Lipopolysaccharide structure and complement system response to selected Escherichia coli strainsKociper, Matej (Avtor) Starčič Erjavec, Marjanca (Mentor) Ihan, Alojz (Komentor) Wuerzner, Reinhard (Komentor) Escherichia colilipopolysaccharidesO-corecomplement systemcomplement regulatory factor Hcomplement particle C7SDS-PAGEpolymerase chain reactionflow cytometryindirect immunofluorescenceEscherichia coli (E. coli) is a Gram-negative motile facultative anaerobic bacterium. It is part of the normal intestinal microbiota in humans and other warm-blooded animals. Usually, it has a mutualistic relationship with its host, but some E. coli strains have acquired specific virulence factors and can cause a variety of infections. E. coli strains involved in extraintestinal infections are known as extraintestinal pathogenic E. coli (ExPEC). Such E. coli strains have characteristic virulence factors involved in adhesion to epithelia, crossing of the body barriers, iron uptake and resistance to the immune system. In the study we investigated whether E. coli strains from the healthy human gut microbiota that have ExPEC virulence factors are able to trigger complement system response. Lipopolysaccharide (LPS) structure was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and silver staining. Selected E. coli strains had smooth LPS profile, except for the strains BJ33, MG1655 and DH5α that were rough. LPS profile of the studied E. coli strains did not necessarily correlate with the strength of the complement response. Smooth strains of bacteria were very resistant to complement lysis, even if they were detected by the complement (determined by binding particle C7), and rough strains were complement sensitive. The outer part of O-core in LPS was determined with specific polymerase chain reaction (O-core PCR). Most of the studied strains exhibited R1 type of the outer O-core region. Further, it was assessed, if E. coli strains differ in their ability to activate complement system (binding of complement particle C7), and binding of specific complement regulatory protein factor H to the surface. Specific IgG antibodies against factor H or particle C7 were bound to E. coli strains and the indirect immunofluorescence analysis was performed on the flow cytometer. E. coli strains were capable of triggering the complement activation in different intensity, some strains even to the extent of uropathogenic strains. Some of the E. coli strains could be able to avoid the immune system activation by binding regulatory factor H. To our knowledge, this is the first research revealing different complement factor H binding abilities of E. coli strains.[M. Kociper]20182018-09-13 07:47:45Magistrsko delo/naloga103065UDK: 579.23:577.27.083.3VisID: 155839COBISS_ID: 4946040sl