Herpes simplex virus infection in capsaicin-treated mice

Area of Science:

• Neurovirology
• Immunology
• Pain research

Background:

• Herpes simplex virus (HSV) establishes latency in the trigeminal ganglion.
• HSV infection can lead to neurological complications and deafferentiation pain syndrome.
• Substance P is a neuropeptide found in sensory neurons involved in pain signaling.

Purpose of the Study:

• To investigate the role of substance P-containing sensory neurons in HSV pathogenesis.
• To evaluate the effect of neonatal capsaicin treatment on HSV infection outcomes.
• To explore the mechanisms underlying HSV-induced deafferentiation pain.

Main Methods:

• Neonatal mice were treated with capsaicin to deplete substance P-containing unmyelinated sensory neurons.
• Mice were inoculated with HSV via the snout.
• Mortality rates, viral spread, and neuronal/glial infection were assessed.
• Substance P immunoreactivity in trigeminal nerve fibers was analyzed.

Main Results:

• Capsaicin treatment significantly reduced mortality in HSV-infected mice.
• A lower percentage of capsaicin-treated mice survived with reactivatable HSV.
• Extensive glial cell infection was observed proximal to the trigeminal nerve transitional zone.
• Increased substance P immunoreactivity was noted in central nerve fibers distal to this zone.

Conclusions:

• Depletion of substance P-containing sensory neurons confers protection against HSV-induced mortality.
• Glial infection in the trigeminal nerve may exacerbate neuronal damage.
• HSV-induced glial infection and subsequent neurodegeneration may contribute to deafferentiation pain syndrome.