Herpes simplex virus infection downmodulates NKG2D ligand expression.

Area of Science:

• Immunology
• Virology
• Cell Biology

Background:

• Herpes simplex virus (HSV) type 1 causes orofacial infections and establishes latency in neural ganglia.
• Natural killer (NK) cells are crucial for controlling herpesvirus infections, potentially via Major Histocompatibility Complex (MHC) class I modulation.
• HSV-1 reactivation involves complex interactions between viral mechanisms and host immune responses.

Purpose of the Study:

• To investigate the impact of HSV-1 infection on NKG2D ligand expression on infected cells.
• To explore the role of NK cell activating receptor NKG2D and its ligands in HSV-1 infection and reactivation.
• To understand the mechanisms by which HSV-1 downregulates NKG2D ligands on the cell surface.

Main Methods:

• Cell lines were infected with HSV-1.
• Surface expression levels of NKG2D ligands (MICA and ULBP2) and MHC class I were analyzed using flow cytometry.
• Total cellular MICA content was assessed.
• NK cells from patients with active HSV-1 infection were analyzed for NKG2D expression.

Main Results:

• HSV-1 infection led to the downregulation of surface MICA and ULBP2.
• MHC class I levels were also reduced by HSV-1, preventing a decrease in NK cell recognition of infected HeLa cells.
• Total cellular MICA remained unchanged, suggesting post-transcriptional regulation like masking or internalization.
• NK cells from individuals with active HSV-1 infection exhibited increased NKG2D expression.

Conclusions:

• HSV-1 employs viral gene products to downregulate NKG2D ligands on infected cells.
• Despite ligand downregulation, increased NKG2D expression on NK cells suggests a potential role in immune response to HSV-1 reactivation.
• NKG2D-MICA interactions are implicated in the immune control of HSV-1 reactivation.