Continuous evaluation of changes in the serum proteome from early to late stages of sepsis caused by Klebsiella pneumoniae

Serum protein profiles of patients with bacterial sepsis from the day of diagnosis until recovery/mortality were compared from early to late stages in response to severe sepsis using two dimensional electrophoresis. The proteins exhibiting changes during the course of sepsis (20-28 day mortality) were selected and identified by matrix-assisted laser desorption ionization-time of flight-tandem mass spectrometry. Among the proteins identified, haptoglobin (Hp), transthyretin (TTR), orosomucoid 1/α1 acid glycoprotein (ORM1), α1 antitrypsin (A1AT), serum amyloid A (SAA) and S100A9 exhibited differential expression patterns between survivors (S; n=6) and non-survivors (NS; n=6), particularly during the early stages of sepsis. Expression factors (EFs), taken as the ratio between the NS and S during early stages, showed ratios of Hp, 0.39 (P≤0.012); TTR, 3.96 (P≤0.03); ORM1, 0.69 (P≤0.79); A1AT, 0.92 (P≤0.87) and SAA, 0.69 (P≤0.01). S100A9, an acute phase protein, exhibited an EF ratio of 1.68 (P≤0.004) during the end stages of sepsis. A delayed rise in levels was observed in Hp, A1AT, ORM1, S100A9 and SAA, whereas TTR levels increased during the early stages of sepsis in NS. Analysis of inflammatory responses in the early stages of sepsis revealed increased mRNA expression in leukocytes of interleukin (IL)-6 (EF, 2.50), IL-10 (EF, 1.70) and prepronociceptin (EF, 1.6), which is a precursor for nociceptin in NS compared with S, and higher Toll-like receptor-4 (EF, 0.30) levels in S compared with NS. Therefore, a weaker acute phase response in the early stages of sepsis in NS, combined with an inefficient inflammatory response, may contribute to sepsis mortality.