There is an urgent need to improve virus-like particle (VLP) biomanufacturing processes to prevent VLP vaccine shortages and reduce cost of goods manufactured. As ~20-200 nm particulate antigens with repetitive surface structure, VLPs drive robust immune responses with high protective antibody responses, making them a very compelling platform for preventative and therapeutic vaccines. Most clinically approved vaccines against Hepatitis B (HBV), Plasmodium falciparum, and HPV are VLP vaccines produced inside yeast cells. Although VLP production in yeast is more cost-effective than in other cellular hosts, the process yields from routine production in fed-batch systems have still resulted in extremely high costs of goods manufactured (COGsM). These high manufacturing costs beget expensive vaccines that are inaccessible to potential beneficiaries in the Global South, including commercial products like Gardasil-9, which has less than 30% uptake in African adolescent girls despite HPV prevalence in Africa being nearly twice that of other continents worldwide.
Sunflower is pioneering an innovative perfusion fermentation approach for the production of VLPs and other protein biologics using fully-automated continuous bioprocesses. Perfusion fermentation enables cultures to build a healthy biomass through continual nutrient replenishment and removing a cell-free harvest (including waste products) from the reactor. Here, we will present data showing the perfusion fermentation of Pichia pastoris using the Daisy Petal TM Perfusion Bioreactor System for intracellular expression of multiple serotypes of a proprietary HPV VLP candidate vaccine. The space-time yield (STY) of the VLPs achieved using perfusion fermentation of yeast was consistently higher than the STY of VLPs achieved using fed-batch processes and particles achieved were capable of inducing robust anti-virus neutralizing antibodies in mice. Given the influence of STY on COGsM, we believe that perfusion fermentation has significant potential to enable lower vaccine costs to patients and enable regional production capabilities as part of small-footprint distributed manufacturing facilities.