients. Length of inappropriate stress ulcer prophylaxis (i.e., did not meet approved guidelines) between phases was compared using a Student's t-test for independent samples (alpha = .05).

SETTING

A 365-bed university medical center.

PATIENTS

Patients admitted to any of the intensive care units and all patients who were placed on histamine-2-antagonists or sucralfate for stress ulcer prophylaxis.

INTERVENTIONS

Educational intervention regarding appropriate stress ulcer prophylaxis directed at the trauma service.

MEASUREMENTS AND MAIN RESULTS

Patient demographics in the two phases were similar and there was no difference in the number of patient risk factors for stress-induced bleeding. The mean length of inappropriate stress ulcer prophylaxis was 5.78 +/- 4.36 days in phase 1 and 4.66 +/- 3.10 days in phase 2 (p < .05). Eighty-nine patients in phase 1 received inappropriate stress ulcer prophylaxis for a drug cost of $2,272.00 (mean $25.53 +/- 25.52) compared with 90 patients in phase 2 with a drug cost of $1,417.00 (mean $15.75 +/- 13.06). Three patients in each phase had clinically important bleeding (hemodynamic compromise or transfusion); all were receiving ranitidine. The mean total cost (fixed and variable) of hospitalization was $69,288.00 and $74,709.00 for the three patients who bled in each phase compared with $19,850.00 and $15,812.00 for all patients admitted to the intensive care unit in phases 1 and 2, respectively. The mean length of hospital stay was 30.00 days and 29.33 days for the three patients who bled in each phase compared with 11.54 days and 10.27 days for all patients admitted to the intensive care unit in phases 1 and 2, respectively.

CONCLUSIONS

Cost savings are associated with more appropriate stress ulcer prophylaxis. Clinically important bleeding is uncommon but results in prolonged hospital stays and increased costs.