Development of Nononcogenic SA7-Adeno-virus 2 Populations That Immunize Against SA7-Transformed Cells

Summary

Several SA7-adenovirus 2 (SA7-Ad2) populations were isolated from progeny obtained after simian cells were doubly infected with simian adenovirus, SA7, and human adenovirus type 2. The SA7-Ad2 isolates induced the synthesis of SA7 T antigen, replicated in simian cells, were antigenically adenovirus 2, and also contained an excess of normal Ad2 virions. The SA7-Ad2 particle which replicated in simian cells was defective as demonstrated by 1) two-hit kinetics of plaque formation in simian cells, and 2) enhanced plaque formation in simian cells in the presence of additional helper human Ad2. Therefore the SA7-Ad2 populations are composed of defective SA7 genomes in Ad2 capsids and complete Ad2. The populations containing the defective particles were nononcogenic in hamsters, while the parental SA7 from which they were derived was highly oncogenic. Although these viruses were nononcogenic, they were able to induce immunity against SA7-induced tumor cells.