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Inhibition of natural killer cells through engagement of CD81 by the major hepatitis C virus envelope protein.

Crotta S, Stilla A, Wack A, D'Andrea A, Nuti S, D'Oro U, Mosca M, Filliponi F, Brunetto RM, Bonino F, Abrignani S, Valiante NM - J. Exp. Med. (2002)

Bottom Line: This inhibitory effect was observed using both activated and resting NK cells.Engagement of CD81 on NK cells blocks tyrosine phosphorylation through a mechanism which is distinct from the negative signaling pathways associated with NK cell inhibitory receptors for major histocompatibility complex class I.These results implicate HCV-E2-mediated inhibition of NK cells as an efficient HCV evasion strategy targeting the early antiviral activities of NK cells and allowing the virus to establish itself as a chronic infection.

View Article: PubMed Central - PubMed

Affiliation: IRIS, Department of Immunology, Chiron S.p.A., 53100 Siena, Italy.

ABSTRACT
The immune response against hepatitis C virus (HCV) is rarely effective at clearing the virus, resulting in approximately 170 million chronic HCV infections worldwide. Here we report that ligation of an HCV receptor (CD81) inhibits natural killer (NK) cells. Cross-linking of CD81 by the major envelope protein of HCV (HCV-E2) or anti-CD81 antibodies blocks NK cell activation, cytokine production, cytotoxic granule release, and proliferation. This inhibitory effect was observed using both activated and resting NK cells. Conversely, on NK-like T cell clones, including those expressing NK cell inhibitory receptors, CD81 ligation delivered a costimulatory signal. Engagement of CD81 on NK cells blocks tyrosine phosphorylation through a mechanism which is distinct from the negative signaling pathways associated with NK cell inhibitory receptors for major histocompatibility complex class I. These results implicate HCV-E2-mediated inhibition of NK cells as an efficient HCV evasion strategy targeting the early antiviral activities of NK cells and allowing the virus to establish itself as a chronic infection.

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CD81 engagement blocks the functions of resting NK cells. PBMCs freshly purified from healthy donors were cultured in complete medium on plastic plates coated with no antibody (A and B), 1 μg/ml of CD16 mAb alone (C and D), or 1 μg/ml of CD16 mAb plus 10 μg/ml of CD81 mAb (E and F). After 4 h of Brefeldin-A treatment, cells were stained for intracellular IFN-γ production (A, C, and E) and for the surface expression of the activation marker CD25. The plots in (A–F) represent the CD3-CD56+ subpopulation as defined by the staining in H. In G, CD16 stimulation is specific for NK cells as the CD3+ (T cell) PBMC subpopulation did not produce any IFN-γ, as assayed by intracellular staining.
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fig2: CD81 engagement blocks the functions of resting NK cells. PBMCs freshly purified from healthy donors were cultured in complete medium on plastic plates coated with no antibody (A and B), 1 μg/ml of CD16 mAb alone (C and D), or 1 μg/ml of CD16 mAb plus 10 μg/ml of CD81 mAb (E and F). After 4 h of Brefeldin-A treatment, cells were stained for intracellular IFN-γ production (A, C, and E) and for the surface expression of the activation marker CD25. The plots in (A–F) represent the CD3-CD56+ subpopulation as defined by the staining in H. In G, CD16 stimulation is specific for NK cells as the CD3+ (T cell) PBMC subpopulation did not produce any IFN-γ, as assayed by intracellular staining.

Mentions: Resting NK cells were also inhibited by CD81 ligation. Freshly isolated PBMCs were incubated with anti-CD16 mAb alone or in combination with the different anti-CD81 or control reagents used in the experiments of Fig. 2 . The NK cells from the mixed PBMC populations were analyzed by flow cytometry via specific gating on the CD56+/CD3− NK cell subset (Fig. 2). Again, the effect of CD81 cross-linking was potent inhibition of CD16-induced IFN-γ production (Fig. 2 A, C, and E) and activation marker (CD25) expression. (Fig. 2 B, D, and F). Thus, resting NK cells are inhibited by CD81 engagement similar to the purified/activated NK cells obtained from bulk culture. This suggests that early in the immune response against HCV and before NK cells are fully activated, binding of HCV-E2 to NK cell CD81 has the potential to dampen significantly the rapid antiviral responses of NK cells.


Inhibition of natural killer cells through engagement of CD81 by the major hepatitis C virus envelope protein.

Crotta S, Stilla A, Wack A, D'Andrea A, Nuti S, D'Oro U, Mosca M, Filliponi F, Brunetto RM, Bonino F, Abrignani S, Valiante NM - J. Exp. Med. (2002)

CD81 engagement blocks the functions of resting NK cells. PBMCs freshly purified from healthy donors were cultured in complete medium on plastic plates coated with no antibody (A and B), 1 μg/ml of CD16 mAb alone (C and D), or 1 μg/ml of CD16 mAb plus 10 μg/ml of CD81 mAb (E and F). After 4 h of Brefeldin-A treatment, cells were stained for intracellular IFN-γ production (A, C, and E) and for the surface expression of the activation marker CD25. The plots in (A–F) represent the CD3-CD56+ subpopulation as defined by the staining in H. In G, CD16 stimulation is specific for NK cells as the CD3+ (T cell) PBMC subpopulation did not produce any IFN-γ, as assayed by intracellular staining.
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Related In: Results  -  Collection

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fig2: CD81 engagement blocks the functions of resting NK cells. PBMCs freshly purified from healthy donors were cultured in complete medium on plastic plates coated with no antibody (A and B), 1 μg/ml of CD16 mAb alone (C and D), or 1 μg/ml of CD16 mAb plus 10 μg/ml of CD81 mAb (E and F). After 4 h of Brefeldin-A treatment, cells were stained for intracellular IFN-γ production (A, C, and E) and for the surface expression of the activation marker CD25. The plots in (A–F) represent the CD3-CD56+ subpopulation as defined by the staining in H. In G, CD16 stimulation is specific for NK cells as the CD3+ (T cell) PBMC subpopulation did not produce any IFN-γ, as assayed by intracellular staining.
Mentions: Resting NK cells were also inhibited by CD81 ligation. Freshly isolated PBMCs were incubated with anti-CD16 mAb alone or in combination with the different anti-CD81 or control reagents used in the experiments of Fig. 2 . The NK cells from the mixed PBMC populations were analyzed by flow cytometry via specific gating on the CD56+/CD3− NK cell subset (Fig. 2). Again, the effect of CD81 cross-linking was potent inhibition of CD16-induced IFN-γ production (Fig. 2 A, C, and E) and activation marker (CD25) expression. (Fig. 2 B, D, and F). Thus, resting NK cells are inhibited by CD81 engagement similar to the purified/activated NK cells obtained from bulk culture. This suggests that early in the immune response against HCV and before NK cells are fully activated, binding of HCV-E2 to NK cell CD81 has the potential to dampen significantly the rapid antiviral responses of NK cells.

Bottom Line: This inhibitory effect was observed using both activated and resting NK cells.Engagement of CD81 on NK cells blocks tyrosine phosphorylation through a mechanism which is distinct from the negative signaling pathways associated with NK cell inhibitory receptors for major histocompatibility complex class I.These results implicate HCV-E2-mediated inhibition of NK cells as an efficient HCV evasion strategy targeting the early antiviral activities of NK cells and allowing the virus to establish itself as a chronic infection.

View Article: PubMed Central - PubMed

Affiliation: IRIS, Department of Immunology, Chiron S.p.A., 53100 Siena, Italy.

ABSTRACT
The immune response against hepatitis C virus (HCV) is rarely effective at clearing the virus, resulting in approximately 170 million chronic HCV infections worldwide. Here we report that ligation of an HCV receptor (CD81) inhibits natural killer (NK) cells. Cross-linking of CD81 by the major envelope protein of HCV (HCV-E2) or anti-CD81 antibodies blocks NK cell activation, cytokine production, cytotoxic granule release, and proliferation. This inhibitory effect was observed using both activated and resting NK cells. Conversely, on NK-like T cell clones, including those expressing NK cell inhibitory receptors, CD81 ligation delivered a costimulatory signal. Engagement of CD81 on NK cells blocks tyrosine phosphorylation through a mechanism which is distinct from the negative signaling pathways associated with NK cell inhibitory receptors for major histocompatibility complex class I. These results implicate HCV-E2-mediated inhibition of NK cells as an efficient HCV evasion strategy targeting the early antiviral activities of NK cells and allowing the virus to establish itself as a chronic infection.

Show MeSH
Related in: MedlinePlus