Role of virus-infected mononuclear leukocytes in herpetic chorioretinitis of newborn rabbits.

The role of virus-infected mononuclear leukocytes (MNLs) in the pathogenesis of neonatal herpetic chorioretinitis in newborn rabbits was investigated. As early as 2 days after inoculating the animals' skins with type 2 herpes simplex virus (HSV-2), infectious MNLs in the infected animals' peripheral blood were found. The virus was associated, for the most part, with MNLs that belonged to phagocytic and adherent cell fractions. Observations by electron microscopy indicated that HSV-2 was actively replicating in the MNLs. It was also found that as few as 80 virus-infected MNLs injected via the right common carotoid artery were capable of inducing the chorioretinal lesions in 50% of the eyes, but that as many as 10(3) Pfu of free virus were required to produce the same lesions in the same percentage of eyes. This result clearly indicated that virus-infected MNLs were far more efficient in producing chorioretinitis than free virus, and may thus play a crucial role in the pathogenesis of herpetic chorioretinitis in newborn rabbits. When 111In-labeled virus-infected or uninfected MNLs were injected into normal rabbits via the right common carotid artery, the virus-infected MNLs localized more readily in the eye than the uninfected MNLs. The virus-infected MNLs also attached to the cultured vascular endothelial cells significantly more often than the uninfected MNLs. These results suggested that virus-infected MNLs might be easily trapped in the circulation of the eye and, in this way, produce the ocular lesions.