Studies of adenovirus SV40 hybrid viruses. I. Assay system and further evidence for hybridization.

The titers of adenovirus and SV40 genetic carriers in hybrid preparations (E46(+)) can be quantitated by determining the percentage of cells showing neoantigens stainable with fluorescent antibody (FA) at 21 to 24 hours; both titers can be obtained with a single coverslip. The adenovirus and SV40 antigen-inducing titers so obtained are of the same order of magnitude in stock preparations of E46(+) grown in either African green monkey kidney (AGMK) or human embryonic kidney tissue culture (HEK), and are generally within one log of the infectivity titer. Quantitative studies of 50 degrees C heat inactivation, ultracentrifugation, and equilibrium density gradient centrifugation of E46(+) gave no indication that SV40 neoantigen induction could be dissociated from adenovirus, whereas adenovirus and SV40 virus grown as a mixed infection were readily dissociated by these procedures. Pretreatment of HEK cells with a medium containing 5-fluorouracil desoxyriboside (FUDR) did not affect induction of either adenovirus or SV40 neoantigen or development of cytopathic effects after infection with E46(+), but did prevent formation of Ad. 7 viral antigen.