CHARACTERIZATION OF A 70-KDA, EBV GP350 220-BINDING PROTEIN ON HSB-2 T-CELLS/

EBV binds and infects HSB-2 T cells via a receptor distinct from CD21. To further study this novel EBV receptor, we expressed the first 470 amino acids of the EBV-gp350/220 using the baculovirus expression syst em. The recombinant gp350/220((1-470)) has a m.w. of 95 kDa, reacts wi th anti-gp350/220 Abs, and binds CD21 in ELISA. Radiolabeled gp350/220 ((1-470)) binds both HSB-2 and Raji cells. The gp350/220((1-470)) prot ein also inhibits EBV binding to both HSB-2 and Raji, detected by flow cytometry. Lysates of HSB-2 cells compete with CD21 for binding to gp 350/220 (1-470), suggesting that the two receptors bind related epitop es on the recombinant protein. Scatchard analysis 220((1-470)), reveal s that gp350/220((1-470)) binds to 34,000 high affinity sites/HSB-2 ce ll (K-d = 0.92 X 10(-8) M) compared with the 97,000 high affinity site s bound/Raji cell (K-d = 1.78 X 10(-8) M). Utilizing a gp350/220((1-47 0))-affinity matrix, we identify a 70-kDa (55-kDa nonreduced) protein on the surfaces of I-125-labeled HSB-2 cells. Binding of this protein to the matrix is inhibited by anti-gp350/220 Ab 72A1. In summary, we c haracterize a novel EBV-binding molecule on HSB-2 cells, compare its r eactivity with gp350/220 to that of CD21, and provide evidence of a gp 350/220-reactive, 70-kDa protein on the surfaces of HSB-2 cells. In vi ew of previous evidence of HSB-2 infectivity by EBV, we propose that t he 70 kDa protein represents the novel EBV receptor.