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Interactions of Haemophilus-Actinobacillus-Pasteurella bacteria with phagocytic cells
1Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison 53706.
Abstract:
The Haemophilus-Actinobacillus-Pasteurella (HAP) group of bacteria contains a number of important veterinary and human pathogens. Although each species has specific characteristics and host range, most share the general property of being resistant to cellular defense mechanisms. In some cases (e.g. Pasteurella multocida, Pasteurella haemolytica and Actinobacillus pleuropneumoniae) resistance results in part from the presence of an antiphagocytic capsule that protects the bacilli against ingestion by neutrophils and macrophages. In other instances the bacteria aggressively attack mononuclear and polymorphonuclear phagocytes. For example, P. haemolytica, A. pleuro-pneumoniae and Actinobacillus actinomycetemcomitans each produce a leukotoxin that functionally impairs, and ultimately kills, leukocytes from cattle, pigs and human beings, respectively. Components of Pasteurella multocida and Haemophilus somnus have also been reported to adversely affect leukocyte functions. Another important area of research that is just emerging concerns the ability of lipopolysaccharide and other components of HAP bacteria to stimulate or modulate macrophage release of inflammatory mediators such as interleukin-1. In this paper, we provide an overview of the interactions of HAP bacteria with phagocytes and identify some of the common strategies by which they evade cellular defenses.
Insights
The Haemophilus-Actinobacillus-Pasteurella (HAP) bacteria group evades host defenses using capsules and leukotoxins. These pathogens resist phagocytosis and attack leukocytes, impacting veterinary and human health.
Area of Science:
- Microbiology
- Immunology
- Pathogenesis
Background:
- The Haemophilus-Actinobacillus-Pasteurella (HAP) bacterial group includes significant veterinary and human pathogens.
- Many HAP species exhibit resistance to host cellular defense mechanisms.
Purpose of the Study:
- To provide an overview of HAP bacterial interactions with phagocytes.
- To identify common evasion strategies employed by HAP bacteria against cellular defenses.
Main Methods:
- Review of existing literature on HAP bacterial interactions with phagocytes.
- Analysis of antiphagocytic capsule functions.
- Examination of leukotoxin production and effects on leukocytes.
- Investigation of lipopolysaccharide and other component effects on macrophage inflammatory mediator release.
Main Results:
- HAP bacteria utilize antiphagocytic capsules to resist phagocytosis by neutrophils and macrophages.
- Species like P. haemolytica and A. pleuropneumoniae produce leukotoxins that impair and kill leukocytes.
- Components of HAP bacteria can modulate macrophage release of inflammatory mediators like interleukin-1.
Conclusions:
- HAP bacteria possess diverse strategies to evade host cellular defenses, including capsules and leukotoxins.
- Understanding these mechanisms is crucial for developing effective treatments against HAP infections.