Effects of serial passage of Autographa californica nuclear polyhedrosis virus in cell culture.

A study of the major genomic alterations occurring during serial passage of Autographa californica nuclear polyhedrosis virus (AcNPV) in a Trichoplusia ni cell line was conducted. Progeny viruses from 24 independent passages were randomly selected and analyzed with restriction endonucleases. Specific deletion mutations were generated repeatedly in the PstI-G (7.6 to 13.1%) and the PstI-I (14.4-17.9%) regions; these mutations became predominant in the serially passaged stocks in which they arose. The deletions in the PstI-G region and two different insertions in this region were mapped to a 1 Kb PvuII-Bg/II fragment (9.85-10.70%) reflecting a high degree of sequence specificity in the initiation or selection of genomic alterations in this region. Insertional mutations were observed frequently and repeatedly within the PstI-E/HindIII-I region (33.6-37.2%) of the AcNPV genome. Individual examples of insertional mutations were observed in several other regions of the genome.