Most adenoviruses that have been historically used for gene therapy have been based on serotype 5 (AdWT). Unfortunately, expression of the primary receptor for Ad5 (the coxsackie-adenovirus receptor, CAR) is highly variable on cancer cells. In fact, several studies have demonstrated a resistance of malignant glioma to adenoviral vectors, a finding that was subsequently attributed to the quantitative deficiency of CAR on brain tumor cells.

First, we tested a variety of tumor specific promoters and identified survivin (S) as an excellent tumor specific promoter for transcriptional control of E1a, a gene essential for CRAd replication (J Neurosurg 104:583, 2006; Cancer Biol Ther 6:679, 2007).

Based on the above date data, we then created a novel oncolytic adenoviral vector which utilizes the survivin promoter and binds to heparan sulfate proteoglycans expressed on malignant brain tumors and named this new vector CRAd-S-pk7 (Hum Gene Ther 18:589, 2007).

The conclusion suggests that some viral assembly principles are limited paradigms for protein associations occurring in the broader range of cell biology including signal transduction, interaction of transcription factors and protein trafficking.

only recently have examples of such viruses that infect animals been discovered (paper link).

six new viruses with segmented RNA genomes, which was confirmed by gel electrophoresis of RNA extracted from virus particles.

results of RNA transfection experiments indicated that this RNA is not needed for viral infectivity.