Related Experiment Video
Updated: May 3, 2026
Alveolar Macrophage Phagocytosis and Bacteria Clearance in Mice
Published on: March 2, 2019
Alveolar macrophages infected with Ames or Sterne strain of Bacillus anthracis elicit differential molecular
Felicia D Langel1, Chih-Yuan Chiang2, Douglas Lane3
1Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America.
Abstract:
Alveolar macrophages (AMs) phagocytose Bacillus anthracis following inhalation and induce the production of pro-inflammatory cytokines and chemokines to mediate the activation of innate immunity. Ames, the virulent strain of B. anthracis, contains two plasmids that encode the antiphagocytic poly-γ-d-glutamic acid capsule and the lethal toxin. The attenuated Sterne strain of B. anthracis, which lacks the plasmid encoding capsule, is widely adapted as a vaccine strain. Although differences in the outcome of infection with the two strains may have originated from the presence or absence of an anti-phagocytic capsule, the disease pathogenesis following infection will be manifested via the host responses, which is not well understood. To gain understanding of the host responses at cellular level, a microarray analysis was performed using primary rhesus macaque AMs infected with either Ames or Sterne spores. Notably, 528 human orthologs were identified to be differentially expressed in AMs infected with either strain of the B. anthracis. Meta-analyses revealed genes differentially expressed in response to B. anthracis infection were also induced upon infections with multiple pathogens such as Francisella Novicida or Staphylococcus aureus. This suggests the existence of a common molecular signature in response to pathogen infections. Importantly, the microarray and protein expression data for certain cytokines, chemokines and host factors provide further insights on how cellular processes such as innate immune sensing pathways, anti-apoptosis versus apoptosis may be differentially modulated in response to the virulent or vaccine strain of B. anthracis. The reported differences may account for the marked difference in pathogenicity between these two strains.
Insights
Alveolar macrophages (AMs) respond differently to virulent Bacillus anthracis (Ames) and vaccine (Sterne) strains. Host immune responses, including gene expression, reveal distinct pathways modulated by each B. anthracis strain, impacting pathogenicity.
Area of Science:
- Immunology
- Microbiology
- Genomics
Background:
- Alveolar macrophages (AMs) are crucial in the innate immune response to inhaled Bacillus anthracis (B. anthracis).
- The virulent Ames strain possesses an antiphagocytic capsule and lethal toxin, while the attenuated Sterne strain lacks the capsule, serving as a vaccine.
- Understanding host responses to different B. anthracis strains is vital for comprehending disease pathogenesis.
Purpose of the Study:
- To investigate cellular-level host responses in rhesus macaque AMs infected with virulent (Ames) and attenuated (Sterne) B. anthracis strains.
- To identify differentially expressed genes and understand how these host responses contribute to varying pathogenicity.
- To explore potential common molecular signatures in response to B. anthracis and other pathogens.
Main Methods:
- Primary rhesus macaque AMs were infected with Ames or Sterne strain spores.
- Microarray analysis was performed to assess gene expression profiles.
- Meta-analyses were conducted to compare gene expression with responses to other pathogens.
- Protein expression data for specific cytokines and chemokines were analyzed.
Main Results:
- 528 human orthologs were differentially expressed in AMs infected with either B. anthracis strain.
- Genes induced by B. anthracis infection showed overlap with those induced by Francisella Novicida and Staphylococcus aureus, suggesting a common immune response signature.
- Microarray and protein data indicated differential modulation of innate immune sensing, anti-apoptosis, and apoptosis pathways by the two B. anthracis strains.
Conclusions:
- The observed differences in gene and protein expression between Ames and Sterne strain infections provide insights into the distinct host responses.
- These differential host responses likely account for the significant difference in pathogenicity between the virulent and vaccine strains of B. anthracis.
- A common molecular signature may exist for host responses to various bacterial pathogens.
Related Concept Videos
01:31Defense Against Bacterial Pathogens
Phagocytes
Phagocytes are the frontline soldiers of the immune system. They include neutrophils and macrophages. Neutrophils are the most abundant type of white blood cell and are quickly mobilized to the site of infection. Macrophages are larger cells that patrol...
01:30Bacterial Phylum Actinobacteria