Outer membrane protein A (OmpA), peptidoglycan-associated lipoprotein (PAL), and murein lipoprotein (MLP) are released in experimental Gram-negative sepsis.
We previously showed that Escherichia coli bacteria incubated in normal human serum release complexes that contain three conserved Gram-negative bacterial outer membrane proteins (OMPs) and LPS. We have identified the OMPs as outer membrane protein A (OmpA), peptidoglycan-associated lipoprotein (PAL), and murein lipoprotein (MLP). These OMPs are conserved among enteric Gram-negative bacteria and are bound by IgG in antisera raised to heat-killed rough bacteria such as E. coli J5 (J5 IgG). The present experiments were performed to further analyze the release of these OMPs in a rat wound infection model of sepsis. Plasma was collected from thermally injured rats with E. coli O18 sepsis and filtered. LPS was affinity-purified from plasma filtrates using monoclonal antibody specific for the O-polysaccharide side chain of E. coli O18 LPS. Plasma filtrates were also incubated with J5 IgG conjugated to magnetic beads. Affinity-purified samples were analyzed for the OMPs by immunoblotting. OmpA, PAL, and MLP were released into septic rat blood in complexes with LPS. PAL was consistently present in samples affinity-purified using J5 IgG. The results indicate that OmpA, PAL, and MLP are released and circulate in experimental Gram-negative sepsis and suggest that a proportion of released OMPs are tightly associated with LPS.
Hellman
J
J
Department of Anesthesia and Critical Care, Massachusetts General Hospital, Charlestown, MA, USA. jhellman@partners.org
Warren
H S
HS
D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000097:blood*; D004195:Disease Models, Animal; D004927:Escherichia coli Infections / Q000097:blood / Q000382:microbiology*; D029968:Escherichia coli Proteins; D015151:Immunoblotting; D008070:Lipopolysaccharides / Q000097:blood; D008074:Lipoproteins / Q000097:blood*; D008297:Male; D010457:Peptidoglycan / Q000097:blood*; D011509:Proteoglycans; D051381:Rats; D017207:Rats, Sprague-Dawley
D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; C031163:ExcC protein, E coli; D008070:Lipopolysaccharides; D008074:Lipoproteins; D010457:Peptidoglycan; D011509:Proteoglycans; C069988:PplA protein, Legionella pneumophila