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Cytokine profiles following interaction between bovine alveolar macrophages and Pasteurella haemolytica
M A Morsey1, A G Van-Kessel, Y Mori
1Pfizer INC, Eastern Point Rd, Groton, CT 06340, USA.
Abstract:
Pasteurella haemolytica is a gram negative bacterium frequently isolated from the lungs of calves suffering from a fibrinous pneumonic condition known as shipping fever. To understand the pathogenesis of this disease, we investigated the induction of cytokin gene expression in cultures of bovine alveolar macrophages (BAM) stimulated with heat-killed P. haemolytica. Northern blot analysis of total RNA showed that P. haemolytica induced early, abundant, and consistent synthesis of IL-1, TNF-alpha, and IL-8 mRNA. Cytokine mRNAs were detected within 1 hr post-stimulation with heat-killed P. haemolytica. IL-1 and IL-8 mRNA accumulated to high levels with increase in stimulation time, whereas TNF-alpha mRNA clearly declined by 4 and 8 h post stimulation. IL-1, TNF-alpha, and IL-8 proteins were also secreted into the culture medium of BAM stimulated with heat-killed P. haemolytica. All three proteins were detected at high levels 8 and 12 h post stimulation with P. haemolytica. BAM cells treated with bovine interferon-alpha and then stimulated with P. haemolytica produced higher amounts of IL-1, IL-8 and TNF-alpha proteins compared to BAM stimulated with P. haemolytica alone. These findings demonstrate the powerful and selective induction of cytokine mRNA and protein synthesis in BAM stimulated with heat-killed P. haemolytica and may explain certain aspects of shipping fever pathogenesis.
Insights
Pasteurella haemolytica infection triggers rapid cytokine gene expression in bovine alveolar macrophages, producing key inflammatory proteins. This response may explain the pathology of shipping fever in calves.
Area of Science:
- Veterinary Immunology
- Bacterial Pathogenesis
- Cellular Immunology
Background:
- Shipping fever is a common pneumonia in calves caused by Pasteurella haemolytica.
- Understanding the host immune response is crucial for elucidating disease pathogenesis.
Purpose of the Study:
- Investigate the induction of cytokine gene expression in bovine alveolar macrophages (BAM) stimulated with P. haemolytica.
- Analyze the kinetics of cytokine mRNA and protein synthesis.
- Determine the effect of interferon-alpha on P. haemolytica-induced cytokine production.
Main Methods:
- Bovine alveolar macrophages (BAM) were stimulated with heat-killed P. haemolytica.
- Northern blot analysis was used to detect cytokine mRNA (IL-1, TNF-alpha, IL-8).
- ELISA or similar assays measured secreted cytokine proteins.
- BAM were pre-treated with bovine interferon-alpha before stimulation.
Main Results:
- P. haemolytica induced rapid and significant mRNA synthesis for IL-1, TNF-alpha, and IL-8 within 1 hour.
- IL-1 and IL-8 mRNA levels peaked with time, while TNF-alpha mRNA declined after 4-8 hours.
- Secreted IL-1, TNF-alpha, and IL-8 proteins were detected at high levels by 8-12 hours post-stimulation.
- Interferon-alpha pre-treatment enhanced the production of all three cytokines.
Conclusions:
- Heat-killed P. haemolytica potently induces cytokine mRNA and protein synthesis in BAM.
- The differential regulation of cytokine expression provides insights into shipping fever pathogenesis.
- Interferon-alpha modulates the inflammatory cytokine response to P. haemolytica.