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Interferon-γ from Brain Leukocytes Enhances Meningitis by Type 4 Streptococcus pneumoniae.

Pettini E, Fiorino F, Cuppone AM, Iannelli F, Medaglini D, Pozzi G - Front Microbiol (2015)

Bottom Line: The amount of lymphocytes, NK cells, neutrophils, monocytes and macrophages in the brain increased 48 h post infection.Pro-inflammatory cytokines such as IL-1β and TNF-α, and TLR2 were also upregulated.This study shows that IFN-γ produced during meningitis by type 4 S. pneumoniae enhances bacterial pathogenesis exerting a negative effect on the disease outcome.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio di Microbiologia Molecolare e Biotecnologia, Dipartimento di Biotecnologie Mediche, Università degli Studi di Siena Siena, Italy.

ABSTRACT
Streptococcus pneumoniae is the leading cause of bacterial meningitis. Pneumococcal meningitis is a life-threatening disease with high rates of mortality and neurological sequelae. Immune targeting of S. pneumoniae is essential for clearance of infection; however, within the brain, the induced inflammatory response contributes to pathogenesis. In this study we investigate the local inflammatory response and the role of IFN-γ in a murine model of pneumococcal meningitis induced by intracranial injection of type 4 S. pneumoniae. Lymphoid and myeloid cell populations involved in meningitis, as well as cytokine gene expression, were investigated after infection. Animals were treated with a monoclonal antibody specific for murine IFN-γ to evaluate its role in animal survival. Intracranial inoculation of 3 × 10(4) colony-forming units of type 4 strain TIGR4 caused 75% of mice to develop meningitis within 4 days. The amount of lymphocytes, NK cells, neutrophils, monocytes and macrophages in the brain increased 48 h post infection. IFN-γ mRNA levels were about 240-fold higher in brains of infected mice compared to controls. Pro-inflammatory cytokines such as IL-1β and TNF-α, and TLR2 were also upregulated. In vivo treatment with anti-IFN-γ antibody increased survival of infected mice. This study shows that IFN-γ produced during meningitis by type 4 S. pneumoniae enhances bacterial pathogenesis exerting a negative effect on the disease outcome.

No MeSH data available.


Related in: MedlinePlus

Cytokine and TLR gene expression in the mouse brain 48 h post infection. The relative IFN-γ, TNF-α, IL-1β, IL-10, TLR2, and TLR4 gene expression was determined by RT-PCR in brains of C57BL/6J mice infected by the intracranial route with 3 × 104 CFU of S. pneumoniae TIGR4 (filled circles). As control, a group of mice was injected with bacteria growth medium (open circles). All animals were sacrificed 48 h post infection. Symbols represent individual mice and bars represent the geometric mean of each group. Data are from two independent experiments with 4–6 mice/group. Statistical analysis was performed on log-transformed data between infected and control group using the two tailed Mann-Whitney test. Asterisks indicate statistical significance (*P ≤ 0.05; ***P ≤ 0.001).
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Figure 2: Cytokine and TLR gene expression in the mouse brain 48 h post infection. The relative IFN-γ, TNF-α, IL-1β, IL-10, TLR2, and TLR4 gene expression was determined by RT-PCR in brains of C57BL/6J mice infected by the intracranial route with 3 × 104 CFU of S. pneumoniae TIGR4 (filled circles). As control, a group of mice was injected with bacteria growth medium (open circles). All animals were sacrificed 48 h post infection. Symbols represent individual mice and bars represent the geometric mean of each group. Data are from two independent experiments with 4–6 mice/group. Statistical analysis was performed on log-transformed data between infected and control group using the two tailed Mann-Whitney test. Asterisks indicate statistical significance (*P ≤ 0.05; ***P ≤ 0.001).

Mentions: Mice challenged with S. pneumoniae TIGR4 were sacrificed 48 h post infection (n = 4–6 mice/group in two independent experiments). Brains were collected and mRNAs were extracted in order to evaluate gene expression of cytokines and TLRs during meningitis (Figure 2). Interestingly, intracranial infection with 3 × 104 CFU/mouse of TIGR4 induced a significant IFN-γ gene expression with an increase of about 240-folds compared to the control group injected with bacterial growth medium (Figure 2; P < 0.001). Also the gene expression of inflammatory cytokines such as TNF-α and IL-1β in brains of infected mice showed a considerable relative increase of about 70- and 140-folds, respectively, compared to the control group (P < 0.001, Figure 2). Gene expression of the regulatory cytokine IL-10 increased of about 20-folds (P < 0.001, Figure 2). On the contrary, no differences between infected and control mice was observed for TGF-β gene expression at this time point (data not shown). The analysis of TLR gene expression during S. pneumoniae meningitis showed a significant increase of about 10-folds (P < 0.001) and 3-folds (P < 0.05) for TLR2 and TLR4, respectively (Figure 2), while no statistically significant increase was observed for TLR9 (data not shown).


Interferon-γ from Brain Leukocytes Enhances Meningitis by Type 4 Streptococcus pneumoniae.

Pettini E, Fiorino F, Cuppone AM, Iannelli F, Medaglini D, Pozzi G - Front Microbiol (2015)

Cytokine and TLR gene expression in the mouse brain 48 h post infection. The relative IFN-γ, TNF-α, IL-1β, IL-10, TLR2, and TLR4 gene expression was determined by RT-PCR in brains of C57BL/6J mice infected by the intracranial route with 3 × 104 CFU of S. pneumoniae TIGR4 (filled circles). As control, a group of mice was injected with bacteria growth medium (open circles). All animals were sacrificed 48 h post infection. Symbols represent individual mice and bars represent the geometric mean of each group. Data are from two independent experiments with 4–6 mice/group. Statistical analysis was performed on log-transformed data between infected and control group using the two tailed Mann-Whitney test. Asterisks indicate statistical significance (*P ≤ 0.05; ***P ≤ 0.001).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664635&req=5

Figure 2: Cytokine and TLR gene expression in the mouse brain 48 h post infection. The relative IFN-γ, TNF-α, IL-1β, IL-10, TLR2, and TLR4 gene expression was determined by RT-PCR in brains of C57BL/6J mice infected by the intracranial route with 3 × 104 CFU of S. pneumoniae TIGR4 (filled circles). As control, a group of mice was injected with bacteria growth medium (open circles). All animals were sacrificed 48 h post infection. Symbols represent individual mice and bars represent the geometric mean of each group. Data are from two independent experiments with 4–6 mice/group. Statistical analysis was performed on log-transformed data between infected and control group using the two tailed Mann-Whitney test. Asterisks indicate statistical significance (*P ≤ 0.05; ***P ≤ 0.001).
Mentions: Mice challenged with S. pneumoniae TIGR4 were sacrificed 48 h post infection (n = 4–6 mice/group in two independent experiments). Brains were collected and mRNAs were extracted in order to evaluate gene expression of cytokines and TLRs during meningitis (Figure 2). Interestingly, intracranial infection with 3 × 104 CFU/mouse of TIGR4 induced a significant IFN-γ gene expression with an increase of about 240-folds compared to the control group injected with bacterial growth medium (Figure 2; P < 0.001). Also the gene expression of inflammatory cytokines such as TNF-α and IL-1β in brains of infected mice showed a considerable relative increase of about 70- and 140-folds, respectively, compared to the control group (P < 0.001, Figure 2). Gene expression of the regulatory cytokine IL-10 increased of about 20-folds (P < 0.001, Figure 2). On the contrary, no differences between infected and control mice was observed for TGF-β gene expression at this time point (data not shown). The analysis of TLR gene expression during S. pneumoniae meningitis showed a significant increase of about 10-folds (P < 0.001) and 3-folds (P < 0.05) for TLR2 and TLR4, respectively (Figure 2), while no statistically significant increase was observed for TLR9 (data not shown).

Bottom Line: The amount of lymphocytes, NK cells, neutrophils, monocytes and macrophages in the brain increased 48 h post infection.Pro-inflammatory cytokines such as IL-1β and TNF-α, and TLR2 were also upregulated.This study shows that IFN-γ produced during meningitis by type 4 S. pneumoniae enhances bacterial pathogenesis exerting a negative effect on the disease outcome.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio di Microbiologia Molecolare e Biotecnologia, Dipartimento di Biotecnologie Mediche, Università degli Studi di Siena Siena, Italy.

ABSTRACT
Streptococcus pneumoniae is the leading cause of bacterial meningitis. Pneumococcal meningitis is a life-threatening disease with high rates of mortality and neurological sequelae. Immune targeting of S. pneumoniae is essential for clearance of infection; however, within the brain, the induced inflammatory response contributes to pathogenesis. In this study we investigate the local inflammatory response and the role of IFN-γ in a murine model of pneumococcal meningitis induced by intracranial injection of type 4 S. pneumoniae. Lymphoid and myeloid cell populations involved in meningitis, as well as cytokine gene expression, were investigated after infection. Animals were treated with a monoclonal antibody specific for murine IFN-γ to evaluate its role in animal survival. Intracranial inoculation of 3 × 10(4) colony-forming units of type 4 strain TIGR4 caused 75% of mice to develop meningitis within 4 days. The amount of lymphocytes, NK cells, neutrophils, monocytes and macrophages in the brain increased 48 h post infection. IFN-γ mRNA levels were about 240-fold higher in brains of infected mice compared to controls. Pro-inflammatory cytokines such as IL-1β and TNF-α, and TLR2 were also upregulated. In vivo treatment with anti-IFN-γ antibody increased survival of infected mice. This study shows that IFN-γ produced during meningitis by type 4 S. pneumoniae enhances bacterial pathogenesis exerting a negative effect on the disease outcome.

No MeSH data available.


Related in: MedlinePlus