Development, optimization, and scale‐up of suspension Vero cell culture process for high titer production of oncolytic herpes simplex virus‐1

Abstract Oncolytic viruses (OVs) have emerged as a novel cancer treatment modality, and four OVs have been approved for cancer immunotherapy. However, high‐yield and cost‐effective production processes remain to be developed for most OVs. Here suspension‐adapted Vero cell culture processes were developed for high titer production of an OV model, herpes simplex virus type 1 (HSV‐1). Our study showed the HSV‐1 productivity was significantly affected by multiplicity of infection, cell density, and nutritional supplies. Cell culture conditions were first optimized in shake flask experiments and then scaled up to 3 L bioreactors for virus production under batch and perfusion modes. A titer of 2.7 × 10 8 TCID50 mL −1 was obtained in 3 L batch culture infected at a cell density of 1.4 × 10 6 cells mL −1 , and was further improved to 1.1 × 10 9 TCID50 mL −1 in perfusion culture infected at 4.6 × 10 6 cells mL −1 . These titers are similar to or better than the previously reported best titer of 8.6 × 10 7 TCID50 mL −1 and 8.1 × 10 8 TCID50 mL −1 respectively obtained in labor‐intensive adherent Vero batch and perfusion cultures. HSV‐1 production in batch culture was successfully scaled up to 60 L pilot‐scale bioreactor to demonstrate the scalability. The work reported here is the first study demonstrating high titer production of HSV‐1 in suspension Vero cell culture under different bioreactor operating modes.