The interaction of non-transforming Epstein-Barr virus (EBV) with cell-associated EBV DNA in superinfected lymphoblastoid cell lines

Abstract

Two human lymphoblastoid cell lines were established by the transformation of human cord‐blood lymphocytes with transforming Epstein‐Barr virus (EBV). One cell line (HLB‐R1) was established with EBV obtained after the superinfection of Raji cells with HR‐1 EBV and the other (HLB‐B1) was established from B95‐8 EBV‐infected human cord‐blood lymphocytes. Both the HLB‐R1 and HLB‐B1 lines were susceptible to superinfection with HR‐1 EBV. We found that EBV DNA was replicated in the superinfected cell lines and that transforming EBV was produced in both the HLB‐B1 and HLB‐R1 cells. The average titer of transforming EBV obtained in the HR‐1 EBV superinfected HLB‐B1 and HLB‐R1 cell lines was 10⁴ transforming units (TU)/ml, whereas the average titers of transforming EBV obtained by the superinfection of Raji cells was 10 TU/ml. Epstein‐Barr virus capable of inducing early antigen (EA) in superinfected Raji cells (lytic virus) was not detected in any transforming virus preparation. Restriction enzyme digestion patterns of virus DNA isolated from HR‐1 and B95‐8 cells, as well as from superinfected cells, were compared. The EBV DNA that was replicated in the superinfected HLB‐R1 and HLB‐B1 cell lines showed a more complex pattern. Our data suggest that recombination between input HR‐1 EBV DNA and latent cell‐associated EBV DNA occurs. Presumably this recombination results in a change in the biological properties of the newly synthesized virus.