The Epstein-Barr virus encoded cytokine viral interleukin-10 enhances transformation of human B lymphocytes.

In vitro infection of human B lymphocytes with Epstein-Barr virus (EBV) results in their growth transformation and establishment of immortalised lymphoblastoid cell lines. The virus was recently found to encode a homologue of the pleitropic cytokine interleukin-10 (IL-10), which has wide ranging effects on the immune system. We have investigated the effect of this virally encoded growth factor on the ability of EBV to immortalize B lymphocytes from tonsils and from adult and neonatal blood. Recombinant viral interleukin-10 (vIL-10) was found to increase dramatically the growth transformation of B cells from all three populations infected with either the highly transforming type 1 strain B95-8 or the less efficient type 2 strain BL16. This striking enhancement of transforming ability in the presence of viral IL-10 may be in part due to increased viability of the B cells during infection and decreased levels of interferon-gamma, a cytokine known to inhibit EBV transformation. Thus viral IL-10 influences a number of cell types of the immune system to allow the enhanced outgrowth of EBV transformed cells.