Hepatitis C virus E2-CD81 interaction induces hypermutation of the immunoglobulin gene in B cells

Area of Science:

• Immunology
• Virology
• Molecular Biology

Background:

• Hepatitis C virus (HCV) is linked to B-lymphocyte disorders like lymphoma.
• HCV's envelope glycoprotein E2 interacts with CD81 on B cells, a proposed viral entry mechanism.

Purpose of the Study:

• To investigate the molecular mechanisms by which HCV E2 interaction with CD81 affects B cells.
• To determine if HCV E2 binding induces genetic alterations in B cells relevant to lymphoproliferative disorders.

Main Methods:

• Purified HCV E2 protein was used to engage primary B cells.
• Monoclonal antibodies against CD81 were used to block E2-CD81 interactions.
• Activation-induced cytidine deaminase (AID) expression and DNA double-strand breaks were assessed.
• AID function was inhibited using small interfering RNA (siRNA).

Main Results:

• HCV E2 engagement induced DNA double-strand breaks specifically in the immunoglobulin V(H) gene locus of B cells.
• This E2-CD81 interaction enhanced activation-induced cytidine deaminase (AID) expression and B-cell activation.
• Blocking CD81 with antibodies abrogated E2-induced DNA breaks and hypermutation.
• AID knockdown prevented E2-induced DNA breaks and V(H) gene hypermutation.

Conclusions:

• HCV E2-CD81 interaction triggers B-cell DNA damage and immunoglobulin gene hypermutation via AID.
• This mechanism may contribute to the pathogenesis of HCV-associated B-cell lymphoproliferative diseases.
• Targeting the E2-CD81-AID pathway could offer therapeutic strategies for HCV-related B-cell malignancies.