Human herpesvirus 8 interaction with target cells involves heparan sulfate.

Area of Science:

• Virology
• Cell Biology
• Molecular Biology

Background:

• Human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus (KSHV), is linked to Kaposi's sarcoma and primary effusion lymphoma.
• HHV-8 exhibits broad cellular tropism, infecting various human and animal cell types, including B cells, endothelial cells, macrophages, and epithelial cells.

Purpose of the Study:

• To investigate the role of heparan sulfate (HS) in the cellular tropism and infection mechanism of HHV-8.
• To determine if HS acts as a cellular receptor for HHV-8 attachment and entry.

Main Methods:

• Inhibition assays using soluble heparin and chondroitin sulfates on HHV-8 infected human foreskin fibroblast (HFF) cells.
• Enzymatic removal of cell surface HS using heparinase I and III to assess its effect on HHV-8 infection.
• Binding studies using radiolabeled HHV-8 with various cell lines (HFF, B cells, 293 cells, CHO-K1, and HS-deficient CHO mutants).
• Displacement assays to evaluate the interaction between cell-bound HHV-8 and soluble heparin.

Main Results:

• Soluble heparin dose-dependently inhibited HHV-8 infection of HFF cells, while chondroitin sulfates had no effect.
• Enzymatic removal of HS from HFF cells significantly reduced HHV-8 infection.
• Soluble heparin inhibited radiolabeled HHV-8 binding to HFF, B cell, and 293 cells, indicating interference with viral attachment.
• Radiolabeled HHV-8 bound to HS-expressing CHO-K1 cells but showed significantly reduced binding to HS-deficient CHO mutants.
• Cell surface-adsorbed HHV-8 could be displaced by soluble heparin.

Conclusions:

• Heparan sulfate (HS) on the cell surface is a crucial factor in the broad cellular tropism of HHV-8.
• HHV-8 utilizes HS-like moieties for initial cell adsorption, similar to other herpesviruses.
• The interaction with HS represents a primary ligand-receptor interaction, facilitating subsequent steps for viral entry.