Identification of BKRF4 in the virion. (A) EBV from B95-8 cells was precleared by low-speed centrifugation and filtration. Virus particles were collected by ultracentrifugation in the presence (lane 2) or absence (lane 1) of NP-40, followed by IB with anti-BKRF4, anti-tubulin, anti-BALF4(gB), anti-BGLF4, and anti-BRRF2 antibodies.