Immunopotency of a viral peptide assembled on the carbohydrate moieties of self immunoglobulins

DNA and protein-generated chimeric molecules for delivery of influenza viral epitopes in mouse and humanized NSG transfer models

Purified subunit viral antigens are weakly immunogenic and stimulate only the antibody but not the T cell-mediated immune response. An alternative approach to inducing protective immunity with small viral peptides may be the targeting of viral epitopes to immunocompetent cells by DNA and protein-engineered vaccines. This review will focus on DNA and protein-generated chimeric molecules carrying engineered fragments specific for activating cell surface co-receptors for inducing protective antiviral immunity. Adjuvanted protein-based vaccine or DNA constructs encoding simultaneously T- and B-cell peptide epitopes from influenza viral hemagglutinin, and scFvs specific for costimulatory immune cell receptors may induce a significant increase of anti-influenza antibody levels and strong CTL activity against virus-infected cells in a manner that mimics the natural infection. Here we summarize the development of several DNA and protein chimeric constructs carrying influenza virus HA317-41 fragment. The generated engineered molecules were used for immunization in intact murine and experimentally humanized NSG mouse models.

Recombinant immunoglobulin-based epitope delivery: a novel class of autoimmune regulators

Over the past decades, there has been significant progress in understanding the mechanisms of autoimmune diseases at a molecular level. Diseases such as juvenile diabetes, multiple sclerosis, celiac disease, rheumatoid arthritis, and others appear to be mediated by pathogenic T cells that recognize self-epitopes and escape natural tolerance. Seminal observations correlating autoimmunity with HLA and disease-associated epitopes, in conjunction with recent characterization of T regulatory (Treg) cells, promoted a renewed interest in antigen or epitope-based methods of interfering with pathogenic autoimmune reactions. Recombinant immunoglobulin-peptides encompassing disease-associated self-epitopes (IgPP) integrate effective targeting of antigen-presenting cells (APCs) with a potential to generate Treg cells and thus are being developed for treatment of selected autoimmune disorders. In the current review, we outline the main features of this new class of active immunotherapeutics and directions of future development.

Construction of recombinant targeting immunogens incorporating an HIV-1 neutralizing epitope into sites of differing conformational constraint

2F5 is one of the very few monoclonal antibodies with the capacity to neutralize a wide spectrum of type 1 human immunodeficiency virus (HIV-1) strains and primary isolates. Constructing an immunogen that contains a conformational mimic of the epitope recognized by 2F5 could provide the means to induce a broadly neutralizing anti-HIV-1 antibody response. Thus, in an effort to create a targeted, adjuvant-independent immunogen able to induce a 2F5-like antibody response, the gp41 sequence recognized by 2F5 (ELDKWAS) was genetically incorporated into different regions of an antibody specific for a framework determinant on human leukocyte antigen (HLA)-DR. All constructs were expressed, secreted from Sf9 insect cells, and found to retain the anti-HLA-DR specificity of the parental antibody. Three of the four constructs in which the ELDKWAS sequence was incorporated into a beta-turn (BT)-like conformational site were recognized by the 2F5 antibody. In contrast, none of the five constructs with the same sequence incorporated into surface-exposed regions of helical turn had any detectable 2F5 reactivity. In addition to demonstrating the significant plasticity of several regions in the antibody molecule in terms of accepting foreign sequences without loss of expression or binding specificity, these results also suggest that the native epitope recognized by the 2F5 antibody may be more beta-turn-like than helical in conformation. Importantly, with respect to vaccine development, the 2F5-reactive antibody constructs represent candidate immunogens for the adjuvant-independent induction of an HIV-1, neutralizing 2F5-like antibody response in humans.

Antigen-specific signaling by a soluble, dimeric peptide/major histocompatibility complex class II/Fc chimera leading to T helper cell type 2 differentiation

Interaction between a T cell receptor (TCR) and various ligands, i.e. , anti-TCR antibodies, superantigens, peptides, or altered peptide ligands in the context of major histocompatibility complex (MHC) molecules can trigger different T helper cell (Th) effector functions. Herein, we studied the T cell response induced by a soluble, dimeric peptide/MHC class II chimera, namely hemagglutinin (HA)110-120/I-E(d)alphabeta/Fcgamma2a (DEF). We have previously demonstrated that the soluble DEF molecule binds stably and specifically to HA110-120-specific TCRs expressed by a T cell hybridoma. Administration of DEF in vivo induced differentiation of resting and activated peptide-specific T cells toward a Th2 response, as indicated by the increase of interleukin (IL)-4, IL-10, and specific immunoglobulin (Ig)G1 antibodies and decrease of IL-2, specific IgG2a antibodies, and cytotoxic T lymphocyte activity. In contrast to HA110-120 peptide presented by the DEF molecule to T cells, the nominal synthetic peptide induced a predominant Th1 response, and the PR8 virus-derived HA110-120 peptides induced a mixed Th1/Th2 response. Independent of antigen processing, soluble DEF was almost 2 logs more potent in stimulating cognate T cells than the nominal peptide. Polarization of cognate T cells toward the Th2 response occurred upon interaction of soluble DEF with TCR and CD4 molecules followed by early activation of p56(lck) and ZAP-70 tyrosine kinases, and negative signaling of the signal transducer and activator of transcription (STAT)4 pathway of Th1 differentiation. DEF-like molecules may provide a new tool to study the mechanisms of signaling toward Th2 differentiation and may also provide a potential immunotherapeutic approach to modulate autoreactive T cells toward protective Th2 immune responses.

Towards development of T-cell vaccines

Recent studies on the recognition of antigens by CD4+ and CD8+ T cells have revealed new ways of preparing efficient T-cell vaccines. Here, Constantin Bona and colleagues discuss several approaches for the development of T-cell vaccines, with applications ranging from the induction of protective immunity against intracellular parasites to the development of therapeutic agents against autoimmune disorders, allergic diseases and cancer.

Presentation of a viral peptide assembled on the carbohydrate moieties of immunoglobulin does not require processing

We have previously demonstrated that an immunodominant CD4 T cell epitope, HA110-120 of the hemagglutinin (HA) of the A/PR/8/34 influenza virus, enzymatically assembled on the carbohydrate moieties of self immunoglobulins (Ig) primed the precursors of peptide-specific T cells and induced efficient proliferation in vivo of naive lymphocytes from transgenic mice expressing the peptide-specific T cell receptor. Here, we show that an immuno-galacto-peptide construct, IgG-gal-HA, does not require intracellular or extracellular processing to present the peptide to the specific T cells. The presentation occurs following the binding of the IgG-gal-HA construct to Fc gamma receptor on the surface of antigen-presenting cells (APC), with concurrent interaction of the peptides to their neighboring major histocompatibility complex class II molecules. This mechanism of peptide presentation may harness the immune response in vivo by the engagement of APC with a low capacity of antigen processing, such as neonatal B cells. In addition, the enzymatic method of assembling various aminated compounds on the sugar moieties of Ig may offer novel perspectives on immuno-targeting of antagonist peptides, cytostatic drugs, and biologically active ligands of therapeutic use.

Immunogenicity of a contiguous T-B synthetic epitope of the A/PR/8/34 influenza virus

A contiguously linked T-B synthetic viral epitope (110HA120-150HA159,T-B) was investigated for its potency in inducing humoral and cellular immune responses in vivo. The T-cell epitope 110HA120 corresponds to the site 1 hemagglutinin (HA) of the A/PR/8/34 (PR8) influenza virus and is recognized by CD4 T cells in association with I-Ed class II major histocompatibility complex molecules. The 150HA159 represents a major B-cell epitope of the HA protein. T-B dipeptide emulsified in Freund's complete adjuvant was able to induce strong antiviral antibody titers and a high frequency of specific T-cell precursors after a single inoculation in BALB/c mice. In contrast, immunization under identical conditions with equimolar mixtures of T and B peptides did not elicit antibody titers or a cellular immune response. As indicated by the isotypes of antiviral antibodies, the T-B dipeptide preferentially induced a Th1-like immune response. Challenge with T-B dipeptide, but not with T or B peptide alone, stimulated peptide-specific T memory cells in mice previously primed with PR8 virus or with T-B dipeptide. As a consequence, 71 and 57% of these mice, respectively, survived infection with two 100% lethal doses of PR8 virus. Our results suggest that, inasmuch as contiguity between T- and B-cell epitopes provides enough signaling capacity to trigger the mechanisms of T-B-cell cooperation in vivo, a T-B contiguous epitope may well represent a minimal built-in subunit vaccine. Aside from their potential bioavailability, the T-B contiguous epitopes may also represent attractive tools for investigating the molecular mechanisms of T-B-cell cooperation responsible for antiviral protection.