Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2014 Sep 8;9(9):e107188.
doi: 10.1371/journal.pone.0107188. eCollection 2014.

Caspase-1-independent interleukin-1β is required for clearance of Bordetella pertussis infections and whole-cell vaccine-mediated immunity

David E Place  1 , Sarah J Muse  2 , Girish S Kirimanjeswara  3 , Eric T Harvill  3
Affiliations

Caspase-1-independent interleukin-1β is required for clearance of Bordetella pertussis infections and whole-cell vaccine-mediated immunity

David E Place et al. PLoS One. .

Abstract

Whooping cough remains a significant disease worldwide and its re-emergence in highly vaccinated populations has been attributed to a combination of imperfect vaccines and evolution of the pathogen. The focus of this study was to examine the role of IL-1α/β and the inflammasome in generation of the interleukin-1 (IL-1) response, which is required for the clearance of Bordetella pertussis. We show that IL-1β but not IL-1α is required for mediating the clearance of B. pertussis from the lungs of mice. We further found that IL-1β and IL-1R deficient mice, compared to wild-type, have similar but more persistent levels of inflammation, characterized by immune cell infiltration, with significantly increased IFNγ and a normal IL-17A response during B. pertussis infection. Contrary to expectations, the cleavage of precursor IL-1β to its mature form did not require caspase-1 during primary infections within the lung despite being required by bone marrow-derived macrophages exposed to live bacteria. We also found that the caspase-1 inflammasome was not required for protective immunity against a B. pertussis challenge following vaccination with heat-killed whole cell B. pertussis, despite IL-1R signaling being required. These findings demonstrate that caspase-1-independent host factors are involved in the processing of protective IL-1β responses that are critical for bacterial clearance and vaccine-mediated immunity.

PubMed Disclaimer

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Bacterial clearance is mediated by IL-1β and IL-1R but not IL-1α.
Groups of 5–8 mice were inoculated with B. pertussis (5×105 CFU) suspended in a 50 µL droplet of PBS and euthanized at indicated time points to determine bacterial CFUs in lung homogenates. The mean ± standard error was graphed for each group at the specified time-point and is representative of three independent experiments. Significance was calculated using one-way ANOVA with Dunnet’s multiple comparison post-hoc analysis. *p<0.05, **p<0.01; WT vs IL-1β−/− (*), vs IL-1α−/− (†), vs IL-1R−/− (‡).
Figure 2
Figure 2. IL-1 signaling limits lung inflammation during B. pertussis infection.
Groups of four mice were either (A–D) uninfected or inoculated with B. pertussis and euthanized at (E–H) 7 days or (I–L) 28 days post-inoculation. Automated H&E staining was performed on 5 µm paraffin-embedded sections. Images were taken and are representative of 10–12 fields per group. Lung homogenate cytokine measurements (M–N) were measured by ELISA from uninfected mice or on days 3, 7, 14, or 28 post-inoculation (n = 4–8). ELISA significance was determined by one-way ANOVA with Dunnet’s post-hoc test. *p<0.05 represents a significant difference from WT mice.
Figure 3
Figure 3. IL-1 is not required for recruitment of immune cells to the lung.
Lungs were excised and made into a single cell suspension for flow cytometry at the indicated days post-inoculation. Cells were stained with anti-CD45 to identify hematopoietic cells and anti-CD11b, CD3, CD4, CD8, Ly6G, and F4/80 for further subsets. Gating for T cells subsets was performed on CD45+CD3+ cells with quadrant gating to identify either (A) CD4+ or (B) CD8+ single-positive T cells. Gating on CD45+CD11b+ cells, (C) Ly6G+ neutrophils or (D) F4/80+ macrophages were identified. Data was collected with a BD LSRII flow cytometer. Bars indicate the mean percentage of each group (n = 6) with (*) indicating p<0.05 using the Kruskal-Wallis test with Dunn’s post-hoc test for multiple comparisons.
Figure 4
Figure 4. IL-1β production is caspase-1 dependent in vitro but independent in vivo.
To determine if in vitro IL-1β processing is dependent upon caspase-1, bone marrow-derived macrophages were (A) primed 3 h prior to inoculation and were washed and treated with fresh media, ATP (5 mM), or live B. pertussis (MOI 10) or (B) seeded at 106 cells/well and primed with LPS or washed and treated with media, ATP (5 mM), or live B. pertussis (MOI 100) for 6 hours in FBS-free DMEM, and supernatant was collected. The requirement for caspase-1 during infection and the ability to produce IL-1β in response to live B. pertussis was assessed by (C) inoculating groups of four mice per time point with B. pertussis (5×105 CFU) and lungs were dissected for determining bacterial CFUs ± standard error. (D) To identify whether cleaved IL-1β was produced in caspase-1 deficient mice, lung homogenates from day 3 post-inoculation were run on 12% gels and probed with anti-IL-1β. Data is representative of at least two independent experiments.
Figure 5
Figure 5. Adaptive immune responses are IL-1 dependent but Caspase-1 independent.
Groups of four mice were either sham vaccinated with PBS or vaccinated with heat-killed B. pertussis (wP) by administering 200 µL i.p. at 28 and 14 days prior to challenge inoculation with 5×105 CFU. Lungs were excised at seven days post-challenge and to determine bacterial CFUs. Bar graphs represent the mean CFU per lung ± standard deviation. Significance was determined by one-way ANOVA and Tukey’s multiple comparison post-hoc test with *p<0.05, ***p<0.001. Data is representative of two independent experiments.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Dinarello CA (2009) Immunological and inflammatory functions of the interleukin-1 family. Annu Rev Immunol 27: 519–550 10.1146/annurev.immunol.021908.132612 - DOI - PubMed
    1. Martin S, Maruta K, Burkart V, Gillis S, Kolb H (1988) IL-1 and IFN-gamma increase vascular permeability. Immunology 64: 301–305. - PMC - PubMed
    1. Ben-Sasson SZ, Hu-Li J, Quiel J, Cauchetaux S, Ratner M, et al. (2009) IL-1 acts directly on CD4 T cells to enhance their antigen-driven expansion and differentiation. PNAS 106: 7119–7124 10.1073/pnas.0902745106 - DOI - PMC - PubMed
    1. Bevilacqua MP, Pober JS, Wheeler ME, Cotran RS, Gimbrone MA Jr (1985) Interleukin 1 acts on cultured human vascular endothelium to increase the adhesion of polymorphonuclear leukocytes, monocytes, and related leukocyte cell lines. J Clin Invest 76: 2003–2011 10.1172/JCI112200 - DOI - PMC - PubMed
    1. Calkins CM, Bensard DD, Shames BD, Pulido EJ, Abraham E, et al. (2002) IL-1 regulates in vivo C-X-C chemokine induction and neutrophil sequestration following endotoxemia. J Endotoxin Res 8: 59–67. - PubMed

Publication types

LinkOut - more resources