RECOVERY OF EPSTEIN-BARR VIRUS FROM NONPRODUCER NEONATAL HUMAN LYMPHOID-CELL TRANSFORMANTS

Lymphoid cell lines (LCL) were established by infection of two batches of human umbilical cord lymphocytes with low multiplicities of the B95-8 strain of Epstein-Barr virus. Three of the 17 lines released minute amounts of transforming virus. The rest did not, nor did they make capsid antigen. However virus could be regularly recovered by lethal X-irradiation of transformed cells followed by cocultivation with primary human umbilical cord leukocytes. By this technique transforming activity could be identified in 15 of the 17 lines. These data indicate that these nonproducer human neonatal cell transformants established by EBV infection in vitro possess sufficient genetic information to code for production of biologically active mature virions. X rays alone failed to cause a detectable increase in the number of cells with capsid antigen or to enhance extracellular virus production. EBV-positive human serum blocked rescue if it was added during the first 2-4 hr after cocultivation, but not thereafter. Transforming virus could be recovered from X-rayed cells which were immediately thereafter lysed by freezing and thawing. These results suggest that recovery of virus following X-ray and cocultivation is not due to activation of the intracellular virus genome. Rather, it is likely that the method detects small numbers of virions which are cell associated. While transforming virus could regularly be rescued from lymphoblastoid cell lines resulting from in vitro transformation, attempts to rescue virus from Raji or EBV-converted BJAB cells were unsuccessful. This discrepancy suggests differences in genome complexity or in genome-cell interactions in different types of EBV-transformed cells. © 1979.