An adenovirus is disclosed, having a capsid comprising a hexon protein of SAdV-42.1 or an amino acid sequence at least about 99% identical thereto, or a hybrid hexon protein. The capsid encapsidates a heterologous nucleic acid molecule carrying a gene sequence operably linked to expression control sequences which direct transcription, translation, and/or expression in a host cell, and further encapsidates 5' and 3' adenovirus cis-elements necessary for replication and encapsidation.