According to World Health Organization's report on "Progress and Challenges with Achieving Universal Immunization Coverage", vaccination is one of the public’s most cost-effective forms of biomedical treatment. However, in 2018, almost 20 million children across the world were left undervaccinated. Thus, it is imperative to develop more cost effective techniques for virus production, making it more affordable to individuals on global level.
Vero cells are the most widely accepted cell type for vaccine production. However, their growth is anchorage-dependent. Until recently, culture at high densities was only made possible through the use of microcarriers, which are glass or plastic beads used as supporting matrices. The main downsides to culturing cells in adherent formats are that these often require additional time and labor-intensive steps compared to suspension applications.
Scientists at the National Research Council of Canada were able to adapt the Vero cell line CCL-81 to suspension culture without the use of microcarriers and effectively propagate vesicular stomatitis virus (VSV) in small and large scale applications (1). They found that the suspension cultured cells achieved a higher viral titer compared to those cultured in adherence format. In addition to this, the suspension cells generated a higher titer with increasing cell concentration, especially in bioreactors compared to small-scale shaker flasks. Cultures in which the fed-batch method was emplyed had an improved yield as well.
An exciting new avenue at the forefront of clinical development includes the use of vaccinations to treat primary or metastatic tumors. Scientists at the University Medical Center Groningen were able to effectively establish a GMP-compliant manufacturing process to produce a vaccine targeting human papillomavirus (HPV) induced tumors. High-risk HPVs can integrate early proteins E6 and E7 into their host’s genome, transforming native cells to a malignant form. The vaccine, named Vvax001, aims to target these proteins.
Vvax001 is based on recombinant Semliki Forest Virus (rSFV). rSFV was chosen as the system for treatment for the following reasons:
- RNA from this virus does not integrate
- rSFV infection is cytolytic via apoptosis
- rSFV activates both the innate and adaptvie immune systems to target viral proteins
- There is no immune response directed at the viral vector itself
Briefly, the Vero cells were subjected to a series of electroporations with viral RNA encoding replicase, the E6 and E7 fusion proteins, capsid and spike proteins. The virus was then purified using anion and cation exchange chromatography, then analyzed for contaminants such as mycoplasma and other viruses. Stability testing confirmed a shelf life of at least 6 months. Researchers were able to achieve a mean viral titer of 4.0 x 108 infectious particles/mL after purification and the mean recovery was 19%.
It is apparent that the vaccine field is rapidly expanding and there is promise of improving techniques to reduce time and cost for production. Ultimately, it is our goal to make these vaccines more available to people across the globe, even those in seemingly unreachable areas so that we can prevent the spread of major biomedical diseases.
Written by Angela
Scientific Support Specialist, Lonza Pharma-Bioscience Solutions at Lonza
