Type b Capsule Inhibits Ingestion of Haemophilus influenzae by Murine Macrophages: Studies with Isogenic Encapsulated and Unencapsulated Strains

Phagocytosis may be important in clearing Haemophilus influenzae from the bloodstream. To define the effect of type b capsule on phagocytosis, binding and ingestion by macrophages was measured for 5 isogenic sets of capsule-sufficient strains (clinical isolates and type b transformants of capsule-de...

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Bibliographic Details
Published in:The Journal of infectious diseases 1992-07, Vol.166 (1), p.178-182
Main Authors: Noel, Gary J., Hoiseth, Susan K., Edelson, Paul J.
Format: Article
Language:English
Subjects:
Agglutination Tests
Animals
Bacteremia
Bacteremia - immunology
Bacteria
Bacterial Capsules - immunology
Bacterial Outer Membrane Proteins - analysis
Blood
Blotting, Southern
Cells, Cultured
Concise Comunications
DNA, Bacterial - analysis
Haemophilus Infections - immunology
Haemophilus influenzae
Haemophilus influenzae - chemistry
Haemophilus influenzae - genetics
Haemophilus influenzae - immunology
Humans
Ingestion
Inoculation
Macrophages
Macrophages - immunology
Male
Mice
Nucleic Acid Hybridization
Phagocytosis
Virulence
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Summary:Phagocytosis may be important in clearing Haemophilus influenzae from the bloodstream. To define the effect of type b capsule on phagocytosis, binding and ingestion by macrophages was measured for 5 isogenic sets of capsule-sufficient strains (clinical isolates and type b transformants of capsule-deficient mutants) and capsule-deficient mutants (strains lacking a 9-kb EcoRI fragment of chromosomal DNA associated with type b capsule expression). Capsule-sufficient strains were not bound in the absence of serum, whereas capsule-deficient strains were bound and ingested (1.8–5.1 organisms/macrophage; 59%–97% ingested). In the presence of nonimmune serum, capsule-sufficient strains were largely bound but not ingested (4.7–7.2 organisms/macrophage; 7%–21%ingested), whereas capsule-deficient strains were nearly all ingested (6.2–10.5 organisms/macrophage; 93%–97% ingested). Strains resisting ingestion caused persistent bacteremia 24 h after intravenous challenge in mice and were more likely than readily ingested strains to cause persistent bacteremia or death in infant rats. Thus, type b capsule inhibits ingestion by macrophages; resistance to ingestion maybe an important virulence determinant of type b organisms.
ISSN:0022-1899
1537-6613
DOI:10.1093/infdis/166.1.178