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Downmodulation of vaccine-induced immunity and protection against the intracellular bacterium Francisella tularensis by the inhibitory receptor FcγRIIB.

Franz BJ, Li Y, Bitsaktsis C, Iglesias BV, Pham G, Sunagar R, Kumar S, Gosselin EJ - J Immunol Res (2015)

Bottom Line: Ft-specific IgA in serum and bronchial alveolar lavage, as well as IFN-γ, IL-10, and TNF-α production by splenocytes harvested from iFt-immunized FcγRIIB KO, were also significantly elevated.Thus, these studies demonstrate for the first time the ability of FcγRIIB to regulate vaccine-induced IgA production and downmodulate immunity and protection.The immune mechanisms behind the above observations and their potential impact on vaccine development are discussed.

View Article: PubMed Central - PubMed

Affiliation: Center for Immunology and Microbial Disease, Albany Medical College, Albany, NY 12208, USA.

ABSTRACT
Fc gamma receptor IIB (FcγRIIB) is the only Fc gamma receptor (FcγR) which negatively regulates the immune response, when engaged by antigen- (Ag-) antibody (Ab) complexes. Thus, the generation of Ag-specific IgG in response to infection or immunization has the potential to downmodulate immune protection against infection. Therefore, we sought to determine the impact of FcγRIIB on immune protection against Francisella tularensis (Ft), a Category A biothreat agent. We utilized inactivated Ft (iFt) as an immunogen. Naïve and iFt-immunized FcγRIIB knockout (KO) or wildtype (WT) mice were challenged with Ft-live vaccine strain (LVS). While no significant difference in survival between naïve FcγRIIB KO versus WT mice was observed, iFt-immunized FcγRIIB KO mice were significantly better protected than iFt-immunized WT mice. Ft-specific IgA in serum and bronchial alveolar lavage, as well as IFN-γ, IL-10, and TNF-α production by splenocytes harvested from iFt-immunized FcγRIIB KO, were also significantly elevated. In addition, iFt-immunized FcγRIIB KO mice exhibited a reduction in proinflammatory cytokine levels in vivo at 5 days after challenge, which correlates with increased survival following Ft-LVS challenge in published studies. Thus, these studies demonstrate for the first time the ability of FcγRIIB to regulate vaccine-induced IgA production and downmodulate immunity and protection. The immune mechanisms behind the above observations and their potential impact on vaccine development are discussed.

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iFt-immunized FcγRIIB KO mice exhibit increased protection against a lethal Ft-LVS challenge as compared to their WT counterparts. WT C57BL/6J and FcγRIIB KO mice were immunized i.n. with 20 μL of PBS (vehicle) or 2 × 107 iFt-organisms in 20 μL of PBS on day 0 and boosted on day 21. On day 35 mice were challenged i.n. with approximately 4 × LD50 (a) or 16 × LD50 (b) of Ft-LVS. Survival was then monitored for 21 to 25 days. Panel (a) represents between 12 and 14 mice/group while panel (b) represents between 17 and 20 mice/group. Statistical analysis was determined by a contingency table analysis and two-tailed Fisher's exact test on survival at day 21. ∗∗P < 0.01. In addition, bacterial burden in the lungs of challenged mice was also determined. WT C57BL/6J and FcγRIIB KO mice were immunized i.n. with 20 μL of PBS (vehicle) or 2 × 107 iFt-organisms in 20 μL of PBS on day 0 and boosted on day 21. On day 35 mice were given a sublethal challenge i.n. with approximately 0.4 × LD50 of Ft-LVS. Five days after challenge lungs were collected, homogenized, and plated on chocolate agar to determine bacterial burden as described in Section 2. Each symbol represents a single mouse. Statistical analysis of the tissue bacterial burden was done via a nonparametric one-way ANOVA (Kruskal-Wallis test) coupled with a Dunn's multiple comparison after test. While there appeared to be a substantial reduction in bacterial burden in the majority of iFt-immunized FcγRIIB KO versus WT mice, the difference was not significant based on this analysis.
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fig3: iFt-immunized FcγRIIB KO mice exhibit increased protection against a lethal Ft-LVS challenge as compared to their WT counterparts. WT C57BL/6J and FcγRIIB KO mice were immunized i.n. with 20 μL of PBS (vehicle) or 2 × 107 iFt-organisms in 20 μL of PBS on day 0 and boosted on day 21. On day 35 mice were challenged i.n. with approximately 4 × LD50 (a) or 16 × LD50 (b) of Ft-LVS. Survival was then monitored for 21 to 25 days. Panel (a) represents between 12 and 14 mice/group while panel (b) represents between 17 and 20 mice/group. Statistical analysis was determined by a contingency table analysis and two-tailed Fisher's exact test on survival at day 21. ∗∗P < 0.01. In addition, bacterial burden in the lungs of challenged mice was also determined. WT C57BL/6J and FcγRIIB KO mice were immunized i.n. with 20 μL of PBS (vehicle) or 2 × 107 iFt-organisms in 20 μL of PBS on day 0 and boosted on day 21. On day 35 mice were given a sublethal challenge i.n. with approximately 0.4 × LD50 of Ft-LVS. Five days after challenge lungs were collected, homogenized, and plated on chocolate agar to determine bacterial burden as described in Section 2. Each symbol represents a single mouse. Statistical analysis of the tissue bacterial burden was done via a nonparametric one-way ANOVA (Kruskal-Wallis test) coupled with a Dunn's multiple comparison after test. While there appeared to be a substantial reduction in bacterial burden in the majority of iFt-immunized FcγRIIB KO versus WT mice, the difference was not significant based on this analysis.

Mentions: Given the integral role Ag-specific IgG plays in FcγRIIB-mediated immune modulation and the absence of increased levels of Ft-specific IgG in iFt-immunized FcγRIIB KO versus WT mice (Figure 2), we sought to determine whether there would be any impact of the presence versus absence of FcγRIIB on protection of iFt-immunized mice. Despite the lack of a significant increased Ft-specific IgG in FcγRIIB KO versus WT mice and in contrast to studies using naïve mice (Figure 1), at a challenge dose of 4 × LD50, the survival of iFt-immunized FcγRIIB KO mice was significantly better than that of WT mice (100% versus 50% resp.) (Figure 3(a)). Similar to that observed in naïve mice (Figure 1), there was no significant difference in survival between FcγRIIB KO and WT mice immunized with PBS (Figure 3(a)). When the challenge dose was increased to 16 × LD50, the overall level of survival decreased. However, a slight increase in the survival of iFt-immunized FcγRIIB KO versus WT mice was still apparent (Figure 3(b)). The increased survival also correlated with a reduction in the median bacterial burden in iFt-immunized FcγRIIB KO (Figure 3(c)).


Downmodulation of vaccine-induced immunity and protection against the intracellular bacterium Francisella tularensis by the inhibitory receptor FcγRIIB.

Franz BJ, Li Y, Bitsaktsis C, Iglesias BV, Pham G, Sunagar R, Kumar S, Gosselin EJ - J Immunol Res (2015)

iFt-immunized FcγRIIB KO mice exhibit increased protection against a lethal Ft-LVS challenge as compared to their WT counterparts. WT C57BL/6J and FcγRIIB KO mice were immunized i.n. with 20 μL of PBS (vehicle) or 2 × 107 iFt-organisms in 20 μL of PBS on day 0 and boosted on day 21. On day 35 mice were challenged i.n. with approximately 4 × LD50 (a) or 16 × LD50 (b) of Ft-LVS. Survival was then monitored for 21 to 25 days. Panel (a) represents between 12 and 14 mice/group while panel (b) represents between 17 and 20 mice/group. Statistical analysis was determined by a contingency table analysis and two-tailed Fisher's exact test on survival at day 21. ∗∗P < 0.01. In addition, bacterial burden in the lungs of challenged mice was also determined. WT C57BL/6J and FcγRIIB KO mice were immunized i.n. with 20 μL of PBS (vehicle) or 2 × 107 iFt-organisms in 20 μL of PBS on day 0 and boosted on day 21. On day 35 mice were given a sublethal challenge i.n. with approximately 0.4 × LD50 of Ft-LVS. Five days after challenge lungs were collected, homogenized, and plated on chocolate agar to determine bacterial burden as described in Section 2. Each symbol represents a single mouse. Statistical analysis of the tissue bacterial burden was done via a nonparametric one-way ANOVA (Kruskal-Wallis test) coupled with a Dunn's multiple comparison after test. While there appeared to be a substantial reduction in bacterial burden in the majority of iFt-immunized FcγRIIB KO versus WT mice, the difference was not significant based on this analysis.
© Copyright Policy - open-access
Related In: Results  -  Collection

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fig3: iFt-immunized FcγRIIB KO mice exhibit increased protection against a lethal Ft-LVS challenge as compared to their WT counterparts. WT C57BL/6J and FcγRIIB KO mice were immunized i.n. with 20 μL of PBS (vehicle) or 2 × 107 iFt-organisms in 20 μL of PBS on day 0 and boosted on day 21. On day 35 mice were challenged i.n. with approximately 4 × LD50 (a) or 16 × LD50 (b) of Ft-LVS. Survival was then monitored for 21 to 25 days. Panel (a) represents between 12 and 14 mice/group while panel (b) represents between 17 and 20 mice/group. Statistical analysis was determined by a contingency table analysis and two-tailed Fisher's exact test on survival at day 21. ∗∗P < 0.01. In addition, bacterial burden in the lungs of challenged mice was also determined. WT C57BL/6J and FcγRIIB KO mice were immunized i.n. with 20 μL of PBS (vehicle) or 2 × 107 iFt-organisms in 20 μL of PBS on day 0 and boosted on day 21. On day 35 mice were given a sublethal challenge i.n. with approximately 0.4 × LD50 of Ft-LVS. Five days after challenge lungs were collected, homogenized, and plated on chocolate agar to determine bacterial burden as described in Section 2. Each symbol represents a single mouse. Statistical analysis of the tissue bacterial burden was done via a nonparametric one-way ANOVA (Kruskal-Wallis test) coupled with a Dunn's multiple comparison after test. While there appeared to be a substantial reduction in bacterial burden in the majority of iFt-immunized FcγRIIB KO versus WT mice, the difference was not significant based on this analysis.
Mentions: Given the integral role Ag-specific IgG plays in FcγRIIB-mediated immune modulation and the absence of increased levels of Ft-specific IgG in iFt-immunized FcγRIIB KO versus WT mice (Figure 2), we sought to determine whether there would be any impact of the presence versus absence of FcγRIIB on protection of iFt-immunized mice. Despite the lack of a significant increased Ft-specific IgG in FcγRIIB KO versus WT mice and in contrast to studies using naïve mice (Figure 1), at a challenge dose of 4 × LD50, the survival of iFt-immunized FcγRIIB KO mice was significantly better than that of WT mice (100% versus 50% resp.) (Figure 3(a)). Similar to that observed in naïve mice (Figure 1), there was no significant difference in survival between FcγRIIB KO and WT mice immunized with PBS (Figure 3(a)). When the challenge dose was increased to 16 × LD50, the overall level of survival decreased. However, a slight increase in the survival of iFt-immunized FcγRIIB KO versus WT mice was still apparent (Figure 3(b)). The increased survival also correlated with a reduction in the median bacterial burden in iFt-immunized FcγRIIB KO (Figure 3(c)).

Bottom Line: Ft-specific IgA in serum and bronchial alveolar lavage, as well as IFN-γ, IL-10, and TNF-α production by splenocytes harvested from iFt-immunized FcγRIIB KO, were also significantly elevated.Thus, these studies demonstrate for the first time the ability of FcγRIIB to regulate vaccine-induced IgA production and downmodulate immunity and protection.The immune mechanisms behind the above observations and their potential impact on vaccine development are discussed.

View Article: PubMed Central - PubMed

Affiliation: Center for Immunology and Microbial Disease, Albany Medical College, Albany, NY 12208, USA.

ABSTRACT
Fc gamma receptor IIB (FcγRIIB) is the only Fc gamma receptor (FcγR) which negatively regulates the immune response, when engaged by antigen- (Ag-) antibody (Ab) complexes. Thus, the generation of Ag-specific IgG in response to infection or immunization has the potential to downmodulate immune protection against infection. Therefore, we sought to determine the impact of FcγRIIB on immune protection against Francisella tularensis (Ft), a Category A biothreat agent. We utilized inactivated Ft (iFt) as an immunogen. Naïve and iFt-immunized FcγRIIB knockout (KO) or wildtype (WT) mice were challenged with Ft-live vaccine strain (LVS). While no significant difference in survival between naïve FcγRIIB KO versus WT mice was observed, iFt-immunized FcγRIIB KO mice were significantly better protected than iFt-immunized WT mice. Ft-specific IgA in serum and bronchial alveolar lavage, as well as IFN-γ, IL-10, and TNF-α production by splenocytes harvested from iFt-immunized FcγRIIB KO, were also significantly elevated. In addition, iFt-immunized FcγRIIB KO mice exhibited a reduction in proinflammatory cytokine levels in vivo at 5 days after challenge, which correlates with increased survival following Ft-LVS challenge in published studies. Thus, these studies demonstrate for the first time the ability of FcγRIIB to regulate vaccine-induced IgA production and downmodulate immunity and protection. The immune mechanisms behind the above observations and their potential impact on vaccine development are discussed.

Show MeSH
Related in: MedlinePlus