Enhancement of adenovirus vector entry into CD70-positive B-cell Lines by using a bispecific CD70-adenovirus fiber antibody.

Although many recombinant adenovirus vectors (rAd) have been developed, especially by using group C adenoviruses, to transfer and express genes, such rAd do not readily infect B-cell lines due to the lack of the coxsackievirus-adenovirus receptor. Bispecific antibodies have been used in different cell systems to facilitate entry of rAd into otherwise nonpermissive cells. Bispecific antibody is synthesized by covalently linking two monoclonal antibodies with distinct specificities. It has been shown that lymphoproliferative tumors commonly express the cell surface protein CD70, while this receptor is normally expressed on only a small subset of highly activated B cells and T cells. We therefore investigated whether a bispecific antibody with specificities for the adenovirus fiber protein and CD70 can facilitate rAd entry and subsequent expression of rAd-encoded genes in CD70-positive B cells. We found high CD70 expression on Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCLs), as well as some, but not all, Burkitt lymphoma (BL) lines. We show here that rAd encoding green fluorescent protein (Ad-GFP) infects EBV-transformed LCLs and a CD70-positive BL line 10- to 20-fold more efficiently in the presence of the CD70-fiber bispecific antibody. In contrast, the bispecific antibody does not enhance Ad-GFP infection in CD70-deficient BL cells. Using the CD70-fiber bispecific antibody, we increased the ability of rAd vectors encoding the EBV immediate-early proteins BZLF1 and BRLF1 to induce the lytic form of EBV infection in LCLs. These results indicate that the CD70-fiber bispecific antibody can enhance rAd infection of CD70-positive B cells and suggest the use of this vector to explore EBV-positive LCLs.