Mechanism of C5a-induced immunologic derangement in sepsis

Active immunotherapy for C5a-mediated inflammation using adjuvant-free self-assembled peptide nanofibers

The terminal protein in the complement cascade C5a is a potent inflammatory molecule and chemoattractant that is involved in the pathology of multiple inflammatory diseases including sepsis and arthritis, making it a promising protein to target with immunotherapies. Active immunotherapies, in which patients are immunized against problematic self-molecules and generate therapeutic antibodies as a result, have received increasing interest as an alternative to traditional monoclonal antibody treatments. In previous work, we have designed supramolecular self-assembling peptide nanofibers as active immunotherapies with defined combinations of B- and T-cell epitopes. Herein, the self-assembling peptide Q11 platform was employed to generate a C5a-targeting active immunotherapy. Two of three predicted B-cell epitope peptides from C5a were found to be immunogenic when displayed within Q11 nanofibers, and the nanofibers were capable of reducing C5a serum concentrations following immunization. Contrastingly, C5a's precursor protein C5 maintained its original concentration, promising to minimize side effects heretofore associated with C5-targeted therapies. Immunization protected mice against an LPS-challenge model of sepsis, and it reduced clinical severity in a model of collagen-antibody induced arthritis. Together, this work indicates the potential for targeting terminal complement proteins with active immunotherapies by leveraging the immunogenicity of self-assembled peptide nanomaterials. STATEMENT OF SIGNIFICANCE: Chronic inflammatory diseases such as rheumatoid arthritis, psoriasis, and inflammatory bowel disease are currently treated primarily with monoclonal antibodies against key inflammatory mediators. While helpful for many patients, they have high non-response rates, are costly, and commonly fail as anti-drug antibodies are raised by the patient. The approach we describe here explores a fundamentally different treatment paradigm: raising therapeutic antibody responses with an active immunotherapy. We employ innovative supramolecular peptide nanomaterials to elicit neutralizing antibody responses against complement component C5a and demonstrate therapeutic efficacy in preclinical mouse models of sepsis and rheumatoid arthritis. The strategy reported may represent a potential alternative to monoclonal antibody therapies.

Inflammatory liver diseases and susceptibility to sepsis

Patients with inflammatory liver diseases, particularly alcohol-associated liver disease and metabolic dysfunction-associated fatty liver disease (MAFLD), have higher incidence of infections and mortality rate due to sepsis. The current focus in the development of drugs for MAFLD is the resolution of non-alcoholic steatohepatitis and prevention of progression to cirrhosis. In patients with cirrhosis or alcoholic hepatitis, sepsis is a major cause of death. As the metabolic center and a key immune tissue, liver is the guardian, modifier, and target of sepsis. Septic patients with liver dysfunction have the highest mortality rate compared with other organ dysfunctions. In addition to maintaining metabolic homeostasis, the liver produces and secretes hepatokines and acute phase proteins (APPs) essential in tissue protection, immunomodulation, and coagulation. Inflammatory liver diseases cause profound metabolic disorder and impairment of energy metabolism, liver regeneration, and production/secretion of APPs and hepatokines. Herein, the author reviews the roles of (1) disorders in the metabolism of glucose, fatty acids, ketone bodies, and amino acids as well as the clearance of ammonia and lactate in the pathogenesis of inflammatory liver diseases and sepsis; (2) cytokines/chemokines in inflammatory liver diseases and sepsis; (3) APPs and hepatokines in the protection against tissue injury and infections; and (4) major nuclear receptors/signaling pathways underlying the metabolic disorders and tissue injuries as well as the major drug targets for inflammatory liver diseases and sepsis. Approaches that focus on the liver dysfunction and regeneration will not only treat inflammatory liver diseases but also prevent the development of severe infections and sepsis.

CD63 and C3AR1: The Potential Molecular Targets in the Progression of Septic Shock

Background

The molecular mechanism of septic shock is unknown. We studied the pathogenesis of septic shock and provide a novel strategy for treating and improving the prognosis of septic shock.

Methods

Gluten-Sensitive Enteropathy (GSE) 131761, GSE119217, GSE26378 datasets were downloaded from the Gene Expression Omnibus (GEO) database. The three datasets included 204 septic shock samples and 48 normal samples. The R packages “affy” and “limma” were employed to identify the differently expressed genes (DEGs) between septic shock and normal samples. Weighted gene co-expression network analysis (WGCNA) was performed to search for modules that play an important role in septic shock. Functional annotation of DEGs and construction and analysis of hub genes were used to explore the pathomechanism of septic shock. The receiver operating characteristic (ROC) curves were obtained using MedCalc software. The drug molecules that could regulate hub genes associated with septic shock were searched for in the CMap database. An animal model of septic shock was constructed to analyze the role of these hub genes.

Results

The merged series contained 321 up-regulated and 255 down-regulated genes. WGCNA showed the brown module had the highest correlation with the status of septic shock. GO and KEGG enrichment analysis results of the brown module genes showed they were mainly enriched in “leukocyte differentiation”, “Ras-proximate-1 (Rap1) signaling pathway”, and “cytokine–cytokine receptor interaction”. Through construction and analysis of a protein–protein interaction (PPI) network, cluster of differentiation 63 (CD63) and complement component 3a receptor 1 (C3AR1) were identified as hub genes of septic shock. The area under curve (AUC) of C3AR1 for the septic shock is 0.772 (P<0.001), and the AUC of CD63 for the septic shock is 0.871 (P<0.001). Small molecule drugs were filtered by the number of instances (n>3) and P-values <0.05, including “monensin”, “verteporfin”, “ikarugamycin”, “tetrahydroalstonine”, “cefamandole”, “etoposide”. In the animal model, the relative expression levels of interleukin-6 (IL-6), Tumor Necrosis Factor-α (TNF-α), and lactic acid were significantly higher in the septic shock group compared with the control group. Results of Real Time Quantitative PCR (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA) analysis for CD63 and C3AR1 showed that their relative expression levels were significantly lower in the septic shock group compared with the control group (P<0.05).

Conclusion

CD63 and C3AR1 are significant hub genes of septic shock and may represent potential molecular targets for future studies of septic shock.

Sepsis target validation for repurposing and combining complement and immune checkpoint inhibition therapeutics

Introduction: Sepsis is a disease that occurs due to an adverse immune response to infection by bacteria, viruses and fungi and is the leading pathway to death by infection. The hallmarks for maladapted immune reactions in severe sepsis, which contribute to multiple organ failure and death, are bookended by the exacerbated activation of the complement system to protracted T-cell dysfunction states orchestrated by immune checkpoint control. Despite major advances in our understanding of the condition, there remains to be either a definitive test or an effective therapeutic intervention.Areas covered: The authors consider a combinational drug therapy approach using new biologics, and mathematical modeling for predicting patient responses, in targeting innate and adaptive immune mediators underlying sepsis. Special consideration is given for emerging complement and immune checkpoint inhibitors that may be repurposed for sepsis treatment.Expert opinion: In order to overcome the challenges inherent to finding new therapies for the complex dysregulated host response to infection that drives sepsis, it is necessary to move away from monotherapy and promote precision for personalized combinatory therapies. Notably, combinatory therapy should be guided by predictive systems models of the immune-metabolic characteristics of an individual's disease progression.

Complement levels in patients with bloodstream infection due to Staphylococcus aureus or Gram-negative bacteria

The complement system is a vital component of the innate immune system, though its role in bacteremia is poorly understood. We present complement levels in Staphylococcus aureus bacteremia (SAB) and Gram-negative bacteremia (GNB) and describe observed associations of complement levels with clinical outcomes. Complement and cytokine levels were measured in serum samples from 20 hospitalized patients with SAB, 20 hospitalized patients with GNB, 10 non-infected hospitalized patients, and 10 community controls. C5a levels were significantly higher in patients with SAB as compared to patients with GNB. Low C4 and C3 levels were associated with septic shock and 30-day mortality in patients with GNB, and elevated C3 was associated with a desirable outcome defined as absence of (1) septic shock, (2) acute renal failure, and (3) death within 30 days of bacteremia. Low levels of C9 were associated with septic shock in patients with GNB but not SAB. Elevated IL-10 was associated with increased 30-day mortality in patients with SAB. Complement profiles differ in patients with SAB and those with GNB. Measurement of IL-10 in patients with SAB and of C4, C3, and C9 in patients with GNB may help to identify those at higher risk for poor outcomes.

Posterior Reversible Encephalopathy Syndrome and Septic Encephalopathy: Neuroimaging, Inflammation and Neurodegeneration Findings

Posterior reversible encephalopathy syndrome (PRES) is known to be associated with septic encephalopathy. The pathophysiology of septic encephalopathy is thought to involve inflammatory immune response pathways. We are reporting a patient with septic encephalopathy and PRES with well documented inflammatory biomarkers and neuroradiological findings.

High levels of circulating GM-CSF+CD4+ T cells are predictive of poor outcomes in sepsis patients: a prospective cohort study

Granulocyte colony-stimulating factor (GM-CSF), produced by CD4⁺ T cells, has recently been implicated in the pathogenesis of inflammatory diseases, such as multiple sclerosis and juvenile arthritis. However, the role of GM-CSF-producing CD4⁺ T cells in sepsis remains unknown. This study reports peripheral changes in GM-CSF-producing CD4⁺ T cells in septic patients and the possible underlying mechanism by which GM-CSF influences the outcome of sepsis. Forty-three septic patients, 20 SIRS patients, and 20 healthy controls were enrolled in this study and followed for 28 days to assess mortality. We measured the peripheral frequency of GM-CSF⁺CD4⁺ T cells and recorded their associated relationship with disease progression. Our data demonstrated that peripheral GM-CSF-producing CD4⁺ T cells were significantly higher in septic patients than in both SIRS patients and healthy controls. These cells exhibit a memory phenotype and impaired IFN-γ-secreting capacity in sepsis patients. Using a receiver operating curve analysis with 8.01% as a cut-off point, the percentage of GM-CSF⁺CD4⁺ T cells could predict the outcome of septic patients^. Combined with the increase in GM-CSF-producing CD4⁺ T cells, inflammatory cytokines IL-1β and IL-6 were also upregulated. Using an in vitro neutrophil model, we found that GM-CSF inhibited C3aR expression, while inducing IL-8 production. Furthermore, this effect was transferrable in plasma from sepsis patients and was attenuated by inhibition of GM-CSF using an anti-GM-CSF antibody. These results indicate that GM-CSF-producing CD4⁺ T cells may serve as a marker of sepsis severity. Thus, targeting GM-CSF overproduction may benefit sepsis patients.

Association Between Inflammatory Markers and Cognitive Outcome in Patients with Acute Brain Dysfunction Due to Sepsis

Introduction

Sepsis-induced brain dysfunction (SIBD) has been neglected until recently due to the absence of specific clinical or biological markers. There is increasing evidence that sepsis may pose substantial risks for long term cognitive impairment.

Methods

To find out clinical and inflammatory factors associated with acute SIBD serum levels of cytokines, complement breakdown products and neurodegeneration markers were measured by ELISA in sera of 86 SIBD patients and 33 healthy controls. Association between these biological markers and cognitive test results was investigated.

Results

SIBD patients showed significantly increased IL-6, IL-8, IL-10 and C4 d levels and decreased TNF-α, IL-12, C5a and iC3b levels than healthy controls. No significant alteration was observed in neuronal loss and neurodegeneration marker [neuron specific enolase (NSE), amyloid β, tau] levels. Increased IL-1β, IL-6, IL-8, IL-10, TNF-α and decreased C4 d, C5a and iC3b levels were associated with septic shock, coma and mortality. Transient mild cognitive impairment was observed in 7 of 21 patients who underwent neuropsychological assessment. Cognitive dysfunction and neuronal loss were associated with increased duration of septic shock and delirium but not baseline serum levels of inflammation and neurodegeneration markers.

Conclusion

Increased cytokine levels, decreased complement activity and increased neuronal loss are indicators of poor prognosis and adverse events in SIBD. Cognitive dysfunction and neuronal destruction in SIBD do not seem to be associated with systemic inflammation factors and Alzheimer disease-type neurodegeneration but rather with increased duration of neuronal dysfunction and enhanced exposure of the brain to sepsis-inducing pathogens.