Quantification of herpes simplex virus infection in cervical ganglia of mice

Mice were inoculated with herpes simplex virus (HSV) type 1 in the skin of the neck. The extent of primary and latent infection in the second and third cervical ganglia was investigated. Immunoperoxidase staining of ganglia during primary infection demonstrated HSV antigens initially in a restricted area of the ganglion. By the 5th day after infection, antigen was more widespread. Such a change in the staining pattern is explicable in terms of the zosteriform spread of virus from neurons innervating the site of infection to others supplying other areas of the dermatome. A maximum of approximately 10% of neurons became infected. By the 7th day staining was limited to a few cells. During latent infection, enzymic disaggregation of ganglia followed by immunoperoxidase staining or infectious centre assay indicated that virus reactivation began within 30 h of removal of ganglia and occurred in approximately 1% of viable neurons.