Improved efficiency in determining the titer of the Autographa californica baculovirus nonoccluded virus.

An economical and time-efficient method for titering the Autographa californica multiple-embedded nuclear polyhedrosis virus (AcMNPV) by the endpoint method is described. The method uses an electronic pipetting device to perform dilutions in the same 60-well microplate as is used for the assay, thus eliminating the need for test tubes or vials for making dilutions. Additionally, since small volumes are used for the dilutions, a substantial savings in medium is achieved. The effect of using three different lepidopteran cell lines in this assay for AcMNPV is also described. This test revealed that one line (the Trichoplusia ni IPLB-TN-R2 line) is at least 1.5 logs more sensitive to AcMNPV when using occlusion body formation as the measure of infection. The titer was about 6- to 12-fold higher in the IPLB-TN-R2 cell line than the other two lines when plaque assay procedures were used. The titer of a recombinant baculovirus with a bacterial beta-galactosidase gene was also measured in the three cell lines using X-gal as an indicator and showed the IPLB-TN-R2 line to be fourfold more sensitive to this virus.