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Recombinant GPΔTM: The Backbone of Filovirus Vaccine Innovation—Powered by IBT Bioservices
Published On 03/25/2025 3:35 PM
Introduction: Why GPΔTM Matters
Filoviruses—like Zaire Ebola virus (EBOV), Marburg virus (MARV), and Sudan virus (SUDV)—are among the most deadly pathogens known to humans, with case fatality rates reaching up to 90%. A shared feature among these viruses is a single envelope-anchored glycoprotein (GP) that mediates cell entry, triggers immune responses, and serves as the primary target for neutralizing antibodies and vaccines.
To safely study and exploit GP for vaccine and antibody development, researchers use a truncated form called GPΔTM, which removes the transmembrane (TM) domain to make it soluble while preserving its trimeric structure and immunogenic epitopes.
IBT Bioservices has become a leading supplier of recombinant GPΔTM antigens, enabling preclinical development, serological assays, and structure-guided vaccine design.
Structural Biology: Stabilized, Trimeric, and Conformation-Accurate
Background
The GP trimer exists in a metastable prefusion conformation, which undergoes dramatic rearrangement during viral entry. Preserving this conformation in recombinant proteins is essential to elicit antibodies that neutralize real infections.
Scientific Insight
By removing the TM domain and stabilizing the ectodomain (GPΔTM), researchers can produce trimeric GP that structurally mimics the surface of the virus. These constructs are vital in vaccine design and antibody epitope mapping.
Lee et al. (2025) characterized Sudan virus GPΔTM at 3.13 Å resolution, identifying structurally conserved epitopes, especially in the glycan cap and base regions.
For EBOV, GPΔTM constructs have been solved in complex with monoclonal antibodies such as c2G4 and c13C6, highlighting critical neutralization zones (Murin et al.).
Immunogenicity and Antibody Discovery Using IBT’s GPΔTM
Background
GPΔTM antigens serve as ideal surrogates for stimulating immune responses in vaccine models or for measuring antibody titers in ELISA and neutralization assays. These soluble forms retain the GP1-GP2 interface, which is the main site of antibody recognition.
Scientific Insight
IBT’s GPΔTM reagents have been used in many studies for profiling the quality and function of vaccine-induced antibodies:
Ilinykh et al. (2024) used IBT's EBOV GPΔTM (Mayinga) to demonstrate that antibodies targeting the glycan cap potently activate the complement cascade—a key antiviral mechanism.
Qiu et al. (2016) showed that a two-mAb cocktail protected macaques against lethal EBOV challenge, with binding validated using IBT GPΔTM.
In Banadyga et al. (2021), GPΔTM from IBT was used to investigate escape mutations in EBOV following antibody treatment.
GPΔTM in Vaccines: From Multivalent Platforms to Cross-Species Coverage
Background
While rVSV-ZEBOV is FDA-approved for EBOV, vaccines for SUDV and MARV are still in development. GPΔTM forms the immunogenic backbone for most subunit or vector-based vaccine platforms, including DNA, adenoviral, mRNA, and rVSV.
Scientific Insight
IBT’s GPΔTM reagents have been critical to developing and validating candidate vaccines:
Marzi et al. (2022) used IBT’s EBOV GPΔTM (#0501-001) to boost immune responses in a VSV-based Sudan virus vaccine, demonstrating species-specific protection in macaques.
Grant-Klein et al. (2015) reported that MARV GPΔTM delivered via intramuscular electroporation induced 259.8 ELISA units/mL IgG titers in macaques—a strong immunogenic signal.
Liu et al. (2023) demonstrated broad protection using multivalent cocktails incorporating GPΔTM antigens from EBOV, SUDV, MARV, and BDBV.
Expression Systems and Assay Integration: Why IBT’s Format Matters
Background
GPΔTM must be properly glycosylated and folded to reflect native viral surfaces. Expression systems such as Sf9 insect cells strike a balance between scalability and post-translational fidelity.
Scientific Insight
IBT’s GPΔTM proteins are validated for:
ELISA coating
Bead-based antibody screening
Biotinylation for SPR and BLI binding kinetics
In Holtsberg et al. (2016), IBT's biotinylated GPΔTM was conjugated to magnetic beads for identifying pan-filovirus neutralizing antibodies. Similarly, Cagigi et al. (2018) used IBT reagents to detect cross-species binding to the conserved HR2/MPER region.
Table: How IBT’s GPΔTM Supports Research Goals
| Feature | EBOV GPΔTM (IBT) | SUDV GPΔTM (IBT) | MARV GPΔTM (IBT) |
| ELISA & Neutralization | X | X | X |
| Challenge Model Studies | X | X | X |
| Vaccine Boosting (e.g. VSV) | X | X | Experimental |
| mAb Discovery & Binding | X | X | X |
| Used in High-impact Journals | Nature, Sci Transl Med, mBio | biorxiv, JID | JVI, JID |
Conclusion: IBT GPΔTM Enables the Filovirus Research Frontier
Whether for vaccine R&D, monoclonal antibody discovery, or structural immunology, IBT’s GPΔTM reagents offer unparalleled reliability and peer-reviewed validation.
Trusted by top-tier labs and cited across Nature, Science, PNAS, and JVI—IBT's GPΔTM products are the preferred tools behind many of today’s most promising filovirus countermeasures.
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Application and Technique Notes
