Abstract
Background Tuberculosis (TB) is the second leading cause of death by infectious disease worldwide. About 1.4 million people die of TB each year. Parenterally administered Mycobacterium bovis BCG vaccine confers only limited immune protection from pulmonary tuberculosis in humans. There is a need for developing effective boosting vaccination strategies. AdAg85A adenovirus, a new promising tuberculosis vaccine candidate, has been studied with mouse, guinea pig, goat and cow animal models, and was shown to be effective against Mycobacterium tuberculosis (Mtb) infection [1]. A phase I trial on Ad5Ag85A adenovirus was also conducted, which demonstrated that AdAg85A adenovirus was safe and highly immunogenic [2]. To further evaluate the efficacy of this vaccine and reduce the cost of this promising vaccine candidate, a feasible and cost-effective large-scale cell culture production process had to be developed for manufacturing large quantities of AdAg85A adenovirus required for further clinical trials. Furthermore, the process had to be designed to meet all requirements for industrialization and commercialization of this vaccine candidate. Here we report our study on optimization of cell culture conditions, scale up of AdAg85A adenovirus production in 60L bioreactor and purification of the AdAg85A adenovirus at different scales. The optimized conditions for AdAg85A adenovirus production and purification were transferred to a GMP facility for manufacturing of AdAg85A adenovirus for further clinical trials. Materials and methods Four commercial serum-free cell culture media (SFM4HEK-293 and SFM4Transfx-293 from HyClone; Adenovirus Expression Medium (AEM) and CD 293 from Life Technologies), were evaluated for supporting the growth of HEK293SF-3F6 cell in suspension and also for the production of AdAg85a adenovirus in 125 mL shake flask cultures under various experimental conditions. The production of the AdAg85A adenovirus was then scaled up to 3L controlled bioreactor under the optimized conditions obtained from the shake flask experiment, further validated in a 60L bioreactor. Purification of the AdAg85A adenovirus was accomplished through many different steps. Some of the critical steps include cell lysis, benzonase treatment, Q-Sepharose HP anion exchange chromatography for capture of adenovirus/purification, Capto Core 700 multimodal chromatography for polishing, concentration and diafiltration into formulation buffer. The purification processes were also scaled up from 3L to 60 L production scale.
Highlights
Tuberculosis (TB) is the second leading cause of death by infectious disease worldwide
CD293 medium did not support the cell growth, the virus production was further improved by more than two folds when the cells were grown in SFM4HEK293 medium to respective cell density of 2x106 cells/mL and 4x106 cells/mL, and diluted with the same amount of CD 293 medium before the virus infection
Highest titer (5x1010 total viral particles/mL) of AdAg85A adenovirus was achieved by growing HEK293SF-3F6 cell in one of the above 3 media to a cell density of about 4x106 cells/mL, and diluting the culture with the same of CD293 before the virus infection
Summary
Tuberculosis (TB) is the second leading cause of death by infectious disease worldwide. About 1.4 million people die of TB each year. Administered Mycobacterium bovis BCG vaccine confers only limited immune protection from pulmonary tuberculosis in humans. There is a need for developing effective boosting vaccination strategies. AdAg85A adenovirus, a new promising tuberculosis vaccine candidate, has been studied with mouse, guinea pig, goat and cow animal models, and was shown to be effective against Mycobacterium tuberculosis (Mtb) infection [1]. A phase I trial on Ad5Ag85A adenovirus was conducted, which demonstrated that AdAg85A adenovirus was safe and highly immunogenic [2]
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