A Comprehensive Tool Set for COVID-19 Research

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has resulted in unprecedented devastation to the global economy. Timely responses to virus outbreaks in terms of the developments of both diagnostic tools and therapeutics are essential to combat such invisible enemies. SARS-CoV-2 is comprised of genetic materials encapsulated by a coat of proteins, which are major components of the crucial machinery for viral invasion and propagation. With advanced recombinant protein expression platforms and antibody discovery capabilities, Sino Biological has created a comprehensive collection of SARS-CoV-2 reagents to serve as ingredients for serologic assays and targets for anti-viral drug developments. Here we provide a general introduction and guideline to our SARS-CoV-2 reagent inventory.

Recombinant Virus Proteins

The basis for recombinant protein expression is to over-produce a foreign protein within a host cell by harnessing the power of the cellular protein generation machinery. The foreign protein is usually carried in a vector (e.g. a plasmid) and introduced into the host cell via non-invasive methods. Recombinant protein expression is a well-established technology for about 5 decades and it is the basis of modern biotechnology and biopharmaceutics. A variety of expression hosts, including E. coli, yeast, insect cells, HEK293, and CHO… have been established.

Based on their function, several SARS-CoV-2 proteins are key targets for serologic test development (spike protein and nucleocapsid protein) and anti-viral drug discoveries (spike protein and enzymes such as 3CLpro, PLPro, RdRp…). These proteins, along with many other components of the SARS-CoV-2 proteome, have been generated as recombinant proteins with confirmed biological activities.

Spike protein is the attachment point of the SARS-CoV-2 virus to the host cell and it is the gateway for virus invasion. The full-length spike protein as well as its segments, e.g. S1, receptor-binding domain (RBD), N-terminal domain (NTD), and S2, has been produced in HEK293 cells based on the reference sequences and validated for their interactions against human ACE2. We are also monitoring the mutations occurring in the spike protein, especially in RBD, constantly and adding high-abundance mutations into the inventory continuously. So far, a library of >40 RBD mutants has been constructed, covering all major RBD mutations. This library is useful for screening of broad-spectrum neutralizing antibodies against spike protein-ACE2 interactions. Besides the array of RBD mutants, an S1 version bearing the dominant D614G mutation is made and with confirmed ACE2 binding activity. Lastly, under a non-exclusive license, Sino Biological is eligible for the manufacturing of “Hexapro”, an engineered spike protein with a stable pre-fusion state that is an excellent candidate for SARS-CoV-2 antibody assay development. Hexapro has been produced in HEK293 with enhanced yield, stability, and well-defined conformational status.

E.coli is also extensively used in producing SARS-CoV-2 proteins. The nucleocapsid protein of the CoV-2 virus has been produced in E.coli as a stable oligomer while several major enzymes, including 3CLpro and PLPro, have been expressed in E.coli with confirmed enzymatic activities against corresponding fluorescent peptide substrates, providing the scientific community with tools for high through-put biochemical assays to identify potential inhibitors as anti-viral drugs.

Antibodies against SARS-CoV-2

During the progress of the pandemic, sufficient testing is required to identify infected people, both symptomatic and asymptomatic, to enhance proper isolation efforts, and to prevent further spreading. Genetic testing is needed for such effort but it is not time efficient and usually requires high-end equipment. Serological testing is speedy with minimum equipment requirements. The combination of the two testing powers is crucial in paving the way to safely restore life to the pre-pandemic era. One format of virus serological tests involves the use of antibodies to detect virus fragments in serum samples, which requires high-quality anti-virus antibody reagents with high sensitivity and specificity.

Antibodies (immunoglobulin) are bio-macromolecules generated by the immune system of vertebrates to "flag’ exogenous agents that are subsequently neutralized by various immune cells. To generate antibodies against a certain entity, it requires unique pieces of that entity to be recognized by the immune system as foreign objects. For the SARS-CoV-2 virus, its surface glycoprotein (spike protein) and its nucleocapsid protein are good candidates for this purpose. To ensure the speedy generation of anti-CoV-2 antibodies, we used both the antibody library screening and antibody discovery via immunization methods. During antibody library screening, we investigated the pre-existing antibody library against SARS-CoV and identified several antibodies with high sensitivities against the spike and the nucleocapsid proteins of SARS-CoV-2. While during the antibody discovery campaigns, immunogens such as S1 and RBD of the spike protein and nucleocapsid protein of SARS-CoV-2 were used for the immunization of mice and rabbits. Via techniques such as hybridoma and phage display, we identified SARS-CoV-2 specific antibodies with no cross-reactivates against other coronavirus strains and several neutralizing antibodies that blocked the interaction of SARS-CoV-2 pseudovirus with ACE2 over-expressing HEK293 cells.

All antibodies, including 9 antibodies against the nucleocapsid protein and 12 against the spike protein, are available as reagents for SARS-CoV-2 research and serologic assay ingredients. In the meantime, a CoV-2 spike-displaying pseudovirus system using the HIV backbone has also been developed, which would be extremely useful for quick screening of SARS-CoV-2 neutralizing antibodies or other inhibitory molecules that block the interaction between CoV-2 spike protein and ACE2.

Sino Biological Tech Portfolio

Sino Biological is a world-leading provider of recombinant protein and antibody reagents, with an extensive collection of cancer immunotherapy target proteins and various virus protein reagents. Major technological platforms include recombinant protein expression, antibody discovery, as well as assay developments. A broad selection of expression hosts, including E.coli, yeast, the baculovirus mediated insect cell expression system, HEK293, and CHO, are available to ensure the production of active recombinant proteins close to their natural status. Proprietary vector systems promote the high-level expression of target proteins and antibodies while a broad range of cell culturing systems enables small scale (mg) to large scale (g) protein/antibody productions.

For antibody discovery, we employ conventional mouse hybridoma technique and phage display library screening (rabbit) methods to identify antibodies with high specificity and sensitivity, while a more advanced B cell sorting route is also available for the identification of high-affinity antibodies or antibodies with more sophisticated functions (neutralizing, blocking…).

Sino Biological has a special focus on the virus and other forms of infectious diseases. With the establishment of the ProVir (https://www.sinobiological.com/research/virus) viral antigen bank and a large selection of anti-viral antibodies, ELISA kits, cell lysates, we are dedicated for contributing to the research of these disease areas. Besides catalog products, most sections of our recombinant protein/antibody expression and antibody discovery platforms are available for contracted research projects.

Sino Biological Europe is located in Frankfurt, Germany, providing the close-to-customer local services. If you have any questions, please feel free to contact our local team in Germany (order_eu@sinobiological.com).

Contact:

Sino Biological Europe GmbH
order_eu@sinobiological.com
Sino Biological Inc.
marketing@sinobiological.com
www.sinobiological.com