CoV-2 S2, Sf9
Description
Introduction to SARS-CoV-2 Spike Protein and S2 Subunit
The SARS-CoV-2 spike (S) protein, a critical mediator of viral entry, comprises two functional subunits: S1 (responsible for receptor binding) and S2 (driving membrane fusion). The S2 subunit is a highly conserved region across variants, making it a promising target for broad-spectrum therapeutics and vaccines . Its structural elements include the fusion peptide (FP), heptad repeats (HR1/HR2), and transmembrane domain (TM1), which coordinate host-cell membrane fusion .
The Sf9 cell line (derived from Spodoptera frugiperda insect cells) is widely used in recombinant protein production, including SARS-CoV-2 vaccines. These cells enable high-yield expression of viral antigens through baculovirus systems .
Sf9-Cell-Based Recombinant Vaccines Targeting SARS-CoV-2
While most Sf9-produced vaccines focus on the receptor-binding domain (RBD) of the S1 subunit , the S2 subunit’s conservation has spurred interest in its potential for pan-coronavirus vaccines. Below are findings from Sf9-cell-based RBD vaccines:
Table 1: Immunogenicity and Efficacy of Sf9-Cell-Produced Vaccines
This data highlights the superior immunogenicity of Sf9-produced RBD vaccines compared to inactivated platforms .
S2 as a Target for Broad Neutralization
Antibodies targeting the S2 subunit’s FP and stem helix (SH) regions demonstrate cross-reactive neutralization against SARS-CoV-2 variants, SARS-CoV-1, and zoonotic sarbecoviruses . For example:
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C20.119 mAb: Targets the FP, neutralizing Omicron variants with 50% inhibitory concentrations (IC₅₀) < 1 µg/mL .
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ADCC Activity: S2-targeting antibodies exhibit Fc-effector functions, enhancing viral clearance .
Table 2: S2-Specific Antibody Neutralization Breadth
| Antibody Target | Neutralization Scope | Mechanism |
|---|---|---|
| Fusion peptide | SARS-CoV-2 variants, SARS-CoV-1 | Blocks membrane fusion |
| Stem helix | Omicron BA.1/BA.2/BA.4/BA.5 | Stabilizes prefusion S2 |
Challenges and Future Directions
Product Specs
The 2019 novel coronavirus (2019-nCoV), a human-infecting coronavirus responsible for causing viral pneumonia, emerged in December 2019 in a fish market in Wuhan, Hubei province, China.
Genetic analysis reveals an 87% similarity between 2019-nCoV and the bat-derived severe acute respiratory syndrome virus (SARS-CoV-2) identified in Zhoushan, eastern China, in 2018. Despite some amino acid variations, 2019-nCoV possesses a receptor-binding domain (RBD) structure comparable to that of the 2018 SARS-CoV, suggesting its potential to bind to the human angiotensin-converting enzyme 2 (ACE2) receptor protein.
While bats are suspected to be the natural reservoir of 2019-nCoV, researchers hypothesize that an intermediate animal host, potentially from the seafood market, played a role in transmitting the virus to humans. Studies from the Royal Society of Chemistry (RSCU) suggest that 2019-nCoV might be a recombinant virus, with its spike glycoprotein originating from a combination of bat coronavirus and an unidentified coronavirus.
This recombinant protein, expressed in Sf9 insect cells, encompasses the S2 subunit of the Spike Glycoprotein from the Wuhan-Hu-1 strain of the Coronavirus 2019 (CoV-2). It spans amino acids 685 to 1211, resulting in a molecular weight of 60.1 kDa, and includes a C-terminal 6xHis tag for purification purposes.
The CoV-2 S2 protein solution is provided in Dulbecco's Phosphate-Buffered Saline (DPBS).
The CoV-2 S2 Glycoprotein is shipped using ice packs to maintain its stability. Upon receipt, it should be stored at -20 degrees Celsius.
SDS-PAGE analysis confirms that the protein purity exceeds 85%.
Sf9, Baculovirus Cells.
Purified by Metal-Afinity chromatographic technique.
Product Science Overview
The Coronavirus 2019 Spike Glycoprotein-S2, Sf9 Recombinant, is a crucial component in the study and development of vaccines and therapeutic agents against SARS-CoV-2, the virus responsible for the COVID-19 pandemic. The spike glycoprotein (S) of SARS-CoV-2 plays a pivotal role in the virus’s ability to infect host cells. It is composed of two subunits, S1 and S2, each with distinct functions. The S2 subunit is particularly important for the fusion of the viral membrane with the host cell membrane, facilitating viral entry.
The spike glycoprotein is a trimeric protein that protrudes from the viral surface, giving the virus its characteristic crown-like appearance. The S2 subunit contains several key regions, including the fusion peptide, heptad repeat regions (HR1 and HR2), and the transmembrane domain. These regions are essential for the conformational changes required for membrane fusion.
The production of recombinant spike glycoprotein-S2 in Sf9 cells involves the use of the baculovirus expression system. Sf9 cells, derived from the fall armyworm (Spodoptera frugiperda), are commonly used in biotechnology for the production of recombinant proteins. The baculovirus expression system is advantageous due to its high yield and proper post-translational modifications, which are crucial for the functionality of the spike protein.
The recombinant spike glycoprotein-S2 is used extensively in vaccine research. It serves as an antigen to elicit an immune response in the host, leading to the production of neutralizing antibodies. These antibodies can block the virus from binding to and entering host cells, thereby preventing infection. The S2 subunit is particularly attractive for vaccine development because it is more conserved across different coronavirus strains compared to the S1 subunit, which undergoes frequent mutations.
In addition to its role in vaccine development, the S2 subunit is a target for therapeutic interventions. Monoclonal antibodies targeting the S2 subunit have shown promise in neutralizing the virus and preventing its spread. Furthermore, small molecules and peptides that inhibit the fusion process are being explored as potential antiviral drugs.
