Highly Efficient Gene-Transfer into Chronic Lymphocytic Leukemia Cells Using Adenovirus Type 35 Genetic Vectors.

Adenovirus (Ad) vectors have been used to introduce genetic material into mammalian cells for gene-expression studies and/or gene therapy. Ad serotypes 2 and 5, the most widely used Ad virus vectors, belong to the group C adenoviruses, which bind to the coxsakie/adenovirus receptor (CAR) present on cells that are most susceptible to virus infection. Because lymphoid cells generally do not express CAR, high-titer virus and optimal conditions are required to infect lymphocytes, including the neoplastic cells of most lymphoid malignancies. Ad35, on the other hand, is a member of the group B adenoviruses that infect cells by binding CD46, a receptor expressed on most cell types. We found chronic lymphocytic leukemia B cells (n = 10) expressed high-levels of CD46 by flow cytometry, whereas none of the CLL samples expressed CAR by immunoblot analyses. We examined and compared the relative susceptibility of CLL cells to infection by Ad5 versus Ad35 vectors at various multiplicity of infection (MOI). These studies revealed that CLL cells were 100-fold more sensitive to infection with Ad35 than with Ad5. To examine whether this improved tropism of Ad35 for CLL cells was due to the adenovirus receptor for CD46, we examined the relative susceptibility of CLL cells to infection by Ad5 vectors that had been engineered to express the Ad35 knob fiber protein (Shayakhmetov DM, et al., J Virol 2000, vol 74, pp. 2567-83) responsible for binding CD46, designated Ad5F35. Titration studies evaluating for expression of a reporter transgene in infected CLL cells (e.g. the gene encoding green fluorescence protein (GFP)), found that Ad5F35 vectors also were > 100-fold more effective than Ad5 vectors at transducing CLL B cells. These studies reveal that Ad5F35 is a highly efficient vector for transducing CLL cells, a quality that should make these vectors better suited than Ad5 virus vectors for studies requiring gene transfer and/or gene therapy of this and related lymphoid malignancies.