The baculovirus–insect cell expression system—insect cells used in conjunction with the baculovirus expression vector system (BEVS)—remains a crucial technology for manufacturing large and complex proteins. This eukaryotic expression system offers inherent safety, ease of scale-up, flexible product design, and versatility for a broad range of proteins. This article from biopharmaceutical company Sino Biological talks through the benefits and drawbacks of the technique.
Advantages of Baculovirus–Insect Cell Expression Systems
The baculovirus–insect cell expression system is a powerful and versatile platform for producing a wide range of proteins, and it offers several advantages compared with other expression systems.
One significant advantage is the system's ability to insert large DNA molecules into the vector, enabling the production of high-molecular-weight proteins. Additionally, the system can accommodate multi-gene insertions, allowing for the co-expression of different proteins simultaneously. These features make the baculovirus–insect cell expression system an attractive choice for the production of complex and diverse protein products.
Second, insect cells used in the baculovirus–insect cell expression system can perform a wide range of post-translational modifications (PTMs), such as glycosylation and acetylation. These PTMs are essential for ensuring proper protein folding, enhanced stability, and biological activity of the expressed proteins. As a result, insect cells can produce proteins with complex structures similar to those obtained through mammalian cell culture. This is a significant advantage over bacterial and yeast-based expression systems, which either lack or have limited ability to perform PTMs. The ability of insect cells to carry out these critical PTMs is often crucial for achieving the desired biological or therapeutic activity of the protein product, making the baculovirus–insect cell expression system an attractive option for the production of functional and biologically active proteins.
Third, the baculovirus–insect cell expression system excels at achieving high-density cell culture, resulting in substantial protein yields. This makes it a highly efficient platform for protein production. The system is versatile and can be used to express various types of proteins, including intracellular, membrane-bound, or secreted proteins. Additionally, it is well-suited for large-scale production, making it advantageous for industrial applications.
Moreover, the baculovirus–insect cell expression system provides an inherent safety advantage. Baculoviruses, the viral vectors used in this system, have a narrow host range, restricted to infecting specific insects. They are incapable of replicating in mammalian cells, which ensures that the manufacturing process and the final protein product maintain a high level of safety. This characteristic reduces the risk of potential contaminants and ensures the production of pure and safe proteins suitable for various medical, research, and industrial purposes. The safety profile of the baculovirus–insect cell expression system further contributes to its widespread use and reliability in protein manufacturing.
Considerable Market Need
The demand for expression systems based on insect cells continues to be significant and is expected to remain so in the future. This is mainly due to the fact that many complex therapeutic protein candidates currently in development cannot be efficiently produced using traditional mammalian expression systems. Bacterial expression systems, on the other hand, are typically unsuitable for such proteins due to their inability to perform specific critical PTMs necessary for proper protein folding and function.
In addressing this need, Sino Biological offers an extensive range of catalogue proteins expressed using the baculovirus–insect cell expression system. These proteins are continually in high demand, particularly viral proteins, such as antigens from pathogens like SARS-CoV-2, influenza virus, respiratory syncytial virus (RSV), and others. Additionally, enzymes, such as kinases, are also effectively produced using this system.
Baculovirus–Insect Cell System Transformative Development
The 1980s marked a groundbreaking milestone in the adoption of insect cells for producing pharmaceutical proteins when the baculovirus expression vector system (BEVS) was introduced. This pivotal advancement coincided with the establishment of common insect cell lines like Sf9 and Hi5, forming the foundation for the baculovirus–insect cell expression system.
Since its inception, this system has played a vital role in generating various vaccines, diagnostics, and research reagents. Notably, it has excelled in producing complex and challenging proteins, such as viral antigens, enzymes, transcription factors, and monoclonal antibodies. By providing access to high yields of properly folded proteins with essential PTMs, it has opened new avenues for biotechnologists to achieve their research objectives effectively. As a result, the baculovirus–insect cell expression system continues to be a cornerstone in the field of protein production for pharmaceutical applications.
A Few Challenges and Limitations
While the baculovirus–insect cell expression system offers numerous advantages, there are still some challenges and limitations to consider:
Complex glycosylation: Insect cells lack the ability to perform complex glycosylation, which can be important for certain proteins. Researchers have addressed this limitation through engineering insect cells to alter their glycosylation pathways, allowing for the production of proteins with more mammalian and human-like glycosylation patterns.
Industry conservatism: The biopharmaceutical industry tends to be conservative, often favoring well-established methods like mammalian cell expression systems. Switching to baculovirus–insect cell expression systems may be met with resistance despite their advantages. Proteins expressed in mammalian cells are perceived to be closer to their native form and are preferred during drug discovery screening. Ensuring the absence of residual insect cell proteins in the final product is crucial for regulatory compliance.
Expertise and process development: Not just experience but also baculovirus–insect cell expression systems expertise is necessary to successfully develop robust and scalable processes for each individual program.
Cost and complexity: Some proteins are difficult and expensive to produce using mammalian systems. The awareness of the benefits of using baculovirus–insect cell systems for expressing challenging compounds is growing, but cost considerations and complexity may still be factors to be addressed.
Despite these challenges, technological improvements are expected to enhance yields and purity while expanding the range of complex proteins that can be produced using baculovirus–insect cell expression systems. These advancements are likely to influence the broader adoption of this versatile and powerful protein expression technology in the biopharmaceutical industry.
Deep Experience with Baculovirus–Insect Cell Protein Expression at Sino Biological
Sino Biological works at the forefront of both the bioreagents and contract-research services industries, providing a full slate of high-quality recombinant proteins and corresponding antibodies, as well as custom development and production solutions for particularly difficult projects. With headquarters in Beijing, China, and subsidiaries in the United States, Germany, and Japan, the company has more than 900 employees and serves researchers in academia and industry worldwide.
Sino Biological has the thorough experience and expertise with baculovirus–insect cell protein expression to ensure the development of optimal processes. The insect cell expression and production team within the company comprises a large group with advanced degrees and years of experience working with a wide variety of processes and protein products. In fact, Sino Biological has produced and purified close to 2,000 different proteins using baculovirus–insect cell expression systems— and that knowledge is applied to each customer project.
The team begins a project by evaluating the target sequence to identify relevant features, such as problematic (e.g., hydrophobic) but unnecessary regions that can be deleted. Sino Biological has also developed proprietary serum-free media specifically for insect cell culture that supports healthy cell growth to cell densities of up to 1.2 x 107 cells per milliliter. The larger the healthy cell population, the higher the protein yield. Sino Biological ensures maximum efficiency, productivity, and quality through intensive optimization of the virus packaging, transfection reagents, culture and purification conditions, and more. Flexible culture volumes from 20mL to 1,500L address different production demands and allow rapid screening of protein production from early-phase development to commercial-scale manufacturing.
As a global leader in recombinant technology, Sino Biological also has other expression systems in place, such as FucoFree cell line, stable cell line, HEK293/CHO, and E. coli, to facilitate biomedical research. Sino Biological has invested significantly in building the expertise and production platforms needed to synthesize many different, challenging proteins and antibodies. For example, the company has developed three HEK293 expression-based platforms—VLP, detergent micelle, and SMA-nanodisc platforms—to generate premium transmembrane proteins.
New US-based centre for bioprocessing
In October 2023, Sino Biological announced the formal opening of its new centre for Bioprocessing (C4B) in Houston, Texas, which marks a significant milestone in Sino Biological’s global presence. The new center specialises in CRO services, including custom recombinant protein and recombinant antibody development and manufacture. The C4B represents Sino Biological’s natural global expansion of its CRO service capabilities and extends upon the company’s already strong CRO service offering at its Beijing headquarters. The team is committed to delivering high-quality, custom recombinant proteins and antibodies and looks forward to partnering with researchers and industry leaders worldwide to forge a brighter future in the life sciences.
This content has been created in collaboration with Pharma’s Almanac.
Author: Yingmin Zhu, Ph.D., Head, Center for Bioprocessing, Amy Sheng, Ph.D., Head, CRO Program, and Xuejiao Zhang, Ph.D., R&D Project Manager, Sino Biological
