Protective Effects of Human and Mouse Soluble Scavenger-Like CD6 Lymphocyte Receptor in a Lethal Model of Polymicrobial Sepsis

Abstract

Sepsis still constitutes an unmet clinical need, which could benefit from novel adjunctive strategies to conventional antibiotic therapy. The soluble form of the scavenger-like human CD6 lymphocyte receptor (shCD6) binds to key pathogenic components from Gram-positive and -negative bacteria and shows time-and dose-dependent efficacy in mouse models of monobacterial sepsis. The objective of the present work was to demonstrate the effectiveness of infusing mouse and human sCD6 by different systemic routes, either alone or as adjunctive therapy to gold standard antibiotics, in a lethal model of polymicrobial sepsis. To this end, C57BL/6 mice undergoing high-grade septic shock induced by cecal ligation and puncture (CLP; Ն90% lethality) were infused via the intraperitoneal (i.p.) or intravenous (i.v.) route with shCD6 at different doses and time points, either alone or in combination with imipenem/cilastatin (I/C) at a dose of 33 mg/kg of body weight every 8 h. Significantly reduced mortality and proinflammatory cytokine levels were observed by i.p. infusion of a single shCD6 dose (1.25 mg/kg) 1 h pre-or post-CLP. When using the i.v. route, mice survival was significantly extended by starting shCD6 infusion at later time points post-CLP (up to 6 h after CLP). Significant adjunctive effects on mouse survival were observed by i.p. or i.v. infusion of shCD6 in combination with i.p. I/C post-CLP. Similar results were obtained in mice expressing high sustained levels (5 to 10 g/ml) of mouse sCD6 in serum by means of transduction with hepatotropic adeno-associated virus (AAV). Taken together, the data support the conserved antibacterial effects of human and mouse sCD6 and their use as adjunctive therapy in experimental models of complex and severe polymicrobial sepsis.KEYWORDS soluble CD6, cecal ligation and puncture, polymicrobial peritonitis, scavenger receptors, sepsis, septic shock, adjunctive therapy S epsis, severe sepsis, and septic shock still present unmet clinical needs with a predicted increase in occurrence and a huge socioeconomic burden as a result of population aging, increases in invasive medical procedures, the emergence of multidrug-resistant (MDR) bacteria, and the increased prevalence of chronic diseases (1). Sepsis is considered a dysregulated systemic inflammatory response syndrome

Commentary: The Scavenger Receptor SSc5D Physically Interacts with Bacteria through the SRCR-Containing N-Terminal Domain

“…They were chosen based on previously reported information showing that Spα (4) and CD6 (6–8) but not CD5 (9) exhibit broad bacterial-binding properties. While the authors confirmed the work on Spα and CD5, they were unable to replicate that on CD6.…”

“…While the authors confirmed the work on Spα and CD5, they were unable to replicate that on CD6. Exclusively based on a single experimental evidence, the authors cast doubt on the well-documented bacterial-binding properties of CD6 (6–8). These properties were unveiled by using a recombinant soluble form of human CD6 (rshCD6) encompassing from D 25 to M 400 and, indistinctly, produced in different mammalian cell expression systems (NSO, HEK293-EBNA, and CHO cells).…”

“…Accordingly, it was later reported that rshCD6 infusion significantly reduces mouse mortality following septic shock induced by intraperitoneal monobacterial infection of Gram-positive ( S. aureus ) or Gram-negative ( A. baumannii ) origin (7). More recently, new evidence shows that not only rshCD6 but also adenovirally expressed mouse sCD6 have protective survival effects on polymicrobial septic shock induced by cecal ligation and puncture (8), the gold standard model for experimental sepsis.…”

Multifaceted effects of soluble human CD6 in experimental cancer models

“…Production and purification of endotoxin-free purified recombinant shCD6 and shCD5 proteins (in PBS with 10% glycerol, pH 7.4) from SURE CHO-M cell line clones was done following previously reported methods. 23 Human (HSA) and bovine (BSA) serum albumin were from Sigma-Aldrich.…”

“…Construction and production of recombinant adenoassociated virus (AAV) Construction and production of recombinant AAV8 virus expressing soluble mouse CD6 (AAV-smCD6) or luciferase (AAV-Luc) proteins under the control of a chimerical liver-specific (EalbAAT) promoter was carried out as previously reported. 23 elisA assays The plasma levels of shCD6 and smCD6 were quantified with the human soluble CD6 PicoKine ELISA Kit (Boster Bio) and the DuoSet mouse CD6 kit (R&D Systems), respectively, following manufacturer's instructions. bromodeoxyuridine incorporation and treg suppression assays Detection of in vivo proliferating cells with bromodeoxyuridine (BrdU) was performed as reported elsewhere.…”