Recombinant Proteins

Available Products

Overview

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

Product Features

High Protein Affinity
We verified the activity of our heterodimers, such as CD3E/G-His Tag and CD3E/D-His Tag, via ELISA and SPR.

Equal Expression of Subunits
A proprietary design, expression, and purification system ensures the two subunits of the heterodimers are expressed in equal proportions with greater than 95% purity, verfied by SDS-PAGE and SEC-HPLC.

Stability
Our CD3 proteins have high batch-to-batch consistency and long-term stability as verified by ELISA.

CD3 Proteins Overview

About CD3 Proteins

CD3 (Cluster of differentiation 3) is one of the proteins expressed on the surface of T cells. It consists of six peptide chains, one γ chain, one δ chain, two ε chains and two ζ chains. These six peptide chains are all transmembrane, and the transmembrane region is connected with TCR through a salt bridge to form a tight TCR-CD3 complex, which jointly participates in the recognition and signal transduction of T cells to antigens. The activation signal generated by TCR recognition of antigen is transduced into T cells by the ITAM sequence in the cytoplasmic region of CD3, and then a series of immune responses are initiated.

Applications

Antibody Discovery

Immunization

Antibody Screening

Functional characterization

Affinity Determination (ELISA, SPR, BLI)

TCR/CD3 signaling (Louis-Dit-Sully C et. al, 2012）

Product Performance Validation

High Binding Affinity by SPR

Human CD3E/CD3D His tag, captured on CM5 chip via anti-His antibody, binds OKT3 mFc Tag with an affinity constant of 0.36nM as determined in SPR assay (Biacore T200).

Batch-to-Batch Consistency

Immobilized Human CD3E/CD3G, hFc Tag, at 1μg/mL (100μL/well). Dose-response curve for anti-CD3E/CD3G antibody (OKT3, mFc Tag). The EC50s are 20.7, 21.0 and 20.ong/mL respectively as determined by ELISA.

Temperature Stability

Immobilized Human CD3E/CD3G, hFc Tag, at 1μg/mL (100μL/well). Dose-response curve for anti-CD3E/CD3G antibody (OKT3, mFc Tag). The EC50s are 20.7, 19.5, 20.0 and 20.7ng/mL respectively, as determined by ELISA

High Purity by SEC-HPLC

The purity of Cynomolgus CD3E is greater than 95% as determined by SEC-HPLC.

High Purity by Tris-Bis PAGE

Cynomolgus CD3E/CD3D on Tris-Bis PAGE under reduced conditions. The purity is greater than 95%.

Browse CD3 Proteins

Browse our popular CD3 proteins here or click below to view the full catalog selection:

More Products:

Background

FGFR (Fibroblast Growth Factor Receptors), generally includes four types of FGFR1-4 (also known as CD331-334). FGFR is a branch of the tyrosinase receptor family, which is a type I transmembrane protein usually functioning as a dimer. Among them, the extracellular domain contains three Ig-like regions D1 (IgI), D2 (IgII), and D3 (IgIII), of which D1 and the Acidic box form an autoinhibitory region, and D2 and D3 are responsible for ligand binding (D2 and cell surface Heparan sulfate is combined, D3 has two forms of IIIb and IIIc due to alternative splicing, and only one isoform of IIIc is currently found in FGFR4). According to the number of Ig-like domains, FGFR can be divided into two forms, one is α-type, which contains three regions of IgI, IgII, and IgIII; the other is β-type, which only contains IgII and IgIII.

Figure 1. FGFR structure (Babina IS, et al., 2017)

The ligand of FGFR is FGF. There are 18 kinds of human FGFs that have been discovered. Except for FGF19, FGF21, and FGF23, which are endocrine, the rest are paracrine. Among them, FGF7 can only bind to type IIIb FGFR2. The combination of FGFR and FGF mediates the activation and transmission of signaling pathways such as RAS-RAF-MAPK, PI3K-AKT, JAK-STAT and PLCγ, and participates in important physiological functions such as cell growth, differentiation, migration, neovascularization, regulation of organ development and wound healing. FGFR gene mutations are commonly found in solid tumors such as lung cancer, liver cancer, intrahepatic cholangiocarcinoma, breast cancer, gastric cancer, uterine cancer, and bladder cancer, and there are differences in the types and frequencies of FGFR mutations in different cancer types.

Figure 2. FGF-FGFR-mediated signaling pathway (Mason I, 2007)

KACTUS has deeply analyzed the structural differences of FGFR family proteins and successfully prepared various types of FGFR recombinant proteins, covering α and β isoforms, as well as different forms such as IIIb and IIIc, supporting the differentiated research of FGFR-targeted drugs.

Product Performance Validation

Human FGFR2 beta (IIIb) Protein (FGR-HM1BB)

Figure 3. Immobilized Human FGFR2 beta(IIIb) at 0.5μg/ml on the plate. Dose response curve for Anti-FGFR2 Ab., hFc Tag with the EC50 of 20.2ng/ml determined by ELISA.

Figure 4. Anti-FGFR2 Ab., hFc Tag can bind Human FGFR2 beta IIIb, His Tag with an affinity constant of 1.98nM as determined in a SPR assay (Biacore T200).

Human FGFR2 alpha (IIIb) Protein (FGR-HM1BD)

Figure 5. Serial dilutions of Anti-FGFR2 alpha (IIIb) Antibody were added into Human FGFR2 alpha (IIIb), His Tag : Biotinylated Human FGF10, No Tag binding reactioins.

Products

Background

Immune blockade therapy is becoming a new weapon in oncology due to the development of immune checkpoint proteins targeting in cancer, especially after the success of antibody drugs targeting programmed cell death-1 (PD-1), programmed cell death ligand-1 (PD-L1) and cytotoxic T-lymphocyte antigen-4 (CTLA-4). Although immune checkpoint blockade therapy often leads to a more durable response than chemo or targeted therapies in some cases, clinical data shows a limitation that in most cancers, the response rate is low (10-30%). Therefore, more associated studies focus on the mechanisms of non-responsiveness, as well as developing new targeting strategies using other immune checkpoint proteins.

Utilizing our featured SAMSTM platform, KACTUS has developed a series of immune checkpoint proteins with multiple pre-labels.

Background

FcR is the receptor of immunoglobulin (Ig), which causes corresponding cell-specific immune response by binding to the specific region of the Fc segment of Ig, acting as a bridge between humoral immunity and cellular immunity. Gene polymorphisms of FcR enable it to induce various intracellular biological effects, which are closely related to the occurrence and development of various immune-related diseases such as autoimmune diseases SLE and RA. Fc receptor proteins are one of the most important protein families in the immune system, mediating antibody-dependent ADCP, ADCC and CDC effects, and playing a key role in immune system activation and antibody function.

Currently the most widely used are mainly IgG receptors including FcRn and FcγR. FcyRs can be divided into three classes: FcyRI, FcyRII and FcyRIII. FcγRI has high affinity for IgG (10-9M) and is mainly expressed in monocyte-macrophages. FcγRII, FcγRIII and IgG have low affinity (10-6M) and are widely distributed. FcγRII is divided into 3 types: FcγRIIa, FcγRIIb and FcγRIIc according to the structure of the cytoplasmic region. It exists in B cells, macrophages, polymorphonuclear cells, platelets and monocytes, and FcγRIIb is the only inhibitory receptor. FcγRIII is present in granulocytes, NK cells, macrophages and activated monocytes. The combination of FcγR and antibody can activate immune cells and produce endocytosis, phagocytosis, ADCC and other functions.

Products

Background

CD47 is an immunoglobulin that is overexpressed on the surface of many types of cancer cells. CD47 forms a signaling complex with signal-regulatory protein α (SIRPα), enabling the escape of these cancer cells from macrophage-mediated phagocytosis. In recent years CD47 has been shown to be highly expressed by various types of solid tumors and to be associated with poor patient prognosis in various types of cancer.

A growing number of studies have since demonstrated that inhibiting the CD47-SIRPα signaling pathway promotes the adaptive immune response and enhances the phagocytosis of tumor cells by macrophages. Improved understanding in this field of research could lead to the development of novel and effective anti-tumor treatments that act through the inhibition of CD47 signaling in cancer cells.

Products

Transforming growth factor β (TGF-β) is a highly pleiotropic cytokine that plays an important role in wound healing, angiogenesis, immunoregulation and cancer. The cells of the immune system produce the TGF-β1 isoform, which exerts powerful anti-inflammatory functions and is a master regulator of the immune response.

Products