Process Development, Ology Bioservices, Alachua, FL 32615, USA
Isabel Scholz*, Christopher Montoya & Eric Vela

Viral vectors are increasingly gaining importance in vaccine development, gene therapy and as oncolytic vectors. Vesicular stomatitis virus (VSV), an enveloped virus carrying a negative-sense RNA genome, has proven to be an excellent vaccine vector candidate against infectious diseases and specific cancers.

A variety of assays are available to determine yield of physical particles as well as infectious particles. However, several of the most well-characterized methods, such as plaque assays and tissue culture (TC) infectious dose 50 (TCID50) assays, are associated with a wide variance and are also time- and labor-intensive. Therefore, rapid and reliable means of assaying virus products are welcome advances, especially if the assay easily adapts to multiple product lines.

In this report, we describe a novel viral infection analysis method using a live VSV-based Lassa virus (LASV) vaccine candidate. The recombinant VSV has been genetically altered to express the LASV Josiah glycoprotein (VSVΔG/LASVGP), and infection in Vero cells was examined by microscopy using the Ovizio qMod camera and OsOne software. We assessed characteristics of infected Vero cells over the course of infection, obtained feature measurements of individual cells and examined very early biophysical distinctions of infected cells.

Viral infection of cultured cells induces changes in the biophysical characteristics of the affected cells. Advanced microscopic cameras such as Ovizio’s QMod, coupled with the appropriate software, can measure a variety of characteristics on a per-cell basis. We have employed this system to monitor the progression of vesicular stomatitis virus infection in Vero cells and to describe the cellular changes associated with advancing vesicular stomatitis virus infection. The measurements of cellular characteristics are operator-independent, and the goal is to establish a robust method to mathematically determine viral infection levels in a given sample. This will provide a means to measure viral titer in a faster and less subjective way than manual reading of plaque assays or tissue culture infectious dose 50 assays.