Cell Type-Specific Interferon-γ-mediated Antagonism of KSHV Lytic Replication.

Area of Science:

• Virology
• Immunology
• Oncology

Background:

• Kaposi's sarcoma-associated herpesvirus (KSHV) causes Kaposi's sarcoma (KS), multicentric Castleman's disease (MCD), and primary effusion lymphoma (PEL).
• KS is a common AIDS-related malignancy characterized by angioproliferation and immune cell infiltration.
• The role of the inflammatory microenvironment in regulating KSHV gene expression and replication remains largely unknown.

Purpose of the Study:

• To investigate the impact of inflammatory cytokines, specifically IFN-γ and TNF-α, on KSHV replication and gene expression.
• To determine the stage of the KSHV life cycle affected by these cytokines.

Main Methods:

• Primary human lymphatic endothelial cells (LECs) and KSHV-producer cells (iSLK.219) were used.
• Cells were induced for KSHV lytic replication with doxycycline.
• The effects of IFN-γ and TNF-α on KSHV progeny production and gene expression were analyzed.

Main Results:

• IFN-γ and TNF-α significantly inhibited KSHV progeny production in both LECs and iSLK.219 cells.
• IFN-γ suppressed overall KSHV gene expression.
• TNF-α affected a subset of KSHV genes, also downregulated by IFN-γ.
• IFN-γ effectively inhibited viral production even when added 36 hours post-induction, indicating an early-stage inhibitory effect.

Conclusions:

• IFN-γ and TNF-α demonstrate potent inhibitory effects on KSHV replication.
• These findings suggest that targeting the inflammatory microenvironment could be a viable therapeutic strategy for KSHV-induced malignancies like KS and MCD.
• The inhibitory action occurs early in the KSHV life cycle.