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Updated: May 24, 2026
Opsono-Adherence Assay to Evaluate Functional Antibodies in Vaccine Development Against Bacillus anthracis and Other Encapsulated Pathogens
Published on: May 19, 2020
Updating perspectives on the initiation of Bacillus anthracis growth and dissemination through its host
Zachary P Weiner1, Ian J Glomski
1Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, Virginia, USA.
Abstract:
Since 1957, it has been proposed that the dissemination of inhalational anthrax required spores to be transported from the lumena of the lungs into the lymphatic system. In 2002, this idea was expanded to state that alveolar macrophages act as a "Trojan horse" capable of transporting spores across the lung epithelium into draining mediastinal lymph nodes. Since then, the Trojan horse model of dissemination has become the most widely cited model of inhalational infection as well as the focus of the majority of studies aiming to understand events initiating inhalational anthrax infections. However, recent observations derived from animal models of Bacillus anthracis infection are inconsistent with aspects of the Trojan horse model and imply that bacterial dissemination patterns during inhalational infection may be more similar to the cutaneous and gastrointestinal forms than previously thought. In light of these studies, it is of significant importance to reassess the mechanisms of inhalational anthrax dissemination, since it is this form of anthrax that is most lethal and of greatest concern when B. anthracis is weaponized. Here we propose a new "jailbreak" model of B. anthracis dissemination which applies to the dissemination of all common manifestations of the disease anthrax. The proposed model impacts the field by deemphasizing the role of host cells as conduits for dissemination and increasing the role of phagocytes as central players in innate defenses, while moving the focus toward interactions between B. anthracis and lymphoid and epithelial tissues.
Insights
The "Trojan horse" model for inhalational anthrax spread is challenged. A new "jailbreak" model suggests Bacillus anthracis dissemination relies less on host cells and more on phagocyte interactions.
Area of Science:
- Infectious Diseases
- Microbiology
- Immunology
Background:
- The established "Trojan horse" model posits alveolar macrophages transport Bacillus anthracis spores from lungs to lymph nodes.
- This model has guided inhalational anthrax research for decades, focusing on host cell-mediated dissemination.
- Recent findings in animal models challenge the "Trojan horse" model, suggesting alternative dissemination pathways.
Purpose of the Study:
- To reassess the mechanisms of inhalational anthrax dissemination, particularly for the most lethal form of the disease.
- To propose a new model for Bacillus anthracis dissemination applicable to all anthrax manifestations.
- To shift focus from host cells as conduits to the role of phagocytes in innate defense.
Main Methods:
- Review and re-evaluation of existing animal model data for Bacillus anthracis infection.
- Comparative analysis of dissemination patterns across inhalational, cutaneous, and gastrointestinal anthrax.
- Development of a novel conceptual model for bacterial spread.
Main Results:
- Observations from animal models are inconsistent with the "Trojan horse" model of inhalational anthrax.
- Inhalational anthrax dissemination may share similarities with cutaneous and gastrointestinal anthrax.
- A new "jailbreak" model is proposed for Bacillus anthracis dissemination.
Conclusions:
- The "Trojan horse" model requires re-evaluation due to conflicting experimental evidence.
- The proposed "jailbreak" model emphasizes phagocyte roles in innate immunity and host-pathogen interactions.
- This new perspective impacts understanding of anthrax pathogenesis and potential therapeutic strategies.
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