Fig 1.
Experimental design and routes used for challenge.
In this study 10-week-old female CD-1 mice were challenged with B. pertussis and euthanized at 1 hour, 3 days, or 7 days post-challenge. The lungs, trachea, and nasal lavage fluid were collected to enumerate bacterial burden at each time point. Intranasal administration of B. pertussis was compared to aerosol challenge using a range of challenge doses.
Fig 2.
Intranasal and aerosol administration of B. pertussis (UT25Sm1) lead to dose-dependent colonization of the respiratory tract in mice.
Mice were challenged utilizing an aerosol chamber (20 mL total) with doses of B. pertussis from 109 CFU/mL to 106 CFU/mL, or by intranasal administration (20 μL total) of B. pertussis with doses from 107 CFU to 102 CFU. Bacterial burden was quantified one-hour post-challenge in the A) nasal lavage fluid, B) trachea, and C) lung. Error bars are mean ± SEM (n = 5 per group). A simple linear regression was performed on Y = Log(Y) transformed CFU data to compare the dose administered by D) aerosol challenge E) to the number of bacteria recovered from the lung. High and low doses for each challenge route are highlighted with a gray box. This figure was created with BioRender.com and is published under a CC BY license, with permission from Biorender, original copyright 2023.
Fig 3.
Intranasal administration of high doses of B. pertussis (UT25Sm1) leads to increased colonization of the respiratory tract compared to aerosol challenge.
Bacterial burden in the A) nasal lavage fluid, B) trachea, and C) lung. The p-values were calculated using ANOVA followed by a Tukey’s multiple-comparison test, *p < 0.05, ***p < 0.001, and **** p < 0.0001. Error bars are mean ± SEM values.
Fig 4.
The distribution of bacteria in the nasal wash, lung, and trachea correlates with the challenge dose rather than the route of administration.
A) Visual representation of the bacterial burden in the nasal lavage fluid, trachea, and lung at each time point. B) Principle component analysis of the bacterial burden for each challenge group.
Fig 5.
White blood cell and neutrophil counts in whole blood following infection (B. pertussis UT25Sm1).
A) White blood cells and B) neutrophils were measured in the whole blood a days 3 and 7 post-challenge. The p-values were calculated using ANOVA followed by a Tukey’s multiple-comparison test, **** p < 0.0001 (n = 5 per group). Error bars are mean ± SEM values.
Fig 6.
High dose intranasal challenge (UT25Sm1) leads to a significant increase in cytokine responses compared to aerosol challenge.
The dose is shown on the x-axis. Values are in pg/mL on the y-axis. A) Heat map of cytokines measured in the lung supernatant at 1 hour, day 3, and day 7 post-challenge. A) IL-6 and B) IL-17/IL-17A represented as pg/mL. The p-values were calculated using ANOVA followed by a Tukey’s multiple-comparison test, * p < 0.05 and *** p < 0.001 (n = 5 per group). Stars represent comparison to baseline unless otherwise indicated. Error bars are mean ± SEM values.
Fig 7.
Model comparing intranasal challenge and aerosol challenge at high doses.
Intranasal challenge is associated with an increase in bacterial burden over time. The distribution of bacteria following intranasal challenge is associated with the upper respiratory tract compared to aerosol challenge which is associated with the lower respiratory tract. Intranasal administration stimulates increases in leukocytosis and cytokine production compared to aerosol administration. This figure was created with BioRender.com and is published under a CC BY license, with permission from Biorender, original copyright 2023.