Replication of herpes simplex virus type 1 (HSV-1) in the adrenal gland of
mice was observed 12 h after intravenous inoculation, peaked at 48 h (7 x 1
0(7) PFU/tissue), and was maintained until death. Virus spread to the bilat
eral intermediolateral column of the thoracic spinal cord. Infected cells a
ppeared in the fascicular zone of the adrenal cortex 12 h after infection,
and cell death was evident in lesions found in the adrenal cortex. Lesions
involved the medulla 48 h after inoculation. In cortical lesions, cell nucl
ei were fragmented or shrunken with little damage to the cytoplasm. DNA fra
gmentation appeared 12h after inoculation and increased mainly in cortical
lesions, which were characterized by apoptosis induced by HSV-1 infection.
In the adrenal medulla, cells were fused and formed multinucleated giant ce
lls but rarely displayed cell death. Macrophages, which serve as a frontal
barrier to viral infection in the adrenal gland, especially the cortex, wer
e fewer in number than those found in the liver or spleen. It is likely tha
t HSV-1 easily infects the adrenal gland, resulting in suppression of local
immunity, and that adrenal cell apoptosis serves as a primitive type of im
munity to limit viral replication.