Cover photograph (Copyright © 2006, American Society for Microbiology. All Rights Reserved.): Astrocytes express &bgr;-galactosidase (&bgr;-Gal) encoded from the regulatable, gutless adenovirus vector delivered into the striatum. Sections were stained with rabbit anti-&bgr;-Gal (red) to detect transgene expression and chicken anti-MAP-2 (green) to label neurons. Confocal serial optical sections were combined to produce the three-dimensional projection shown. Transgene expression was achieved even in the presence of an immune response against adenoviruses, as would be encountered in human patients undergoing clinical trials. (See related article on page 27.)