Detection of baculovirus-infected insect cells by flow cytometric side-scatter analyses

Background: The baculovirus expression vector system (BEVS), utilizing the Autographa californica nuclear polyhedrosis virus (AcNPV), has turned out t o be an attractive alternative for high-level expression (<600 mg/l) of rec ombinant proteins. However, there is a shortage of reliable methods for mon itoring the infection process in situations where marker proteins cannot be used. Methods: Three recombinant baculoviruses, FastBac1-wtGFP, VTBac-GFP, and VL 1392-hIL-2R alpha, all having the genes inserted under the transcriptional control of the polyhedrin gene promoter of the Autographa californica nucle ar polyhedrosis virus (AcNPV), were used to infect Spodoptera frugiperda (S f9) and Mamestra brassicae (IZD-MB-0503) insect cells. The infection proces s of the recombinant baculoviruses was monitored by now cytometric side-sca tter and fluorescence intensity analyses over a period of 6-96 h. Results: A clear correlation between the side-scatter (SSC) signal and the relative fluorescence was observed for both of the infected cell lines, com pared to noninfected cells. Comparison of SSC histograms from noninfected i nsect cells with cells infected with the nonfluorescent recombinant baculov irus VL1392-hIL-2R alpha showed a clear increase of SSC for the infected ce lls. Conclusions: The SSC parameter call therefore be utilized for flow cytometr ic monitoring of a baculovirus infection process in situations where suitab le markers are not available. Cytometry 37:238-242, 1999. (C) 1999 Wiley-Li ss, Inc.