Pertussis Toxin Targets Airway Macrophages To PromoteBordetella pertussisInfection of the Respiratory Tract

Abstract

Pertussis toxin (PT), a secreted virulence factor of Bordetella pertussis, ADP ribosylates mammalian G i proteins and plays an important early role in respiratory tract infection by this pathogen in a mouse intranasal infection model. To test the hypothesis that PT targets resident airway macrophages (AM) to promote this infection, we depleted AM by intranasal administration of liposome-encapsulated clodronate prior to bacterial inoculation. This treatment enhanced respiratory tract infection by B. pertussis, even though it also induced a rapid influx of neutrophils to the airways. Strikingly, AM depletion also enhanced infection by mutant strains deficient in PT production or activity to the same level as the wild-type infection, indicating that AM may be the primary target cells for PT in promoting infection. The enhancing effect of clodronate-liposome treatment on infection (i) was shown to be due to macrophage depletion rather than neutrophil influx; (ii) was observed for both tracheal infection and lung infection; (iii) was observed during the early and peak phases of the infection but was lost by day 14 postinoculation, during clearance of the infection; (iv) persisted for at least 1 week (prior to bacterial inoculation); and (v) was equivalent in magnitude to the effect of PT pretreatment and the effects were not additive, consistent with the idea that PT targets AM. We found that PT efficiently ADP ribosylated AM G proteins both in vitro and after intranasal administration of PT in mice and that the duration of G protein modification in vivo was equivalent to the duration of the enhancing effect of PT treatment on the bacterial infection. Collectively, these observations indicate that PT targets AM to promote early infection of the respiratory tract by B. pertussis.

O Antigen Protects Bordetella parapertussis from Complement

“…In order to investigate the immune mechanism that O antigen protects against, we blocked various innate immune functions and examined bacterial numbers 3 days postinoculation. Neutrophils or alveolar macrophages were depleted from wild-type mice with ␣Ly6G antibody or clodronate liposome treatment, respectively (11,27,51). These mice were then inoculated with B. parapertussis or B. parapertussis ⌬wbm as described above and dissected 3 days postinoculation.…”

“…For complement depletion, mice were intraperitoneally injected with 5 U of CVF in PBS (Sigma, St. Louis, MO) at 26 and 24 h prior to inoculation, and every 5 days thereafter until the completion of the experiment (50). For alveolar macrophage depletion, mice were given an intranasal dose of 100 l of clodronate liposomes (Roche Diagnostics, Mannheim, Germany) 48 h prior to inoculation (11). The presence or absence of alveolar macrophage or neutrophils in the lungs was determined via visual identification of cells from bronchoalveolar lavage fluid spun onto slides via Cytospin and then stained with modified Wright-Giemsa stain (Fisher Scientific, Kalamazoo, MI).…”

Pertussis Toxin Inhibits Early Chemokine Production To Delay Neutrophil Recruitment in Response toBordetella pertussisRespiratory Tract Infection in Mice

“…Several systemic symptoms have been attributed to PT activity, and although PT is considered to be essential for virulence, the role for PT during infection is still under investigation (4). PT has been shown to have inhibitory effects on several parts of the immune response, including macrophage function, serum antibody production, and the expression of surface molecules on dendritic cells (6,8,24).…”

“…B. pertussis binds to ciliated cells and proliferates within the upper and lower respiratory tract, where several toxins are released (11,17,30,47). Pertussis toxin (PT) is produced exclusively by B. pertussis and is thought to play a major role in the development of the infection (8,12). PT is an exotoxin with an AB 5 structure that ADP-ribosylates heterotrimeric G i proteins in mammalian cells, leading to disruption of downstream cell signaling events (28).…”

A rapid, sensitive method for testing the activity of Escherichia coli 0157:H7 secreted cytotoxins against epithelial cells from the jejunum and descending colon of cattle

“…In contrast, Rashid et al (2006) determined that Shiga toxin expression is not different for human and cattle systems suggesting that cytotoxins could play a similar role in both systems. Bacterial cytotoxins contribute to pathogen colonization directly by influencing the number of colonization sites (Robinson et al 2006) and indirectly by influencing the immune response to infection (Carbonetti et al 2007;Ferens and Hovde 2000). In cattle, Shiga toxins are likely degraded before they can influence the immune response (Hoey et al 2003) and they are also not involved in EHEC O157:H7 colonization of the lymphoid follicle-associated epithelium in the terminal rectum (Sheng et al 2006).…”