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

A flow cytometric granularity assay for the quantification of infectious virus

A flow cytometry-based assay was developed to assess the infective titer of two recombinant viruses: a recombinant herpes simplex type 2 (rHSV-2) and a recombinant canary pox (rALVAC.gfp). This method uses granularity of infected Vero and QT-35 cells, respectively, and correlates this to the infectious titer of virus samples. The percent of the cell populations with a high level of granularity could accurately be correlated to viral titers obtained through a traditional plaque assay, with R² values greater than 0.8 using a semi-logarithmic scale. This approach offers a rapid, high-throughput method for infectious virus titration with similar accuracy to a traditional plaque assay.

Characterization of viability and proliferation of alginate-poly-L-lysine-alginate encapsulated myoblasts using flow cytometry

Genetically modified cells encapsulated in alginate-poly-L-lysine-alginate (APA) are being developed to deliver therapeutic products to treat a variety of diseases. The characterization of the encapsulated cells thus becomes paramount. This study reports a novel method to assess the viability, granularity and proliferation of encapsulated cells based on flow cytometry. The in vitro viability of encapsulated G8 murine myoblasts secreting canine FVIII (cFVIII) measured by flow cytometry was comparable to the traditional trypan blue exclusion method and both correlated with cFVIII secretion levels. In contrast, after implantation into mice, only viability measured by flow cytometry correlated with cFVIII secretion. Further, flow cytometry analysis of encapsulated cells maintained in vitro and in vivo revealed a greater fraction of granular cells compared to free cells, suggesting that encapsulation influences the morphology (cytoplasmic composition) of cells within APA microcapsules. Interestingly, the proliferation study showed that encapsulated cells proliferate faster, on average, and were more heterogeneous in vivo compared to in vitro culture conditions, suggesting that encapsulated cell proliferation is complex and environment-dependent. In conclusion, we show that flow cytometry analysis allows for a more consistent and comprehensive examination of encapsulated cells to aid in the development of cell therapy protocols.

Prediction of recombinant protein production in an insect cell–baculovirus system using a flow cytometric technique

The baculovirus expression vector system (BEVS) utilising the Autographa californica nucleopolyhedrovirus (AcMNPV) is widely becoming the system of choice for the production of many recombinant protein products due to the high yields obtained. However, there is a need to develop a simple reliable on-line method to monitor the production of recombinant proteins that have no intrinsic reporter properties. Here we utilise flow cytometry to measure cell size, granularity and DNA content in a single step analysis and correlate these parameters with the production of the recombinant protein beta-galactosidase. Clear correlations between these parameters and productivity are made with forward and side scatter signals showing the highest correlation coefficients. Measuring these parameters does not require any processing of the cells from culture to analysis. These parameters can therefore be used successfully to predict the amount of recombinant protein product in a BEVS system on-line.