Modulation of CD8+ CTL effector function by fibroblasts derived from the immunoprivileged cornea

Area of Science:

• Immunology
• Virology
• Ophthalmology

Background:

• Herpes simplex virus (HSV) type 1 establishes lifelong infections, often reactivating in the cornea.
• CD8(+) cytotoxic T-lymphocytes (CTLs) are crucial for controlling HSV infections.
• Immune privilege in the cornea can modulate T-cell responses.

Purpose of the Study:

• To investigate how HSV-1-infected corneal fibroblasts (HSV-cFb) and skin fibroblasts (HSV-sFb) influence the function of HSV-specific CD8(+) CTL precursors (HSV-CTLps).
• To compare the effects of HSV-infected cells from immunoprivileged (cornea) versus nonprivileged (skin) sites on CTL activity and cytokine production.
• To determine the impact of co-exposure to infected splenocytes (HSV-Spls) and infected fibroblasts on HSV-CTL responses.

Main Methods:

• Chromium release assays for cytotoxicity.
• Flow cytometry for granzyme B, CD107a (lytic granule exocytosis), and intracellular IFN-gamma.
• BLT esterase assay for granzyme A release.
• [(3)H]-Thymidine incorporation for CTLp proliferation.

Main Results:

• HSV-cFb, HSV-sFb, and HSV-Spls individually stimulated robust HSV-CTL cytotoxic and IFN-gamma responses.
• Co-exposure to HSV-Spls and HSV-cFb abrogated cytotoxicity but enhanced IFN-gamma production.
• Co-exposure to HSV-Spls and HSV-sFb did not alter HSV-CTL responses compared to single stimuli.
• Abrogation of cytotoxicity was linked to reduced granzyme A/B, but not impaired lytic granule release.

Conclusions:

• Corneal immune privilege involves a regulatory mechanism protecting the eye from excessive CTL damage.
• This mechanism maintains CTL capacity to control viral replication via IFN-gamma production.
• Understanding this circuit offers insights into managing ocular HSV infections.