E46+ virus purified by limiting dilution and plaque isolation in AGMK cells consists of a mixture of hybrid and non-hybrid virus particles. Of 102 plaque isolates obtained in HEK cells, 98 contained no detectable hybrid virus, while 4 contained a small proportion of hybrid virus. Plaque isolates from AGMK cells uniformly induced SV40 neoantigen, but when these plaque isolates were plaqued in HEK cells the progeny were again non-hybrid adenovirus. It thus appears impossible to obtain a pure line of hybrid virus.
The proportion of hybrid virus produced in HEK cells fell progressively with decreasing multiplicity of infection, and plaque induction by E46+ virus in AGMK followed 2-hit kinetics, indicating that the hybrid virus particles are defective and require dual infection with non-hybrid virus for their propagation.