Stable cell pools are receiving a renewed interest as a potential alternative system to clonal cell lines. The shorter development timelines and the capacity to achieve high product yields make them an interesting approach for recombinant protein production. In this study, stable High Five cell pools are assessed for the production of a simple protein, mCherry, and the more complex HIV-1 Gag-eGFP virus-like particles (VLPs). Random integration coupled to fluorescence-activated cell sorting (FACS) in suspension conditions is applied to accelerate the stable cell pool generation process and enrich it with high producer cells. This methodology is successfully transferred to a bioreactor for VLP production, resulting in a 2-fold increase in VLP yields with respect to shake flask cultures. In these conditions, maximum viable cell concentration improves by 1.5fold, and by-product formation is significantly reduced. Remarkably, a global increase in the uptake of amino acids in the Gag-eGFP stable cell pool is observed when compared with parental High Five cells, reflecting the additional metabolic burden associated with VLP production. These results suggest that stable High Five cell pools are a robust and powerful approach to produce VLPs and other recombinant proteins, and put the basis for future studies aiming to scale up this system.

BACKGROUND: The emergence of infectious diseases is accelerating the intensification of bioprocess strategies to support the increasing demand for the manufacture of higher quantities of vaccines in short timeframes. Here, the development of stable Sf9 cell pools producing human immunodeficiency virus serotype 1 (HIV-1) Gag-eGFP virus-like particles (VLPs) is assessed.RESULTS: Fluorescence-activated cell sorting (FACS) was employed to select high producing cells, achieving an 8.1-fold increase in fluorescence intensity compared to unsorted cell pools after three rounds of cell sorting. The transferability of this system to bioreactor scale was also successfully achieved, attaining a 1.4-fold increase in VLP production and maintaining a higher cell viability than shake flask controls. Analysis of the metabolism of stable cell pools and parental Sf9 cells did not show significant differences regarding metabolite consumption and production, even though a better performance and more efficient metabolism were observed in bioreactor compared with shake flask cultures, highlighting the flexibility of these cells to adapt to different culture conditions and heterologous recombinant protein production.CONCLUSIONS: Stable Sf9 cell pools represent a suitable system for shortening bioprocess development times and accelerating vaccine production.