Properties of a Small Virus Associated with Adenovirus Type 4

Summary One of our laboratory strains of adenovirus 4 was found to be contaminated with a virus having the following characteristics: it is small (18 × 21 mµ in diameter), angular in outline, probably icosahedral in symmetry, has a netlike capsid similar to reovirus, with about 100 antigenically reactive sites available on its surface, requires adenovirus for replication, suppresses the growth rate and ultimate yield of adenovirus in cell cultures, is serologically similar to another small virus from adenovirus 7 but distinct from one found associated with adenovirus 18, is structurally and serologically distinct from adenoviruses, and is stable to 60°C heating for 30 min, as well as to treatment with anionic detergent (SLS) and diethyl ether. These characteristics identify this agent as an adeno-associated virus (AAV), a member of a newly recognized group of small, defective DNA viruses (3, 4).