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Targeting of a Fixed Bacterial Immunogen to Fc Receptors Reverses the Anti-Inflammatory Properties of the Gram-Negative Bacterium, Francisella tularensis, during the Early Stages of Infection.

Babadjanova Z, Wiedinger K, Gosselin EJ, Bitsaktsis C - PLoS ONE (2015)

Bottom Line: It is well established that IL-10 has the ability to inhibit robust antigen presentation by dendritic cells and macrophages, thus suppressing the generation of protective immunity.The pathogenesis of F. tularensis is not fully understood, and research has failed to develop an effective vaccine to this date.These results provide important insight for further understanding the protective immune mechanisms generated when targeting immunogens to Fc receptors.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Seton Hall University, South Orange, New Jersey, United States of America.

ABSTRACT
Production of pro-inflammatory cytokines by innate immune cells at the early stages of bacterial infection is important for host protection against the pathogen. Many intracellular bacteria, including Francisella tularensis, the agent of tularemia, utilize the anti-inflammatory cytokine IL-10, to evade the host immune response. It is well established that IL-10 has the ability to inhibit robust antigen presentation by dendritic cells and macrophages, thus suppressing the generation of protective immunity. The pathogenesis of F. tularensis is not fully understood, and research has failed to develop an effective vaccine to this date. In the current study, we hypothesized that F. tularensis polarizes antigen presenting cells during the early stages of infection towards an anti-inflammatory status characterized by increased synthesis of IL-10 and decreased production of IL-12p70 and TNF-α in an IFN-ɣ-dependent fashion. In addition, F. tularensis drives an alternative activation of alveolar macrophages within the first 48 hours post-infection, thus allowing the bacterium to avoid protective immunity. Furthermore, we demonstrate that targeting inactivated F. tularensis (iFt) to Fcγ receptors (FcɣRs) via intranasal immunization with mAb-iFt complexes, a proven vaccine strategy in our laboratories, reverses the anti-inflammatory effects of the bacterium on macrophages by down-regulating production of IL-10. More specifically, we observed that targeting of iFt to FcγRs enhances the classical activation of macrophages not only within the respiratory mucosa, but also systemically, at the early stages of infection. These results provide important insight for further understanding the protective immune mechanisms generated when targeting immunogens to Fc receptors.

No MeSH data available.


Related in: MedlinePlus

tularensis LPS contributes to the anti-inflammatory properties of F. tularensis LVS during the early stages of infection.F. PECs from C57BL/6 mice were obtained and cultured in a 96-well plate at 2 x 105 cells/well in the presence or absence of either Ft-LPS or E. coli-LPS at 1 ng/mL, 10 ng/mL and 20 ng/ml. Cells incubated with PBS were used as a control. Levels of IL-12p70, TNF-α and IL-10 were measured using BD Biosciences Cytometric Bead Array (CBA) following vendor instructions. Results are representative of three independent experiments. (*) P-value < 0.1; (**) P-value < 0.05; bars represent SD.
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pone.0129981.g003: tularensis LPS contributes to the anti-inflammatory properties of F. tularensis LVS during the early stages of infection.F. PECs from C57BL/6 mice were obtained and cultured in a 96-well plate at 2 x 105 cells/well in the presence or absence of either Ft-LPS or E. coli-LPS at 1 ng/mL, 10 ng/mL and 20 ng/ml. Cells incubated with PBS were used as a control. Levels of IL-12p70, TNF-α and IL-10 were measured using BD Biosciences Cytometric Bead Array (CBA) following vendor instructions. Results are representative of three independent experiments. (*) P-value < 0.1; (**) P-value < 0.05; bars represent SD.

Mentions: It is well established that F. tularensis LPS is structurally different from other intracellular bacteria and elicits a subdued inflammatory response in the initial stages of infection, which otherwise are critical in controlling bacterial burden [21–24]. To investigate the effect F. tularensis LPS on the cytokine profile produced by PECs, we measured the levels of IL-12p70, TNF-α and IL-10 in the supernatants of PECs from naïve C57BL/6 mice cultured with various concentrations of F. tularensis LPS. As expected, incubation with F. tularensis LPS at different concentrations triggered significantly lower levels of IL-12p70 (Fig 3A) and TNF-α (Fig 3B) secretion compared to E. coli LPS (positive control). In contrast, IL-10 production was elevated in the presence of F.tularensis LPS (Fig 3C). This observation not only confirms the low endotoxic activity of F. tularensis LPS but also indicates that it down-regulates Th1 cell mediated inflammatory responses via up-regulation of IL-10 and down-regulation of IL-12p70 and TNF-α.


Targeting of a Fixed Bacterial Immunogen to Fc Receptors Reverses the Anti-Inflammatory Properties of the Gram-Negative Bacterium, Francisella tularensis, during the Early Stages of Infection.

Babadjanova Z, Wiedinger K, Gosselin EJ, Bitsaktsis C - PLoS ONE (2015)

tularensis LPS contributes to the anti-inflammatory properties of F. tularensis LVS during the early stages of infection.F. PECs from C57BL/6 mice were obtained and cultured in a 96-well plate at 2 x 105 cells/well in the presence or absence of either Ft-LPS or E. coli-LPS at 1 ng/mL, 10 ng/mL and 20 ng/ml. Cells incubated with PBS were used as a control. Levels of IL-12p70, TNF-α and IL-10 were measured using BD Biosciences Cytometric Bead Array (CBA) following vendor instructions. Results are representative of three independent experiments. (*) P-value < 0.1; (**) P-value < 0.05; bars represent SD.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4482730&req=5

pone.0129981.g003: tularensis LPS contributes to the anti-inflammatory properties of F. tularensis LVS during the early stages of infection.F. PECs from C57BL/6 mice were obtained and cultured in a 96-well plate at 2 x 105 cells/well in the presence or absence of either Ft-LPS or E. coli-LPS at 1 ng/mL, 10 ng/mL and 20 ng/ml. Cells incubated with PBS were used as a control. Levels of IL-12p70, TNF-α and IL-10 were measured using BD Biosciences Cytometric Bead Array (CBA) following vendor instructions. Results are representative of three independent experiments. (*) P-value < 0.1; (**) P-value < 0.05; bars represent SD.
Mentions: It is well established that F. tularensis LPS is structurally different from other intracellular bacteria and elicits a subdued inflammatory response in the initial stages of infection, which otherwise are critical in controlling bacterial burden [21–24]. To investigate the effect F. tularensis LPS on the cytokine profile produced by PECs, we measured the levels of IL-12p70, TNF-α and IL-10 in the supernatants of PECs from naïve C57BL/6 mice cultured with various concentrations of F. tularensis LPS. As expected, incubation with F. tularensis LPS at different concentrations triggered significantly lower levels of IL-12p70 (Fig 3A) and TNF-α (Fig 3B) secretion compared to E. coli LPS (positive control). In contrast, IL-10 production was elevated in the presence of F.tularensis LPS (Fig 3C). This observation not only confirms the low endotoxic activity of F. tularensis LPS but also indicates that it down-regulates Th1 cell mediated inflammatory responses via up-regulation of IL-10 and down-regulation of IL-12p70 and TNF-α.

Bottom Line: It is well established that IL-10 has the ability to inhibit robust antigen presentation by dendritic cells and macrophages, thus suppressing the generation of protective immunity.The pathogenesis of F. tularensis is not fully understood, and research has failed to develop an effective vaccine to this date.These results provide important insight for further understanding the protective immune mechanisms generated when targeting immunogens to Fc receptors.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Seton Hall University, South Orange, New Jersey, United States of America.

ABSTRACT
Production of pro-inflammatory cytokines by innate immune cells at the early stages of bacterial infection is important for host protection against the pathogen. Many intracellular bacteria, including Francisella tularensis, the agent of tularemia, utilize the anti-inflammatory cytokine IL-10, to evade the host immune response. It is well established that IL-10 has the ability to inhibit robust antigen presentation by dendritic cells and macrophages, thus suppressing the generation of protective immunity. The pathogenesis of F. tularensis is not fully understood, and research has failed to develop an effective vaccine to this date. In the current study, we hypothesized that F. tularensis polarizes antigen presenting cells during the early stages of infection towards an anti-inflammatory status characterized by increased synthesis of IL-10 and decreased production of IL-12p70 and TNF-α in an IFN-ɣ-dependent fashion. In addition, F. tularensis drives an alternative activation of alveolar macrophages within the first 48 hours post-infection, thus allowing the bacterium to avoid protective immunity. Furthermore, we demonstrate that targeting inactivated F. tularensis (iFt) to Fcγ receptors (FcɣRs) via intranasal immunization with mAb-iFt complexes, a proven vaccine strategy in our laboratories, reverses the anti-inflammatory effects of the bacterium on macrophages by down-regulating production of IL-10. More specifically, we observed that targeting of iFt to FcγRs enhances the classical activation of macrophages not only within the respiratory mucosa, but also systemically, at the early stages of infection. These results provide important insight for further understanding the protective immune mechanisms generated when targeting immunogens to Fc receptors.

No MeSH data available.


Related in: MedlinePlus