Emergence of antibodies endowed with proteolytic activity against High-mobility group box 1 protein (HMGB1) in patients surviving septic shock

Effect of HMGB1 and HBD-3 levels in the diagnosis of sepsis- A comparative descriptive study

Sepsis is a life-threatening condition characterized by a dysregulated host response to infection. Early and accurate diagnosis of sepsis is crucial for timely intervention and improved patient outcomes. In recent years, there has been growing interest in identifying reliable biomarkers to aid in the diagnosis of sepsis. This study aims to evaluate the levels of two potential biomarkers, high-mobility group box 1 (HMGB1) and human β-defensin 3 (HBD-3), and compare their diagnostic efficacy in sepsis. We aimed to assess HMGB-1 and HBD-3 levels in sepsis and assess the combined diagnostic validity of HMGB-1 and HBD-3. In this case-control study, the plasma concentration of HMGB-1 and HBD-3 was measured using an enzyme-linked immunosorbent assay (ELISA). Two groups, totaling 144 people, were formed; 66 patients treated in the ICU for sepsis were included in the patient group. 78 Blood donors from the Salmaniya Medical Complex Blood Bank who had no prior infection or inflammatory disease made up the Control group. The statistical computations were performed using the STATA 8® statistical software tool (StataCorp LP, College Station, TX, USA). In patients' mean HMGB-1 levels were 2.1442 ng/ml, compared to 0.62141 ng/ml in the control group. The mean HBD-3 level was 1068.453 ng/ml in sepsis patients versus 589.935 ng/ml in controls. A significant difference between the two groups has been observed in both biomarkers (P < 0.05). The sensitivity of HMGB-1 was 75.8% and 41.3%, respectively. The sensitivity and specificity of HBD-3 were 63.6% and 93.5%, respectively. The levels of HMGB-1 and HBD-3 between healthy and septic subjects varied significantly. HMGB-1 and HBD-3 levels in the blood tested together might accurately identify sepsis. These findings contribute to the growing body of evidence supporting the utility of biomarkers in sepsis diagnosis, and may ultimately aid in the development of more effective diagnostic strategies for sepsis management.

HMGB1 is a critical molecule in the pathogenesis of Gram-negative sepsis

Gram-negative sepsis is a severe clinical syndrome associated with significant morbidity and mortality. Lipopolysaccharide (LPS), expressed on Gram-negative bacteria, is a potent pro-inflammatory toxin that induces inflammation and coagulation via two separate receptor systems. One is Toll-like receptor 4 (TLR4), expressed on cell surfaces and in endosomes, and the other is the cytosolic receptor caspase-11 (caspases-4 and -5 in humans). Extracellular LPS binds to high mobility group box 1 (HMGB1) protein, a cytokine-like molecule. The HMGB1-LPS complex is transported via receptor for advanced glycated end products (RAGE)-endocytosis to the endolysosomal system to reach the cytosolic LPS receptor caspase-11 to induce HMGB1 release, inflammation, and coagulation that may cause multi-organ failure. The insight that LPS needs HMGB1 assistance to generate severe inflammation has led to successful therapeutic results in preclinical Gram-negative sepsis studies targeting HMGB1. However, to date, no clinical studies have been performed based on this strategy. HMGB1 is also actively released by peripheral sensory nerves and this mechanism is fundamental for the initiation and propagation of inflammation during tissue injury. Homeostasis is achieved when other neurons actively restrict the inflammatory response via monitoring by the central nervous system and the vagus nerve through the cholinergic anti-inflammatory pathway. The neuronal control in Gram-negative sepsis needs further studies since a deeper understanding of the interplay between HMGB1 and acetylcholine may have beneficial therapeutic implications. Herein, we review the synergistic overlapping mechanisms of LPS and HMGB1 and discuss future treatment opportunities in Gram-negative sepsis.

Immunoglobulins with Non-Canonical Functions in Inflammatory and Autoimmune Disease States

Immunoglobulins are known to combine various effector mechanisms of the adaptive and the innate immune system. Classical immunoglobulin functions are associated with antigen recognition and the initiation of innate immune responses. However, in addition to classical functions, antibodies exhibit a variety of non-canonical functions related to the destruction of various pathogens due to catalytic activity and cofactor effects, the action of antibodies as agonists/antagonists of various receptors, the control of bacterial diversity of the intestine, etc. Canonical and non-canonical functions reflect the extreme human antibody repertoire and the variety of antibody types generated in the organism: antigen-specific, natural, polyreactive, broadly neutralizing, homophilic, bispecific and catalytic. The therapeutic effects of intravenous immunoglobulins (IVIg) are associated with both the canonical and non-canonical functions of antibodies. In this review, catalytic antibodies will be considered in more detail, since their formation is associated with inflammatory and autoimmune diseases. We will systematically summarize the diversity of catalytic antibodies in normal and pathological conditions. Translational perspectives of knowledge about natural antibodies for IVIg therapy will be also discussed.