Cx6Mab-1: A Novel Anti-Mouse CXCR6 Monoclonal Antibody Established by N-Terminal Peptide Immunization

A novel anti-mouse CXCR1 monoclonal antibody, Cx1Mab-8, demonstrates nanomolar affinity in flow cytometry

CXC chemokine receptor 1 (CXCR1) is an important regulator for neutrophil granulocyte activation through binding to the ligand interleukin-8 (IL-8). Upon binding to IL-8, CXCR1 activates downstream signaling, critical for innate and adaptive immune responses. The IL-8-CXCR1 axis also plays an important role in tumor progression, especially in the tumor microenvironment. CXCR1 antagonists or anti-IL-8 monoclonal antibodies (mAbs) have been developed and evaluated in clinical trials for inflammatory diseases and tumors. In this study, we developed novel mAbs for mouse CXCR1 (mCXCR1) using the N-terminal peptide immunization. Among the established anti-mCXCR1 mAbs, Cx1Mab-8 (rat IgG2b, kappa) recognized mCXCR1-overexpressed Chinese hamster ovary-K1 (CHO/mCXCR1) and mCXCR1-overexpressed LN229 (LN229/mCXCR1) by flow cytometry. The dissociation constant (K D) values of Cx1Mab-8 for CHO/mCXCR1 and LN229/mCXCR1 were determined as 4.1 × 10-10 M and 1.5 × 10-9 M, respectively. These results indicated that Cx1Mab-8 is useful for detecting mCXCR1 by flow cytometry with high affinity and could contribute to obtaining the proof of concept in preclinical studies.

Development of specific anti-mouse atypical chemokine receptor 4 monoclonal antibodies

Leukocyte migration is an essential function of innate and adaptive immune responses. Chemokines and their receptors control the migration system. The abundance of chemokines is controlled by atypical chemokine receptors (ACKRs), chemokine receptor-like molecules that do not couple to the G protein signaling pathways. Among them, ACKR4 regulates dendritic cell migration by controlling the ligands and is involved in tumor development in mouse models. Because no anti-mouse ACKR4 (mACKR4) monoclonal antibody (mAb) for flow cytometry has been reported, this study aimed to develop a novel mAb for mACKR4. Among the established anti-mACKR4 mAbs, A4Mab-1 (rat IgG2b, kappa), A4Mab-2 (rat IgG2b, kappa), and A4Mab-3 (rat IgG2b, kappa) recognized mACKR4-overexpressed Chinese hamster ovary-K1 (CHO/mACKR4) by flow cytometry. The dissociation constant (K D) values of A4Mab-1, A4Mab-2, and A4Mab-3 for CHO/mACKR4 were determined as 6.0 × 10-9 M, 1.3 × 10-8 M, and 1.7 × 10-9 M, respectively. Furthermore, A4Mab-1 and A4Mab-2 could detect mACKR4 by western blotting. These results indicated that A4Mab-1, A4Mab-2, and A4Mab-3 help to detect mACKR4 by flow cytometry and western blotting and obtain the proof of concept in preclinical models.

Development of Sensitive Anti-Mouse CCR5 Monoclonal Antibodies Using the N-Terminal Peptide Immunization

One of the G protein-coupled receptors, C-C chemokine receptor 5 (CCR5), is an important regulator for the activation of T and B lymphocytes, dendritic cells, natural killer cells, and macrophages. Upon binding to its ligands, CCR5 activates downstream signaling, which is an important regulator in the innate and adaptive immune response through the promotion of lymphocyte migration and the secretion of proinflammatory cytokines. Anti-CCR5 monoclonal antibodies (mAbs) have been developed and evaluated in clinical trials for tumors and inflammatory diseases. In this study, we developed novel mAbs for mouse CCR5 (mCCR5) using the N-terminal peptide immunization. Among the established anti-mCCR5 mAbs, C5Mab-4 (rat IgG2a, kappa) and C5Mab-8 (rat IgG1, kappa), recognized mCCR5-overexpressing Chinese hamster ovary-K1 (CHO/mCCR5) and an endogenously mCCR5-expressing cell line (L1210) by flow cytometry. The dissociation constant (KD) values of C5Mab-4 and C5Mab-8 for CHO/mCCR5 were determined as 3.5 × 10-8 M and 7.3 × 10-9 M, respectively. Furthermore, both C5Mab-4 and C5Mab-8 could detect mCCR5 by western blotting. These results indicated that C5Mab-4 and C5Mab-8 are useful for detecting mCCR5 by flow cytometry and western blotting and provide a possibility to obtain the proof of concept in preclinical studies.

Cx1Mab-1: A Novel Anti-mouse CXCR1 Monoclonal Antibody for Flow Cytometry

The C-X-C motif chemokine receptor-1 (CXCR1) is a rhodopsin-like G-protein-coupled receptor, expressed on the cell surface of immune cells and tumors. CXCR1 interacts with some C-X-C chemokines, such as CXCL6, CXCL7, and CXCL8/interleukin-8, which are produced by various cells. Since CXCR1 is involved in several diseases including tumors and diabetes mellitus, drugs targeting CXCR1 have been developed. Therefore, the development of sensitive monoclonal antibodies (mAbs) for CXCR1 has been desired for the diagnosis and treatment. This study established a novel anti-mouse CXCR1 (mCXCR1) mAb, Cx1Mab-1 (rat IgG1, kappa), using the Cell-Based Immunization and Screening method. Cx1Mab-1 reacted with mCXCR1-overexpressed Chinese hamster ovary-K1 (CHO/mCXCR1) and mCXCR1-overexpressed LN229 glioblastoma (LN229/mCXCR1) in flow cytometry. Cx1Mab-1 demonstrated a high binding affinity for CHO/mCXCR1 and LN229/mCXCR1 with a dissociation constant of 2.6 × 10-9 M and 2.1 × 10-8 M, respectively. Furthermore, Cx1Mab-1 could detect mCXCR1 by Western blot analysis. These results indicated that Cx1Mab-1 is useful for detecting mCXCR1, and provides a possibility for targeting mCXCR1-expressing cells in vivo experiments.

Establishment of a Novel Anti-Human CCR6 Monoclonal Antibody C6Mab-19 with the High Binding Affinity in Flow Cytometry

CC chemokine receptor 6 (CCR6) is a member of the G-protein-coupled receptor family that is highly expressed in B lymphocytes, effector and memory T cells, regulatory T cells, and immature dendritic cells. CCR6 has been revealed to have important functions in many pathological conditions, such as cancer, intestinal bowel disease, psoriasis, and autoimmune diseases. The only CCR6 chemokine ligand, CC motif chemokine ligand 20 (CCL20), is also involved in pathogenesis by interacting with CCR6. The CCL20/CCR6 axis is drawing attention as an attractive therapeutic target for various diseases. In this study, we developed novel monoclonal antibodies (mAbs) against human CCR6 (hCCR6) using the peptide immunization method, which are applicable to flow cytometry and immunohistochemistry. The established anti-hCCR6 mAb, clone C6Mab-19 (mouse IgG1, kappa), reacted with hCCR6-overexpressed Chinese hamster ovary-K1 (CHO/hCCR6), human liver carcinoma (HepG2), and human differentiated hepatoma (HuH-7) cells in flow cytometry. The dissociation constant (KD) of C6Mab-19 was determined as 3.0 × 10-10 M for CHO/hCCR6, 6.9 × 10-10 M for HepG2, and 1.8 × 10-10 M for HuH-7. Thus, C6Mab-19 could bind to exogenously and endogenously expressed hCCR6 with extremely high affinity. Furthermore, C6Mab-19 could stain formalin-fixed paraffin-embedded lymph node tissues from a patient with non-Hodgkin lymphoma by immunohistochemistry. Therefore, C6Mab-19 is suitable for detecting hCCR6-expressing cells and tissues and could be useful for pathological analysis and diagnosis.

Identification of the Binding Epitope of an Anti-Mouse CCR6 Monoclonal Antibody (C6Mab-13) Using 1× Alanine Scanning

CC chemokine receptor 6 (CCR6) is one of the members of the G-protein-coupled receptor (GPCR) family that is upregulated in many immune-related cells, such as B lymphocytes, effector and memory T cells, regulatory T cells, and immature dendritic cells. The coordination between CCR6 and its ligand CC motif chemokine ligand 20 (CCL20) is deeply involved in the pathogenesis of various diseases, such as cancer, psoriasis, and autoimmune diseases. Thus, CCR6 is an attractive target for therapy and is being investigated as a diagnostic marker for various diseases. In a previous study, we developed an anti-mouse CCR6 (mCCR6) monoclonal antibody (mAb), C₆Mab-13 (rat IgG₁, kappa), that was applicable for flow cytometry by immunizing a rat with the N-terminal peptide of mCCR6. In this study, we investigated the binding epitope of C₆Mab-13 using an enzyme-linked immunosorbent assay (ELISA) and the surface plasmon resonance (SPR) method, which were conducted with respect to the synthesized point-mutated-peptides within the 1-20 amino acid region of mCCR6. In the ELISA results, C₆Mab-13 lost its ability to react to the alanine-substituted peptide of mCCR6 at Asp11, thereby identifying Asp11 as the epitope of C₆Mab-13. In our SPR analysis, the dissociation constants (K_D) could not be calculated for the G9A and D11A mutants due to the lack of binding. The SPR analysis demonstrated that the C₆Mab-13 epitope comprises Gly9 and Asp11. Taken together, the key binding epitope of C₆Mab-13 was determined to be located around Asp11 on mCCR6. Based on the epitope information, C₆Mab-13 could be useful for further functional analysis of mCCR6 in future studies.

Epitope Mapping of the Novel Anti-Human CCR9 Monoclonal Antibody (C9Mab-11) by 2 × Alanine Scanning

We recently developed a novel anti-human C-C chemokine receptor 9 (hCCR9) monoclonal antibody (mAb), C₉Mab-11, which is applicable to flow cytometry, western blotting, and enzyme-linked immunosorbent assay (ELISA). This study aims to identify the binding epitope of C₉Mab-11 by using 1 × and 2 × alanine (or glycine) substituted-hCCR9 peptides (1 × and 2 × Ala-scan) by ELISA. According to the 1 × Ala-scan analysis, the response of C₉Mab-11 was diminished against M13A of the hCCR9 peptide, but was not eliminated. In the 2 × Ala-scan analysis, the reactions were abolished in the substitution of P11A-N12A, N12A-M13A, and M13A-A14G of hCCR9 N-terminal peptides. The results indicate that the binding epitope of C₉Mab-11 includes Pro11, Asn12, Met13, and Ala14 of hCCR9, with the region around Met13 being particularly important. The successful identification of the C₉Mab-11 epitope might be useful for the future pathophysiological analysis of hCCR9.

Epitope Mapping of an Anti-EpCAM Monoclonal Antibody (EpMab-37) Using the Alanine Scanning Method

The epithelial cell adhesion molecule (EpCAM) is a type I transmembrane glycoprotein, and plays critical roles in cell adhesion, proliferation, and tumorigenesis. EpCAM has been considered as a promising target for tumor diagnosis and therapy. Anti-EpCAM monoclonal antibodies (mAbs) have been developed for EpCAM-overexpressed tumors, and several clinical trials have demonstrated promising outcomes. We previously established an anti-EpCAM mAb, EpMab-37 (mouse IgG₁, kappa), using the Cell-Based Immunization and Screening method. EpMab-37 was revealed to recognize the conformational epitope of EpCAM. In this study, we determined the critical epitope of EpMab-37 by flow cytometry using the 1 × alanine scanning (1 × Ala-scan) and the 2 × alanine scanning (2 × Ala-scan) method. We first performed flow cytometry by 1 × Ala-scan using one alanine (or glycine)-substituted EpCAM mutants, which were expressed on Chinese hamster ovary-K1 cells, and found that the EpMab-37 did not recognize the R163A mutant of EpCAM. We next performed flow cytometry by 2 × Ala-scan using two alanine (or glycine) residues-substituted EpCAM mutants, and confirmed that EpMab-37 did not recognize R163A-including mutants of EpCAM. The results indicated that the critical binding epitope of EpMab-37 includes Arg163 of EpCAM.

Epitope Mapping Using the Cell-Based 2 × Alanine Substitution Method About the Anti-mouse CXCR6 Monoclonal Antibody, Cx6Mab-1

An anti-mouse CXC chemokine receptor 6 (mCXCR6) monoclonal antibody (mAb), Cx₆Mab-1, was developed recently. Cx₆Mab-1 is applicable for flow cytometry, Western blotting, and enzyme-linked immunosorbent assay. The purpose of this study is to determine the binding epitope of Cx₆Mab-1 using 2 × alanine mutated mCXCR6. Analysis of flow cytometry revealed that Cx₆Mab-1 did not recognize S8A-A9G, L10A-Y11A, D12A-G13A, and H14A-Y15A mutants of mCXCR6. The results clearly indicate that the binding epitope of Cx₆Mab-1 includes Ser8, Ala9, Leu10, Tyr11, Asp12, Gly13, His14, and Tyr15 of mCXCR6. The successful determination of the Cx₆Mab-1 epitope might contribute to the pathophysiological investigation of mCXCR6.

Establishment of a Sensitive Monoclonal Antibody Against Mouse CCR9 (C9Mab-24) for Flow Cytometry

The CC chemokine receptor 9 (CCR9), also known as CD199, is one of chemokine receptors. The CC chemokine ligand 25 (CCL25) is known to be the only ligand for CCR9. The CCR9-CCL25 interaction plays important roles in chemotaxis of lymphocytes and tumor cell migration. Therefore, CCR9-CCL25 axis is a promising target for tumor therapy and diagnosis. In this study, we established a sensitive and specific monoclonal antibody (mAb) against mouse CCR9 (mCCR9) using N-terminal peptide immunization method. The established anti-mCCR9 mAb, C₉Mab-24 (rat immunoglobulin [IgG]_2a, kappa), reacted with mCCR9-overexpressed Chinese hamster ovary-K1 (CHO/mCCR9) and mCCR9-endogenously expressed cell line, RL2, through flow cytometry. Kinetic analyses using flow cytometry showed that the dissociation constants (K_D) of C₉Mab-24 for CHO/mCCR9 and RL2 cell lines were 6.0 × 10^-9 M and 4.7 × 10^-10 M, respectively. Results indicated that C₉Mab-24 is useful for detecting mCCR9 through flow cytometry, thereby providing a possibility for targeting mCCR9-expressing cells in vivo experiments.

Determination of the Binding Epitope of an Anti-Mouse CCR9 Monoclonal Antibody (C9Mab-24) Using the 1× Alanine and 2× Alanine-Substitution Method

C-C chemokine receptor 9 (CCR9) is a receptor for C-C-chemokine ligand 25 (CCL25). CCR9 is crucial in the chemotaxis of immune cells and inflammatory responses. Moreover, CCR9 is highly expressed in tumors, including several solid tumors and T-cell acute lymphoblastic leukemia. Several preclinical studies have shown that anti-CCR9 monoclonal antibodies (mAbs) exert antitumor activity. Therefore, CCR9 is an attractive target for tumor therapy. In this study, we conducted the epitope mapping of an anti-mouse CCR9 (mCCR9) mAb, C₉Mab-24 (rat IgG_2a, kappa), using the 1× alanine (1× Ala)- and 2× alanine (2× Ala)-substitution methods via enzyme-linked immunosorbent assay. We first performed the 1× Ala-substitution method using one alanine-substituted peptides of the mCCR9 N-terminus (amino acids 1-19). C₉Mab-24 did not recognize two peptides (F14A and F17A), indicating that Phe14 and Phe17 are critical for C₉Mab-24-binding to mCCR9. Furthermore, we conducted the 2× Ala-substitution method using two consecutive alanine-substituted peptides of the mCCR9 N-terminus, and showed that C₉Mab-24 did not react with four peptides (M13A-F14A, F14A-D15A, D16A-F17A, and F17A-S18A), indicating that _13-MFDDFS_-18 is involved in C₉Mab-24-binding to mCCR9. Overall, combining, the 1× Ala- or 2× Ala-scanning methods could be useful for understanding for target-antibody interaction.

Epitope Mapping of Anti-Mouse CCR3 Monoclonal Antibodies Using Flow Cytometry

The CC chemokine receptor 3 (CCR3) is a receptor for CC chemokines, including CCL5/RANTES, CCL7/MCP-3, and CCL11/eotaxin. CCR3 is expressed on the surface of eosinophils, basophils, a subset of Th2 lymphocytes, mast cells, and airway epithelial cells. CCR3 and its ligands are involved in airway hyperresponsiveness in allergic asthma, ocular allergies, and cancers. Therefore, CCR3 is an attractive target for those therapies. Previously, anti-mouse CCR3 (mCCR3) monoclonal antibodies (mAbs), C₃Mab-3 (rat IgG_2a, kappa), and C₃Mab-4 (rat IgG_2a, kappa) were developed using the Cell-Based Immunization and Screening (CBIS) method. In this study, the binding epitope of these mAbs was investigated using flow cytometry. A CCR3 extracellular domain-substituted mutant analysis showed that C₃Mab-3, C₃Mab-4, and a commercially available mAb (J073E5) recognized the N-terminal region (amino acids 1-38) of mCCR3. Next, alanine scanning was conducted in the N-terminal region. The results revealed that the Ala2, Phe3, Asn4, and Thr5 of mCCR3 are involved in C₃Mab-3 binding, whereas Ala2, Phe3, and Thr5 are essential to C₃Mab-4 binding, and Ala2 and Phe3 are crucial to J073E5 binding. These results reveal the involvement of the N-terminus of mCCR3 in the recognition of C₃Mab-3, C₃Mab-4, and J073E5.

Development of a Novel Anti-Mouse CCR6 Monoclonal Antibody (C6Mab-13) by N-Terminal Peptide Immunization

The CC chemokine receptor 6 (CCR6) is a G protein-coupled receptor family member that is highly expressed in B lymphocytes, certain subsets of effector and memory T cells, and immature dendritic cells. CCR6 has only one chemokine ligand, CCL20. The CCL20-CCR6 axis has been recognized as a therapeutic target for autoimmune diseases and tumor. This study developed specific monoclonal antibodies (mAbs) against mouse CCR6 (mCCR6) using the peptide immunization method. The established anti-mCCR6 mAb, C₆Mab-13 (rat IgG₁, kappa), reacted with mCCR6-overexpressed Chinese hamster ovary-K1 (CHO/mCCR6), and mCCR6-endogenously expressed P388 (mouse lymphoid neoplasma) and J774-1 (mouse macrophage-like) cells in flow cytometry. The dissociation constant (K_D) of C₆Mab-13 for CHO/mCCR6 cells was determined to be 2.8 × 10^-9 M, indicating that C₆Mab-13 binds to mCCR6 with high affinity. In summary, C₆Mab-13 is useful for detecting mCCR6-expressing cells through flow cytometry.

Epitope Mapping of an Anti-Mouse CCR2 Monoclonal Antibody (C2Mab-6) Using Enzyme-Linked Immunosorbent Assay

CC chemokine receptor type-2 (CCR2) is a member of the G protein-coupled receptors, and is mainly expressed on cell surface of immune cells. CCR2 binds to its ligand, C-C motif chemokine 2 (also named as monocyte chemoattractant protein-1), which involves in the tumor progression by modulating the tumor microenvironment. Therefore, the monoclonal antibody (mAb) targeting CCR2 could be one of the strategies for cancer treatment. In this study, we investigated the critical epitope of C₂Mab-6, an anti-mouse CCR2 (mCCR2) mAb developed by N-terminal peptides immunization. We first performed enzyme-linked immunosorbent assay (ELISA) using N-terminal peptides of mCCR2 and demonstrated that C₂Mab-6 recognizes 1-19 amino acids of mCCR2. We further performed ELISA using 20 alanine-substituted peptides of mCCR2. C₂Mab-6 lost the reaction to the alanine-substituted peptides of D3A, N4A, M6A, P8A, Q9A, and F10A. These results indicate that the binding epitope of C₂Mab-6 includes Asp3, Asn4, Met6, Pro8, Gln9, and Phe10 of mCCR2.