Early elevation of plasma soluble CD14 subtype, a novel biomarker for sepsis, in a rabbit cecal ligation and puncture model

Abstract

Introduction To reduce the mortality rates of patients with sepsis, rapid diagnosis and therapeutic decision are required. We have therefore discovered the soluble CD14 subtype (sCD14-ST), which is specific for sepsis and is elevated at an early stage during the disease progression [1]. Additionally, we have been researching a novel fusion protein, MR1007, which consists of the modified light chain of interalpha inhibitor and the anti-CD14 antibody as an anti-sepsis agent. Methods We developed an ELISA using two rat monoclonal antibodies against N-terminal and C-terminal peptide sequences of rabbit sCD14-ST, respectively, to determine sCD14-ST concentrations in rabbit plasma. Survival rates and the time course of plasma levels of sCD14-ST, IL-6, and D-dimer were examined in a rabbit cecal ligation and puncture (CLP) model. Blood bacterial counts were also determined as colony-forming units. Results The plasma sCD14-ST levels in seven dead animals clearly increased at 2 hours or later together with blood bacterial counts, reached the peak at 3 hours, and then gradually decreased at 4–8 hours, whereas those in one surviving animal did not. The induction phase was about 24 minutes and the half-life ranged from 4 to 5 hours. Additionally, the plasma IL-6 and D-dimer levels in dead animals clearly increased at 3 hours or later, whereas those in one surviving animal did not. Intravenous administration of MR1007 with an antibiotic, latamoxef sodium, following the observation of increases in sCD14-ST levels and blood bacterial counts, improved the survival and the plasma D-dimer levels in a rabbit CLP model (n = 9, P < 0.05). Conclusion Plasma sCD14-ST levels were elevated earlier than IL-6 and D-dimer along with occurrence of blood bacteria in a rabbit CLP model. Therapy with an anti-sepsis agent such as MR1007 following the elevation of sCD14-ST improved the outcome in the CLP model. These results suggest that sCD14-ST is useful to determine the earlier initiation of anti-sepsis therapy.