Recombination between simian virus 40 and adeno-associated virus: virion coinfection compared to DNA cotransfection

Recombination between simian virus 40 (SV40) and adeno-associated virus (AAV) has been detected, by infectious center in situ plaque hybridization procedures, after both DNA contransfection and virion coinfection of monkey BSC-1 cells. The number of cells producing recombinants (1 in a 1000) was the same irrespective of the way in which the SV40 and AAV genomes were delivered to the cell, despite the fact that 5-10 times more cells were infected after virion coinfection. Several other dosage-response parameters of the recombination process consequent to virion coinfection were comparable to those after DNA cotransfection. The sole difference observed between the two infection systems was that the SV40/AAV recombinants formed after virion coinfection contained an inordinately high proportion of AAV terminal DNA sequences. By separating the SV40 and AAV infections in time, such that the AAV infection was delayed until after certain events in the SV40 cycle had taken place, an optimum phase for recombination in the SV40 cycle was identified. This phase occurs a few hours after infection, well before the onset of SV40 DNA replication and the synthesis of SV40-specific early proteins.