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Actin polymerization enhances Pasteurella haemolytica leukotoxicity
R J Basaraba1, A N Byerly, D A Mosier
1Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, USA. basaraba@vet.ksu.edu
Veterinary Microbiology
|March 4, 1999
Summary
Pasteurella haemolytica leukotoxin damages bovine leukocytes by increasing cell permeability and releasing actin. The bacteria then use this actin to enhance their own leukotoxin production, harming the host.
Area of Science:
- Veterinary Microbiology
- Cell Biology
- Immunology
Background:
- Pasteurella haemolytica leukotoxin is a key virulence factor causing bovine leukocyle damage.
- Actin, a cytoskeletal protein, plays crucial roles in cellular functions and immune responses.
Purpose of the Study:
- To investigate if leukotoxin induces actin release from bovine leukocytes.
- To determine the effect of purified actin on P. haemolytica growth and leukotoxin production.
Main Methods:
- Assessing bovine leukocyte viability and permeability after exposure to P. haemolytica culture supernatants.
- Analyzing beta-actin release into supernatants.
- Treating P. haemolytica with purified actin (G-actin and F-actin) and evaluating bacterial growth and leukotoxicity.
- Investigating the role of immune serum and bacterial streptomycin resistance on actin polymerization.
Main Results:
- P. haemolytica supernatants decreased bovine leukocyte viability and increased permeability, leading to beta-actin release.
- Purified actin induced G-actin to F-actin polymerization in P. haemolytica, an effect partially inhibited by immune serum.
- Incubation with F-actin, but not G-actin or albumin, significantly increased P. haemolytica leukotoxicity in a dose-dependent manner, correlating with enhanced leukotoxin secretion.
Conclusions:
- The interaction between P. haemolytica and actin contributes to bovine leukotoxicity.
- Actin polymerization by the bacteria and subsequent enhancement of leukotoxin production represent a detrimental mechanism for the host animal.