Use of DNA immunization to produce polyclonal antibodies against the native human neurokinin-1 receptor for substance P

Generation of High-Specificity Antibodies against Membrane Proteins Using DNA-Gold Micronanoplexes for Gene Gun Immunization

Membrane proteins are the molecular interface of the cell and its environs; however, studies of membrane proteins are highly technically challenging, mainly due to instability of the isolated protein. Towards the production of antibodies that recognize properly folded and stabilized forms of membrane protein antigen, we describe a DNA-based immunization method for mice that expresses the antigen in the membranes of dendritic cells, thus allowing direct presentation to the immune system. This genetic immunization approach employs a highly efficient method of biolistic delivery based on DNA-gold micronanoplexes, which are complexes of micron-sized gold particles that allow dermal penetration and nanometer-sized gold particles that provide a higher surface area for DNA binding than micron gold alone. In contrast to antibodies derived from immunizations with detergent-solubilized protein or with protein fragments, antibodies from genetic immunization are expected to have a high capacity for binding conformational epitopes and for modulating membrane protein activity. © 2018 by John Wiley & Sons, Inc.

Biomaterials for polynucleotide delivery to anchorage-independent cells

Comparison of various chemical vectors used for polynucleotide delivery to mammalian anchorage-independent cells.

Construction and characterization of monoclonal antibodies against the extracellular domain of B-lymphocyte antigen CD20 using DNA immunization method

To date, several new anti-CD20 monoclonal antibodies (mAbs) have been developed for potential efficacies compared with familiar mAb rituximab. Despite the recent advances in development of anti-CD20 mAbs for the treatment of B cell malignancies, the efforts should be continued to develop novel antibodies with improved properties. However, the development of mAbs against CD20 as a multi-transmembrane protein is challenging due to the difficulty of providing a lipid environment that can maintain native epitopes. To overcome this limitation, we describe a simple and efficient DNA immunization strategy for the construction of a novel anti-CD20 mAb with improved anti-tumour properties. Using a DNA immunization strategy that includes intradermal (i.d.) immunization with naked plasmid DNA encoding the CD20 gene, we generated the hybridoma cell line D4, which secretes functional mAbs against an extracellular epitope of CD20. Immunocytochemistry analysis and a cell-based enzyme-linked immunosorbent assay using a Burkitt's lymphoma cell line showed that D4 mAbs are capable of binding to native extracellular epitopes of CD20. Moreover, the binding specificity of D4 mAbs was determined by western blot analysis. Cell proliferation was examined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis was detected by the annexin V/propidium iodide staining and dye exclusion assay. The results showed that D4 anti-CD20 mAbs produced by DNA immunization exhibit potent growth inhibitory activity and have superior direct B-cell cytotoxicity compared to rituximab. We propose that antibody-induced apoptosis is one of the mechanisms of cell growth inhibition. Taken together, the data reported here open the path to DNA-based immunization for generating pharmacologically active monoclonal antibodies against CD20. In addition, the data support future in vivo animal testing and subsequent procedures to produce a potential therapeutic mAb.

Polyclonal Antibody Production for Membrane Proteins via Genetic Immunization

Antibodies are essential for structural determinations and functional studies of membrane proteins, but antibody generation is limited by the availability of properly-folded and purified antigen. We describe the first application of genetic immunization to a structurally diverse set of membrane proteins to show that immunization of mice with DNA alone produced antibodies against 71% (n = 17) of the bacterial and viral targets. Antibody production correlated with prior reports of target immunogenicity in host organisms, underscoring the efficiency of this DNA-gold micronanoplex approach. To generate each antigen for antibody characterization, we also developed a simple in vitro membrane protein expression and capture method. Antibody specificity was demonstrated upon identifying, for the first time, membrane-directed heterologous expression of the native sequences of the FopA and FTT1525 virulence determinants from the select agent Francisella tularensis SCHU S4. These approaches will accelerate future structural and functional investigations of therapeutically-relevant membrane proteins.

Generation and characterization of rendomab-B1, a monoclonal antibody displaying potent and specific antagonism of the human endothelin B receptor

Endothelin B receptor (ETBR) is a G protein-coupled receptor able to bind equally to the three identified human endothelin peptides. It is expressed primarily on vascular endothelial cells and involved in various physiological processes including vascular tone homeostasis, enteric nervous system development, melanogenesis and angiogenesis. Furthermore, overactivation or overexpression of ETBR have been associated with the development of various diseases such as cardiovascular disorders and cancers. Therefore, ETBR appears to be relevant target for the therapy or diagnosis of highly prevalent human diseases. In this study, we report the in vitro characterization of rendomab-B1, a monoclonal antibody (mAb) obtained by genetic immunization, which selectively recognizes the native form of human ETBR (hETBR). Rendomab-B1 is the first-reported mAb that behaves as a potent antagonist of hETBR. It recognizes an original extracellular conformational epitope on the receptor, distinct from the endothelin-1 (ET-1) binding site. Rendomab-B1 not only blocks ET-1-induced calcium signaling pathway and triggers rapid receptor internalization on recombinant hETBR-expressing cells, but also exerts pharmacological activities on human vascular endothelial cells, reducing both cell viability and ET-1-induced hETBR synthesis. In addition, binding experiments using rendomab-B1 on different melanoma cell lines reveal the structural and functional heterogeneity of hETBR expressed at the surface of these cancer cells, strongly suggesting the existence of tumor-specific receptors. Collectively, our results underscore the value of rendomab-B1 for research, therapeutic and diagnostic applications dealing with hETBR.

Electroporation-aided DNA immunization generates polyclonal antibodies against the native conformation of human endothelin B receptor

Endothelin B receptor (ET(B)R) is a G protein-coupled receptor (GPCR) specific for endothelin peptides (including endothelin-1, ET1), which mediates a variety of key physiological functions in normal tissues, such as modulation of vasomotor tone, tissue differentiation, or cell proliferation. Moreover, ET(B)R, overexpressed in various cancer cells including melanoma, has been implicated in the growth and progression of tumors, as well as in controlling T cell homing to tumors. To gather information on receptor structure and function, antibodies are generally considered choice molecular probes, but generation of such reagents against the native conformation of GPCRs is a real technical challenge. Here, we show that electroporation-aided genetic immunization, coupled to cardiotoxin pretreatment, is a simple and very efficient method to raise large amounts of polyclonal antibodies highly specific for native human ET(B)R (hET(B)R), as assessed by both flow cytometry analysis of different stably transfected cell lines and a new and rapid cell-based enzyme-linked immunosorbent assay that we also describe. The antibodies recognized two major epitopes on hET(B)R, mapped within the N-terminal extracellular domain. They were used to reveal hET(B)R on membranes of three different human melanoma cell lines, by flow cytometry and confocal microscopy, a method that we show is more relevant than mRNA polymerase chain reaction in assessing receptor expression. In addition, ET-1 partially competed with antibodies for receptor binding. The strategy described here, thus, efficiently generated new immunological tools to further analyze the role of ET(B)R under both normal and pathological conditions, including cancers. Above all, it can now be used to raise monoclonal antibodies against hET(B)R and, more generally, against GPCRs that constitute, by far, the largest reservoir of potential pharmacological targets.

Enhancement of antibody responses in DNA vaccination using a vector encoding a universal T-helper cell epitope

DNA vaccination appears as a very promising approach to raise protective antibodies against a variety of proteins from pathogens or tumor cells, but is often hindered by the low immunogenicity of the genetic vectors used for the immunizations. To enhance the humoral response through improvement of the antigenic presentation of newly synthesized proteins upon vaccination, we engineered a plasmid coding for a low immunogenic protein (an scFv, i.e. the single-chain Fragment variable of a well-characterized antibody) fused to a small-size universal T-helper cell epitope derived from tetanus toxin, whose efficiency in classical protein-based immunization protocols has already been demonstrated. We found that immunization of C57Bl/6 mice using this vector greatly enhanced the production not only of specific antibodies recognizing essentially conformational epitopes on the undenatured scFv protein but also of antibodies against linear epitopes on the denatured protein. Since this T-epitope is known to be accommodated by several haplotypes of H-2 molecules in mice, as well as by various class II MHC molecules in humans, the results reported here allow us to conclude that this method could be of general interest for future applications of genetic immunization, including DNA-based vaccinations in humans.