Recombinant Epstein-Barr virus with small RNA (EBER) genes deleted transforms lymphocytes and replicates in vitro.

Strains of Epstein-Barr virus (EBV) with deletions of the small RNA (EBER) genes were made by homologous recombination using the EBV P3HR-1 strain, which has undergone deletion of the essential transforming gene that encodes the EBV nuclear antigen, EBNA-2, and a DNA fragment that was wild type at the EBNA-2 locus but from which the EBER genes had been deleted. Even though the EBER and EBNA-2 genes are separated by 40 kilobases, selection for transforming P3HR-1 recombinants that required a restored EBNA-2 gene resulted in 20% cotransfer of the EBER deletion. EBER-deleted recombinants transformed primary B lymphocytes into lymphoblastoid cell lines (LCLs), which were indistinguishable form LCLs transformed by wild-type EBV in their proliferation, in latency-associated EBV gene expression, and in their permissiveness for EBV replication cycle gene expression. EBER-deleted virus from infected LCL clones could infect and growth-transform primary B lymphocytes. These procedures should be applicable to the construction of other EBV recombinants within 40 kilobases of the EBNA-2 gene. The EBER-deleted EBV recombinants should be useful in further evaluating the role of EBERs in EBV infection.