Improved replication of Autographa californica nuclear polyhedrosis virus in roller bottles: characterization of the progeny virus

A reproducible growth curve was established for the propagation of Autographa californica (Speyer) nuclear polyhedrosis virus (ACMNPV) In a continuous insect line from Spodoptera frugiperda (J. E. Smith) during large-volume production. A newly developed method for quantitation of polyhedra inclusion bodies (PIB) by electron microscopy (EM) during the growth cycle was compared to hemocytometer counts. The virus particles (VP) ratio to PFU and VP per PIB were established by EM methods. Optimal yields of PIB and cell-free virus with biological activities were obtained in six consecutive production lots when the growth curve conditions were followed. The DNA of the viruses produced in the 1st and 8th passages in the S. frugiperda cell line was treated with restriction endonucleases and compared with that from the E-2 cloned variant of this virus. Data confirmed that the virus was the ACMNPV and also indicated that there were no detectable changes after 8 passages in insect cell culture.