Process intensification of the baculovirus expression vector system using a perfusion process with a low multiplicity of infection at high cell concentrations.

Abstract

The emergence of new viruses and the spread of existing pathogens necessitate efficient vaccine production methods. The baculovirus expression vector system (BEVS) is an efficient and scalable system for subunit and virus-like particle vaccine production and gene therapy vectors. However, current production processes are often limited to low cell concentrations (1-4 × 10⁶ cells/mL) in fed-batch mode. To improve the volumetric productivity of the BEVS, a medium exchange strategy was investigated. Screening experiments were performed to test baculovirus (expressing green fluorescent protein; GFP) infection and productivity of insect cell cultures infected at high cell concentration (1-2 × 10⁷ cells/mL), showing that infection at high cell concentrations was possible with medium exchange. Next, duplicate perfusion runs with baculovirus infection were performed using a cell concentration upon infection (CCI) of 1.2 × 10⁷ cells/mL and a multiplicity of infection (MOI) of 0.01, reaching a maximum viable cell concentration of 2.8 × 10⁷ cells/mL and a maximum GFP production of 263 mg/L. The volumetric productivity of these perfusion runs was 4.8 times higher than for reference batch processes with a CCI of 3 × 10⁶ cells/mL and an MOI of 1. These results demonstrate that process intensification can be achieved for the BEVS by implementing perfusion, resulting in a higher volumetric productivity.