Defective immune response to Epstein-Barr virus in patients with acute lymphocytic leukemia

Thirteen children with acute lymphocytic leukemia (ALL) receiving maintenance chemotherapy were tested for anti-Epstein-Barr virus (EBV) antibodies, EBV specific cytotoxic T lymphocyte (EBV-CTL) activity and spontaneous cytotoxicity against Raji cells in order to define the defective cellular immunity in ALL children during complete remission. Among 10 seropositive patients, anti-virus capsid antigen (VCA) antibody titer varied from 1:20 to 1:320 and anti-EBV nuclear antigen (EBNA) antibody was not detectable in four. No patients were positive for anti-early antigen (EA) antibody. EBV-CTL activity and interleukin 2 (IL-2) or interferon alpha (IFN-alpha) augmented EBV-CTL activity in eight seropositive patients was significantly lower than that in the seropositive age matched control group. IFN-alpha, OK-432 or IL-2 augmented spontaneous cytotoxicity were also significantly lower in the patients compared to those in the control group. These defective killer cell activities may allow EBV-infections to enter a severe, fulminant or persistently active state in the patients with ALL receiving aggressive maintenance chemotherapy.