Macrophage antiviral activity: extrinsic versus intrinsic activity

Area of Science:

• Immunology
• Virology
• Cell Biology

Background:

• Mouse hepatitis virus (MHV) strain JHM poses a significant challenge to mouse models.
• Peritoneal exudate cells (PECs) are crucial in innate and adaptive immune responses.
• Understanding antiviral mechanisms in macrophages is key to controlling viral infections.

Purpose of the Study:

• To investigate extrinsic and intrinsic antiviral activities in mouse peritoneal exudate cells.
• To differentiate these activities based on host resistance to MHV.
• To identify the cellular characteristics of macrophages mediating antiviral effects.

Main Methods:

• Isolation and characterization of peritoneal exudate cells from MHV-resistant and susceptible mouse strains.
• Assay of antiviral activity by measuring suppression of viral growth in permissive cells.
• Characterization of active cells based on adherence, radiation resistance, and cell surface markers (Thy-1.2, Ia).
• Assessment of cytotoxicity and interferon production.

Main Results:

• Both elicited and resident PECs suppressed viral growth, indicating extrinsic antiviral activity.
• The active cell was identified as adherent, radiation-resistant, and Thy-1.2/Ia antigen-negative.
• Suppression was not due to non-specific cytotoxicity or interferon.
• Extrinsic antiviral activity was independent of host resistance factors (age, genetics).
• Intrinsic antiviral activity correlated with host resistance to MHV infection.
• Macrophage's ability to support viral replication was independent of its ability to suppress viral growth in other cells.

Conclusions:

• Two distinct in vitro macrophage-mediated antiviral activities exist: extrinsic and intrinsic.
• Intrinsic antiviral activity is linked to host resistance against MHV.
• These findings highlight key differences in macrophage antiviral mechanisms relevant to host immunity.