Inhibition of Epstein-Barr virus transformation: evidence for a block between EBNA production and cell proliferation.

Non-adherent lymphocyte populations prepared from donors with previous EBV infection transformed in the usual way in response to EBV. However, transformation was completely inhibited in the presence of adult but not fetal human fibroblasts. Such inhibition was associated with lymphocytes from donors with prior EBV infection, but not from those without, and there appears to be an immunological basis for inhibition. Inhibition was associated with production of EBNA and was reversible. Addition of adult fibroblasts to non-adherent lymphocytes up to 2-4 days after infection with EBV also resulted in inhibition of transformation. These results are interpreted as indicating that EBV transformation involves two recognizable phases, with an immunological block between EBNA production and cell proliferation.