Isolation and characterization of a specific deletion mutant of human adenovirus type 2

Abstract

A specific deletion mutant of human adenovirus type 2 (Ad2) was detected when pools of wild-type Ad2 were grown at high multiplicity of infection in HeLa cells. This deletion mutant, designated dl-Ad2, was enriched when the defective Ad2-SV40 hybrids of the Ad2 ++HEY population were cloned in monkey cells in the presence of an added excess of wild-type Ad2. Electron microscope heteroduplex analysis and restriction endonuclease examination established the Ad-specific nature of the dl-Ad2 DNA and revealed a single, homogeneous deletion of about 0.08 to 0.09 fractional genome length situated between 0.78 and 0.87 Ad2 map unit. This genome structure is very similar to that of several other incomplete adenoviruses already described. The deleted segment encompasses one of the four early genome regions of Ad2. dl-Ad2 particles are not infectious in both human and monkey cells, although the mutant DNA is replicated in these cell types. dl-Ad2 is able to interfere efficiently with SV40 DNA replication in coinfected monkey cells. Furthermore, virus populations could be cloned consisting exclusively of Ad2 ++HEY hybrid viruses and dl-Ad2 “helper” viruses, indicating that dl-Ad2 can complement sufficiently for the large Ad2 DNA deletion in the Ad2 ++HEY hybrid genomes.