Evaluation of Expression System

Creative Biolabs provides comprehensive information about protein expression for vaccine development and will help you choose the right expression system for your specific applications.

The development of highly efficient expression system is important to the manufacture of vaccines. Vaccine production may require relatively small quantities of expressed material but represent a very diverse category of different target antigens with significant structural differences. Thus, vaccine production requires production systems with very large outputs, which drives the quest for efficient and cost-effective systems.

Pathogen proteins need to be grown and harvested using the following mechanisms: a) The viruses are grown on primary cells such as chicken embryos or fertilized eggs, or on continuous cell lines such as cultured human cells; b) Bacteria are grown in bioreactors, which are devices that use specific growth media to optimize antigen production. Vaccine production techniques are evolving. Due to the lower incidence of pollution problems and higher productivity, non-conventional expression systems such as cultured mammalian cells are expected to become increasingly important compared to traditional methods such as chicken eggs.

Creative Biolabs provides not only traditional expression systems, including mammalian cells, yeast and E. coli, but also alternative systems such as transgenic animals, other bacteria than E. coli, plants and microalgae, insect cells, filamentous fungi, and cell-free systems.

Evaluation of Expression System

Expression system can be divided into two main types, Prokaryotic and Eukaryotic. Prokaryotic expression systems include bacteria such as E. coli and eukaryotic systems include yeast, mammalian or insect cells. Several factors need to be considered before choosing the right vaccine antigen expression system: expression levels, selection marker and the presence or absence of post-translational modifications. These are important factors that influence the efficacy of recombinant antigens as vaccines. Bacterial expression systems are widely used due to their ability of easily handling and high-level expression. However, for antigens that require post-translational modifications, mammalian, yeast, mammalian or insect cells are considered.

  • Prokaryotic: Small protein, high yield, low cost
  • Eukaryotic: Large protein, low yield, high cost

Bacterial Expression System

Bacteria are easy to culture, growth fast and produce high yields of recombinant proteins, thus act as a rapid and simple system for the expression of recombinant proteins. The culture medium is inexpensive and the method suitable for scale-up production is straightforward. The most widely used bacterial system is E. coli because of their well-understood genetics, genomic sequence, and physiology. The genetic manipulation is simple, and they are suitable for large-scale fermentation. However, the expressed multidomain eukaryotic proteins are generally non-functional, since the bacteria are unable to perform the desired post-translational modifications or molecular folding.

Yeast Expression System

Expression of proteins in yeast is a common alternative to prokaryotic and higher eukaryotic expression. Yeast cells take the advantages of producing proteins in microbes (growth speed, easy genetic manipulation, low-cost media) while offering some of the attributes of higher eukaryotic systems (post-translational modifications and secretory expression). So far available recombinant vaccines against HBV and HPV are based on antigens expressed in the conventional yeast strain Saccharomyces cerevisiae. The vaccines are formulated with HBV or HPV antigens expressed in S. cerevisiae. Recombinant vaccines produced in yeast strains other than S. cerevisiae are of great interest for production of vaccine antigens and immunotherapeutics such as Pichia pastoris, which has developed as a new heterologous expression system for its industrial high cell density, highly developed genetic system, ease of use and low costs.

Baculovirus-Insect Expression System

Baculovirus is a member of the insect-borne virus family and was originally used as a biopesticide with a large double-stranded circular DNA genome. Huge quantities of polyhedrin produced by baculovirus are the fundamental features to develop the viruses as vectors for foreign protein production. Nowadays, baculovirus-insect expression system has been relatively mature in many labs for protein production and is becoming a leading method to produce high-quality proteins among the eukaryotic expression systems.

Mammalian Cell Expression System

Mammalian expression systems can be used to produce diverse immuno- and biotherapeutic molecules that have the most native structure and activity due to their physiologically relevant environment and ability to perform complex post-transcriptional modifications. Mammalian expression systems can be used to produce proteins transiently or through stable cell lines and large amounts of proteins can be produced in one or two weeks. These transient, high-yield mammalian expression systems utilize suspension cultures and can produce gram-per-liter yields.

Creative Biolabs provides viral vaccine production using various mammalian cell lines, including the Chinese Hamster Ovary (CHO), the Human Embryonic Kidney 293 (HEK293) cell lines, Vero, PER.C6, EB66, PER.C6, CAP, AGE1.CR and so on.

Plant Expression System

The plant expression system prepares a vaccine mainly by transferring a vector carrying an antigen gene into a plant cell and expressing the corresponding gene of interest in the plant in manners of stable transformation or transient transformation. Its advantages are that it is easy to expand the production of vaccine antigens through the transgenic seed bank and possible to express vaccines in fruits and other edible plant organs, thus oral administration of such vaccines avoiding the cumbersomeness of subsequent processing of traditional vaccines. The Chloroplast Genetic Engineering System is the most promising method in transient transformation. Commonly used methods to express recombinant subunit vaccines in transient transformation system are genetically modified plant virus and particle bombardment.

Cell-free Expression System

The cell-free protein expression system (CFPS) utilizes enzymes and protein factors from cell extracts, exogenous DNA or mRNA as a template, and complements the substrate and energy substances required for translation to achieve in vitro synthesis of the target protein. Cell-free expression systems have once again gained attention and application due to their invulnerability to complex intracellular environment, high tolerance to toxic proteins and low cost of product separation.

Chloroplast Genetic Engineering System

The chloroplast genetic engineering technology has many advantages, including high-level expression of the target gene, single transformation of multiple genes, maternal inheritance of the transgene, and avoidance of gene silencing and side effects. Due to maternal inheritance, chloroplast expression is largely less risky for transgenic crops to transfer foreign genes to other crops through pollen. These characteristics enable the chloroplast genetic engineering system a promising technology to produce vaccines against bacteria, virus and other pathogens.

Filamentous Fungi Expression System

Filamentous fungi are lower eukaryotes commonly used to produce subunit vaccines with outstanding advantages including excellent protein secretion and post-translational modification capabilities similar to other eukaryotic proteins. The secreted proteins produced by filamentous fungi undergo a process of folding, proteolytic processing and other modifications such as glycosylation, giving them a similar function as natural proteins.

Ciliate Expression System

Ciliate expression system utilizes Ciliate for its simple nutritional requirements, fast growth rate, and having the ability of eukaryotes to post-translationally modify proteins. After improving T. thermophila strain, studying the mechanism involving regulation, controlling of protein synthesis, post-translational modification and sorting, optimizing the fermentation process, Ciliate expression system presents an excellent performance in producing biopharmaceutical proteins.

As vaccine manufacturing specialists, Creative Biolabs has a wealth of expertise and the world's most advanced manufacturing equipment to meet your specific application requirements. We guarantee a high yield with the best quality.


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