Pneumolysin-induced complement depletion during experimental pneumococcal bacteremia.
To quantify complement depletion by pneumolysin during Streptococcus pneumoniae bacteremia, cirrhotic and control rats were infected intravenously with one of three isogenic mutant strains of S. pneumoniae expressing different forms of pneumolysin. Outcome measures included clearance of the organisms from the bloodstream, alterations in 50% serum hemolytic complement (CH(50)) activity and complement C3 levels during infection, and serum opsonic capacity at 18 h postinfection. Cirrhotic rats had significantly lower CH(50) and C3 levels than control rats, both before and after infection. However, initial complement levels did not predict bacterial load after 18 h of infection. Changes in CH(50) and C3 levels over the 18-h period correlated with numbers of H+C+ but not H+C- or PLY- organisms in the bloodstream at 18 h postinfection. The sera of cirrhotic rats infected with the H+C+ strain had significantly decreased levels of C3 and showed significantly lower opsonizing activity for S. pneumoniae than sera from H+C+-infected control rats. These studies suggest that under limiting concentrations of complement, the expression of pneumolysin by pneumococci has a significant, negative effect on serum complement levels and reduces serum opsonic activity.
Alcantara
R B
RB
Veterans Affairs Medical Center, Omaha, Nebraska 68105, USA.
Preheim
L C
LC
Gentry-Nielsen
M J
MJ
D000818:Animals; D016470:Bacteremia / Q000276:immunology* / Q000382:microbiology; D001426:Bacterial Proteins; D002251:Carbon Tetrachloride / Q000494:pharmacology; D003167:Complement Activation / Q000187:drug effects; D003176:Complement C3 / Q000032:analysis; D003165:Complement System Proteins / Q000378:metabolism*; D004195:Disease Models, Animal; D008104:Liver Cirrhosis, Alcoholic / Q000209:etiology / Q000276:immunology / Q000382:microbiology; D008297:Male; D010587:Phagocytosis; D011008:Pneumococcal Infections / Q000276:immunology* / Q000382:microbiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013296:Streptococcus pneumoniae / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D013301:Streptolysins / Q000502:physiology*
D001426:Bacterial Proteins; D003176:Complement C3; D013301:Streptolysins; C032290:plY protein, Streptococcus pneumoniae; D003165:Complement System Proteins; D002251:Carbon Tetrachloride