Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 8, 1996
Publication Date: N/A
Interpretive Summary: Pasteurella multocida is a bacterium which is a major cause of disease in livestock and poultry. The bacterium produces a capsule that inhibits its uptake and killing by host phagocytic cells. The capsule is composed of hyaluronic acid, a chemical compound identical with that found in host animal tissues. This research showed that P. multocida was recognized by macrophages and would bind to their cell surface. However, the bacteria could not be ingested by macrophages and killed unless the capsule was removed. A receptor specific for hyaluronic acid was identified on the macrophages. These findings are important because they demonstrate a mechanism of pathogenicity of the bacterium and identify a host cell receptor that has not been previously identified. This research will benefit other scientists studying the pathogenicity of P. multocida and the role that host cell receptors have in disease processes.
Technical Abstract: Serogroup A strains of Pasteurella multocida, the major cause of fowl cholera, are resistant to phagocytosis in non-immunized birds. Adherence studies with a capsulated strain of P. multocida (serotype A:3) and turkey air sac macrophages in culture showed that the bacteria were capable of adhering in large numbers to the macrophages but were not internalized. A noncapsulated variant of the bacteria (serotype -:3) showed little or no adherence and was not internalized. These data indicated that the adhesive properties were due to the presence of a capsule on the bacteria. The role of capsular hyaluronic acid in adherence to macrophages was investigated. Depolymerization of the bacterial capsule with hyaluronidase increased phagocytosis by macrophage cultures, and addition of hyaluronic acid to the macrophages inhibited bacterial adherence. Additionally, exposure of macrophages to chondroitin sulfate B, an anionic polysaccharide similar to hyaluronic acid, did not affect the adhesive properties and resistance to phagocytosis of capsulated organisms. Treatment of macrophages with sodium metaperiodate or trypsin suppressed bacterial binding. Collectively, these data indicate that P. multocida adhesion to air sac macrophages, but not internalization, is mediated by capsular hyaluronic acid and suggest that recognition of this bacterial polysaccharide is due to a specific glycoprotein receptor.