Limits...
Programmed death 1 protects from fatal circulatory failure during systemic virus infection of mice.

Frebel H, Nindl V, Schuepbach RA, Braunschweiler T, Richter K, Vogel J, Wagner CA, Loffing-Cueni D, Kurrer M, Ludewig B, Oxenius A - J. Exp. Med. (2012)

Bottom Line: In the absence of regulation via PD-1, CD8 T cells killed infected vascular endothelial cells via perforin-mediated cytolysis, thereby severely compromising vascular integrity.This resulted in systemic vascular leakage and a consequential collapse of the circulatory system.Our results indicate that the PD-1-PD-L1 pathway protects the vascular system from severe CD8 T cell-mediated damage during early systemic LCMV infection, highlighting a pivotal physiological role of T cell down-regulation and suggesting the potential development of immunopathological side effects when interfering with the PD-1-PD-L1 pathway during systemic virus infections.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Microbiology, ETH Zurich, 8093 Zurich, Switzerland.

ABSTRACT
The inhibitory programmed death 1 (PD-1)-programmed death ligand 1 (PD-L1) pathway contributes to the functional down-regulation of T cell responses during persistent systemic and local virus infections. The blockade of PD-1-PD-L1-mediated inhibition is considered as a therapeutic approach to reinvigorate antiviral T cell responses. Yet previous studies reported that PD-L1-deficient mice develop fatal pathology during early systemic lymphocytic choriomeningitis virus (LCMV) infection, suggesting a host protective role of T cell down-regulation. As the exact mechanisms of pathology development remained unclear, we set out to delineate in detail the underlying pathogenesis. Mice deficient in PD-1-PD-L1 signaling or lacking PD-1 signaling in CD8 T cells succumbed to fatal CD8 T cell-mediated immunopathology early after systemic LCMV infection. In the absence of regulation via PD-1, CD8 T cells killed infected vascular endothelial cells via perforin-mediated cytolysis, thereby severely compromising vascular integrity. This resulted in systemic vascular leakage and a consequential collapse of the circulatory system. Our results indicate that the PD-1-PD-L1 pathway protects the vascular system from severe CD8 T cell-mediated damage during early systemic LCMV infection, highlighting a pivotal physiological role of T cell down-regulation and suggesting the potential development of immunopathological side effects when interfering with the PD-1-PD-L1 pathway during systemic virus infections.

Show MeSH

Related in: MedlinePlus

Endothelial PD-L1 expression inhibits CD8 T cell–mediated killing. (A) CD31+CD144+ cells from lungs and livers of naive WT, infected WT, and infected PD-1 KO mice were analyzed for PD-L1 expression and LCMV infection (VL-4 staining) on day 6 after 106 pfu LCMV docile infection. Histograms depict data from one representative of two analyzed mice per group. Data from one representative of three experiments are shown. (B) Lung CD31+CD144+ cells of naive and 102 pfu LCMV WE–infected WT mice were analyzed for PD-L1 expression and LCMV infection (VL-4 staining) on day 6 p.i. Histograms depict data from one mouse each. Data from one representative of two experiments are shown. (C) Untreated, IFN-γ–treated, and IFN-γ + αPD-L1–treated MS-I cells were analyzed for PD-L1 expression and pulsed with GP33+NP396 peptide to serve as target cells in a chromium release assay. (D) PD-1 expression levels of endogenous CD8 T cells and transferred P14 cells were determined on day 6 after systemic infection. C and D: histograms depict data from one representative of two experiments. (E) CD8 T cells were purified from four P14-transferred mice on day 6 p.i. and mixed with chromium-labeled, antigen-pulsed MS-I cells at the indicated effector to target ratios. Chromium release was analyzed in duplicates. Means ± SEM from one representative of three experiments are shown.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC3526355&req=5

fig4: Endothelial PD-L1 expression inhibits CD8 T cell–mediated killing. (A) CD31+CD144+ cells from lungs and livers of naive WT, infected WT, and infected PD-1 KO mice were analyzed for PD-L1 expression and LCMV infection (VL-4 staining) on day 6 after 106 pfu LCMV docile infection. Histograms depict data from one representative of two analyzed mice per group. Data from one representative of three experiments are shown. (B) Lung CD31+CD144+ cells of naive and 102 pfu LCMV WE–infected WT mice were analyzed for PD-L1 expression and LCMV infection (VL-4 staining) on day 6 p.i. Histograms depict data from one mouse each. Data from one representative of two experiments are shown. (C) Untreated, IFN-γ–treated, and IFN-γ + αPD-L1–treated MS-I cells were analyzed for PD-L1 expression and pulsed with GP33+NP396 peptide to serve as target cells in a chromium release assay. (D) PD-1 expression levels of endogenous CD8 T cells and transferred P14 cells were determined on day 6 after systemic infection. C and D: histograms depict data from one representative of two experiments. (E) CD8 T cells were purified from four P14-transferred mice on day 6 p.i. and mixed with chromium-labeled, antigen-pulsed MS-I cells at the indicated effector to target ratios. Chromium release was analyzed in duplicates. Means ± SEM from one representative of three experiments are shown.

Mentions: Several studies described a strong up-regulation of PD-L1 expression on vascular endothelial cells under inflammatory conditions (Eppihimer et al., 2002; Rodig et al., 2003; Grabie et al., 2007). We speculated that vascular endothelial cells might up-regulate PD-L1 under the inflammatory conditions of a systemic LCMV infection and thereby inhibit the killing of LCMV-infected endothelium by activated, PD-1–expressing CD8 T cells. In contrast, PD-1–deficient CD8 T cells would not be inhibited by PD-L1 and thus effectively kill LCMV-infected vascular endothelial cells. To test this hypothesis, the expression level of PD-L1 on liver and lung endothelial cells was analyzed ex vivo on day 6 p.i. We detected a strong up-regulation of PD-L1 on endothelial cells from both organs in infected WT and PD-1 KO mice compared with endothelial cells from naive WT mice (Fig. 4 A). Furthermore, we found the vast majority of liver and lung endothelial cells to be infected with LCMV on day 6 p.i., indicated by strong intracellular staining with the LCMV nucleoprotein-specific antibody VL-4 (Fig. 4 A).


Programmed death 1 protects from fatal circulatory failure during systemic virus infection of mice.

Frebel H, Nindl V, Schuepbach RA, Braunschweiler T, Richter K, Vogel J, Wagner CA, Loffing-Cueni D, Kurrer M, Ludewig B, Oxenius A - J. Exp. Med. (2012)

Endothelial PD-L1 expression inhibits CD8 T cell–mediated killing. (A) CD31+CD144+ cells from lungs and livers of naive WT, infected WT, and infected PD-1 KO mice were analyzed for PD-L1 expression and LCMV infection (VL-4 staining) on day 6 after 106 pfu LCMV docile infection. Histograms depict data from one representative of two analyzed mice per group. Data from one representative of three experiments are shown. (B) Lung CD31+CD144+ cells of naive and 102 pfu LCMV WE–infected WT mice were analyzed for PD-L1 expression and LCMV infection (VL-4 staining) on day 6 p.i. Histograms depict data from one mouse each. Data from one representative of two experiments are shown. (C) Untreated, IFN-γ–treated, and IFN-γ + αPD-L1–treated MS-I cells were analyzed for PD-L1 expression and pulsed with GP33+NP396 peptide to serve as target cells in a chromium release assay. (D) PD-1 expression levels of endogenous CD8 T cells and transferred P14 cells were determined on day 6 after systemic infection. C and D: histograms depict data from one representative of two experiments. (E) CD8 T cells were purified from four P14-transferred mice on day 6 p.i. and mixed with chromium-labeled, antigen-pulsed MS-I cells at the indicated effector to target ratios. Chromium release was analyzed in duplicates. Means ± SEM from one representative of three experiments are shown.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3526355&req=5

fig4: Endothelial PD-L1 expression inhibits CD8 T cell–mediated killing. (A) CD31+CD144+ cells from lungs and livers of naive WT, infected WT, and infected PD-1 KO mice were analyzed for PD-L1 expression and LCMV infection (VL-4 staining) on day 6 after 106 pfu LCMV docile infection. Histograms depict data from one representative of two analyzed mice per group. Data from one representative of three experiments are shown. (B) Lung CD31+CD144+ cells of naive and 102 pfu LCMV WE–infected WT mice were analyzed for PD-L1 expression and LCMV infection (VL-4 staining) on day 6 p.i. Histograms depict data from one mouse each. Data from one representative of two experiments are shown. (C) Untreated, IFN-γ–treated, and IFN-γ + αPD-L1–treated MS-I cells were analyzed for PD-L1 expression and pulsed with GP33+NP396 peptide to serve as target cells in a chromium release assay. (D) PD-1 expression levels of endogenous CD8 T cells and transferred P14 cells were determined on day 6 after systemic infection. C and D: histograms depict data from one representative of two experiments. (E) CD8 T cells were purified from four P14-transferred mice on day 6 p.i. and mixed with chromium-labeled, antigen-pulsed MS-I cells at the indicated effector to target ratios. Chromium release was analyzed in duplicates. Means ± SEM from one representative of three experiments are shown.
Mentions: Several studies described a strong up-regulation of PD-L1 expression on vascular endothelial cells under inflammatory conditions (Eppihimer et al., 2002; Rodig et al., 2003; Grabie et al., 2007). We speculated that vascular endothelial cells might up-regulate PD-L1 under the inflammatory conditions of a systemic LCMV infection and thereby inhibit the killing of LCMV-infected endothelium by activated, PD-1–expressing CD8 T cells. In contrast, PD-1–deficient CD8 T cells would not be inhibited by PD-L1 and thus effectively kill LCMV-infected vascular endothelial cells. To test this hypothesis, the expression level of PD-L1 on liver and lung endothelial cells was analyzed ex vivo on day 6 p.i. We detected a strong up-regulation of PD-L1 on endothelial cells from both organs in infected WT and PD-1 KO mice compared with endothelial cells from naive WT mice (Fig. 4 A). Furthermore, we found the vast majority of liver and lung endothelial cells to be infected with LCMV on day 6 p.i., indicated by strong intracellular staining with the LCMV nucleoprotein-specific antibody VL-4 (Fig. 4 A).

Bottom Line: In the absence of regulation via PD-1, CD8 T cells killed infected vascular endothelial cells via perforin-mediated cytolysis, thereby severely compromising vascular integrity.This resulted in systemic vascular leakage and a consequential collapse of the circulatory system.Our results indicate that the PD-1-PD-L1 pathway protects the vascular system from severe CD8 T cell-mediated damage during early systemic LCMV infection, highlighting a pivotal physiological role of T cell down-regulation and suggesting the potential development of immunopathological side effects when interfering with the PD-1-PD-L1 pathway during systemic virus infections.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Microbiology, ETH Zurich, 8093 Zurich, Switzerland.

ABSTRACT
The inhibitory programmed death 1 (PD-1)-programmed death ligand 1 (PD-L1) pathway contributes to the functional down-regulation of T cell responses during persistent systemic and local virus infections. The blockade of PD-1-PD-L1-mediated inhibition is considered as a therapeutic approach to reinvigorate antiviral T cell responses. Yet previous studies reported that PD-L1-deficient mice develop fatal pathology during early systemic lymphocytic choriomeningitis virus (LCMV) infection, suggesting a host protective role of T cell down-regulation. As the exact mechanisms of pathology development remained unclear, we set out to delineate in detail the underlying pathogenesis. Mice deficient in PD-1-PD-L1 signaling or lacking PD-1 signaling in CD8 T cells succumbed to fatal CD8 T cell-mediated immunopathology early after systemic LCMV infection. In the absence of regulation via PD-1, CD8 T cells killed infected vascular endothelial cells via perforin-mediated cytolysis, thereby severely compromising vascular integrity. This resulted in systemic vascular leakage and a consequential collapse of the circulatory system. Our results indicate that the PD-1-PD-L1 pathway protects the vascular system from severe CD8 T cell-mediated damage during early systemic LCMV infection, highlighting a pivotal physiological role of T cell down-regulation and suggesting the potential development of immunopathological side effects when interfering with the PD-1-PD-L1 pathway during systemic virus infections.

Show MeSH
Related in: MedlinePlus