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
. 2008 May;82(9):4441-8.
doi: 10.1128/JVI.02541-07. Epub 2008 Feb 20.

Alveolar macrophages are a major determinant of early responses to viral lung infection but do not influence subsequent disease development

Philippa K Pribul  1 , James Harker, Belinda Wang, Hongwei Wang, John S Tregoning, Jürgen Schwarze, Peter J M Openshaw
Affiliations

Alveolar macrophages are a major determinant of early responses to viral lung infection but do not influence subsequent disease development

Philippa K Pribul et al. J Virol. 2008 May.

Abstract

Macrophages are abundant in the lower respiratory tract. They play a central role in the innate response to infection but may also modulate excessive inflammation. Both macrophages and ciliated epithelial cells respond to infection by releasing soluble mediators, leading to the recruitment of innate and adaptive effector cells. To study the role of lung macrophages in acute respiratory viral infection, we depleted them by the inhalation of clodronate liposomes in an established mouse model of respiratory syncytial virus (RSV) disease. Infection caused an immediate local release of inflammatory cytokines and chemokines, peaking on day 1, which was virtually abolished by clodronate liposome treatment. Macrophage depletion inhibited the activation (days 1 to 2) and recruitment (day 4) of natural killer (NK) cells and enhanced peak viral load in the lung (day 4). However, macrophage depletion did not affect the recruitment of activated CD4 or CD8 T cells, weight loss, or virus-induced changes in lung function. Therefore, lung macrophages play a central role in the early responses to viral infection but have remarkably little effect on the adaptive response occurring at the time of peak disease severity.

PubMed Disclaimer

Figures

FIG. 1.
FIG. 1.
Immune response to RSV titration in a BALB/c mouse model. Mice were infected i.n. with 100 μl containing 5 × 105, 2 × 105, or 1 × 105 PFU of RSV or PBS (control). Illness was assessed by weight loss (a) and whole-body plethysmography (b). Viral titer was measured in the lung on day 4 by infectious-focus assay (c). On day 7, APC (CD11c+ MHC-II+) numbers (d) and CD4+ (e) and CD8+ (f) T-cell numbers plus their activation states (g and h) were analyzed. Bars/data points represent the means ± SEM of the results from four animals and are representative of two separate experiments. ***, P < 0.001; **, P < 0.01; *, P < 0.05, for test versus control values (a and b), and where indicated by solid horizontal lines (c, e, f, g, and h), determined by ANOVA.
FIG. 2.
FIG. 2.
Macrophage depletion by CL treatment. Mice were given i.n. 100 μl of liposomes, containing undiluted clodronate (100% CL), 30% CL in PBS, or undiluted empty liposomes (PL). AM in BAL cells (a), macrophages (Mφ) in lung cells (b), total BAL cells (c), and total lung cells (d) were counted on days 1 and 3 posttreatment. Values from naïve animals are displayed as broken lines on each plot. Bars represent means ± SEM of the results from five animals, and data are representative of three separate experiments. *, P < 0.05, where indicated by solid horizontal lines (determined by ANOVA); ns, not significant.
FIG. 3.
FIG. 3.
Clodronate treatment during RSV infection depletes macrophages. Mice were treated with 30% CL 3 days prior to i.n. infection with 2 × 105 PFU of RSV. Using fluorescence-activated cell sorter analysis, macrophages were defined as CD11c+ MHC-IIlo and DC were defined as CD11c+ MHC-IIhi. The percentages of BAL cells (a) and lung macrophages (Mφ) (b and c) and the percentages of DC (d and e) were plotted. Data points represent means ± SEM of the results from five animals, and data are representative of three separate experiments. ***, P < 0.001; **, P < 0.01; *, P < 0.05, for test versus control values determined by ANOVA.
FIG. 4.
FIG. 4.
Macrophage depletion reduces early cytokine and chemokine production. Mice were treated with 30% CL 3 days prior to i.n. infection with 2 × 105 PFU of RSV. Intracellular TNF in lung macrophages (Mφ) (a) and DC (b) was measured by flow cytometry. TNF (c), IL-6 (d), CCL3 (e), IFN-α (f), CCL5 (g), and IFN-γ (h) levels in BAL cells were measured by ELISA. Data points represent means ± SEM of the results from five animals; data are representative of three separate experiments. ***, P < 0.001; **, P < 0.01; *, P < 0.05, for test versus control values determined by ANOVA.
FIG. 5.
FIG. 5.
Macrophage depletion during RSV infection does not affect weight loss but increases viral load. Mice were treated with 30% CL 3 days prior to i.n. infection with 2 × 105 PFU of RSV. Weight (a) and body plethysmography (b) were recorded throughout. (c) Viral titer was measured on harvested lung tissue supernatants by infectious-focus assay. Data points represent means ± SEM of the results from five animals; data are representative of three separate experiments. ***, P < 0.001; **, P < 0.01; *, P < 0.05, for test versus control values determined by ANOVA.
FIG. 6.
FIG. 6.
Macrophage depletion reduces NK cell recruitment and activation but does not alter the adaptive immune responses. Mice were treated with 30% CL 3 days prior to i.n. infection with 2 × 105 PFU of RSV. Total lung cell counts (a) and percentages of CD4 (b), CD8 (c), activated CD4 (d), activated CD8 (e), and RSV-specific CD8 T cells (f) in the lungs of CL- or PBS-treated mice at different time points after RSV infection are shown. (g) Anti-RSV serum antibody was detected by RSV-specific immunoglobulin ELISA, and values from 1/400 serum dilutions are shown. NK cell number (h) and activation (i) in lung postinfection are shown. Data points/bars represent means ± SEM of the results from five animals, and data are representative of three separate experiments. ***, P < 0.001; **, P < 0.01; *, P < 0.05, for test versus control values determined by ANOVA; ns, not significant; Ig, immunoglobulin; OD, optical density.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Aberle, J. H., S. W. Aberle, W. Rebhandl, E. Pracher, M. Kundi, and T. Popow-Kraupp. 2004. Decreased interferon-gamma response in respiratory syncytial virus compared to other respiratory viral infections in infants. Clin. Exp. Immunol. 137146-150. - PMC - PubMed
    1. Becker, S., J. Quay, and J. Soukup. 1991. Cytokine (tumor necrosis factor, IL-6, and IL-8) production by respiratory syncytial virus-infected human alveolar macrophages. J. Immunol. 1474307-4312. - PubMed
    1. Benoit, A., Y. Huang, J. Proctor, G. Rowden, and R. Anderson. 2006. Effects of alveolar macrophage depletion on liposomal vaccine protection against respiratory syncytial virus (RSV). Clin. Exp. Immunol. 145147-154. - PMC - PubMed
    1. Culley, F. J., A. M. J. Pennycook, J. S. Tregoning, J. S. Dodd, G. Walzl, T. N. Wells, T. Hussell, and P. J. M. Openshaw. 2006. Role of CCL5 (RANTES) in viral lung disease. J. Virol. 808151-8157. - PMC - PubMed
    1. Durbin, J. E., T. R. Johnson, R. K. Durbin, S. E. Mertz, R. A. Morotti, R. S. Peebles, and B. S. Graham. 2002. The role of IFN in respiratory syncytial virus pathogenesis. J. Immunol. 1682944-2952. - PubMed