Epstein-Barr virus nuclear antigen 2 specifically induces expression of the B-cell activation antigen CD23.

Abstract

Epstein-Barr virus (EBV) infection of EBVnegative Burkitt lymphoma (BL) cells induces some changes similar to those seen in normal B lymphocytes that have been growth transformed by EBV. The role of individual EBV genes in this process was evaluated by introducing each of the viral genes that are normally expressed in EBV growth-transformed and latently infected lymphoblasts into an EBV-negative BL cell line, using recombinant retrovirus-mediated transfer. Clones of cells were derived that stably express the EBV nuclear antigen 1 (EBNA-1), EBNA-2, EBNA-3, EBNA-leader protein, or EBV latent membrane protein (LMP). These were compared with control clones infected with the retrovirus vector. All 10 clones converted to EBNA-2 expression differed from control clones or clones expressing other EBV proteins by growth in tight clumps and by markedly increased expression of one particular surface marker of B-cell activation, CD23. Other activation antigens were unaffected by EBNA-2 expression, as were markers already expressed on the parent BL cell line, including BL markers (cALLA and BLA), proliferation markers (transferrin receptor and BK19.9), and cell adhesionrelated molecules (LFA-1 and LFA-3). Increased CD23 expression in cells expressing EBNA-2 was apparent from monoclonal anti-CD23 antibody binding to the cell surface, from immunoprecipitation of the 45-kDa and 90-kDa CD23 proteins with monoclonal antibody, and from RNA blots probed with labeled CD23 DNA. The results indicate that EBNA-2 is a specific direct or indirect trans-activator of CD23. This establishes a link between an EBV gene and cell gene expression. Since CD23 has been implicated in the transduction of B-cell growth signals, its specific induction by EBNA-2 could be important in EBV induction of B-lymphocyte transformation.

Immortalization of Epstein--Barr virus-infected CD23-negative B lymphocytes by the addition of B cell growth factor

“…1 a). This result is interesting since the induction of CD23 has been specifically associated with EBNA 2 expression (Wang et al, 1987;Calender et al, 1987). Our assumption is that a subpopulation of resting B cells exists which does not respond to EBNA 2 expression by becoming activated and expressing CD23.…”

“…Up-regulation of CD23 has been reported after transfection of the isolated EBNA 2 or LMP genes into EB virus-negative Burkitt's lymphoma cells (Wang et al, 1987(Wang et al, , 1988. This suggests that these gene products are responsible, at least in part, for maintaining the high levels of expression of CD23 after the initial transient activation mediated by EB virus receptor binding.…”

“…Immortalized B ceils also express cellular activation antigens consistent with their lymphoblastoid stage of differentiation. These include CD23 , which is upregulated by the EBNA 2 gene product (Wang et al, 1987) and is cleaved and shed from the cell surface acting as an autocrine growth factor for LCL (Swendeman & Thorley-Lawson, 1987). A heterogeneity in the response of B cells to EB virus infection has been noted based on their expression of CD23.…”

Epstein--Barr virus (EBV) nuclear antigen 6 induces expression of the EBV latent membrane protein and an activated phenotype in Raji cells

“…Both EBNA 2 and LMP have been shown, in gene 0001-1330 © 1993 SGM transfer experiments, to induce cellular changes consistent with B cell activation; in particular, both stimulate expression of the cell surface antigen CD23 Wang et al, 1987Wang et al, , 1990a. In addition EBNA 2 is a transcription factor which can activate the expression of LMP (Fahraeus et al, 1990;Wang e t al., 1990 b) and, by acting on the major rightward promoter (Cp or BCR 2) in the BamHI C region of EBV (Sung et al, 1991;Woisetschlaeger e t al., 1991), may also initiate or enhance the expression of EBNAs 1, 3, 4 and 6 (Woisetschlaeger et al, 1991).…”

Tumorigenicity of EBNA2‐transfected cells

“…These findings suggest the important role of EBNA2 in transformation. Transactivation of CD21 [12], CD23 [13], c-fgr [14] and LMPI [15.16] has been demonstrated and thought to be a mechanism of lymphocyte Immortahzation by EBNA2. But the process and mechanism oftumorigenesis by EBNA2 is now unclear.…”