Immune Netw.  2015 Apr;15(2):73-82. 10.4110/in.2015.15.2.73.

Caspase-1 Independent Viral Clearance and Adaptive Immunity Against Mucosal Respiratory Syncytial Virus Infection

• Shim YR
• Lee HK

• KMID: 2168032
• DOI: http://doi.org/10.4110/in.2015.15.2.73

Abstract

Respiratory syncytial virus (RSV) infection is recognized by the innate immune system through Toll like receptors (TLRs) and retinoic acid inducible gene I. These pathways lead to the activation of type I interferons and resistance to infection. In contrast to TLRs, very few studies have examined the role of NOD-like receptors in viral recognition and induction of adaptive immune responses to RSV. Caspase-1 plays an essential role in the immune response via the maturation of the proinflammatory cytokines IL-1beta and IL-18. However, the role of caspase-1 in RSV infection in vivo is unknown. We demonstrate that RSV infection induces IL-1beta secretion and that caspase-1 deficiency in bone marrow derived dendritic cells leads to defective IL-1beta production, while normal RSV viral clearance and T cell responses are observed in caspase-1 deficient mice following respiratory infection with RSV. The frequencies of IFN-gamma producing or RSV specific T cells in lungs from caspase-1 deficient mice are not impaired. In addition, we demonstrate that caspase-1 deficient neonatal or young mice also exhibit normal immune responses. Furthermore, we find that IL-1R deficient mice infected with RSV exhibit normal Th1 and cytotoxic T lymphocytes (CTL) immune responses. Collectively, these results demonstrate that in contrast to TLR pathways, caspase-1 might not play a central role in the induction of Th1 and CTL immune responses to RSV.

Keyword

RSV; Caspase-1; IL-1beta; Adaptive immunity

MeSH Terms

Adaptive Immunity*
Animals
Bone Marrow
Cytokines
Dendritic Cells
Immune System
Interferon Type I
Interleukin-18
Lung
Mice
Respiratory Syncytial Viruses*
T-Lymphocytes
T-Lymphocytes, Cytotoxic
Toll-Like Receptors
Tretinoin
Cytokines
Interferon Type I
Interleukin-18
Toll-Like Receptors
Tretinoin

Figure

• 

  Figure 1 The upregulation of CD86 and proinflammatory cytokines, but not IL-1β, are not impaired in caspase-1 deficient BMDCs and BMMs. BMDCs and BMMs were differentiated from the bone marrow of wild type and caspase-1-/- mice and stimulated with RSV (moi=1, 5), 2.5 µg/ml CpG2216, and 100 ng/ml LPS. After 20 hr, IL-1β, IL-6, and IL-12p40 in supernatants from BMDCs (A~C) and BMMs (D~F) were measured by ELISA. CD86 levels from BMDCs (G) and BMMs (H) were analyzed by flow cytometry (red line=caspase-1+/-; blue line=caspase-1-/-). Data are representative of two independent experiments. Error bars indicate SD.

• 

  Figure 2 Caspase-1 does not affect RSV viral clearance or the adaptive immune response in adult mice. Caspase-1+/- and caspase-1-/- mice (10~12 weeks) were infected intranasally with 1×107 pfu of RSV. Caspase-1+/- mice were infected with PBS as a mock control (C, D). (A) On days 5 or 10 post infection, the RSV titer in the lungs was measured by plaque assay on HEp2 cells. (B~E) On day 8 post RSV infection, mice were sacrificed. (B) Isolated CD4+ and CD8+ T cells from the mouse spleens were stimulated with the indicated heat-inactivated RSV or RSV M187-195 peptide, respectively, and pulsed with irradiated APCs. After 72 hr, IFN-γ in the supernatants from CD4+ T cells (left) and CD8+ T cells (right) was measured by ELISA. (C, D) IFN-γ-producing CD4+ T cells (C, up) and CD8+ T cells (C, down and D) were detected in the lungs by intracellular staining after re-stimulation with (C) PMA and ionomycin or (D) RSV M187-195 peptide. (E) RSV-specific CD8+ T cells were stained with RSV tetramer (H-2Db M187-195). Data are representative of three independent experiments, and error bars indicate SEM.

• 

  Figure 3 Caspase-1 is not required for RSV viral clearance in young mice. Caspase-1+/- and caspase-1-/- mice (1- or 3-weeks) were infected intranasally with 1×106 pfu of RSV. On days 5 or 10 post infection, the RSV titer in the lungs from 3 week mice (A) and 1 week mice (B) were measured by plaque assay on HEp2 cells.

• 

  Figure 4 In 3-week- and 1-week-old mice, the caspase-1-/- mice T cell responses are normal. Three week (A, C, E, G) or one week (B, D, F, H) old caspase-1+/- and caspase-1-/- mice were intranasally infected with 1×106 pfu of RSV. Caspase-1+/- mice were infected with PBS as a mock control (C~H). On day 8 after RSV infection, the mice were sacrificed. (A, B) CD4+ and CD8+ T cells from the mouse spleens were stimulated with the indicated heat-inactivated RSV or RSV M187-195 peptide, respectively, and pulsed with irradiated APCs. After 72 hr, IFN-γ in supernatants from the CD4+ T cells (left) and CD8+ T cells (right) were measured by ELISA. (C, D) IFN-γ-producing CD4+ T cells (up) and CD8+ T cells (down) were detected in the lungs by intracellular staining after re-stimulation with PMA and ionomycin or (E, F) RSV M187-195 peptide. (G, H) RSV-specific CD8+ T cells were stained with RSV tetramer (H-2Db M187-195) (G: 3-week, H: 1-week). Data are representative of two to three independent experiments. Error bars indicate SD.

• 

  Figure 5 IL-1R signaling is not required for the induction of Th1 and CTL priming against RSV infection. IL-1R+/- and IL-1R-/- mice were intranasally infected with 1×107 pfu of RSV. IL-1R+/- mice were infected with PBS as a mock control (C, D). On day 8 after RSV infection, mice were sacrificed. Isolated CD4+ and CD8+ T cells from the mouse spleens were stimulated with the indicated heat-inactivated RSV or RSV M187-195 peptide, respectively, and pulsed with irradiated APCs. After 72 hr, the IFN-γ in the supernatants from CD4+ T cells (A) and CD8+ T cells (B) were measured by ELISA. The absolute numbers of IFN-γ producing CD4+ T cells (C) and CD8+ T cells (D) were detected in the lungs by intracellular staining after re-stimulation with PMA and ionomycin. Data are representative of two to three independent experiments. Error bars indicate SD.

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