Heterogeneity of Epstein-Barr virus derived from a nasopharyngeal carcinoma that has transforming and lytic properties.

The biological activities of Epstein-Barr virus (EBV) from a human epithelial hybrid cell line derived from a nasopharyngeal carcinoma (NPC-KT) were studied. Low concentrations of virus from the NPC-KT cell line stimulated DNA synthesis of human cord blood lymphocytes (CBL) and induced CBL to form EBV nuclear antigen-positive continuous cell lines. The CBL exposed to higher doses of virus showed stimulated DNA synthesis 2 days after infection, followed by cell lysis. Virus from the NPC-KT cell line induced EBV-specific antigens in nonproducer Raji cells and reduced the colony-forming ability of the super-infected cells. The ratio of transforming activity to early antigen-inducing ability was not constant during cell passage. The data obtained suggest that NPC-KT clone 1 cells are producing virus with cytotoxic and transforming properties.