Enhancement of Adenovirus Vector Entry into CD70-Positive B-Cell Lines by Using a Bispecific CD70-Adenovirus Fiber Antibody

Abstract

The consistent presence of the Epstein-Barr virus (EBV) genome in certain malignancies, particularly its nearly universal presence in AIDS-related central nervous system lymphomas (4, 6, 29) and nasopharyngeal carcinomas (31), suggests that EBV itself could serve as a target for the preferential killing of tumor cells using gene delivery methods. Although the use of adenovirus vectors expressing EBV-specific toxins could potentially be useful for treating EBV-positive epithelial cell tumors, EBV-associated B-cell tumors are unlikely to be susceptible to conventional adenovirus-mediated delivery. The recently identified adenovirus receptor for serogroups 2 and 5, the coxsackievirus-adenovirus receptor (CAR), is not expressed in most hematologic cell lines (19,28,44), and consequently, adenovirus delivery to most B-cell lines is extremely inefficient. Nevertheless, other advantageous aspects of recombinant adenovirus vectors (rAd), including the extremely high achievable titers and the large size (10 kb) of the gene inserts tolerated, continue to make rAd the most attractive currently available gene delivery vectors. Therefore, there has been intense interest in modifying rAd to improve their delivery into hematopoietic cell types.Bispecific antibodies (BsAb) are covalently linked antibodies with distinct specificities (40). BsAb can extend a virus's normal tropism by using specific antibodies to the virus's receptor (the fiber protein, in the case of adenovirus [41]) and an alternate cellular ligand. For example, the delivery of rAd with a FLAG epitope-modified adenovirus fiber protein to T cells was shown to be greatly enhanced when a bispecific antibody directed against the FLAG epitope and the T-cell-specific CD3 cell surface receptor (48) was used. The method has been applied to other virus-cell surface ligand systems (5,7,49).In this study, we have investigated the use of an anti-CD70-antifiber BsAb to enhance adenovirus delivery to CD70-positive B-cell lines. CD70 expression is usually limited to a small subset of highly activated B and T cells (42). In contrast, EBV-immortalized B cells (lymphoblastoid cell lines [LCLs]) routinely express CD70 (42), as do a number of EBV-positive, as well as EBV-negative, B-cell lymphomas (17,27). Expression of CD70 (which has been identified as the CD27 ligand) on T cells appears to have a physiological role in inducing CD27 ϩ B cells to proliferate and differentiate into plasma cells (2), while on B cells, CD70 seems to have a costimulatory effect upon T cells (3). Interestingly, although CD70 expression in vivo is usually limited to a few highly activated B cells and T cells, CD70 is also expressed in EBV-positive nasopharyngeal carcinomas (1, 31). Thus, CD70 expression could potentially

Use of Adenovirus Vectors Expressing Epstein-Barr Virus (EBV) Immediate-Early Protein BZLF1 or BRLF1 To Treat EBV-Positive Tumors

“…Thus, an adenovirus vector is not the optimal vehicle for delivering genes to EBV-positive lymphomas; other vectors would be preferable. Alternatively, approaches which increase adenovirus-mediated gene delivery to lymphocytes, including modification of the viral fiber protein to allow virus binding to alternative cell receptors (9) or the use of bispecific antibodies directed against the adenovirus fiber protein and lymphocyte cell surface antigens (23), may allow the efficient use of the BZLF1 and BRLF1 adenovirus vectors in EBV-positive lymphomas. Westphal et al previously demonstrated that both the BZLF1 and BRLF1 adenovirus vectors induce lytic EBV infection when inoculated directly into an adenovirus-susceptible Burkitt lymphoma tumor (54), thus confirming that if efficient delivery of the BZLF1 or BRLF1 gene can be accomplished in EBV-positive lymphomas, it is likely to induce a similar therapeutic response to that observed for NPC tumors.…”

Regulation of cellular and viral protein expression by the Epstein-Barr virus transcriptional regulator Zta: Implications for therapy of EBV associated tumors

“…The approaches by adenovirus-mediated gene delivery to lymphocytes or the use of bispecific antibodies directed against the adenovirus fiber protein and lymphocyte cell surface antigens have been reported in EBV-positive lymphomas. 106 Other possibilities are also being investigated.…”

Gene therapy progress and prospects: adenoviral vectors

“…Advantages of the two-component system are that many receptors can be targeted and there is no need to genetically engineer the vector. A commonly used example of the two-component method employs bispecific antibodies, 31 one to the fiber and the other to a cell receptor expressed for example on tumor cells 32 or cell surface antigen that is upregulated in angiogenic areas of tumors. 33 This approach has been used frequently to demonstrate proof of concept of a given targeting ligand.…”