VLP-Displayed Antigens for Antibody Drug Discovery

Difficult-to-express target proteins including full-length multipass transmembrane proteins with high immunogenicity for antibody drug discovery.

Available Products


KACTUS manufactures VLP-displayed target proteins/antigens. We've developed various transmembrane protein VLPs using our SAMS™ protein engineering platform to display antigens on VLPs. Our products include biotinylated, non-biotinylated, and fluorescently-labeled VLP proteins. They are suitable for SPR, ELISA, and other experimental scenarios to flexibly meet various experimental demands. Additionally, we offer custom VLP expression services, ensuring strict purity and thorough verification of biological activity.

What are VLP-Displayed Antigens?

Virus-like particles (VLPs) are small nanoparticles made from the shell protein of a virus. They form when one or more of these shell proteins automatically come together. VLPs do not contain viral infectious genomes, so they are relatively safe to use in production operations.

What are the benefits of VLP-Displayed Antigens?

Virus-Like Particles (VLPs) are good at boosting the immune response. This makes them useful for immunization, especially with antigen targets that are usually present in low amounts or don’t trigger a strong immune reaction by themselves. They also allow for soluble expression of multipass transmembrane proteins in their natural configuration.

What are the applications of VLP-Displayed Antigens?

→ Blood sample determination: ELISA

→ In vivo pharmacokinetic analysis

→ Antibody Discovery: Immunization, Screening, Functional Characterization

→ CMC method development

→ Affinity determination: ELISA, SPR

Product Features

Site-Specific Biotinylation

VLP framework optimized to each antigen

Proven biological activity via ELISA and SPR

Mammalian cell expression system for natural folding and glycosylation

Boosted immunogenicity for antibody drug discovery

Immune Response to VLPs

Virus-Like Particles (VLPs) are highly immunogenic, meaning that they can elicit a strong immune response in the host. The immune system recognizes VLPs and antigen-presenting cells (APCs) such as dendritic cells take them up. Once taken up by APCs, VLPs are processed and presented to T cells, which can trigger the activation of B cells to produce antibodies against the displayed antigen. Because VLPs resemble the structure and composition of native viruses, they are highly effective at inducing both humoral and cellular immune responses.

Antibody Discovery for Difficult-to-Express Targets

Discovery of innovative antibody drugs has entered the next-generation phase. Owing to the increasingly fierce competition in antibody drug development, the discovery of differentiated antibodies helps maintain competitiveness in the market.

Antigens shown on Virus-Like Particles activate our body's immune responses effectively. Therefore, they can help find antibodies against targets that usually don’t trigger a strong immune response or are not abundant. Researchers can specially design VLPs to display certain proteins on their surface, especially multipass transmembrane proteins. This allows us to create strong antibodies against those specific proteins.

Case Study: Multi-Transmembrane Protein

Human CCR2b VLP

Challenges in making soluble forms of recombinant proteins with multiple transmembrane regions have slowed down the development of related drugs for these targets. We have developed a series of full-length multipass-transmembrane proteins, without any mutations or modifications. An envelope VLP expresses them to enable solubility and functional transmembrane proteins. 

Immobilized Human CCR2b VLP at 5μg/ml (100μl/Well) on the plate. Dose response curve for Anti-CCR2b Antibody, hFc Tag with the EC50 of 12.0ng/ml determined by ELISA.

As verified by SPR, Biotinylated Human CCR2b VLP can specifically bind to Anti-CCR2b antibody with an affinity constant of 5.24 nM.

Case Study: Boosted Immunogenicity

Human CD24 VLP

The potency of antibodies is dependent on the strength of immunogenicity of the antigenic protein. Some proteins don't create strong antibodies after immunization because of their size, shape, glycosylation modifications, or homology between species. To solve this issue of weak immune responses to proteins, KACTUS developed VLP antigens that are highly immune-reactive and active. These can break through animal immune defenses, helping to find effective antibodies for these targets.

Immobilized Human CD24 VLP at 0.5μg/ml (100μl/Well) on the plate. Dose response curve for Anti-CD24 Antibody, hFc Tag with the EC50 of 22.1ng/ml determined by ELISA.

Using Human CD24 VLP versus non-VLP displayed protein for animal immunization greatly boosts antibody levels, significantly strengthening the immune response.

KACTUS VLP-Displayed Antigens FAQs

Are the VLPs provided in liquid or lyophilized form?

KACTUS can provide VLPs in liquid or lyophilized form. Lyophilized format allows for the use of a custom buffer or adjuvant during screening or immunization as desired. It also ensures stability of the VLPs for use in a variety of settings, such as for screening or immunization. Our lyophilization team tests our catalog products for activity after lyophilization, to ensure you are still receiving a bioactive protein.

What are the size of the VLPs?

Generally, VLPs range in size from approximately 20 to 200 nanometers (nm). Their smaller size lets engineered VLPs focus the immune response on specific surface antigens, more so than cell-based immunization.

What is the copy number of the antigen per VLP?

KACTUS VLPs are produced with high quality standards. Although it is difficult to determine the exact number of copies of the antigen displayed on the surface of the VLP, KACTUS takes steps to validate each batch of VLPs to assure the displayed protein will have consistency across batches.

What quality control standards are used for the VLP-displayed antigens?

To guarantee VLP quality, KACTUS follows a strict validation process involving various analytical techniques for each batch. This process includes techniques such as size exclusion chromatography, ELISA, and SPR.

How do I order a VLP antigen?

Browse the catalog and order directly online via credit card or email us at orders@kactusbio.us to place an order via PO.

How do I order a custom VLP protein?

Contact us here to request a custom VLP protein.

What is the lead time for VLP antigens?

Our catalog products have a lead time of 2 days to 2 weeks. Custom orders have a turnaround time of 6-8 weeks. Contact us for more information.

Where can I get more information regarding VLP antigens?

Contact us to request more information or set up a meeting with one of our team members.

Have questions?