Case study

Defining the suitable expression system and developing a process transferable to cGMP manufacturing for a Placental Malaria (PM) vaccine.

Background and objectives

With funding from the German Ministry for Education and Research, the European Vaccine Initiative and Dr Benoit Gamain at the French National Institute of Health and Medical Research wanted to define the best region of the VAR2CSA Placental Malaria vaccine candidate. They then needed a suitable expression system to further transition this candidate to preclinical and clinical development.

Preliminary results suggested low expression yields for several of the protein’s forms in E. coli. GTP was approached with the objective to express five different recombinant proteins encompassing different regions of VAR2CSA, identify the most suitable expression system, and then develop a robust and efficient process for the manufacturing of clinical batches.

GTP’s solution

Considering the nature of the protein (large protein with a complex structure) and the preliminary results, GTP suggested the evaluation of four different expression systems (E. coliL. lactisP. pastorisCHO). Several constructs of VAR2CSA were expressed to assess the most efficient expression host and to provide enough protein to Dr Gamain’s team for immunogenic assessment.

Based on the expression yields, the potential for further expression improvement, the protein characteristics in in vitro assays and the immunogenicity results obtained in small animal models, one antigen expressed in both E. coli and CHO systems was initially selected.  After consideration of IP issues and production costs, E. coli was chosen for further development.

The complete upstream and downstream processes were developed at GTP. The final process yielded 2.5g of the VAR2CSA antigen, 99% pure, per 50L fermentation.


The process met customer expectations in terms of performance and product quality, and was developed within their tight schedule.

During the process development, the project team selected a CMO for phase I manufacturing. Shortly after completion, the process was transferred to the CMO with full documentation. Since the first transfer batch was consistent with the three validation batches previously done at GTP, the CMO could directly transition the project to GMP grade manufacturing. Phase I clinical trial is ongoing.

P. pastoris Purification System