DBP4 Antibody

What is DPP4 and what are its primary biological functions?

DPP4 (Dipeptidyl Peptidase-4), also known as CD26, is a multifunctional cell surface glycoprotein receptor that plays diverse roles in cellular processes. It functions primarily as a serine exopeptidase with dipeptidyl peptidase activity that regulates various physiological processes by cleaving peptides in circulation, including chemokines, growth factors, neuropeptides, and peptide hormones. DPP4 removes N-terminal dipeptides sequentially from polypeptides with unsubstituted N-termini when the penultimate residue is proline .

Beyond its enzymatic activity, DPP4 serves as a positive regulator of T-cell coactivation by binding to proteins including ADA, CAV1, IGF2R, and PTPRC. Its binding to CAV1 and CARD11 specifically induces T-cell proliferation and NF-kappa-B activation in a T-cell receptor/CD3-dependent manner . DPP4 also participates in cell adhesion processes, as its interaction with ADA regulates lymphocyte-epithelial cell adhesion .

In association with fibroblast activation protein (FAP), DPP4 contributes to pericellular proteolysis of the extracellular matrix (ECM) and facilitates the migration and invasion of endothelial cells. It may also promote lymphatic endothelial cells adhesion, migration, and tube formation .

What species reactivity can be expected from commercial DPP4 antibodies?

Commercial DPP4 antibodies demonstrate variable species cross-reactivity that researchers must consider when designing experiments. Based on the available data, reactivity profiles differ significantly between antibody clones:

When selecting a DPP4 antibody, researchers should verify the validated species reactivity through manufacturer datasheets and peer-reviewed publications. The EPR18215 clone has been documented to work effectively with mouse and rat samples in multiple applications including Western blot and immunohistochemistry . The D6D8K clone appears to be specifically validated for human samples in immunohistochemistry applications .

Always perform preliminary validation experiments with appropriate positive and negative controls when working with new tissue sources or experimental conditions.

What are the recommended protocols for DPP4 detection by Western blotting?

For optimal DPP4 detection by Western blotting, the following methodological approach is recommended based on validated protocols:

• Sample preparation: Prepare tissue lysates from relevant sources. DPP4 is highly expressed in lung, thymus, and liver tissues from mouse and rat models .

• Antigen retrieval: For fixed samples, perform heat-mediated antigen retrieval using Tris-EDTA Buffer (pH 9.0) .

• Blocking conditions: Use 5% non-fat dry milk in TBST as a blocking and dilution buffer .

• Primary antibody incubation: Dilute anti-DPP4 antibody [EPR18215] at 1/1000 in blocking buffer and incubate according to manufacturer's recommendations .

• Secondary antibody detection: Use appropriate HRP-conjugated secondary antibody (e.g., Goat Anti-Rabbit IgG H&L (HRP)) .

• Exposure optimization: Adjust exposure times based on tissue source:

  • Lung tissues: ~30 seconds

  • Liver tissues: ~10-15 seconds

The expected molecular weight of DPP4 is consistent with literature reports (PMID: 25589660), though exact weight may vary with post-translational modifications .

Note: Include proper controls, such as a secondary antibody-only control using PBS instead of primary antibody to assess non-specific binding .

How does DPP4 interact with coronaviruses and what antibody-based approaches can block these interactions?

DPP4 serves as a critical co-receptor for certain coronaviruses, with established evidence for its role in Middle East Respiratory Syndrome Coronavirus (MERS-CoV) infection. The virus initiates infection through engagement of its spike protein with the host cell's DPP4 receptor, particularly in lung alveolar epithelial cells . This receptor-virus interaction represents a promising therapeutic target for intervention strategies.

Recent research has focused on developing bispecific antibodies (BsAbs) that can simultaneously target both the viral spike glycoprotein and DPP4 receptors . One innovative approach identified antibodies Regdanvimab and Begelomab as effective agents for blocking the D614G mutated spike glycoprotein of SARS-CoV-2 and host DPP4 receptor, respectively . When engineered into a bispecific format using KIH (Knobs into Holes) and CrossMAb techniques to prevent heavy/light chain mispairings, these constructs demonstrated superior binding affinity to both targets compared to control antibodies .

Site-specific molecular docking studies revealed that the engineered BsAb exhibits relatively higher binding affinity for both the spike glycoprotein and DPP4 co-receptor than control BsAbs . This approach represents a multi-pronged strategy to obstruct viral entry by blocking critical receptor engagements.

Another innovative approach involves DPP4 immunoadhesin compositions that function as "receptor decoys" to prevent MERS-CoV from interacting with cell-surface DPP4 . These compositions typically comprise:

• The extracellular domain of DPP4 fused to a portion of human immunoglobulin (e.g., hinge and Fc of IgG1)

• Mutated DPP4 peptides containing human DPP4 consensus contact residues with amino acid substitutions that increase affinity for the S1 spike protein

These receptor decoys bind to the MERS-CoV spike protein, blocking its ability to interact with cellular DPP4 and thereby preventing infection . Though recombinant soluble DPP4 demonstrates inhibition of MERS-CoV infection in vitro, relatively high concentrations are required for 50% inhibition (~10 μM) .

What methodological considerations are important for immunohistochemical detection of DPP4?

Successful immunohistochemical detection of DPP4 requires careful optimization of several critical parameters:

• Antibody selection: Choose antibodies specifically validated for immunohistochemistry applications. The D6D8K clone (#40134) is specifically formulated for IHC applications with demonstrated reactivity to human samples .

• Sample preparation: Both frozen and paraffin-embedded tissue sections are suitable for DPP4 detection, with specific protocols required for each:

  • For paraffin sections: Use 1:200 dilution of D6D8K rabbit mAb (#40134)

  • For frozen sections: EPR18215 has been validated for IHC-Fr applications

• Antigen retrieval: For formalin-fixed, paraffin-embedded tissues, heat-mediated antigen retrieval using Tris-EDTA buffer (pH 9.0) is recommended for optimal epitope exposure .

• Controls: Include appropriate controls in each experiment:

  • Positive control: Tissues known to express DPP4 (lung, thymus, liver)

  • Negative control: Secondary antibody only, using PBS instead of primary antibody

• Detection systems: Use detection systems compatible with rabbit monoclonal antibodies, with sensitivity appropriate for the expected expression level of DPP4 in the target tissue.

• Counterstaining: Optimize counterstaining protocols to allow clear visualization of DPP4 staining pattern without obscuring specific signal.

Researchers should also be aware that DPP4 expression patterns may vary significantly between tissues and disease states, requiring careful interpretation of staining results.

How can researchers characterize anti-drug antibodies (ADAs) against DPP4-targeting therapeutics?

The assessment of anti-drug antibodies (ADAs) against DPP4-targeting therapeutics requires a structured multi-tiered testing approach for comprehensive immunogenicity evaluation:

• Initial screening assay: All samples are tested to identify potentially ADA-positive samples. For DPP4-targeting therapeutics, this typically involves detection of antibodies that bind to the drug molecule .

• Confirmatory assay: Samples that test positive in the screening assay undergo confirmatory testing to verify that the detected antibodies are specific to the therapeutic. This step reduces false positives from the screening assay .

• Neutralizing antibody (NAb) assessment: For confirmed positive samples, neutralizing activity is determined. This is particularly important for DPP4-targeted therapeutics, as NAbs could impair drug functionality by interfering with pharmacokinetic performance and decreasing efficacy .

• Titer determination: For samples with confirmed ADA presence, titer values are determined to quantify the antibody levels .

Data organization for ADA analysis follows a structured approach as illustrated in the sample SDTM IS (Immunogenicity Specimen Assessments) Domain Dataset:

This methodical approach enables researchers to comprehensively characterize the immunogenic potential of DPP4-targeting therapeutics, facilitating safety assessment, post-marketing surveillance, and risk mitigation strategies .

What are the cutting-edge approaches for engineering DPP4-targeted antibody therapeutics?

Recent advances in antibody engineering have yielded innovative approaches for developing DPP4-targeted therapeutics with enhanced specificity and efficacy:

• Bispecific antibodies (BsAbs): These engineered antibodies simultaneously target DPP4 and a second target (such as viral proteins) to enhance therapeutic efficacy. Advanced molecular engineering techniques including KIH (Knobs into Holes) and CrossMAb methods prevent heavy chain and light chain mispairings, ensuring structural integrity and functional performance . Molecular docking studies demonstrate that properly engineered BsAbs can achieve higher binding affinity to DPP4 than conventional monospecific antibodies .

• DPP4 immunoadhesins: These fusion proteins combine:

  • The extracellular domain of DPP4

  • A portion of human immunoglobulin (typically the hinge and Fc regions)

  This approach creates "receptor decoys" that can bind to target proteins (like viral spike proteins) with high affinity while leveraging the biological functions of the Fc region . Advanced engineering includes incorporation of mutations in the DPP4 domain to enhance binding affinity for target proteins .

• Multi-component therapeutic systems: These combine antibody technologies with additional functional elements, such as:

  • Bispecific antibodies targeting DPP4 and viral proteins

  • Anti-viral peptides linked to the Fc region

  • Incorporation of cleavable linkers for controlled release of functional components in target tissues

For example, one innovative approach linked an anti-viral peptide to the Fc region of a BsAb that blocks the hACE2 receptor through linker cleavage inside the infected host, providing a "triumvirate" approach to blocking viral entry through multiple mechanisms .

• Sequence optimization: Human DPP4-Fc(39-766) fusion proteins with human IgA2 Fc have been developed for specific applications, representing an alternative approach to IgG-based constructs .

These advanced engineering approaches extend beyond traditional antibody frameworks to create multifunctional therapeutic proteins with enhanced target engagement and biological activities.

What are the most common challenges when using DPP4 antibodies and how can they be addressed?

Researchers frequently encounter several challenges when working with DPP4 antibodies. Here are evidence-based solutions to address these issues:

• Variable expression levels across tissues:
  DPP4 expression varies significantly between tissue types. Mouse and rat lung and thymus tissues show high expression, while liver tissues may require shorter exposure times during Western blot development (10-15 seconds compared to 30 seconds for lung/thymus) . Recommendation: Optimize protein loading and exposure times based on the specific tissue source being examined.

• Non-specific binding:
  Secondary antibody may produce background signal not related to DPP4. Recommendation: Always include a secondary antibody-only control, substituting PBS for primary antibody to assess and account for non-specific binding .

• Antigen accessibility in fixed tissues:
  Formalin fixation can mask DPP4 epitopes. Recommendation: Perform heat-mediated antigen retrieval using Tris-EDTA Buffer (pH 9.0) for optimal epitope exposure in fixed samples .

• Species cross-reactivity limitations:
  Different antibody clones show varied species reactivity. The EPR18215 clone works with mouse and rat samples , while D6D8K is validated for human samples . Recommendation: Carefully verify the species reactivity of your selected antibody through both manufacturer specifications and independent validation.

• Molecular weight variability:
  Post-translational modifications can affect the apparent molecular weight of DPP4. Recommendation: Refer to literature-validated molecular weights (PMID: 25589660) and include positive control samples with known DPP4 expression .

How can researchers validate the specificity of DPP4 antibodies for their experimental systems?

Thorough validation of DPP4 antibodies is essential for generating reliable experimental data. The following methodological approach ensures appropriate antibody validation:

• Multi-technique confirmation:
  Validate antibody specificity using complementary techniques:

  • Western blotting with positive control tissues (lung, thymus, liver)

  • Immunohistochemistry on tissues with known DPP4 expression patterns

  • Flow cytometry for cell surface expression analysis

• Positive and negative tissue controls:
  Include tissues with established DPP4 expression profiles as controls:

  • High expression: Lung, thymus samples from appropriate species

  • Moderate expression: Liver samples

  • Negative control: Tissues known to lack DPP4 expression or samples from DPP4 knockout models

• Peptide competition assays:
  Pre-incubate the antibody with excess DPP4 peptide/protein before application to samples. Specific binding should be blocked by competition, resulting in reduced or absent signal.

• Functional correlation:
  Correlate antibody detection with functional assays of DPP4 activity:

  • Enzymatic assays measuring dipeptidyl peptidase activity

  • T-cell activation assays that depend on DPP4's costimulatory function

• Genetic manipulation controls:
  If available, use samples from:

  • DPP4 knockout models (negative control)

  • DPP4 overexpression systems (positive control)

  • siRNA/shRNA knockdown cells (reduced expression control)

• Epitope mapping:
  If possible, determine the specific epitope recognized by the antibody to predict potential cross-reactivity and limitations in detecting specific DPP4 isoforms or post-translationally modified variants.

By implementing this comprehensive validation strategy, researchers can ensure their selected DPP4 antibody delivers reliable data for their specific experimental system.

How is DPP4 being investigated as a therapeutic target for viral infections?

DPP4 has emerged as a critical target for antiviral therapeutic development, particularly for coronaviruses. Current research demonstrates several promising approaches:

• Receptor decoy strategies:
  DPP4 immunoadhesin compositions function as molecular decoys that prevent viral interaction with cellular DPP4. These constructs typically combine:

  • The extracellular domain of DPP4

  • A portion of human immunoglobulin (e.g., the hinge and Fc regions of IgG1)

  This approach has shown promise for preventing MERS-CoV infections by binding to the viral spike protein, thereby blocking its availability to interact with DPP4 on cell surfaces . While recombinant soluble DPP4 inhibits MERS-CoV infection in vitro, the concentration required for 50% inhibition is relatively high (~10 μM), suggesting optimization opportunities .

• Bispecific antibody approaches:
  Advanced bispecific antibodies simultaneously target:

  • Viral spike glycoproteins

  • Host DPP4 receptors

  One promising approach identified Regdanvimab and Begelomab as effective agents for blocking the D614G mutated spike glycoprotein of SARS-CoV-2 and host DPP4 receptor, respectively . Molecular engineering using KIH (Knobs into Holes) and CrossMAb techniques prevents heavy/light chain mispairings while maintaining target-binding capabilities .

• Multi-component therapeutic systems:
  Research has expanded beyond single-mechanism approaches to create multi-component systems that target virus-host interactions through multiple pathways simultaneously. For example:

  • Bispecific antibodies targeting DPP4 and viral proteins

  • Anti-viral peptides linked to the Fc region of antibodies

  • Mechanisms to block the primary viral entry receptor (hACE2) through linker cleavage inside infected hosts

These "triumvirate" approaches offer promising strategies to obstruct viral entry by blocking multiple receptor engagement pathways simultaneously .

• Structure-guided optimization:
  Molecular docking studies and structural biology insights are enabling the rational design of DPP4-targeting therapeutics with enhanced binding affinities. Research has identified specific DPP4 consensus contact residues and implemented amino acid substitutions that increase affinity for viral spike proteins .

These innovative approaches represent the cutting edge of DPP4-focused antiviral research with significant therapeutic potential.

What role does DPP4 play in T-cell biology and how can antibodies help elucidate these functions?

DPP4 (CD26) serves as a multifunctional regulator of T-cell biology, with antibodies providing crucial tools for investigating these complex roles:

• T-cell activation and costimulation:
  DPP4 functions as a positive regulator of T-cell coactivation by binding to multiple molecular partners including ADA, CAV1, IGF2R, and PTPRC . Its interaction with CAV1 and CARD11 specifically induces T-cell proliferation and NF-kappa-B activation in a T-cell receptor/CD3-dependent manner . Antibodies targeting specific epitopes can help dissect these interactions by:

  • Blocking specific protein-protein interaction interfaces

  • Modulating DPP4's enzymatic activity while preserving protein-binding capabilities

  • Selectively targeting DPP4 on specific T-cell subpopulations

• Cell adhesion regulation:
  DPP4's interaction with adenosine deaminase (ADA) regulates lymphocyte-epithelial cell adhesion . Antibodies can help elucidate this function by:

  • Blocking the ADA-binding site on DPP4

  • Modulating adhesion dynamics in controlled experimental systems

  • Visualizing the cellular distribution of DPP4 during adhesion processes

• Enzymatic versus non-enzymatic functions:
  DPP4 possesses both enzymatic (peptidase) and non-enzymatic (protein-binding) activities. Antibodies that selectively inhibit one function while preserving others can help dissect the relative contributions of each to T-cell biology. For example:

  • Antibodies binding near the catalytic site may inhibit peptidase activity

  • Antibodies targeting protein-interaction domains may block specific signaling functions

  • Conformation-specific antibodies may distinguish between different functional states

• Migration and tissue infiltration:
  In association with fibroblast activation protein (FAP), DPP4 contributes to pericellular proteolysis of the extracellular matrix (ECM) and influences cell migration and invasion . Antibodies can help track and modulate these processes by:

  • Visualizing DPP4 distribution during migration

  • Blocking specific interactions with ECM components

  • Modulating DPP4-dependent proteolytic processes

By developing and characterizing antibodies that target specific functional domains or conformational states of DPP4, researchers can systematically investigate its multifaceted roles in T-cell biology, potentially leading to novel immunomodulatory therapeutic strategies.

What are the most significant recent advances in DPP4 antibody research?

Recent advances in DPP4 antibody research have significantly expanded our understanding of this multifunctional protein and its therapeutic targeting potential. The most notable developments include:

• Novel bispecific antibody formats that simultaneously target DPP4 and viral proteins, representing a significant advancement for antiviral therapeutic strategies. These engineered antibodies incorporate KIH (Knobs into Holes) and CrossMAb technologies to prevent heavy/light chain mispairings while maintaining enhanced binding affinity for both targets .

• Immunoadhesin compositions that function as "receptor decoys" by combining the extracellular domain of DPP4 with portions of human immunoglobulin, creating molecules that can efficiently bind viral proteins and prevent their interaction with cellular DPP4 .

• Multi-component therapeutic systems that combine antibody technologies with additional functional elements such as anti-viral peptides linked to the Fc region through cleavable linkers, enabling targeted delivery and activation in infected tissues .

• Structure-guided optimization approaches that introduce specific amino acid substitutions to enhance the binding affinity of DPP4-derived constructs for viral spike proteins, improving their effectiveness as antiviral agents .

• Standardized immunogenicity assessment protocols for characterizing anti-drug antibody responses against DPP4-targeting therapeutics, facilitating better understanding of potential immunogenicity challenges and enabling more effective risk mitigation strategies .