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

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 x 108 TCID50 mL-1 was obtained in 3 L batch culture infected at a cell density of 1.4 x 106 cells mL-1, and was further improved to 1.1 x 109 TCID50 mL-1 in perfusion culture infected at 4.6 x 106 cells mL-1. These titers are similar to or better than the previously reported best titer of 8.6 x 107 TCID50 mL-1 and 8.1 x 108 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. Oncolytic viruses (OVs) are wild type or engineered viruses which selectively replicate in and kill cancer cells while sparing normal tissues. Several OVs have been approved for use as immunotherapy for treatment of cancer. Vero cell, an African green monkey kidney cell line, is a suitable system for cultivation of many oncolytic viruses (OVs). The authors used a modified Vero cell line, which can grow in suspension (or free-floating) in the culture media and is more friendly and cost effective in large scale manufacturing, to improve the productivity of herpes simplex virus type 1 (HSV-1), one of the most important OVs. Through the optimization of cell culture conditions, such as nutrient supply and virus infection conditions, the productivity of HSV-1 was improved over one log. This is the first study demonstrating the suspension Vero cell technology could be a cost-effective for production of OVs at bioreactor cultures up to pilot-scale.image

Automated summary

This study develops suspension-adapted Vero cell culture processes for high titer production of oncolytic virus HSV-1. Optimization of cell culture conditions and scaling up to bioreactors successfully achieved high titers of HSV-1. This is the first study to demonstrate high titer production of HSV-1 in suspension Vero cell culture.