Melissa H. Bloodworth

Respiratory syncytial virus infection activates IL-13–producing group 2 innate lymphoid cells through thymic stromal lymphopoietin

Background Respiratory syncytial virus (RSV) is a major health care burden with a particularly high worldwide morbidity and mortality rate among infants. Data suggest that severe RSV-associated illness is in part caused by immunopathology associated with a robust type 2 response. Objective We sought to determine the capacity of RSV infection to stimulate group 2 innate lymphoid cells (ILC2s) and the associated mechanism in a murine model. Methods Wild-type (WT) BALB/c, thymic stromal lymphopoietin receptor (TSLPR) knockout (KO), or WT mice receiving an anti-TSLP neutralizing antibody were infected with the RSV strain 01/2-20. During the first 4 to 6 days of infection, lungs were collected for evaluation of viral load, protein concentration, airway mucus, airway reactivity, or ILC2 numbers. Results were confirmed with 2 additional RSV clinical isolates, 12/11-19 and 12/12-6, with known human pathogenic potential. Results RSV induced a 3-fold increase in the number of IL-13–producing ILC2s at day 4 after infection, with a concurrent increase in total lung IL-13 levels. Both thymic stromal lymphopoietin (TSLP) and IL-33 levels were increased 12 hours after infection. TSLPR KO mice did not mount an IL-13–producing ILC2 response to RSV infection. Additionally, neutralization of TSLP significantly attenuated the RSV-induced IL-13–producing ILC2 response. TSLPR KO mice displayed reduced lung IL-13 protein levels, decreased airway mucus and reactivity, attenuated weight loss, and similar viral loads as WT mice. Both 12/11-19 and 12/12-6 similarly induced IL-13–producing ILC2s through a TSLP-dependent mechanism. Conclusion These data demonstrate that multiple pathogenic strains of RSV induce IL-13–producing ILC2 proliferation and activation through a TSLP-dependent mechanism in a murine model and suggest the potential therapeutic targeting of TSLP during severe RSV infection.

Prostaglandin I2 Signaling and Inhibition of Group 2 Innate Lymphoid Cell Responses

RATIONALE Group 2 innate lymphoid cells (ILC2s) robustly produce IL-5 and IL-13, cytokines central to the asthma phenotype; however, the effect of prostaglandin (PG) I2 on ILC2 function is unknown. OBJECTIVES To determine the effect of PGI2 on mouse and human ILC2 cytokine expression in vitro and the effect of endogenous PGI2 and the PGI2 analog cicaprost on lung ILC2s in vivo. METHODS Flow-sorted bone marrow ILC2s of wild-type (WT) and PGI2 receptor-deficient (IP(-/-)) mice were cultured with IL-33 and treated with the PGI2 analog cicaprost. WT and IP(-/-) mice were challenged intranasally with Alternaria alternata extract for 4 consecutive days to induce ILC2 responses, and these were quantified. Prior to A. alternata extract, challenged WT mice were treated with cicaprost. Human flow-sorted peripheral blood ILC2s were cultured with IL-33 and IL-2 and treated with the PGI2 analog cicaprost. MEASUREMENT AND MAIN RESULTS We demonstrate that PGI2 inhibits IL-5 and IL-13 protein expression by IL-33-stimulated ILC2s purified from mouse bone marrow in a manner that was dependent on signaling through the PGI2 receptor IP. In a mouse model of 4 consecutive days of airway challenge with an extract of A. alternata, a fungal aeroallergen associated with severe asthma exacerbations, endogenous PGI2 signaling significantly inhibited lung IL-5 and IL-13 protein expression, and reduced the number of lung IL-5- and IL-13-expressing ILC2s, as well as the mean fluorescence intensity of IL-5 and IL-13 staining. In addition, exogenous administration of a PGI2 analog inhibited Alternaria extract-induced lung IL-5 and IL-13 protein expression, and reduced the number of lung IL-5- and IL-13-expressing ILC2s and the mean fluorescence intensity of IL-5 and IL-13 staining. Finally, a PGI2 analog inhibited IL-5 and IL-13 expression by human ILC2s that were stimulated with IL-2 and IL-33. CONCLUSIONS These results suggest that PGI2 may be a potential therapy to reduce the ILC2 response to protease-containing aeroallergens, such as Alternaria.

The histone deacetylase inhibitor trichostatin A suppresses murine innate allergic inflammation by blocking group 2 innate lymphoid cell (ILC2) activation

Background Group 2 innate lymphoid cells (ILC2) are an important source of the type 2 cytokines interleukin (IL)-5 and IL-13 that are critical to the allergic airway phenotype. Previous studies reported that histone deacetylase (HDAC) inhibition by trichostatin A (TSA) downregulated adaptive allergic immune responses; however, the effect of HDAC inhibition on the early innate allergic immune response is unknown. Therefore, we investigated the effect of TSA on innate airway inflammation mediated by ILC2 activation. Methods BALB/c mice were challenged intranasally with Alternaria extract, exogenous recombinant mouse IL-33 (rmIL-33) or the respective vehicles for four consecutive days following TSA or vehicle treatment. Bronchoalveolar lavage (BAL) fluids and lungs were harvested 24 h after the last challenge. Results We found that TSA treatment significantly decreased the number of ILC2 expressing IL-5 and IL-13 in the lungs challenged with Alternaria extract or rmIL-33 compared with vehicle treatment (p<0.05). TSA treatment significantly decreased protein expression of IL-5, IL-13, CCL11 and CCL24 in the lung homogenates from Alternaria extract-challenged mice or rmIL-33-challenged mice compared with vehicle treatment (p<0.05). Further, TSA treatment significantly decreased the number of perivascular eosinophils and mucus production in the large airways that are critical components of the asthma phenotype (p<0.05). TSA did not change early IL-33 release in the BAL fluids; however, TSA decreased lung IL-33 expression from epithelial cells 24 h after last Alternaria extract challenge compared with vehicle treatment (p<0.05). Conclusions These results reveal that TSA reduces allergen-induced ILC2 activation and the early innate immune responses to an inhaled protease-containing aeroallergen.

STAT1 Represses Cytokine-Producing Group 2 and Group 3 Innate Lymphoid Cells during Viral Infection

The appropriate orchestration of different arms of the immune response is critical during viral infection to promote efficient viral clearance while limiting immunopathology. However, the signals and mechanisms that guide this coordination are not fully understood. IFNs are produced at high levels during viral infection and have convergent signaling through STAT1. We hypothesized that STAT1 signaling during viral infection regulates the balance of innate lymphoid cells (ILC), a diverse class of lymphocytes that are poised to respond to environmental insults including viral infections with the potential for both antiviral or immunopathologic functions. During infection with respiratory syncytial virus (RSV), STAT1-deficient mice had reduced numbers of antiviral IFN-γ+ ILC1 and increased numbers of immunopathologic IL-5+ and IL-13+ ILC2 and IL-17A+ ILC3 compared with RSV-infected wild-type mice. Using bone marrow chimeric mice, we found that both ILC-intrinsic and ILC-extrinsic factors were responsible for this ILC dysregulation during viral infection in STAT1-deficient mice. Regarding ILC-extrinsic mechanisms, we found that STAT1-deficient mice had significantly increased expression of IL-33 and IL-23, cytokines that promote ILC2 and ILC3, respectively, compared with wild-type mice during RSV infection. Moreover, disruption of IL-33 or IL-23 signaling attenuated cytokine-producing ILC2 and ILC3 responses in STAT1-deficient mice during RSV infection. Collectively, these data demonstrate that STAT1 is a key orchestrator of cytokine-producing ILC responses during viral infection via ILC-extrinsic regulation of IL-33 and IL-23.

A template for non-religious-based discussions against euthanasia

We submit this manuscript as part of the ongoing conversation in society at large about physician-assisted death (PAD) and euthanasia. This outlines an approach used by lay healthcare professionals in arguing against PAD/euthanasia during a 1-hour debate conducted on a secular medical school campus. We have included the elements chosen for the “con” side of the argument (i.e., against PAD) by the medical students and attending physician. The goal of this manuscript is to provide a focused and pithy template upon which to build an approach that honors the dignity of life in all circumstances. Lay summary: The discussion over physician assisted death and euthanasia remains ongoing in secular academic medical institutions across the United States and much of the western world. These debates have incentivized efforts to develop a framework for arguments against Euthanasia that will find traction in an environment generally hostile to religion and religious thought. In this essay, we present arguments given by the “con” side in a student-led debate over physician assisted death and euthanasia at Vanderbilt University with the hope that they will provide a foundation for future discussions promoting truth and life without alienating our secular colleagues.

Association of ST2 polymorphisms with atopy, asthma, and leukemia

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Glucagon-like peptide 1 receptor signaling attenuates respiratory syncytial virus–induced type 2 responses and immunopathology

GLP-1R signaling, an emerging anti-inflammatory therapeutic target, attenuated type 2-associated immunopathology in mice infected with a strain of RSV that was isolated from a hospitalized infant with severe lower respiratory tract infection and bronchiolitis.

The PGI2 Analog Cicaprost Inhibits IL-33–Induced Th2 Responses, IL-2 Production, and CD25 Expression in Mouse CD4+ T Cells

IL-33 has pleiotropic functions in immune responses and promotes the development of allergic diseases and asthma. IL-33 induces Th2 differentiation and enhances type 2 cytokine production by CD4+ T cells. However, the regulation of IL-33–driven type 2 cytokine responses is not fully defined. In this study, we investigated the effect of PGI2, a lipid mediator formed in the cyclooxygenase pathway of arachidonic acid metabolism, on naive CD4+ T cell activation, proliferation, and differentiation by IL-33. Using wild-type and PGI2 receptor (IP) knockout mice, we found that the PGI2 analog cicaprost dose-dependently inhibited IL-33–driven IL-4, IL-5, and IL-13 production by CD4+ T cells in an IP-specific manner. In addition, cicaprost inhibited IL-33–driven IL-2 production and CD25 expression by CD4+ T cells. Furthermore, IP knockout mice had increased IL-5 and IL-13 responses of CD4+ T cells to Alternaria sensitization and challenge in mouse lungs. Because IL-33 is critical for Alternaria-induced type 2 responses, these data suggest that PGI2 not only inhibits IL-33–stimulated CD4+ Th2 cell responses in vitro but also suppresses IL-33–induced Th2 responses caused by protease-containing allergens in vivo.