The transcriptional responses of respiratory epithelial cells to Bordetella pertussis reveal host defensive and pathogen counter-defensive strategies

Abstract

Bordetella pertussis, the causative agent of whooping cough, has many well-studied virulence factors and a characteristic clinical presentation. Despite this information, it is not clear how B. pertussis interaction with host cells leads to disease. In this study, we examined the interaction of B. pertussis with a human bronchial epithelial cell line (BEAS-2B) and measured host transcriptional profiles by using high-density DNA microarrays. The early transcriptional response to this pathogen is dominated by altered expression of cytokines, DNA-binding proteins, and NFkappaB-regulated genes. This previously unrecognized response to B. pertussis was modified in similar but nonidentical fashions by the antiinflammatory agents dexamethasone and sodium salicylate. Cytokine protein expression was confirmed, as was neutrophil chemoattraction. We show that B. pertussis induces mucin gene transcription by BEAS-2B cells then counters this defense by using mucin as a binding substrate. A set of genes is described for which the catalytic activity of pertussis toxin is both necessary and sufficient to regulate transcription. Host genomic transcriptional profiling, in combination with functional assays to evaluate subsequent biological events, provides insight into the complex interaction of host and pathogen.

Figure 1

(a–c) Changes in secreted chemokine abundance after exposure of an epithelial cell line to B. pertussis for 24 h. Representative data from duplicate experiments are shown. Assays were performed for IL-8 (a), MCP-1 (b), and IL-6 (c). (d) Migration of neutrophils in response to the supernatants of B. pertussis-infected epithelial cells. In duplicate experiments, neutrophils migrated toward the supernatant with or without 10 μg/ml anti-IL-8 Ab. Migration index is the ratio of cells that migrated to a supernatant in comparison to the uninfected supernatant. Error bars represent the 95% confidence interval of the mean of three wells.

Figure 2

(a and b) Induction of mucin reporter genes by B. pertussis infection. In duplicate experiments, an epithelial cell line carrying a mucin-luciferase reporter gene fusion was exposed to varying numbers of B. pertussis for increasing periods of time. Representative data from one experiment in which the fusion contained the promoter from MUC2 (a) or the promoter from MUC5AC (b) are shown. (c) Binding of B. pertussis to mucin-coated plates. One set of data from triplicate experiments that demonstrates binding of B. pertussis to mucin-coated and blocked wells vs. those coated with blocking agent alone. Background fluorescence of the mucin and nonfat milk are demonstrated by the third and fourth bars. Error bars represent the 95% confidence interval.