Protein C in murine neonatal sepsis

Neonatal sepsis is frequently associated with activation of the coagulation system. Generally, protein C levels are markedly reduced in the majority of septic patients, being associated with an increased risk of death. There is an activated protein C concentrate licensed for the treatment of severe sepsis in adults. However, the risk of severe bleeding may limit its use in neonates. Since the likelihood to induce bleeding with the zymogen form of protein C may be reduced, we therefore assessed both human and recombinant murine protein C zymogen in a murine neonatal sepsis model. In this model neonatal mice were challenged with viable group B streptococci (GBS). The impact of this septic condition on endogenous protein C levels was evaluated and the effect of treatment with either recombinant murine protein C or human plasma-derived (non-activated) protein C (Ceprotin^®) investigated. During severe GBS sepsis murine endogenous protein C levels decreased over time in neonatal mice, resulting in a maximum decrease of 30% at 16 hours after GBS challenge and returned towards baseline at 30 hours. Concomitantly, there was an increase in endogenous protein C activation up to 59% at 6 hours after GBS challenge, returning to baseline levels at 16 hours. Blocking endogenous murine protein C with an anti-mouse monoclonal antibody increased the mortality rate significantly from 62% to 91%. Treatment of neonatal septic mice (n = 36) with 300 U/kg murine protein C subcutaneously 4 hours before GBS challenge decreases the mortality rate significantly in severe sepsis (LD90) to 64% (P = 0.002). Similarly, pretreatment with human plasma-derived protein C (200 U/kg) 4 hours before GBS challenge increased the survival rate significantly in severe septic mice. Human plasma derived protein C at the dose of 200 IU/kg was even effective given 18 hours after GBS challenge, leading to a decrease of the mortality rate in severe sepsis from 87.5% to 48%. Despite the species differences human protein C zymogen was activated to activated protein C and was detectable in the circulation of mice, showing a slow and low in vivo recovery, possibly due to the subcutaneous route of administration. This is the first preclinical study where a beneficial effect of a non-activated protein C could be shown in an animal model of severe neonatal sepsis.