Any of a group (genus) of defective viruses which seem unable to reproduce without help from adenoviruses. They were formerly known as adeno-associated viruses and belong to the family Parvoviridae. These 20-nanometer virus particles were found during electron microscopic studies in several preparations of adenovirus from both human and monkey sources, and have since been observed in many adenovirus stocks.Adenoviridae

Like adenovirus, the dependovirus has a deoxyribonucleic acid (DNA) core. However, the dependovirus, although dependent upon adenovirus for its growth, does not appear to be structurally related to its “helper.” Its genetic content, as well as its size, is much smaller than that of adenovirus, and its protein coat is completely different from that of adenovirus. These particles contain single-stranded DNA and a protein coat with icosahedral symmetry. The single-stranded DNA has been shown to be present within the dependovirus virion as either plus or minus complementary strands in separate particles. Upon extraction, the minus and plus strands unite to form a double-stranded helix.

The genetic material of dependovirus not only can persist in cultured cells for long periods without giving evidence of its presence but also can survive within human beings in a latent state, becoming detectable only in specimens taken when the person is concurrently infected with adenovirus. This characteristic permits survival of a defective virus in nature, even though it cannot regularly replicate or be passed in infective form from host to host.