Circulating lipoproteins are a crucial component of host defense against invasive Salmonella typhimurium infection.
BACKGROUND
Circulating lipoproteins improve the outcome of severe Gram-negative infections through neutralizing lipopolysaccharides (LPS), thus inhibiting the release of proinflammatory cytokines.


RESULTS
Low density lipoprotein receptor deficient (LDLR-/-) mice, with a 7-fold increase in LDL, are resistant against infection with Salmonella typhimurium (survival 100% vs 5%, p<0.001), and 100 to 1000-fold lower bacterial burden in the organs, compared with LDLR+/+ mice. Protection was not due to differences in cytokine production, phagocytosis, and killing of Salmonella organisms. The differences were caused by the excess of lipoproteins, as hyperlipoproteinemic ApoE-/- mice were also highly resistant to Salmonella infection. Lipoproteins protect against infection by interfering with the binding of Salmonella to host cells, and preventing organ invasion. This leads to an altered biodistribution of the microorganisms during the first hours of infection: after intravenous injection of Salmonella into LDLR+/+ mice, the bacteria invaded the liver and spleen within 30 minutes of infection. In contrast, in LDLR-/- mice, Salmonella remained constrained to the circulation from where they were efficiently cleared, with decreased organ invasion.


CONCLUSIONS
plasma lipoproteins are a potent host defense mechanism against invasive Salmonella infection, by blocking adhesion of Salmonella to the host cells and subsequent tissue invasion.
Netea
Mihai G
MG
Department of Medicine, Division of General Internal Medicine, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands.
Joosten
Leo A B
LA
Keuter
Monique
M
Wagener
Frank
F
Stalenhoef
Anton F H
AF
van der Meer
Jos W M
JW
Kullberg
Bart Jan
BJ
D000818:Animals; D001057:Apolipoproteins E / Q000235:genetics; D016207:Cytokines / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism; D007249:Inflammation; D008074:Lipoproteins / Q000097:blood* / Q000276:immunology; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D009000:Monocytes / Q000378:metabolism; D010586:Phagocytes; D011973:Receptors, LDL / Q000235:genetics; D012481:Salmonella Infections, Animal / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology; D012486:Salmonella typhimurium / Q000378:metabolism*
D001057:Apolipoproteins E; D016207:Cytokines; D008074:Lipoproteins; D011973:Receptors, LDL