High mobility group box 1 (HMGB1) is a host-derived proinflammatory molecule released during cell injury. Elevated extracellular HMGB1 levels have been associated with disease severity. HMGB1 contributes to host influenza responses by stimulating TLR4/MD-2 signaling, amplifying lung inflammation, and tissue damage via cytokine production and leukocyte infiltration. HMGB1 also plays a central role in other inflammatory diseases, including sepsis and liver toxicity, making it both a biomarker of disease severity and a potential therapeutic target. We previously reported development of a non-replicating adenovirus (AdV) vector that carries an inflammation-inducible cassette that remains dormant in the absence of inflammation but produces recombinant HMGB1 Box A, a competitive antagonist of HMGB1, in response to inflammatory stimuli. Therapeutic treatment with AdV.C3-Tat/HIV-Box A mitigated lung and systemic inflammation in response to influenza in mice and cotton rats. Herein, we have optimized vector delivery and expanded its use in multiple models of infectious and non-infectious HMGB1-induced inflammation. IMPORTANCE:Despite promising preclinical outcomes, clinical translation of high mobility group box 1 (HMGB1) or TLR4/MD-2 antagonists for inflammatory diseases has been limited by challenges of drug synthesis, dosing, delivery, and off-target effects. Recombinant Box A (rBox A) is a competitive inhibitor of HMGB1 that binds to TLR4 and disrupts HMGB1-mediated TLR4/MD-2 signaling. rBox A exhibits broad anti-inflammatory activity across multiple diseases (e.g., endotoxemia, sepsis, neuroimmune disorders, ischemia/reperfusion); however, its therapeutic utility is constrained by the need for high, repeated dosing. We have engineered a non-replicating adenoviral (AdV) vector (AdV.C3-Tat/HIV-Box A) that produces recombinant (r)Box A when "sensed" by an inflammation-responsive complement C3 (C3) promoter. Therapeutic administration of AdV.C3-Tat/HIV-Box A resulted in significant protection and reduced inflammation in multiple HMGB1-mediated disease models, advancing a first-in-class, broadly applicable, host-directed gene therapy that selectively disrupts HMGB1-TLR4 signaling and has potential as both a broad-spectrum therapeutic for HMGB1-driven inflammatory diseases and a rapid-response countermeasure against emerging respiratory pathogens.

Traumatic brain injury (TBI) induces long-term, secondary injury processes that contribute to chronic neurodegeneration and associated neurological deficits. Previously, we demonstrated that controlled cortical impact in mice, a well-established experimental model of TBI, causes acute neuroinflammatory changes, including upregulation of interferon-β (IFN-β) and other type I interferon (IFN-I)-related genes in the injured cortex and hippocampus. Early inhibition of IFN-β signaling, either through intracerebroventricular administration of an anti-type I IFN receptor antibody or use of global IFN-β knockout mice (IFN-β-/-), attenuates post-traumatic neuroinflammation and neurodegeneration and improves neurological outcomes for up to 28 days postinjury (dpi), with the knockout model showing more robust and sustained protective effects. However, the consequences of sustained suppression of these pathways after TBI have not been studied. Here, we examine the long-term effects of IFN-β deficiency on microglial activation, neuropathology, and neurological function during the chronic phase post-TBI (60-90 dpi). Transcriptomic analysis of isolated microglia from wild-type mice after TBI revealed persistent upregulation of IFN-I and other key neuroinflammatory genes, including classical pro-inflammatory and disease-associated microglia (DAM) at both 60 and 90 dpi. The IFN-I pathway was significantly attenuated in IFN-β-/- mice at these later timepoints. However, IFN-β deficiency did not significantly alter the trauma-induced upregulation of DAM markers, indicating selectivity of chronic IFN-β modulation on injury-induced microglia-reactive phenotypes. Moreover, although IFN-β deficiency significantly attenuated pro-inflammatory phenotypes at 60 dpi, it enhanced the injury-mediated downregulation of homeostatic microglial genes at 90 dpi. In addition, no significant reduction in lesion volume or fine motor deficits was observed in IFN-β-/- mice at chronic timepoints, although chronic post-traumatic cognitive impairment was attenuated. These findings suggest that global IFN-β deficiency has complex, time-dependent effects on chronic outcomes following TBI; although it improves cognitive function, it further suppresses homeostatic microglia that may partially limit long-term therapeutic benefits.

Influenza is a highly contagious virus with most individuals showing recovery within a week after symptom onset. However, children, the elderly, and those with chronic health conditions are at high risk of developing serious complications. Extensive immune cell infiltration of the lung and massive production of pro-inflammatory cytokines can result in lung tissue damage and disruption, resulting in hypoxia and death. During the 2024-2025 influenza season in the USA, influenza caused an estimated 27,000-130,000 deaths. Our previous studies have shown that agents known to drive polarization of macrophages into the M2a phenotype mitigated inflammatory responses to influenza H1N1 A/PR/8/34 (PR8). Since IRS2 dampens the IL-4-induced differentiation to the M2a subtype, we sought to determine the impact of IRS2 on PR8 infection. Contrary to expectations, IRS2 -/- mice exhibited enhanced susceptibility to PR8 when compared to IRS2 +/+ mice, which was associated with a significant drop in blood oxygen saturation. Additionally, PR8 infection induced significantly greater inflammation in the lungs of IRS2 -/- mice than IRS2 +/+ mice. Conversely, viral replication was not significantly different. Significantly increased levels of the inflammatory mediator HMGB1 and airway epithelial cell denuding were observed in the lungs of IRS2 -/- mice, with a concomitant decrease in M2a gene expression. Mice with myeloid-specific knockout of IRS2 showed no enhanced sensitivity to PR8, supporting the hypothesis that the major impact of IRS2-deficiency on host response to PR8 infection is not myeloid cell-intrinsic. Overall, these results suggest that in the absence of IRS2, airway epithelial cells are especially sensitive to influenza-induced damage through dysregulated inflammation, resulting in increased susceptibility during infection.

Background Acute Lung Injuries (ALI) are a severe consequence of influenza-induced cytokine storm that can cause respiratory failure and death. It has been demonstrated that Toll-like Receptor 4 (TLR4) is involved in cytokine storm and that TLR4 −/− mice are protected against ALI. Therefore, TLR4 is a prime target for protection against ALI. FP12 is a known TLR4 antagonist that reduces TLR4-dependent immune activation and it is a promising lead compound for the treatment of innate immunity related pathologies. Objectives We present here the preclinical development of FP12 as an anti-inflammatory lead compound acting on influenza-induced ALI. Methods In vitro: We pre-treated THP-1 cells with FP12 (10 μM) for 0.5 h, then exposed to LPS (100 ng/ml) for 0 to 16 h. In some experiments, cells were simultaneously incubated with FP12 and LPS, or FP12 was added 30 min after LPS. Cytokine levels were measured by Western blot and ELISA assays. In vivo: WT C57BL/6J mice were infected with mouse-adapted influenza virus (PR8). Two days after infection, mice received either vehicle, FP7 (200 µg/mouse), or FP12 (200 µg/mouse) once daily (Day 2 to Day 6). Mice were monitored daily for survival for 14 days. Data were collected through histological staining, qRT-PCR, and ELISA assay. Results FP12 treatment inhibited both LPS- and HMGB1-induced TLR4 intracellular pathways (MyD88 and TRIF) leading to significantly reduced levels of a variety of proinflammatory cytokines including Type I interferon (IFN-β), highlighting its effectiveness in controlling proinflammatory protein production and reducing inflammation. FP12 protected mice therapeutically from influenza virus-induced lethality and reduced both cytokine gene expression and High Mobility Group Box 1 (HMGB1) levels in the lungs as well as ALI. Conclusion FP12 can antagonize TLR4 activation in vitro and protects mice from severe influenza infection, most likely by reducing the TLR4-dependent cytokine storm mediated by danger-associated molecular patterns (DAMPs).

We previously identified a small molecule, UM101, predicted to bind to the substrate-binding groove of p38a mitogen-activated protein kinase (MAPK) near the binding site of its proinflammatory substrate, mitogen-activated protein kinase-activated protein kinase (MK)2. UM101 exhibited anti-inflammatory, endothelial-stabilizing, and lung-protective effects. To overcome its limited aqueous solubility and p38a binding affinity, we designed an analog of UM101, GEn-1124, with improved aqueous solubility, stability, and p38a-binding affinity. Compared with UM101, GEn-1124 has 18-fold greater p38a-binding affinity as measured by surface plasmon resonance, 11-fold greater aqueous solubility, enhanced barrier-stabilizing activity in thrombin-stimulated human pulmonary artery endothelial cells in vitro, and greater lung protection in vivo. GEn-1124 improved survival from 10%-40% in murine acute lung injury induced by combined exposure to intratracheal bacterial endotoxin lipopolysaccharide instillation and febrile-range hyperthermia and from 0% to 50% in a mouse influenza pneumonia model. Gene expression analysis by RNASeq in tumor necrosis factor a-treated human pulmonary artery endothelial cells showed that the gene-modifying effects of GEn1124 were much more restricted to tumor necrosis factor a-inducible genes than those of the catalytic site p38 inhibitor, SB203580. Gene expression pathway analysis, confocal immunofluorescence analysis of p38a and MK2 subcellular trafficking, and surface plasmon resonance analysis of phosphorylated p38a:MK2 binding affinity supports a novel mechanism of action. GEn-1124 destabilizes the activated p38a:MK2 complex and dissociates nuclear export of MK2 and p38a, thereby promoting intranuclear retention and enhanced intranuclear signaling by phosphorylated p38a and accelerated inactivation of p38-free cytosolic MK2 by unopposed phosphatases.

An oral Controlled Human Infection Model (CHIM) with wild-type S. Typhi was re-established allowing us to explore the development of immunity. In this model, ~55% of volunteers who received the challenge reached typhoid diagnosis criteria (TD), while ~45% did not (NoTD). Intestinal macrophages are one of the first lines of defense against enteric pathogens. Most organs have self-renewing macrophages derived from tissue-resident progenitor cells seeded during the embryonic stage; however, the gut lacks these progenitors, and all intestinal macrophages are derived from circulating monocytes. After infecting gut-associated lymphoid tissues underlying microfold (M) cells, S. Typhi causes a primary bacteremia seeding organs of the reticuloendothelial system. Following days of incubation, a second bacteremia and clinical disease ensue. S. Typhi likely interacts with circulating monocytes or their progenitors in the bone marrow. We assessed changes in circulating monocytes after CHIM. The timepoints studied included 0 hours (pre-challenge) and days 1, 2, 4, 7, 9, 14, 21 and 28 after challenge. TD participants provided extra samples at the time of typhoid diagnosis, and 48-96 hours later (referred as ToD). We report changes in Classical Monocytes -CM-, Intermediate Monocytes -IM- and Non-classical Monocytes -NCM-. Changes in monocyte activation markers were identified only in TD participants and during ToD. CM and IM upregulated molecules related to interaction with bacterial antigens (TLR4, TLR5, CD36 and CD206). Of importance, CM and IM showed enhanced binding of S. Typhi. Upregulation of inflammatory molecules like TNF-α were detected, but mechanisms involved in limiting inflammation were also activated (CD163 and CD354 downregulation). CM upregulated molecules to interact/modulate cells of the adaptive immunity, including T cells (HLA-DR, CD274 and CD86) and B cells (CD257). Both CM and IM showed potential to migrate to the gut as integrin α4β7 was upregulated. Unsupervised analysis revealed 7 dynamic cell clusters. Five of these belonged to CM showing that this is the main population activated during ToD. Overall, we provide new insights into the changes that diverse circulating monocyte subsets undergo after typhoid diagnosis, which might be important to control this disease since these cells will ultimately become intestinal macrophages once they reach the gut.

We previously identified a small molecule, UM101, predicted to bind to the substrate-binding groove of p38α Mitogen-activated Protein Kinase (MAPK) near the binding site of its proinflammatory substrate, MAPK-activated protein kinase (MK2). UM101 exhibited anti-inflammatory, endothelial-stabilizing, and lung-protective effects. To overcome its limited aqueous solubility and p38α binding affinity, we designed an analog of UM101, GEn-1124, with improved aqueous solubility, stability, and p38α binding affinity. Compared with UM101, GEn-1124 has 18-fold greater p38α-binding affinity as measured by Surface Plasmon Resonance (SPR), 11-fold greater aqueous solubility, enhanced barrier-stabilizing activity in thrombin-stimulated human pulmonary artery endothelial cells (hPAEC) in vitro, and greater lung protection in vivo. GEn-1124 improved survival from 10% to 40% in murine acute lung injury (ALI) induced by combined exposure to intratracheal bacterial endotoxin lipopolysaccharide (LPS) instillation and febrile-range hyperthermia (FRH) and from 0% to 50% in a mouse influenza pneumonia model. Gene expression analysis by RNASeq in TNFα-treated hPAEC showed that the gene-modifying effects of GEn-1124 were much more restricted to TNFα-inducible genes than the catalytic site p38 inhibitor, SB203580. Gene expression pathway analysis, confocal immunofluorescence analysis of p38α and MK2 subcellular trafficking, and SPR analysis of phosphorylated p38α:MK2 binding affinity supports a novel mechanism of action. GEn-1124 destabilizes the activated p38α:MK2 complex, dissociates nuclear export of MK2 and p38α, thereby promoting intranuclear retention and enhanced intranuclear signaling by phosphorylated p38α retention, and accelerated inactivation of p38-free cytosolic MK2 by unopposed phosphatases.

ABSTRACT Influenza, as well as other respiratory viruses, can trigger local and systemic inflammation resulting in an overall “cytokine storm” that produces serious outcomes such as acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). We hypothesized that gene therapy platforms could be useful in these cases if the production of an anti-inflammatory protein reflects the intensity and duration of the inflammatory condition. The recombinant protein would be produced and released only in the presence of the inciting stimulus, avoiding immunosuppression or other unwanted side effects that may occur when treating infectious diseases with anti-inflammatory drugs. To test this hypothesis, we developed AdV.C3-Tat/HIV-Box A, an inflammation-inducible cassette that remains innocuous in the absence of inflammation but releases HMGB1 Box A, an antagonist of high mobility group box 1 (HMGB1), in response to inflammatory stimuli such as lipopolysaccharide (LPS) or influenza virus infection. We report here that this novel inflammation-inducible HMGB1 Box A construct in a non-replicative adenovirus (AdV) vector mitigates lung and systemic inflammation therapeutically in response to influenza infection. We anticipate that this strategy will apply to the treatment of multiple diseases in which HMGB1-mediated signaling is a central driver of inflammation. IMPORTANCE Many inflammatory diseases are mediated by the action of a host-derived protein, HMGB1, on Toll-like receptor 4 (TLR4) to elicit an inflammatory response. We have engineered a non-replicative AdV vector that produces HMGB1 Box A, an antagonist of HMGB1-induced inflammation, under the control of an endogenous complement component C3 (C3) promoter sequence, that is inducible by LPS and influenza in vitro and ex vivo in macrophages (Mϕ) and protects mice and cotton rats therapeutically against infection with mouse-adapted and human non-adapted influenza strains, respectively, in vivo . We anticipate that this novel strategy will apply to the treatment of multiple infectious and non-infectious diseases in which HMGB1-mediated TLR4 signaling is a central driver of inflammation.

Gastrin-releasing peptide (GRP), an evolutionarily conserved neuropeptide, significantly contributes to influenza-induced lethality and inflammation in rodent models. Because GRP is produced by pulmonary neuroendocrine cells (PNECs) in response to γ-aminobutyric acid (GABA), we hypothesized that influenza infection promotes GABA release from PNECs that activate GABAB receptors on PNECs to secrete GRP. Oxidative stress was increased in the lungs of influenza A/PR/8/34 (PR8)-infected mice, as well as serum glutamate decarboxylase 1, the enzyme that converts L-glutamic acid into GABA. The therapeutic administration of saclofen, a GABAB receptor antagonist, protected PR8-infected mice, reduced lung proinflammatory gene expression of C-C chemokine receptor type 2 (Ccr2), cluster of differentiation 68 (Cd68), and Toll like receptor 4 (Tlr4) and decreased the levels of GRP and high-mobility group box 1 (HMGB1) in sera. Conversely, baclofen, a GABAB receptor agonist, significantly increased the lethality and inflammatory responses. The GRP antagonist, NSC77427, as well as the GABAB antagonist, saclofen, blunted the PR8-induced monocyte infiltration into the lung. Together, these data provide the first report of neuroregulatory control of influenza-induced disease.

ABSTRACT Toll-like receptor 4 (TLR4) is an innate immune receptor responsive to lipopolysaccharide (LPS). Single nucleotide polymorphisms (SNPs) in human TLR4 that encode an A896G transition at SNP rs4986790 (D299G) and a C1196T transition at SNP rs4986791 (T399I) render individuals hyporesponsive to LPS. In humans, these SNPs are also associated with increased susceptibility to inflammatory bowel diseases (IBDs). Using knock-in mice engineered to express the murine homologs of these human TLR4 mutations (“TLR4-SNP” mice), we have shown that TLR4-SNP mice develop significantly more severe colitis induced by dextran sodium sulfate (DSS) than wild-type (WT) mice, similar to IBD in humans expressing these SNPs. Previous studies have provided indirect evidence for “tissue repair” M2 macrophages (Mφ) in the resolution of colitis. Signaling through the IL-4/IL-13 receptor, IL-4Rα, and the transcription factor, peroxisome proliferator-activated receptor (PPARγ), have been shown to be required for induction of M2a Mφ, and our data provide direct evidence for the involvement of both in the repair of DSS-induced colonic damage. In response to DSS, colons of TLR4-SNP mice produced reduced levels of M2a Mφ marker mRNA and protein, including PPARγ, and therapeutic administration of the PPARγ agonist ligand, rosiglitazone, resolved colitis in TLR4-SNP mice, and increased expression of the M2a protein, Ym1. Together, these data indicate that the failure of TLR4-SNP mice to resolve DSS-induced colitis may be secondary to their failure to induce “tissue repair” M2a Mφ. Importance Inflammatory bowel disease (IBD), including Crohn’s disease and ulcerative colitis, impacts millions of individuals worldwide and severely impairs the quality of life for patients. Dysregulation of innate immune signaling pathways reduces barrier function and exacerbates disease progression. Macrophage (Mφ) signaling pathways are potential targets for IBD therapies. While multiple treatments are available for IBD, (i) not all patients respond, (ii) responses may diminish over time, and (iii) treatments often have undesirable side effects. Genetic studies have shown that the inheritance of two co-segregating SNPs expressed in the innate immune receptor, TLR4, is associated with human IBD. Mice expressing homologous SNPs (“TLR4-SNP” mice) exhibited more severe colitis than WT mice in a DSS-induced colonic inflammation/repair model. We identified a critical role for M2a “tissue repair” Mφ in the resolution of colitis. Our findings provide insight into potential development of novel therapies targeting Mφ signaling pathways that aim to alleviate the debilitating symptoms experienced by individuals with IBD.

Dedication: This article is dedicated to Howard Young, an exceptional scientist who has provided outstanding mentorship to many postbaccalaureates, graduate students, and postdoctoral fellows during his career. Howard has been a colleague to many and was never tired of learning new things. He has brought "thinking out of the box" to the level of an art form and has always provided thoughtful and constructive suggestions to those who have sought his counsel. I am personally greatly indebted to Howard for his guidance in molecular biology over the past 30 years, and hope that we will continue to share a passion for learning and mentoring others for years to come. Thank you, Howard! -Stephanie N. Vogel The SARS-CoV-2 pandemic has led to an unprecedented explosion in studies that have sought to identify key mechanisms that underlie the ravaging aspects of this disease on individuals. SARS-CoV-2 virus gains access to cells by (1) binding of the viral spike (S) protein to cell-associated angiotensin-converting enzyme 2 (ACE2), a key receptor in the renin-angiotensin system (RAS), followed by (2) cleavage of S protein by a cellular serine protease ("S protein priming") to facilitate viral entry. Dysregulation of the RAS system has been implicated in the spectrum of clinical symptoms associated with SARS-CoV-2, including hypercytokinemia, elevated markers of endothelial injury and thrombosis, and both localized and systemic inflammation. However, the underlying mechanisms have yet to be fully delineated.

SESSION TITLE: Biological Markers in Patients with COVID-19 Abstract PostersSESSION TYPE: Original Investigation PostersPRESENTED ON: 10/18/2022 01:30 pm - 02:30 pmPURPOSE: Pandemic SARS-CoV-2 infection (COVID-19), like other respiratory viruses, caused a massive incidence of acute respiratory distress syndrome (ARDS). Prior literature showed that influenza infection results in a significant increase in the level of circulating High Mobility Group Box 1 (HMGB1) in infected mice, cotton rats, and in humans; and a small molecule inhibitor of HMGB1 blocked lung pathology and lethality in influenza-infected mice and cotton rats. Moreover, HMGB1 has also been shown to be elevated in the serum of patients with ARDS and is an indicator of increased mortality. Gastrin Releasing Peptide (GRP) has been implicated in bronchopulmonary dysplasia, chronic obstructive pulmonary disease, chronic bronchitis, emphysema, and fibrosis. In addition to HMGB1, GRP represents a novel DAMP that, when targeted therapeutically in influenza-infected mice, is highly protective. The interaction between GRP and HMGB1 is currently under study. We examined if these DAMPS are associated with poor clinical outcomes in patients with COVID-19 ARDS.METHODS: Deidentified patient plasma and serum samples were obtained from discarded, clinical blood samples from 100 patients with COVID-19 admitted to UMMC's intensive care unit (ICU). Demographic and clinical data were collected from the patient’s electronic medical record. HMGB1 and GRP ELISA kits were used to analyze their concentrations in patients’ sera at Day 1 of admission to ICU. Cox proportional hazards models were used to examine the relationship between risk factors and severity of hypoxemia (P/F ratio), need for mechanical ventilation, and need for mechanical circulatory support (VV-ECMO).RESULTS: The average age of study participants was 59.1 years of which 59.2% were men and 57.1% were African American. The mean BMI was 34.3 kg/m2. The prevalence of hypertension, hyperlipidemia, diabetes, pulmonary and cardiovascular disease was 57.1%, 26.5%, 42.9%, 32.7%, and 42.9%, respectively. We found that GRP concentration was associated with worsening hypoxemia (mild 31.9, mod. 42.7, severe 79.0 ng/ml; p=0.014), requirement for mechanical ventilation (No 40.1, Yes 61.5 ng/ml; p=0.063), and need for VV-ECMO (No 48.6, Yes 93.1 ng/ml; p=0.026). HMGB1 concentration was associated with worsening hypoxemia (mild 24.4, mod. 55.1, severe 40.9 ng/ml; p=0.021) but did not correlate with other outcomes.CONCLUSIONS: GRP and HMGB1 have been previously implicated in the pathogenesis of viral infections, such as influenza, and ARDS in animal models and human. Our results suggest that these DAMPs maybe associated with severity of disease in critically ill patients with COVID-19 infection.CLINICAL IMPLICATIONS: Future studies should elucidate the specific cellular and biochemical pathways implicated in pathogenesis of ARDS, identify whether HMGB1 and GRP could be potential biomarkers for severe illness outcomes, and test novel anti-HMGB1 and GRP therapeutics in ARDS.DISCLOSURES: No relevant relationships by Fahid Alghanimno disclosure on file for Jeffrey Hasday;Consultant relationship with Guidepoint Please note: $1-$1000 by Carl Shanholtz, value=Consulting feestock holder relationship with Teva Pharmaceuticals Please note: $1001 - $5000 by Carl Shanholtz, value=stockiinvestor relationship with illumina Please note: $1001 - $5000 by Carl Shanholtz, value=optionsNo relevant relationships by Kari Ann ShireyNo relevant relationships by Mohan TulapurkarNo relevant relationships by Stefanie Vogel SESSION TITLE: Biological Markers in Patients with COVID-19 Abstract Posters SESSION TYPE: Original Investigation Posters PRESENTED ON: 10/18/2022 01:30 pm - 02:30 pm PURPOSE: Pandemic SARS-CoV-2 infection (COVID-19), like other respiratory viruses, caused a massive incidence of acute respiratory distress syndrome (ARDS). Prior literature showed that influenza infection results in a significant increase in the level of circulating High Mobility Group Box 1 (HMGB1) in infected mice, cotton rats, and in humans; and a small molecule inhibitor of HMGB1 blocked lung pathology and lethality in influenza-infected mice and cotton rats. Moreover, HMGB1 has also been shown to be elevated in the serum of patients with ARDS and is an indicator of increased mortality. Gastrin Releasing Peptide (GRP) has been implicated in bronchopulmonary dysplasia, chronic obstructive pulmonary disease, chronic bronchitis, emphysema, and fibrosis. In addition to HMGB1, GRP represents a novel DAMP that, when targeted therapeutically in influenza-infected mice, is highly protective. The interaction between GRP and HMGB1 is currently under study. We examined if these DAMPS are associated with poor clinical outcomes in patients with COVID-19 ARDS. METHODS: Deidentified patient plasma and serum samples were obtained from discarded, clinical blood samples from 100 patients with COVID-19 admitted to UMMC's intensive care unit (ICU). Demographic and clinical data were collected from the patient’s electronic medical record. HMGB1 and GRP ELISA kits were used to analyze their concentrations in patients’ sera at Day 1 of admission to ICU. Cox proportional hazards models were used to examine the relationship between risk factors and severity of hypoxemia (P/F ratio), need for mechanical ventilation, and need for mechanical circulatory support (VV-ECMO). RESULTS: The average age of study participants was 59.1 years of which 59.2% were men and 57.1% were African American. The mean BMI was 34.3 kg/m2. The prevalence of hypertension, hyperlipidemia, diabetes, pulmonary and cardiovascular disease was 57.1%, 26.5%, 42.9%, 32.7%, and 42.9%, respectively. We found that GRP concentration was associated with worsening hypoxemia (mild 31.9, mod. 42.7, severe 79.0 ng/ml; p=0.014), requirement for mechanical ventilation (No 40.1, Yes 61.5 ng/ml; p=0.063), and need for VV-ECMO (No 48.6, Yes 93.1 ng/ml; p=0.026). HMGB1 concentration was associated with worsening hypoxemia (mild 24.4, mod. 55.1, severe 40.9 ng/ml; p=0.021) but did not correlate with other outcomes. CONCLUSIONS: GRP and HMGB1 have been previously implicated in the pathogenesis of viral infections, such as influenza, and ARDS in animal models and human. Our results suggest that these DAMPs maybe associated with severity of disease in critically ill patients with COVID-19 infection. CLINICAL IMPLICATIONS: Future studies should elucidate the specific cellular and biochemical pathways implicated in pathogenesis of ARDS, identify whether HMGB1 and GRP could be potential biomarkers for severe illness outcomes, and test novel anti-HMGB1 and GRP therapeutics in ARDS. DISCLOSURES: No relevant relationships by Fahid Alghanim no disclosure on file for Jeffrey Hasday; Consultant relationship with Guidepoint Please note: $1-$1000 by Carl Shanholtz, value=Consulting fee stock holder relationship with Teva Pharmaceuticals Please note: $1001 - $5000 by Carl Shanholtz, value=stock iinvestor relationship with illumina Please note: $1001 - $5000 by Carl Shanholtz, value=options No relevant relationships by Kari Ann Shirey No relevant relationships by Mohan Tulapurkar No relevant relationships by Stefanie Vogel

Many respiratory viruses cause lung damage that may evolve into acute lung injury (ALI), a cytokine storm, acute respiratory distress syndrome, and ultimately, death. Peroxisome proliferator activated receptor gamma (PPARγ), a member of the nuclear hormone receptor (NHR) family of transcription factors, regulates transcription by forming heterodimers with another NHR family member, Retinoid X Receptor (RXR). Each component of the heterodimer binds specific ligands that modify transcriptional capacity of the entire heterodimer by recruiting different co-activators/co-repressors. However, the role of PPARγ/RXR ligands in the context of influenza infection is not well understood. PPARγ is associated with macrophage differentiation to an anti-inflammatory M2 state. We show that mice lacking the IL-4Rα receptor, required for M2a macrophage differentiation, are more susceptible to mouse-adapted influenza (A/PR/8/34; "PR8")-induced lethality. Mice lacking Ptgs2, that encodes COX-2, a key proinflammatory M1 macrophage mediator, are more resistant. Blocking the receptor for COX-2-induced Prostaglandin E2 (PGE2) was also protective. Treatment with pioglitazone (PGZ), a PPARγ ligand, increased survival from PR8 infection, decreased M1 macrophage gene expression, and increased PPARγ mRNA in lungs. Conversely, conditional knockout mice expressing PPARγ-deficient macrophages were significantly more sensitive to PR8-induced lethality. These findings were extended in cotton rats: PGZ blunted lung inflammation and M1 cytokine gene expression after challenge with non-adapted human influenza. To study mechanisms by which PPARγ/RXR transcription factors induce canonical M2a genes, WT mouse macrophages were treated with IL-4 in the absence or presence of rosiglitazone (RGZ; PPARγ ligand), LG100754 (LG; RXR ligand), or both. IL-4 dose-dependently induced M2a genes Arg1, Mrc1, Chil3, and Retnla. Treatment of macrophages with IL-4 and RGZ and/or LG differentially affected induction of Arg1 and Mrc1 vs. Chil3 and Retnla gene expression. In PPARγ-deficient macrophages, IL-4 alone failed to induce Arg1 and Mrc1 gene expression; however, concurrent treatment with LG or RGZ + LG enhanced IL-4-induced Arg1 and Mrc1 expression, but to a lower level than in WT macrophages, findings confirmed in the murine alveolar macrophage cell line, MH-S. These findings support a model in which PPARγ/RXR heterodimers control IL-4-induced M2a differentiation, and suggest that PPARγ/RXR agonists should be considered as important tools for clinical intervention against influenza-induced ALI.

Asthma is a common and ubiquitous chronic respiratory disease that is associated with airway inflammation and hyperreactivity resulting in airway obstruction. It is now accepted that asthma is controlled by a combination of host genetics and environment in a rather complex fashion; however, the link between sensing of the environment and development and exacerbation of allergic lung inflammation is unclear. Human populations expressing cosegregating D299G and T399I polymorphisms in the TLR4 gene are associated with a decreased risk for asthma in adults along with hyporesponsiveness to inhaled LPS, the TLR4 ligand. However, these data do not account for other human genetic or environmental factors. Using a novel mouse strain that expresses homologous human TLR4 polymorphisms (TLR4-single nucleotide polymorphism [SNP]), we directly tested the effect of these TLR4 polymorphisms on in vivo responses to allergens using two models of induction. We report that intact TLR4 is required for allergic inflammation when using the OVA and LPS model of induction, as cellular and pathological benchmarks were diminished in both TLR4-SNP and TLR4-deficent mice. However, in the more clinically relevant model using house dust mite extract for induction, responses were enhanced in the TLR4-SNP mice, as evidenced by greater levels of eosinophilic inflammation, Th2 cytokine production, and house dust mite-specific IgG1 production compared with wild-type mice; however, mucus production and airway hyperreactivity were not affected. These results suggest that the TLR4 polymorphic variants (genes) interact differently with the allergic stimulation (environment).

Respiratory viral infections have been a long-standing global burden ranging from seasonal recurrences to the unexpected pandemics. The yearly hospitalizations from seasonal viruses such as influenza can fluctuate greatly depending on the circulating strain(s) and the congruency with the predicted strains used for the yearly vaccine formulation, which often are not predicted accurately. While antiviral agents are available against influenza, efficacy is limited due to a temporal disconnect between the time of infection and symptom development and viral resistance. Uncontrolled, influenza infections can lead to a severe inflammatory response initiated by pathogen-associated molecular patterns (PAMPs) or host-derived danger-associated molecular patterns (DAMPs) that ultimately signal through pattern recognition receptors (PRRs). Overall, these pathogen-host interactions result in a local cytokine storm leading to acute lung injury (ALI) or the more severe acute respiratory distress syndrome (ARDS) with concomitant systemic involvement and more severe, life threatening consequences. In addition to traditional antiviral treatments, blocking the host’s innate immune response may provide a more viable approach to combat these infectious pathogens. The SARS-CoV-2 pandemic illustrates a critical need for novel treatments to counteract the ALI and ARDS that has caused the deaths of millions worldwide. This review will examine how antagonizing TLR4 signaling has been effective experimentally in ameliorating ALI and lethal infection in challenge models triggered not only by influenza, but also by other ALI-inducing viruses.

DNA damage and type I interferons (IFNs) contribute to inflammatory responses after traumatic brain injury (TBI). TBI-induced activation of microglia and peripherally-derived inflammatory macrophages may lead to tissue damage and neurological deficits. Here, we investigated the role of IFN-β in secondary injury after TBI using a controlled cortical impact model in adult male IFN-β-deficient (IFN-β −/− ) mice and assessed post-traumatic neuroinflammatory responses, neuropathology, and long-term functional recovery. TBI increased expression of DNA sensors cyclic GMP-AMP synthase and stimulator of interferon genes in wild-type (WT) mice. IFN-β and other IFN-related and neuroinflammatory genes were also upregulated early and persistently after TBI. TBI increased expression of proinflammatory mediators in the cortex and hippocampus of WT mice, whereas levels were mitigated in IFN-β −/− mice. Moreover, long-term microglia activation, motor, and cognitive function impairments were decreased in IFN-β −/− TBI mice compared with their injured WT counterparts; improved neurological recovery was associated with reduced lesion volume and hippocampal neurodegeneration in IFN-β −/− mice. Continuous central administration of a neutralizing antibody to the IFN-α/β receptor (IFNAR) for 3 d, beginning 30 min post-injury, reversed early cognitive impairments in TBI mice and led to transient improvements in motor function. However, anti-IFNAR treatment did not improve long-term functional recovery or decrease TBI neuropathology at 28 d post-injury. In summary, TBI induces a robust neuroinflammatory response that is associated with increased expression of IFN-β and other IFN-related genes. Inhibition of IFN-β reduces post-traumatic neuroinflammation and neurodegeneration, resulting in improved neurological recovery. Thus, IFN-β may be a potential therapeutic target for TBI. SIGNIFICANCE STATEMENT TBI frequently causes long-term neurological and psychiatric changes in head injury patients. TBI-induced secondary injury processes including persistent neuroinflammation evolve over time and can contribute to chronic neurological impairments. The present study demonstrates that TBI is followed by robust activation of type I IFN pathways, which have been implicated in microglial-associated neuroinflammation and chronic neurodegeneration. We examined the effects of genetic or pharmacological inhibition of IFN-β, a key component of type I IFN mechanisms to address its role in TBI pathophysiology. Inhibition of IFN-β signaling resulted in reduced neuroinflammation, attenuated neurobehavioral deficits, and limited tissue loss long after TBI. These preclinical findings suggest that IFN-β may be a potential therapeutic target for TBI.

OBJECTIVES:Respiratory infections in the postacute phase of traumatic brain injury impede optimal recovery and contribute substantially to overall morbidity and mortality. This study investigated bidirectional innate immune responses between the injured brain and lung, using a controlled cortical impact model followed by secondary Streptococcus pneumoniae infection in mice. DESIGN:Experimental study. SETTING:Research laboratory. SUBJECTS:Adult male C57BL/6J mice. INTERVENTIONS:C57BL/6J mice were subjected to sham surgery or moderate-level controlled cortical impact and infected intranasally with S. pneumoniae (1,500 colony-forming units) or vehicle (phosphate-buffered saline) at 3 or 60 days post-injury. MAIN RESULTS:At 3 days post-injury, S. pneumoniae-infected traumatic brain injury mice (TBI + Sp) had a 25% mortality rate, in contrast to no mortality in S. pneumoniae-infected sham (Sham + Sp) animals. TBI + Sp mice infected 60 days post-injury had a 60% mortality compared with 5% mortality in Sham + Sp mice. In both studies, TBI + Sp mice had poorer motor function recovery compared with TBI + PBS mice. There was increased expression of pro-inflammatory markers in cortex of TBI + Sp compared with TBI + PBS mice after both early and late infection, indicating enhanced post-traumatic neuroinflammation. In addition, monocytes from lungs of TBI + Sp mice were immunosuppressed acutely after traumatic brain injury and could not produce interleukin-1β, tumor necrosis factor-α, or reactive oxygen species. In contrast, after delayed infection monocytes from TBI + Sp mice had higher levels of interleukin-1β, tumor necrosis factor-α, and reactive oxygen species when compared with Sham + Sp mice. Increased bacterial burden and pathology was also found in lungs of TBI + Sp mice. CONCLUSIONS:Traumatic brain injury causes monocyte functional impairments that may affect the host's susceptibility to respiratory infections. Chronically injured mice had greater mortality following S. pneumoniae infection, which suggests that respiratory infections even late after traumatic brain injury may pose a more serious threat than is currently appreciated.

TLRs are a family of PRRs that respond to PAMPs or host-derived Danger-Associated Molecular Patterns (DAMPs) to initiate host inflammation and immune responses. TLR dimerization and recruitment of adapter molecules is critical for intracellular signaling and is mediated through intracellular Toll-Interleukin 1 Receptor Resistance (TIR) domain interactions. Human TIR domains, including reported structures of TIR1, TIR2, TIR6, TIR10, TIRAP, and MyD88, contain Cysteine (Cys) interactions or modifications that are disproportionally at, or near, reported biological TIR interfaces, or in close proximity to functionally important regions. Therefore, we hypothesized that intracellular TIR Cys regulation may have greater functional importance than previously appreciated. Expression of mutant TLR4-C747S or treatment of TLR4 reporter cells with a small molecule, Cys-binding inhibitor of TLR4, TAK-242, abrogated LPS signaling in vitro. Using TAK-242, mice were protected from lethal influenza challenge as previously reported for extracellular TLR4 antagonists. Molecular modeling and sequence analysis of the region surrounding TLR4-Cys747 indicate conservation of a WxxxE motif identified among bacterial and NAD+-consuming TIRs, as well as within the TIRs domains of surface TLRs 1, 2, 4, 6, and 10. Together, these data support the hypothesis that critical Cys within the TIR domain are essential for TLR4 functionality.

Two cosegregating single-nucleotide polymorphisms (SNPs) in human TLR4, an A896G transition at SNP rs4986790 (D299G) and a C1196T transition at SNP rs4986791 (T399I), have been associated with LPS hyporesponsiveness and differential susceptibility to many infectious or inflammatory diseases. However, many studies failed to confirm these associations, and transfection experiments resulted in conflicting conclusions about the impact of these SNPs on TLR4 signaling. Using advanced protein modeling from crystallographic data of human and murine TLR4, we identified homologous substitutions of these SNPs in murine Tlr4, engineered a knock-in strain expressing the D298G and N397I TLR4 SNPs homozygously, and characterized in vivo and in vitro responses to TLR4 ligands and infections in which TLR4 is implicated. Our data provide new insights into cellular and molecular mechanisms by which these SNPs decrease the TLR4 signaling efficiency and offer an experimental approach to confirm or refute human data possibly confounded by variables unrelated to the direct effects of the SNPs on TLR4 functionality.

TIR domain containing proteins are important immune associated proteins shared among Toll-like and interleukin-1/18 receptor family members. In a recent discovery select bacterial, plant and human TIR proteins exhibit enzymatic activity in binding and processing nicotinamide adenine dinucleotide (NAD+). Based on their abilities to facilitate signaling across biology, we hypothesize that TIR proteins represent unique therapeutic targets for modulating infection, inflammation and disease. Our previous structural studies of bacterial-host TIR proteins B. melitensis (TcpB) and uropathogenic E. coli CFT073 (TcpC) with human host TIRAP and MyD88 characterized peptides that negatively regulate signaling and infection. From these studies we identified interactions that are at or near reported biological TIR protein interfaces. In particular, we identified a functionally important motif found conserved on the C helix of most bacterial, human host and NAD+ consuming TIR proteins. As proof of concept for select targeting of TIR proteins and this region in particular we have used the TLR4 antagonist, TAK-242, which selectively binds within this motif. Treatment with TAK-242 or TLR4-C747S blocks LPS signaling. Additionally, TAK-242 protected mice from lethal influenza challenge similar to an extracellular TLR4 antagonist, Eritoran. Bioinformatic analysis of the region targeted by TAK242 show that it is located within the WxxxE structural motif identified to be important for protecting against microtubule destabilization and includes a catalytically essential glutamic acid (E) residue conserved among nearly all NAD+ consuming TIR proteins. These studies provide a framework for future studies targeting TIR protein function.