DNA immunization as a technology platform for monoclonal antibody induction

To combat the threat of many emerging infectious diseases, DNA immunization offers a unique and powerful approach to the production of high-quality monoclonal antibodies (mAbs) against various pathogens. Compared with traditional protein-based immunization approaches, DNA immunization is efficient for testing novel immunogen designs, does not require the production or purification of proteins from a pathogen or the use of recombinant protein technology and is effective at generating mAbs against conformation-sensitive targets. Although significant progress in the use of DNA immunization to generate mAbs has been made over the last two decades, the literature does not contain an updated summary of this experience. The current review provides a comprehensive analysis of the literature, including our own work, describing the use of DNA immunization to produce highly functional mAbs, in particular, those against emerging infectious diseases. Critical factors such as immunogen design, delivery approach, immunization schedule, use of immune modulators and the role of final boost immunization are discussed in detail

Bacterial Transmembrane Proteins that Lack N-Terminal Signal Sequences

Tail-anchored membrane proteins (TAMPs), a class of proteins characterized by their lack of N-terminal signal sequence and Sec-independent membrane targeting, play critical roles in apoptosis, vesicle trafficking and other vital processes in eukaryotic organisms. Until recently, this class of membrane proteins has been unknown in bacteria. Here we present the results of bioinformatic analysis revealing proteins that are superficially similar to eukaryotic TAMPs in the bacterium Streptomyces coelicolor. We demonstrate that at least four of these proteins are bona fide membrane-spanning proteins capable of targeting to the membrane in the absence of their N-terminus and the C-terminal membrane-spanning domain is sufficient for membrane targeting. Several of these proteins, including a serine/threonine kinase and the SecE component of the Sec translocon, are widely conserved in bacteria

A human PrM antibody that recognizes a novel cryptic epitope on dengue E glycoprotein

10.1371/journal.pone.0033451PLoS ONE74

A Simplified Positive-Sense-RNA Virus Construction Approach That Enhances Analysis Throughput

Here we present an approach that advances the throughput of a genetic analysis of a positive-sense RNA virus by simplifying virus construction. It enabled comprehensive dissection of a complex, multigene phenotype through rapid derivation of a large number of chimeric viruses and construction of a mutant library directly from a virus pool. The versatility of the approach described here expands the applicability of diverse genetic approaches to study these viruses

Adaptor protein 1A facilitates dengue virus replication

10.1371/journal.pone.0130065PLoS ONE106e013006

Cross-Reacting Antibodies Enhance Dengue Virus Infection in Humans

Dengue virus co-circulates as four serotypes and sequential infections with more than one serotype are common. One hypothesis for the increased severity seen in secondary infections is antibody dependent enhancement (ADE) leading to increased replication in Fc-receptor-bearing cells. In this study we have generated a panel of human monoclonal antibodies to dengue virus. Antibodies to the structural precursor-membrane protein (prM) dominate the response. These antibodies are highly cross-reactive among the dengue virus serotypes and, even at high concentrations, do not neutralise infection but potently promote ADE. We propose that the partial cleavage of prM from the viral surface reduces the density of antigen available for viral neutralisation, leaving dengue viruses susceptible to ADE by anti-prM, a finding which has implications for future vaccine design

Characterization of a potent and highly unusual minimally enhancing antibody directed against dengue virus

Dengue virus is a major pathogen and severe infections can lead to life threatening dengue hemorrhagic fever (DHF). Dengue exists as four serotypes and DHF is often associated with secondary heterologous infections. Antibody dependent enhancement (ADE) may drive higher virus loads in these secondary infections, and is purported to result from antibodies that recognize dengue but fail to fully neutralize. We have characterized two antibodies, 2C8 and 3H5, which bind to the envelope protein. 3H5 is highly unusual as it is both potently neutralizing, but promotes little if any ADE, whereas 2C8 has strong capacity to promote ADE. We show that 3H5 shows resilient binding in endosomal pH conditions and neutralizes at low occupancy. Immune complexes of 3H5 and dengue virus do not efficiently interact with Fcγ receptors, which we propose is due to the binding mode of 3H5 and which constitutes the primary mechanism of how ADE is avoided

Characterization of a potent and highly unusual minimally enhancing antibody directed against dengue virus

Dengue virus is a major pathogen and severe infections can lead to life threatening dengue hemorrhagic fever (DHF). Dengue exists as four serotypes and DHF is often associated with secondary heterologous infections. Antibody dependent enhancement (ADE) may drive higher virus loads in these secondary infections, and is purported to result from antibodies that recognize dengue but fail to fully neutralize. We have characterized two antibodies, 2C8 and 3H5, which bind to the envelope protein. 3H5 is highly unusual as it is both potently neutralizing, but promotes little if any ADE, whereas 2C8 has strong capacity to promote ADE. We show that 3H5 shows resilient binding in endosomal pH conditions and neutralizes at low occupancy. Immune complexes of 3H5 and dengue virus do not efficiently interact with Fcγ receptors, which we propose is due to the binding mode of 3H5 and which constitutes the primary mechanism of how ADE is avoided

Antibody production by injection of living cells expressing non self antigens as cell surface type II transmembrane fusion protein.

Antigen expression and purification are laborious, time consuming and frequently difficult steps in the process of antibody production. In the present study, we developed a method avoiding these two steps. This method relies on the injection of histocompatible living cells stably expressing the antigen as a cell surface type II transmembrane fusion protein. A vector, nicknamed pCD1-CD134L, was constructed to express the antigen fused at the carboxyterminal end of the human CD134 ligand (CD134L) type II transmembrane protein on the surface of eucaryotic cells. This vector was shown to induce cell surface expression of epitopes from human c-Myc (soluble protein), uterogloblin-related protein 1 (secreted protein) and CD94 (type II transmembrane protein). Using this vector, we developed a method to produce antibodies without antigen production. The flowchart of this method is as follows: (i) cloning of the antigen in the pCD1-CD134L vector; (ii) production of a histocompatible cell line stably expressing the CD134L-antigen fusion protein; (iii) testing for cell surface expression of the fusion protein by targeting the CD134L carrier; and (iv) prime-boost immunisation with living cells expressing the fusion protein. This method was successfully used for production of polyclonal antibodies raised against Ixodes ricinus calreticulin (secreted protein) in mice and for production of monoclonal antibodies raised against an epitope of Vaccinia virus A56 (type I transmembrane protein) protein in rat. The present study is the first to demonstrate the use of a type II transmembrane protein as a carrier for cell surface display of antigens