Further studies on inhibition of Epstein-Barr virus release by bovine serum: partial purification and characterization of the inhibitor.

The antivirus release factor (AVRF) was extracted from adult bovine serum and was partially purified in three steps by 1) ammonium sulfate precipitation, 2) Sephadex G-200 chromatography, and 3) DEAE-Sephadex chromatography, procedures that together increased specific activity 160 times. In molecular sieve chromatography, AVRF was found in fractions close to IgM. The AVRF activity was sensitive to KIO4 (0.04 M) but not to trypsin (0.1%), UV irradiation, ethyl ether, and heating at 56 degrees C for 30 minutes. The AVRF neither neutralized infectivity of Epstein-Barr virus (EBV) from the P3HR-1 cell line nor inhibited intracellular virus yields at concentrations that inhibited release of virus into culture fluid. Cellular release of two other strains of EBV (QIMR-WIL and B95-8) was also inhibited by AVRF. Electron microscopic examination of P3HR-1 cells cultured in the presence of AVRF revealed peculiar interacytoplasmic vacuoles containing many mature virus particles with tail-like structures.