Rapid quantification of vesicular stomatitis virus in Vero cells using Laser Force Cytology

•Viral infectivity methods are often slow, tedious, labor intensive, and difficult to standardize.•Laser Force Cytology uses optical and fluidic forces to quantify cellular changes upon infection.•Non-subjective measurements were made in 16 h that correlated with TCID50 results requiring 72 h.•Real-time Laser Force Cytology based measurements were correlated with TCID50 of the supernatant.•Rapid infectivity measurements can improve vaccine research, development and manufacturing. The ability to rapidly and accurately determine viral infectivity can help improve the speed of vaccine product development and manufacturing. Current methods to determine infectious viral titers, such as the end-point dilution (50% tissue culture infective dose, TCID50) and plaque assays are slow, labor intensive, and often subjective. In order to accelerate virus quantification, Laser Force Cytology (LFC) was used to monitor vesicular stomatitis virus (VSV) infection in Vero (African green monkey kidney) cells. LFC uses a combination of optical and fluidic forces to interrogate single cells without the use of labels or antibodies. Using a combination of variables measured by the Radiance™ LFC instrument (LumaCyte), an infection metric was developed that correlates well with the viral titer as measured by TCID50 and shortens the timeframe from infection to titer determination from 3 days to 16 h (a 4.5 fold reduction). A correlation was also developed between in-process cellular measurements and the viral titer of collected supernatant, demonstrating the potential for real-time infectivity measurements. Overall, these results demonstrate the utility of LFC as a tool for rapid infectivity measurements throughout the vaccine development process.