Abstract
By filtration of normal human serum through a Sephadex G-200 column, an anti-virus release factor (AVRF), which is capable of inhibiting the release of Epstein-Barr virus (EBV) from cells cultured in vitro, was found in the fractions corresponding to IgM. Another component, antagonistic to the activity of AVRF, was found in the fractions close to those of albumin. Both AVRF and anti-AVRF were found in all sera from four EBV seropositive and three seronegative adults tested. EBV-release inhibition by AVRF was reversible. AVRF did not neutralize virus infectivity or inhibit intracellular virus growth. Virus adsorption on to cells was not prevented by AVRF but cap formation of EBV antigens on cells was augmented by it.