Immunology


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0 Q&A 825 Views Feb 20, 2023

Development of the hybridoma technology by Köhler and Milstein (1975) has revolutionized the immunological field by enabling routine use of monoclonal antibodies (mAbs) in research and development efforts, resulting in their successful application in the clinic today. While recombinant good manufacturing practices production technologies are required to produce clinical grade mAbs, academic laboratories and biotechnology companies still rely on the original hybridoma lines to stably and effortlessly produce high antibody yields at a modest price. In our own work, we were confronted with a major issue when using hybridoma-derived mAbs: there was no control over the antibody format that was produced, a flexibility that recombinant production does allow. We set out to remove this hurdle by genetically engineering antibodies directly in the immunoglobulin (Ig) locus of hybridoma cells. We used clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) and homology-directed repair (HDR) to modify antibody’s format [mAb or antigen-binding fragment (Fab’)] and isotype. This protocol describes a straightforward approach, with little hands-on time, leading to stable cell lines secreting high levels of engineered antibodies. Parental hybridoma cells are maintained in culture, transfected with a guide RNA (gRNA) targeting the site of interest in the Ig locus and an HDR template to knock in the desired insert and an antibiotic resistance gene. By applying antibiotic pressure, resistant clones are expanded and characterized at the genetic and protein level for their ability to produce modified mAbs instead of the parental protein. Finally, the modified antibody is characterized in functional assays. To demonstrate the versatility of our strategy, we illustrate this protocol with examples where we have (i) exchanged the constant heavy region of the antibody, creating chimeric mAb of a novel isotype, (ii) truncated the antibody to create an antigenic peptide-fused Fab’ fragment to produce a dendritic cell–targeted vaccine, and (iii) modified both the constant heavy (CH)1 domain of the heavy chain (HC) and the constant kappa (Cκ) light chain (LC) to introduce site-selective modification tags for further derivatization of the purified protein. Only standard laboratory equipment is required, which facilitates its application across various labs. We hope that this protocol will further disseminate our technology and help other researchers.


Graphical abstract


0 Q&A 3491 Views Jun 20, 2022

Phage display is a proven and widely used technology for selecting specific antibodies against desired targets. However, an immense amount of effort is required to identify and screen the desired positive clones from large and diverse combinatorial libraries. On the other hand, the selection of positive binding clones from synthetic and semi-synthetic libraries has an inherent bias toward clones with randomly produced amber stop codons, making it more difficult to identify desirable binding antibodies. To overcome the screening of desired clones with amber codons, we present a step-by-step approach for effective phage library screening to isolate useful antibodies. The procedure calls for creating a simple new vector system for soluble production of phage ELISA positive binding clones with one or more amber stop codons in their single-chain antibody fragment (scFv) gene sequences, which is otherwise difficult in standard screening.


Graphical abstract:




0 Q&A 11756 Views Aug 5, 2016
The immunoglobulin G (IgG) fragment crystallizable (Fc) domain contains a single, highly conserved asparagine 297 (N297) glycosylation site in the CH2 domain, which is buried within the hydrophobic core of each of the two heavy chains. The biantennary core glycan structure, composed of 2 N-acetylglucosamine (GlcNAc) and 3 mannose residues, can be further decorated with fucose, bisecting GlcNAc and terminal GlcNAc, galactose, and sialic acid. Presence or absence of distinct residues can alter IgG effector functions such as antibody-dependent cell-mediated cytotoxicity (ADCC) or complement-dependent cytotoxicity (CDC). Here, we provide a protocol for the generation of IgG-Fc de-galactosylated, galactosylated, de-sialylated and sialylated IgG antibodies using recombinant glycosidases and glycosyltransferases.



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