Evaluation of Multiplicity of Infection (MOI) and Harvesting Time on the Production of CVS-11 Strain of Rabies Virus in BSR Cell Line

Introduction: Rabies is a zoonotic fatal viral disease caused by the rabies virus of the genus Lyssavirus, and the family Rhabdoviridae. Challenge virus standard (CVS-11) strain of rabies virus is a key element in rabies reference laboratories, as many gold-standard tests depend on a suitable titer of this strain for interpretation of results. The present study investigated the optimal CVS-11 production in BSR cells (a clone of BHK-21). Methods: We analyzed the kinetic growth of BSR cells in a T-flask and inoculated BSR cells with different MOI of CVS-11 strain of rabies virus, and harvested the produced virus at different time points. Results: Our data showed that BSR cells had a doubling time of around 24-30 h, and at least 95% of cells kept their viability three days after culture. The virus reached the highest titer when the cells were infected at an MOI of 0.1 in DMEM medium, equal to 1.5 × 107 fluorescent focus units (FFU)/ml. Time-course analysis of CVS-11 titer showed that the highest titer was achieved around 72 h post-infection. All tests were performed in triplicate. Conclusion: Since producing the virus in mammalian cell culture is an expensive and complicated method, optimizing the virus production process may be an excellent strategy to lower the cost, save the laboratory resources and maximize productivity.