Epstein-Barr virus lacking latent membrane protein 2 immortalizes B cells with efficiency indistinguishable from that of wild-type virus

Epstein-Barr virus (EBV) is a human herpesvirus that efficiently transforms and immortalizes human primary B lymphocytes, In this study, the role of l atent membrane protein 2 (LMP2) in EBV growth transformation was investigat ed. LMP2 is a virally encoded membrane protein expressed in EBV-immortalize d B cells previously shown to be nonessential for EBV transformation. Howev er, a recent study reported that LMP2 may be an important determinant for e fficient B cell transformation (Brielmeier et al., Journal of General Virol ogy 77, 2807-2818, 1996), In this study a deletion mutation was introduced into the LMP2 gene using an E. coil mini-EBV construct containing sufficien t EBV DNA to result in growth transformation of primary B cells. In an alte rnative approach, the introduction of the gene encoding the enhanced green fluorescent protein (EGFP) by homologous recombination into the LMP2 gene o f EBV strain B95-8, generating the same LMP2 deletion mutation is reported. Careful quantification of B cell transformation using the EGFP(+)LMP2(-) r ecombinant virus determined that in liquid culture medium or in culture med ium containing soft agarose there was no difference in the ability of LMP2( -) virus to immortalize primary human B cells when compared to that of wild -type virus.