Induction of an activated b lymphocyte-associated surface moiety defined by the B2 monoclonal antibody by ebv conversion of an EBV-negative lymphoma line (Ramos): differential effect of transforming (B95-8) and nontransforming (P3HR-1) EBV substrains.

Abstract The expression of the B2 antigen, defined by a monoclonal antibody, was studied on Burkitt lymphoma lines, lymphoblastoid cell lines, leukemia and myeloma lines, hybrids between different hemapoetic cell lines, and EBV-converted sublines of originally EBV-negative, B2-negative B lymphoma lines. In confirmation of earlier results, the expression of B2 was found to be restricted to a relatively narrow portion of the B cell maturation pathway. Non-B cell-derived lines were uniformly negative. Hybrids derived from the fusion of highly B2-positive and B2-negative or low B2 expressing lines of B cell origin were B2-positive. In contrast, fusion of B2-positive Burkitt lymphoma lines with the primitive human erythroleukemia line K562 resulted in the complete extinction of B2 expression. These findings are in line with the expected behavior of a B cell differentiation marker. EBV conversion of the EBV-negative, B2-negative Ramos lymphoma line by the transforming B95-8 substrain of the virus regularly induced the expression of B2, whereas conversion with the nontransforming P3HR-1 substrain had no such effect, in spite of the continued presence of EBV-DNA and EBNA in both types of EBV-converted sublines. The possibility that B2 induction may reflect the action of the transforming gene(s), present in B95-8 but deleted from the P3HR-1 virus, and the implications of this possibility for the functional mapping of the EBV genome are discussed.</jats:p

Up regulation of the Epstein-Barr virus (EBV)-encoded membrane protein LMP in the Burkitt's lymphoma line Daudi after exposure to n-butyrate and after EBV superinfection

The Burkitt's lymphoma line Daudi carries a nontransforming Epstein-Barr virus (EBV) strain that has a deletion in the BamHI WYH region of the genome coding for the EBV nuclear antigen 2 (EBNA-2). Daudi cells fail to express the EBV-encoded latent membrane protein (LMP) (D. Ghosh and E. Kieff, J. Virol. 64:1855-1858, 1990). We show that LMP expression can be up regulated by exposure to n-butyrate and by superinfection with the B95-8 (B virus)- and P3HR1 (P virus)-derived EBV strains. Two LMP polypeptides of 60 and 48 kilodaltons (kDa) were detected in immunoblots of Daudi cells that had been exposed to 3 mM n-butyrate for 24 h. The intensity of the 48-kDa LMP increased during 72 h, in parallel with the appearance of early antigen-positive cells. The 60-kDa LMP was expressed at a low level and remained constant. Superinfection of Daudi cells with B and P virus induced the 60-kDa LMP within 3 h. In addition, P virus induced the 48-kDa LMP at a low level. The B virus-encoded EBNA-2 and EBNA-5 were detected 12 h after superinfection. The B virus-encoded 63-kDa LMP was coexpressed with the endogenous LMP after 48 h. Inactivation of the virus by UV illumination abolished the expression of the B virus-encoded antigens but did not affect the induction of the endogenous LMP. The B-cell activation marker CD23 was up regulated by B virus superinfection but not by n-butyrate exposure. CD23 was also expressed at a higher level in a stable B virus-converted subline, E95A-Daudi, that was EBNA-2 positive and coexpressed the Daudi virus- and B virus-encoded LMP. The results suggest that LMP expression is regulated by the interaction of cellular and viral factors. Binding of the virus to its membrane receptor might be involved in the triggering of cellular control mechanisms. Viral gene products are not directly involved in this function but may contribute to create a permissive cellular environment for LMP expression.</jats:p

Studies on the B lymphoblast antigen No. 1 (BB-1) on a series of Burkitt lymphoma lines differing in the expression of the EBV/C3 receptor complex.

Abstract In the Jijoye-P3HR-1 family of Burkitt lymphoma sublines, the expression of the B lymphoblast-1 antigen, BB-1, identified by the monoclonal antibody described by Yokochi and colleagues, was found to be strictly related to the expression of the EBV receptor/C3 receptor (EBVR/C3R) complex. It was absent on the receptor-negative P3HR-1 line, present in the original receptor-positive Jijoye line, and reappeared in nonvirus producer sublines derived from P3HR-1 itself. We suggest the BB-1 antigen is related to the EBVR/C3R complex in the Jijoye family, either at the level of genetic or epigenetic determination or at the level of steric interaction on the cell membrane. In all probability, however, the BB-1 antigen is not identical to the receptor itself. It is also clear that a similar relationship does not necessarily apply to other cell lines. In the course of the studies, it was accidentally discovered that propagation of the P3HR-1 cells on newborn instead of fetal calf serum induces the concomitant expression of EBV receptors, C3 receptors, and the BB-1 antigen. The mechanism of this induction is obscure; it does not appear to be related to any significant change in the frequency of virus-producing cells.</jats:p

Surface marker characterization of EBV target cells in normal blood and tonsil B lymphocyte populations.

Abstract Human FACS-sorted B lymphocyte subpopulations were investigated for their susceptibility to immortalization by Epstein Barr virus (EBV). Only B cells reacting with the monoclonal antibody B2 were immortalized, whereas cells reacting with anti-human IgG or the monoclonal antibody BB2 were not responding. Cells positive or negative for IgM, IgD, Burkitt's lymphoma antigen (BLA), BB1, and HB2 were all transformed by EBV.</jats:p