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Streptococcus pneumoniae nasopharyngeal colonization induces type I interferons and interferon-induced gene expression.

Joyce EA, Popper SJ, Falkow S - BMC Genomics (2009)

Bottom Line: Subsequent to this initial inflammatory response, we observed increases in transcripts associated with T cell development and activation, as well as wounding, basement membrane remodeling, and cell proliferation.Examining multiple time points over six weeks of colonization demonstrated that asymptomatic carriage stimulates a dynamic host response characterized by temporal waves with distinct biological programs.Our data suggest that the usual response to the presence of the pneumocccus is an initial controlled inflammatory response followed by activation of host physiological processes such as response to wounding, basement membrane remodeling, and increasing cellular numbers that ultimately allow the host to maintain an intact epithelium and eventually mount a preventive adaptive immune response.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94131, USA. ejoyce@stanford.edu

ABSTRACT

Background: We employed DNA microarray technology to investigate the host response to Streptococcus pneumoniae in a mouse model of asymptomatic carriage. Over a period of six weeks, we profiled transcript abundance and complexity in the Nasal Associated Lymphoid Tissue (NALT) to identify genes whose expression differed between pneumococcal-colonized and uncolonized states.

Results: Colonization with S. pneumoniae altered the expression of hundreds of genes over the course of the study, demonstrating that carriage is a dynamic process characterized by increased expression of a set of early inflammatory responses, including induction of a Type I Interferon response, and the production of several antimicrobial factors. Subsequent to this initial inflammatory response, we observed increases in transcripts associated with T cell development and activation, as well as wounding, basement membrane remodeling, and cell proliferation. Our analysis suggests that microbial colonization induced expression of genes encoding components critical for controlling JAK/STAT signaling, including stat1, stat2, socs3, and mapk1, as well as induction of several Type I Interferon-inducible genes and other antimicrobial factors at the earliest stages of colonization.

Conclusion: Examining multiple time points over six weeks of colonization demonstrated that asymptomatic carriage stimulates a dynamic host response characterized by temporal waves with distinct biological programs. Our data suggest that the usual response to the presence of the pneumocccus is an initial controlled inflammatory response followed by activation of host physiological processes such as response to wounding, basement membrane remodeling, and increasing cellular numbers that ultimately allow the host to maintain an intact epithelium and eventually mount a preventive adaptive immune response.

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S. pneumoniae colonizes the nasopharynx of mice over a 6 week period. (A) Viable cell counts from head cavities (post-NALT excision) of infected mice. Open circles represent viable counts from a single mouse. Solid lines represent the geometric mean of CFUs/head for each day. Dashed line represents the limit of detection. (B) Confocal immunofluorescence image of S. pneumoniae colonizing NALT tissue 3 days post-inoculation. The green bar bell indicates the lumen of the nasopharynx, the pink bar bell indicates the epithelial monolayer, and the blue bar bell indicates the cells within the NALT. S. pnuemoniae were visualized via fluorescently-conjugated antibody (green) near the surface of the NALT (blue) and were particularly apparent in the mucus layer (red).
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Figure 1: S. pneumoniae colonizes the nasopharynx of mice over a 6 week period. (A) Viable cell counts from head cavities (post-NALT excision) of infected mice. Open circles represent viable counts from a single mouse. Solid lines represent the geometric mean of CFUs/head for each day. Dashed line represents the limit of detection. (B) Confocal immunofluorescence image of S. pneumoniae colonizing NALT tissue 3 days post-inoculation. The green bar bell indicates the lumen of the nasopharynx, the pink bar bell indicates the epithelial monolayer, and the blue bar bell indicates the cells within the NALT. S. pnuemoniae were visualized via fluorescently-conjugated antibody (green) near the surface of the NALT (blue) and were particularly apparent in the mucus layer (red).

Mentions: Pneumococcal colonization of the murine nasal cavity has been previously demonstrated [10,11]. We colonized BALB/c mice intranasally with 2 × 108 Type 2 pneumococci and monitored carriage over a six-week period. At each time point, mice from both infected and mocked-infected groups were sacrificed and NALT tissue was excised as described [12]. NALT was chosen for host transcriptional analysis because it is the functional homolog of human tonsils and adenoids, which are thought to be important local inductive and effector sites for both mucosal and systemic responses to pneumococcal carriage [6,13,14]. The remainder of the head was homogenized in PBS, which was then serially diluted and plated to determine viable counts of the pneumococcus in the nasopharyngeal cavity. Figure 1A shows the pneumococcal load in the nasopharynx over a six-week period. Viable counts decreased approximately three logs over a three week period, and the bacteria were cleared by six-weeks post infection, as we were unable to detect viable pneumococci in the samples. In addition, fluorescence confocal microscopy of nasal tissue allowed us to visualize pneumococci at the NALT. Figure 1B shows a sagittal section through the NALT isolated from a mouse that had been inoculated with S. pneumoniae three days prior. Using a fluorescently conjugated antibody directed against the strain of S. pneumoniae used in these studies, we detected bacteria on the surface of the NALT.


Streptococcus pneumoniae nasopharyngeal colonization induces type I interferons and interferon-induced gene expression.

Joyce EA, Popper SJ, Falkow S - BMC Genomics (2009)

S. pneumoniae colonizes the nasopharynx of mice over a 6 week period. (A) Viable cell counts from head cavities (post-NALT excision) of infected mice. Open circles represent viable counts from a single mouse. Solid lines represent the geometric mean of CFUs/head for each day. Dashed line represents the limit of detection. (B) Confocal immunofluorescence image of S. pneumoniae colonizing NALT tissue 3 days post-inoculation. The green bar bell indicates the lumen of the nasopharynx, the pink bar bell indicates the epithelial monolayer, and the blue bar bell indicates the cells within the NALT. S. pnuemoniae were visualized via fluorescently-conjugated antibody (green) near the surface of the NALT (blue) and were particularly apparent in the mucus layer (red).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC2743716&req=5

Figure 1: S. pneumoniae colonizes the nasopharynx of mice over a 6 week period. (A) Viable cell counts from head cavities (post-NALT excision) of infected mice. Open circles represent viable counts from a single mouse. Solid lines represent the geometric mean of CFUs/head for each day. Dashed line represents the limit of detection. (B) Confocal immunofluorescence image of S. pneumoniae colonizing NALT tissue 3 days post-inoculation. The green bar bell indicates the lumen of the nasopharynx, the pink bar bell indicates the epithelial monolayer, and the blue bar bell indicates the cells within the NALT. S. pnuemoniae were visualized via fluorescently-conjugated antibody (green) near the surface of the NALT (blue) and were particularly apparent in the mucus layer (red).
Mentions: Pneumococcal colonization of the murine nasal cavity has been previously demonstrated [10,11]. We colonized BALB/c mice intranasally with 2 × 108 Type 2 pneumococci and monitored carriage over a six-week period. At each time point, mice from both infected and mocked-infected groups were sacrificed and NALT tissue was excised as described [12]. NALT was chosen for host transcriptional analysis because it is the functional homolog of human tonsils and adenoids, which are thought to be important local inductive and effector sites for both mucosal and systemic responses to pneumococcal carriage [6,13,14]. The remainder of the head was homogenized in PBS, which was then serially diluted and plated to determine viable counts of the pneumococcus in the nasopharyngeal cavity. Figure 1A shows the pneumococcal load in the nasopharynx over a six-week period. Viable counts decreased approximately three logs over a three week period, and the bacteria were cleared by six-weeks post infection, as we were unable to detect viable pneumococci in the samples. In addition, fluorescence confocal microscopy of nasal tissue allowed us to visualize pneumococci at the NALT. Figure 1B shows a sagittal section through the NALT isolated from a mouse that had been inoculated with S. pneumoniae three days prior. Using a fluorescently conjugated antibody directed against the strain of S. pneumoniae used in these studies, we detected bacteria on the surface of the NALT.

Bottom Line: Subsequent to this initial inflammatory response, we observed increases in transcripts associated with T cell development and activation, as well as wounding, basement membrane remodeling, and cell proliferation.Examining multiple time points over six weeks of colonization demonstrated that asymptomatic carriage stimulates a dynamic host response characterized by temporal waves with distinct biological programs.Our data suggest that the usual response to the presence of the pneumocccus is an initial controlled inflammatory response followed by activation of host physiological processes such as response to wounding, basement membrane remodeling, and increasing cellular numbers that ultimately allow the host to maintain an intact epithelium and eventually mount a preventive adaptive immune response.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94131, USA. ejoyce@stanford.edu

ABSTRACT

Background: We employed DNA microarray technology to investigate the host response to Streptococcus pneumoniae in a mouse model of asymptomatic carriage. Over a period of six weeks, we profiled transcript abundance and complexity in the Nasal Associated Lymphoid Tissue (NALT) to identify genes whose expression differed between pneumococcal-colonized and uncolonized states.

Results: Colonization with S. pneumoniae altered the expression of hundreds of genes over the course of the study, demonstrating that carriage is a dynamic process characterized by increased expression of a set of early inflammatory responses, including induction of a Type I Interferon response, and the production of several antimicrobial factors. Subsequent to this initial inflammatory response, we observed increases in transcripts associated with T cell development and activation, as well as wounding, basement membrane remodeling, and cell proliferation. Our analysis suggests that microbial colonization induced expression of genes encoding components critical for controlling JAK/STAT signaling, including stat1, stat2, socs3, and mapk1, as well as induction of several Type I Interferon-inducible genes and other antimicrobial factors at the earliest stages of colonization.

Conclusion: Examining multiple time points over six weeks of colonization demonstrated that asymptomatic carriage stimulates a dynamic host response characterized by temporal waves with distinct biological programs. Our data suggest that the usual response to the presence of the pneumocccus is an initial controlled inflammatory response followed by activation of host physiological processes such as response to wounding, basement membrane remodeling, and increasing cellular numbers that ultimately allow the host to maintain an intact epithelium and eventually mount a preventive adaptive immune response.

Show MeSH
Related in: MedlinePlus