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Identification of high-affinity anti-CD16A allotype-independent human antibody domains.

ABSTRACT: CD16A (Fc?RIIIA) is an activating receptor mostly expressed on natural killer (NK) cells and monocytes/macrophages. It can mediate antibody-dependent cell-mediated cytotoxicity (ADCC) through low-affinity interaction with human immunoglobulin G (IgG) Fc. It can also mediate cell lysis if NK cells are guided by bispecific killer cells engagers (BiKEs). BiKEs showed some success in clinical trials of cancer and are promising candidate therapeutics. However, currently reported BiKEs are based on antibody fragments (scFvs) of relatively large size. The CD16A-specific antibodies are also typically from animal origin. Decreasing the BiKE size could result in enhanced penetration into solid tumor and normal tissues, and using fully human antibodies could decrease the likelihood of immunogenicity. Here we report the identification and characterization of two antibody domains, D6 and E11, isolated from a very large human VH antibody domain library displayed on phage. D6 and E11 bound CD16A with EC50 of 4nM and 8nM, respectively, but not other Fc gamma receptors (Fc?Rs) such as CD64 (Fc?RI), CD32 (Fc?RII) and CD16B (Fc?RIIIB). They bound to both CD16A allotypes (158F,V) with equal affinity and competed with each other as well as with human IgG1 and the mouse anti-CD16A antibody 3G8. These and other results were used to build a molecular docking model predicting that D6 and E11 may bind to the CD16A membrane proximal D2 domain by interacting with its BC, C'E and EF loops. Importantly, cross-linked (bivalent) D6 and E11 induced secretion of IL-2 after binding to CD16A-expressing Jurkat T cells. The small size of these antibody domains combined with their high-affinity, specific, allotype-independent, activating interactions with CD16A could allow generation of novel highly effective BiKEs and other candidate protein therapeutics.

SUBMITTER: Li W

PROVIDER: S-EPMC6957250 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Identification of high-affinity anti-CD16A allotype-independent human antibody domains.

Li Wei W Yang Hongjia H Dimitrov Dimiter S DS

Experimental and molecular pathology 20161003 2

CD16A (FcγRIIIA) is an activating receptor mostly expressed on natural killer (NK) cells and monocytes/macrophages. It can mediate antibody-dependent cell-mediated cytotoxicity (ADCC) through low-affinity interaction with human immunoglobulin G (IgG) Fc. It can also mediate cell lysis if NK cells are guided by bispecific killer cells engagers (BiKEs). BiKEs showed some success in clinical trials of cancer and are promising candidate therapeutics. However, currently reported BiKEs are based on an ...[more]

PMID: 27712994

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Project description:Antibodies facilitate targeted cell killing by engaging with immune cells such as natural killer cells through weak binding interactions with Fcγ receptors on the cell surface. Here, we evaluate the binding affinity of the receptor FcγRIIIa V158 (CD16a) for several therapeutic antibody classes, isoforms, and Fc-fusion proteins using an immobilized receptor affinity liquid chromatography (LC) approach coupled with online mass spectrometry (MS) detection. Aglycosylated FcγRIIIa was used in the affinity chromatography and compared with published affinities using glycosylated receptors. Affinity LC-MS differentiated the IgG1 antibodies primarily according to their Fc glycosylation patterns, with highly galactosylated species having greater affinity for the immobilized receptors and thus eluting later from the column (M5< G0F < G0 afucosylated ≅ G1F < G2F). Sialylated species bound weaker to their asialylated counterparts as reported previously. High mannose glycoforms bound weaker than G0F, contrary to previously published studies using glycosylated receptors. Also, increased receptor binding affinity associated with afucosylated antibodies was not observed with the aglycosylated FcγRIIIa. This apparent difference from previous findings highlighted the importance of the glycans on the receptors for mediating stronger binding interactions. Characterization of temperature-stressed samples by LC-MS peptide mapping revealed over 200 chemical and post-translational modifications, but only the Fc glycans, deamidation of EU N325, and an unknown modification to either proline or cysteine residues of the hinge region were found to have a statistically significant impact on binding.Abbreviations: Antibody-dependent cell-mediated cytotoxicity (ADCC), chimeric antigen receptor (CAR), Chinese hamster ovary (CHO), dithiothreitol (DTT), electrospray ionization (ESI), hydrogen-deuterium exchange (HDX), filter aided-sample preparation (FASP), Fcγ receptor (FcγR), fragment crystallizable (Fc), high-pressure liquid chromatography (HPLC), immunoglobulin G (IgG), liquid chromatography (LC), monoclonal antibody (mAb), mass spectrometry (MS), natural killer (NK), N-glycolylneuraminic acid (NGNA), N-acetylneuraminic acid (NANA), principal component analysis (PCA), surface plasmon resonance (SPR), trifluoroacetic acid (TFA), and extracted mass chromatogram (XMC).

Project description:IntroductionThe Fc region of monoclonal antibodies (mAbs) interacts with the CD16a receptor on natural killer (NK) cells with "low affinity" and "low selectivity". This low affinity/selectivity interaction results in not only suboptimal anticancer activity but also induction of adverse effects. CD16a on NK cells binds to the antibody-coated cells, leading to antibody-dependent cell-mediated cytotoxicity (ADCC). Recent clinical data have shown that the increased binding affinity between mAb Fc region and CD16a receptor is responsible for significantly improved therapeutic outcomes. Therefore, the objective of this study was to develop a bispecific killer cell engager (BiKE) with high affinity and specificity/selectivity toward CD16a receptor for NK cell-based cancer immunotherapy.MethodsTo engineer BiKE, a llama was immunized, then high binding anti-CD16a and anti-HER2 VHH clones were isolated using phage display. ELISA, flow cytometry, and biolayer interferometry (BLI) data showed that the isolated anti-CD16a VHH has high affinity (sub-nanomolar) toward CD16a antigen without cross-reactivity with CD16b-NA1 on neutrophils or CD32b on B cells. Similarly, the data showed that the isolated anti-HER2 VHH has high affinity/specificity toward HER2 antigen. Using a semi-flexible linker, anti-HER2 VHH was recombinantly fused with anti-CD16a VHH to create BiKE:HER2/CD16a. Then, the ability of BiKE:HER2/CD16a to activate NK cells to release cytokines and kill HER2+ cancer cells was measured. As effector cells, both high-affinity haNK92 (CD16+, V176) and low-affinity laNK92 (CD16+, F176) cells were used.Results and discussionThe data showed that the engineered BiKE:HER2/CD16a activates haNK92 and laNK92 cells to release cytokines much greater than best-in-class mAbs in the clinic. The cytotoxicity data also showed that the developed BiKE induces higher ADCC to both ovarian and breast cancer cells in comparison to Trazimera™ (trastuzumab). According to the BLI data, BiKE:HER2/CD16 recognizes a different epitope on CD16a antigen than IgG-based mAbs; thus, it provides the opportunity for not only monotherapy but also combination therapy with other antibody drugs such as checkpoint inhibitors and antibody-drug conjugates. Taken together, the data demonstrate the creation of a novel BiKE with high affinity and specificity toward CD16a on NK cells with the potential to elicit a superior therapeutic response in patients with HER2+ cancer than existing anti-HER2 mAbs.

Dataset Information

Identification of high-affinity anti-CD16A allotype-independent human antibody domains.

Publications

Identification of high-affinity anti-CD16A allotype-independent human antibody domains.

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