Dual inhibition of complement C5 and CD14 attenuates inflammation in a cord blood model.

BACKGROUND: Escherichia coli and Group B streptococci (GBS) are the main causes of neonatal early-onset sepsis (EOS). Despite antibiotic therapy, EOS is associated with high morbidity and mortality. Dual inhibition of complement C5 and the Toll-like receptor co-factor CD14 has in animal studies been a promising novel therapy for sepsis. METHODS: Whole blood was collected from the umbilical cord after caesarean section (n = 30). Blood was anti-coagulated with lepirudin. C5 inhibitor (eculizumab) and anti-CD14 was added 8 min prior to, or 15 and 30 min after adding E. coli or GBS. Total bacterial incubation time was 120 min (n = 16) and 240 min (n = 14). Cytokines and the terminal complement complex (TCC) were measured using multiplex technology and ELISA. RESULTS: Dual inhibition significantly attenuated TCC formation by 25-79% when adding inhibitors with up to 30 min delay in both E. coli- and GBS-induced inflammation. TNF, IL-6 and IL-8 plasma concentration were significantly reduced by 28-87% in E. coli-induced inflammation when adding inhibitors with up to 30 min delay. The dual inhibition did not significantly reduce TNF, IL-6 and IL-8 plasma concentration in GBS-induced inflammation. CONCLUSION: Dual inhibition of C5 and CD14 holds promise as a potential future treatment for severe neonatal EOS. IMPACT: Neonatal sepsis can cause severe host inflammation with high morbidity and mortality, but there are still no effective adjunctive immunologic interventions available. Adding CD14 and complement C5 inhibitors up to 30 min after incubation of E. coli or Group B streptococci in a human umbilical cord blood model significantly reduced complement activation and cytokine release. Dual inhibition of C5 and CD14 is a potential future therapy to modulate systemic inflammation in severe cases of neonatal sepsis.

Staphylococcus epidermidis biofilms induce lower complement activation in neonates as compared with adults.

BACKGROUND: Staphylococcus epidermidis (SE) is an important cause of late-onset sepsis in neonates. SE frequently produces a polysaccharide intercellular adhesin (PIA) biofilm, important in the pathogenesis of these infections. Little is known about how the neonatal innate immune system reacts to SE biofilm-associated infections. Our hypothesis was that SE biofilms induce a lower complement activation in neonates as compared with adults. METHODS: Cord blood from term infants (n = 15) and blood from adults (n = 6) were studied in an ex vivo whole-blood sepsis model. A PIA biofilm-producing strain (SE1457) and its isogenic mutant (M10), producing a non-PIA biofilm, were used. RESULTS: Both SE biofilms induced stronger complement activation in adult than in cord blood (P ≤ 0.033). We found lower levels of antibodies toward both PIA (P = 0.002) and the whole bacterium (P = 0.001) in cord vs. adult blood. By contrast, the interleukin-8 (IL-8) and IL-6 secretion were higher in cord than in adult blood (P ≤ 0.002). The PIA biofilm induced stronger complement activation than the non-PIA biofilm. CONCLUSION: We conclude that the neonatal complement system exhibits a maturational deficiency. This may reduce the ability of neonates to combat biofilm-associated SE infections.

Arginine catabolic mobile element is associated with low antibiotic resistance and low pathogenicity in Staphylococcus epidermidis from neonates.

The arginine catabolic mobile element (ACME) in Staphylococci encodes several putative virulence factors. ACME appears to have been transferred from Staphylococcus epidermidis into Staphylococcus aureus and is strongly associated with the epidemic and virulent S. aureus USA300. We sought to determine the distribution of ACME in 128 S. epidermidis blood culture isolates from neonates and to assess ACME's impact on antibiotic resistance, biofilm production, invasive capacity, and host inflammatory response. ACME was detected in 15/64 (23%) invasive blood culture isolates and 26/64 (40%) blood culture contaminants (p = 0.02). ACME-positive S. epidermidis isolates displayed less antibiotic resistance (p < 0.001) and were collected from more mature neonates (p = 0.001). Biofilm production was more prevalent among ACME-negative isolates (61/87) compared with ACME positive (18/41; p = 0.004). Among the 64 children considered having an invasive infection, ACME did not influence the maximum C-reactive protein level. In an in vitro whole-blood sepsis model, there were no differences in the inflammatory response between ACME-positive and ACME-negative isolates. We conclude that ACME in S. epidermidis from neonates was associated with less antibiotic resistance and also does not seem to be associated with increased pathogenicity.