The entry of oncolytic species B adenovirus into cancer cells

Beat Amstutz
Eliane Wandeler
Fabienne DiGennaro

Cancer comprises a large variety of clinical symptoms, mainly arising through genetic instability, enhanced cell proliferation and deregulated cell death. Tumors often resist currently available anti-cancer treatments, although new therapies including oncolysis and cancer vaccinations are emerging. Viruses are excellent tools for anti-cancer therapies, because they can lytically replicate in rapidely dividing cells, and lead to cancer regression, as documented for the first time nearly one hundred years ago. We are studying cell entry of the lytic human adenovirus serotypes of the species B. These agents are promising vectors for vaccinations, therapeutic gene transfer and oncolysis. They have a low seroprevalence and use a novel entry pathway via the ubiquitous membrane cofactor CD46 as a primary receptor. Using quantitative biochemical assays and fluorescence and electron microscopy in static and dynamic modes, we dissect the productive entry pathways of viral endocytosis leading to the escape of viruses from endosomes and cytoplasmic transport to the nucleus. These are most critical events for the outcome of therapeutic applications of viruses and pathogenesis. Understanding the pathways of entry of the species B adenoviruses is key for establishing effective new anti-cancer strategies on a rational and predictive basis.

Image 5: Adenovirus serotype 3 specifically binds the CD46 cDNA splice form BC1 transfected into baby hamster kidney cells. A large fraction of fluorescently tagged Ad3 (red, left panel) or native Ad3 (right panel) colocalizes with cell surface CD46 as indicated by confocal laser scanning microscopy (left panel, CD46 in green) and immunogold-EM (right panel, gold particles indicating CD46). Data from Sirena et al., JVI, 78, 4454, 2004.

Key publications:

Meier, O., and Greber, U.F. (2003). Adenovirus endocytosis. J. Gene Med. 5, 451–462.    
Imelli, N., Meier, O., Boucke, K., Hemmi, S., and Greber, U.F. (2004). Cholesterol is required for endocytosis and endosomal escape of Adenovirus type 2. J. Virol. 78, 3089-3098.      
Sirena, D., Lilienfeld, B., Eisenhut, M., Kaelin, S., Boucke, K., Beerli, R.R., Vogt, L., Ruedl, C., Bachmann, M.F., Greber, U.F., and Hemmi, S. (2004). The human membrane cofactor CD46 is a receptor for species B Adenovirus serotype 3. J. Virol. 78, 4454-4462.