ImmunoPro™ VLP SuperAntigens

Difficult-to-express antigens with high immunogenicity for antibody drug discovery

Because VLPs can efficiently activate the body's humoral and cellular immune responses, VLP-displayed antigens have great advantages in antibody drug discovery for difficult targets. With the help of our SAMS technology platform, KACTUS has developed a series of high-quality VLP SuperAntigens and VLP expression services with strict purity and biological activity verification.

What are VLP-Displayed Antigens?

Virus-like particles (VLPs) are derived from the capsid protein of a virus and are tiny nanoparticles formed by the automatic assembly of one or more capsid proteins. VLPs do not contain viral infectious genomes, so they are relatively safe to use in production operations.

Why use VLP-Displayed Antigens?

Virus-Like Particles (VLPs) are highly immunogenic and so are advantageous for immunization with antigen targets that have otherwise low abundance or weak immunogenicity. They also allow for soluble expression of multi-transmembrane proteins in their natural configuration.

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

Site-Specific Biotinylation

VLP framework optimized to each antigen

Proven biological activity

Mammalian cell expression system

Boosted immunogenicity

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VLP-Displayed Antigens for Antibody Drug Discovery

Virus-like particles (VLPs) are derived from the outer capsid protein of a virus and are tiny nanoparticles formed by the automatic assembly of one or more capsid proteins. VLPs do not contain viral infectious genomes, so they are relatively safe during production operations. KACTUS has used its self-developed SAMS™ protein engineering platform to express a series of biotinylated, non-biotinylated, and fluorescently-labeled VLP-displayed antigens. They are suitable for SPR, ELISA, CAR-T positive rate detection, and other experimental scenarios to flexibly meet various experimental demands.

Immune Response to VLPs

Virus-Like Particles (VLPs) are highly immunogenic, meaning that they can elicit a strong immune response in the host. VLPs are recognized by the immune system and are taken up by antigen-presenting cells (APCs) such as dendritic cells. 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. VLP-displayed antigens efficiently activate the body's humoral and cellular immune responses and so are advantageous in the discovery antibodies against targets with low immunogenicity or abundance. Additionally, VLPs can be engineered to display specific transmembrane proteins on their surface, allowing for the generation of highly specific and effective antibodies against transmembrane proteins.

Figure 1. Envelope VLP expression.

Case Study: Multi-Transmembrane Protein

Human CCR2b VLP

Difficulty in preparing soluble recombinant forms of multi-transmembrane proteins has led to a lack of development of related drugs for these targets. We have developed a series of full-length multi-transmembrane proteins, without any mutations or modifications. They are expressed through an envelope VLP to allow for 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: Immunogenicity

Human CD24 VLP

The potency of antibodies is dependent on the strength of immunogenicity of the antigenic protein. However, some proteins are unable to elicit optimal antibodies after immunization due to their molecular size, conformation, glycosylation modification, or homology between species. To address the challenge of weak protein immunogenicity, KACTUS has developed highly immunogenic and active VLP antigens that can overcome animal immune tolerance, leading to the discovery of effective antibodies.


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.


Human CD24 VLP used in animal immunization can significantly increase the antibody titer, and the immune effect is significantly enhanced.

KACTUS VLP-Displayed Antigens: FAQs

Are the VLPs provided in liquid or lyophylized 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 is the size of the VLPs?

Generally, VLPs range in size from approximately 20 to 200 nanometers (nm). Compared to a cell-based immunization approach, their smaller size can optimize the immune response to target the specific antigen displayed on the surface of the engineered VLPs.

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 ensure the quality of each batch of VLPs, KACTUS uses a rigorous validation process that includes a range of analytical techniques. This process includes techniques such as size exclusion chromatography, ELISA, and SPR.

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