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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

Anti-inflammatory effect of F. tularensis LPS on mouse PECs is IFN-γ and IL-10 dependent.PECs from naïve and IL-10 genetically deficient C57BL/6 mice were obtained and resuspended in cell culture media. PECs were cultured in a 96-well plate at 2 x 105 cells/well with either Ft-LPS or E. coli-LPS at 1 ng/mL in the presence or absence of recombinant IFN-γ at 100 U/ml. Cells cultured with PBS were used as a control. The cytokine production was 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.g004: Anti-inflammatory effect of F. tularensis LPS on mouse PECs is IFN-γ and IL-10 dependent.PECs from naïve and IL-10 genetically deficient C57BL/6 mice were obtained and resuspended in cell culture media. PECs were cultured in a 96-well plate at 2 x 105 cells/well with either Ft-LPS or E. coli-LPS at 1 ng/mL in the presence or absence of recombinant IFN-γ at 100 U/ml. Cells cultured with PBS were used as a control. The cytokine production was 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: Several studies have shown that IL-10 negatively regulates synthesis of IFN-γ as well as synthesis of other pro-inflammatory cytokines in monocytes and macrophages [29–31]. Due to the increased levels of IL-10 synthesis after incubation of PECs with F. tularensis LPS it was of interest to examine whether this up-regulation correlates with the decrease in TNF-α and IL-12p70 secretion. To investigate this, PECs from C57BL/6 wild-type and IL-10 genetically deficient mice were incubated with F. tularensis LPS or E. coli LPS. As previously observed, in the absence of endogenous IFN-γ, F. tularensis LPS portrayed anti-inflammatory properties via up-regulation of IL-10 production and decrease in the synthesis of IL-12p70 and TNF-α by the PECs. Interestingly, these results were reversed by the addition of exogenous IFN-γ (Fig 4A–4C). Lack of endogenous IL-10, in turn, resulted in an elevated synthesis of IL-12p70 (Fig 4D) and TNF-α (Fig 4E). These results indicate that increased levels of IL-10 synthesis is one of the mechanisms responsible for suppressing the protective pro-inflammatory cytokines such as TNF-α and IL-12p70 leading to an overall suppression of the Th1 response and reduced IFN-γ levels in the early stages of F. tularensis infection. In fact, the importance of IFN-γ during F. tularensis infection was reported by Rawool and colleagues [19], who observed a significant drop in survival rate in the mAb-iFt immunized IFN-γ-/- mice compared to the wild type control.


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)

Anti-inflammatory effect of F. tularensis LPS on mouse PECs is IFN-γ and IL-10 dependent.PECs from naïve and IL-10 genetically deficient C57BL/6 mice were obtained and resuspended in cell culture media. PECs were cultured in a 96-well plate at 2 x 105 cells/well with either Ft-LPS or E. coli-LPS at 1 ng/mL in the presence or absence of recombinant IFN-γ at 100 U/ml. Cells cultured with PBS were used as a control. The cytokine production was 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.g004: Anti-inflammatory effect of F. tularensis LPS on mouse PECs is IFN-γ and IL-10 dependent.PECs from naïve and IL-10 genetically deficient C57BL/6 mice were obtained and resuspended in cell culture media. PECs were cultured in a 96-well plate at 2 x 105 cells/well with either Ft-LPS or E. coli-LPS at 1 ng/mL in the presence or absence of recombinant IFN-γ at 100 U/ml. Cells cultured with PBS were used as a control. The cytokine production was 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: Several studies have shown that IL-10 negatively regulates synthesis of IFN-γ as well as synthesis of other pro-inflammatory cytokines in monocytes and macrophages [29–31]. Due to the increased levels of IL-10 synthesis after incubation of PECs with F. tularensis LPS it was of interest to examine whether this up-regulation correlates with the decrease in TNF-α and IL-12p70 secretion. To investigate this, PECs from C57BL/6 wild-type and IL-10 genetically deficient mice were incubated with F. tularensis LPS or E. coli LPS. As previously observed, in the absence of endogenous IFN-γ, F. tularensis LPS portrayed anti-inflammatory properties via up-regulation of IL-10 production and decrease in the synthesis of IL-12p70 and TNF-α by the PECs. Interestingly, these results were reversed by the addition of exogenous IFN-γ (Fig 4A–4C). Lack of endogenous IL-10, in turn, resulted in an elevated synthesis of IL-12p70 (Fig 4D) and TNF-α (Fig 4E). These results indicate that increased levels of IL-10 synthesis is one of the mechanisms responsible for suppressing the protective pro-inflammatory cytokines such as TNF-α and IL-12p70 leading to an overall suppression of the Th1 response and reduced IFN-γ levels in the early stages of F. tularensis infection. In fact, the importance of IFN-γ during F. tularensis infection was reported by Rawool and colleagues [19], who observed a significant drop in survival rate in the mAb-iFt immunized IFN-γ-/- mice compared to the wild type control.

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