Growth of type 2 herpes simplex virus in newborn and adult mononuclear leukocytes

Growth of type 2 herpes simplex virus (HSV) in newborn and adult human mononuclear leukocytes (MNL) was compared. Phytohemagglutinin stimulation of cultures for 3 days yielded comparable peak titers in newborn (10(5.3) PFU) and adult (10(5.1) PFU) MNL. Unexpectedly, 3-day cultures of unstimulated newborn MNL also substantially replicated HSV (10(4.7) PFU), whereas similarly treated unstimulated adult cells did not. Growth of HSV in freshly isolated human MNL was next investigated. MNL from 4 mothers and 6 nonpregnant adults showed no evidence of virus growth; however, leukocytes from 11 of 24 newborns (46%) supported replication. Newborn MNL manifested an increased ability to replicate HSV within 1 day of culture, whereas comparable growth in adult MNL was not achieved until the 4th day of culture. The significance of the above observations as it relates to visceral dissemination of HSV in the neonate is discussed.