Mitogenic activity in human embryonic fibroblasts early after infection by human cytomegalovirus

We have characterized the nonspecific lymphocyte stimulation by extracts of human cytomegalovirus-infected human embryonic fibroblasts. Cell extracts prepared at 5 h postinfection (early extract) and 72 h postinfection (late extract) were both highly mitogenic in lymphocyte preparations from adult blood, cord blood, and rabbit blood. Maximum stimulation of the lymphocytes was observed on day 3 after the addition of early or late extract under optimal conditions. Early extract stimulated both the E-rosetting and the EAC-rosetting subpopulations of human lymphocytes. The mitogenic activity appeared before 5 h postinfection and was fairly stable at 30 degrees C for 5 h.