An Early Microglial Response Is Needed To Efficiently Control Herpes Simplex Virus Encephalitis

Area of Science:

• Neuroimmunology
• Virology
• Cellular Biology

Background:

• Microglia are key regulators of neuroinflammation in the central nervous system (CNS).
• The role of microglia in herpes simplex virus 1 encephalitis (HSE) requires further characterization.
• The macrophage colony-stimulating factor (MCSF)/macrophage colony-stimulating factor 1 receptor (CSF1R) signaling pathway influences microglial function.

Purpose of the Study:

• To investigate the role of the MCSF/CSF1R signaling pathway in experimental herpes simplex virus 1 encephalitis (HSE).
• To evaluate the therapeutic potential of modulating the MCSF/CSF1R axis in HSE.

Main Methods:

• Two mouse models were used: one treated with exogenous MCSF before HSV-1 infection, and another with genetically depleted CSF1R on microglia.
• Mice were infected intranasally with HSV-1.
• Survival rates, viral titers, cytokine/chemokine levels, and immune cell infiltration (CD68+ cells, monocytes) were assessed.

Main Results:

• MCSF treatment before HSV-1 infection significantly increased mouse survival, decreased brain viral titers, and increased IFN-β levels and CD68+ microglial cells.
• Conditional depletion of CSF1R in microglia significantly reduced survival rates and increased viral loads and cytokine/chemokine levels.
• CSF1R depletion impaired monocyte infiltration into the brain.

Conclusions:

• Microglial cells are crucial for controlling HSE, particularly in the early stages.
• The MCSF/CSF1R axis plays a vital role in microglial response to HSV-1 infection.
• Targeting the MCSF/CSF1R pathway may offer a therapeutic strategy for HSE, potentially combined with antiviral treatments.