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 3L bioreactors for virus production under batch and perfusion modes. A titer of 2.7×108 TCID50mL-1 was obtained in 3L batch culture infected at a cell density of 1.4×106 cellsmL-1 , and was further improved to 1.1×109 TCID50mL-1 in perfusion culture infected at 4.6×106 cellsmL-1 . These titers are similar to or better than the previously reported best titer of 8.6×107 TCID50mL-1 and 8.1×108 TCID50mL-1 respectively obtained in labor-intensive adherent Vero batch and perfusion cultures. HSV-1 production in batch culture was successfully scaled up to 60L 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.