ENHANCED INDUCTION OF GROWTH OF B LYMPHOBLASTS FROM FRESH HUMAN-BLOOD BY PRIMATE TYPE-C RETROVIRUSES (GIBBON APE LEUKEMIA-VIRUS AND SIMIAN SARCOMA-VIRUS)

Cell lines were established from the fresh peripheral blood of over 50% (11 of 21) of Epstein‐Barr virus (EBV) seropositive human donors after exposure to viruses of the gibbon ape leukemia virus (GALV)—simian sarcoma virus/simian sarcoma‐associated virus (SiSV/SiSAV) group. The incidence of growth induction upon exposure to baboon endogenous virus (BaEV), feline leukemia virus (FeLV) or to uninfected monolayer cultures was lower than 10%. Leukocytes from the peripheral blood of leukemic patients gave similar results, but exposure of fresh peripheral blood from eight normal EBV seronegative donors to the same viruses did not result in induction of cell growth. The established cell lines were polyclonal B‐lympho‐blasts as determined by morphological cytochemlcal, immunological and functional properties. The cells expressed EBV nuclear antigen (EBNA test), formed rosettes with complement‐activated sheep or bovine erythrocytes (EAC‐rosette test), but not with untreated erythrocytes (E‐rosette test), and were positive for one or more surface‐bound immunoglobullns. They were also karyotypically normal as determined by standard chromosome analysis and by trypsin‐Giemsa banding techniques. However, unlike other reported newly‐established diploid B‐lymphoblast cell lines, cells from approximately 80% of the cultures tested grew as locally invasive tumors when inoculated into 1‐to 3‐week‐old athymic nude mice and formed colonies in semi‐solid medium. Lymphoblasts from nude mouse tumors were readily re‐established as suspension cultures which retained their lymphoblastic properties and remained karyotypically normal. These studies indicate that under certain conditions, type‐C retroviruses of the GALV‐SISV/ SISAV group directly or indirectly increase the incidence of transformation of human B lymphocytes. Copyright © 1979 Wiley‐Liss, Inc., A Wiley Company