Recombinant CD4-IgE, a novel hybrid molecule, inducing basophils to respond to human immunodeficiency virus (HIV) and HIV-infected target cells

IgE immunotherapy: a novel concept with promise for the treatment of cancer

The importance of antibodies in activating immune responses against tumors is now better appreciated with the emergence of checkpoint blockade antibodies and with engineered antibody Fc domains featuring enhanced capacity to focus potent effector cells against cancer cells. Antibodies designed with Fc regions of the IgE class can confer natural, potent, long-lived immune surveillance in tissues through tenacious engagement of high-affinity cognate Fc receptors on distinct, often tumor-resident immune effector cells, and through ability to activate these cells under tumor-induced Th2-biased conditions. Here, we review the properties that make IgE a contributor to the allergic response and a critical player in the protection against parasites, which also support IgE as a novel anti-cancer modality. We discuss IgE-based active and passive immunotherapeutic approaches in disparate in vitro and in vivo model systems, collectively suggesting the potential of IgE immunotherapies in oncology. Translation toward clinical application is now in progress.

Immunoglobulin E antibodies from pancreatic cancer patients mediate antibody-dependent cell-mediated cytotoxicity against pancreatic cancer cells

In addition to allergy and parasitic infections, immunoglobulin E (IgE) has been shown recently to possess anti-viral and anti-cancer effects. We investigated serum levels of IgE, its low-affinity receptor, soluble CD23 (sCD23) in patients with pancreatic cancer and the effect of IgE against pancreatic cancer cells. Twelve patients were evaluated for pancreatic cancer by imaging and confirmed by biopsy. Fifteen healthy volunteers served as controls. Serum Igs (IgG, IgM, IgA, IgE) and sCD23 levels were determined (enzyme-linked immunosorbent assay, nephelometry) and the presence of cancer-specific IgE was assessed (fluorescence microscopy, Western blot). IgE anti-cancer activity was determined by antibody-dependent cell-mediated cytotoxicity (ADCC). Serum levels of IgE and sCD23 were elevated significantly in patients with pancreatic cancer versus controls, whereas no differences were observed in other Ig isotypes (IgG, IgM, IgA). Flow cytometry and immunofluorescence microscopy demonstrated similar presence of IgG and IgE pancreatic cancer Igs. However, Western blot analysis indicated differences in IgG and IgE antigen-specific antibodies; IgE antibody recognized a 50 kD protein. ADCC studies demonstrated that serum and purified IgE-mediated cytotoxicity against pancreatic cancer cells, effects which were reversed with anti-IgE neutralizing antibody and IgE depletion (immunoaffinity); greater cytotoxicity was observed in patient serum when compared with healthy controls. These data suggest that IgE and sCD23 may serve as useful biomarkers for patients with pancreatic cancer and may be important in the immune response to this disease in that IgE-directed therapy may help to direct treatment.

Immunoadhesins of interleukin-6 and the IL-6/soluble IL-6R fusion protein hyper-IL-6

Signal transduction in response to interleukin-6 (IL-6) results from homodimerization of gp130. This dimerization occurs after binding of IL-6 to its surface receptor (IL-6R) and can also be triggered by the complex of soluble IL-6R and IL-6. We fused IL-6 to the constant region of a human IgG1 heavy chain (Fc). IL-6Fc was expressed in COS-7 cells and purified via Protein A Sepharose. Using three different assays we found that the biological activity of this dimeric IL-6 protein is comparable with monomeric IL-6. Recently, we described the designer cytokine Hyper-IL-6 (H-IL-6) in which soluble IL-6R and IL-6 are connected via a flexible peptide linker. This molecule turned out to be 100-1000 times more effective than unlinked IL-6 and soluble IL-6R. Hyper-IL-6 acts on cells only expressing gp130 and is a potent stimulator of in vitro expansion of early hematopoietic precursors. Here we show that a Fc fusion protein of H-IL-6 (H-IL-6Fc) has the same biological activity on BAF/gp130 cells as H-IL-6. Furthermore, both H-IL-6 forms have a similar ability to induce the synthesis of acute phase proteins in human hepatoma cells HepG2 and in mice in vivo. The introduction of a thrombin cleavage site between H-IL-6 and the Fc portion of H-IL-6Fc made it possible to specifically recover biologically active monomeric H-IL-6 by limited proteolysis of the fusion protein. A more general use of cleavable immunoadhesins expressed in mammalian cells is discussed.

Fc receptors as targets for immunotherapy

Human membrane and soluble Fc epsilon receptors (Fc epsilon RI, Fc epsilon RII/CD23) and Fc gamma receptors (Fc gamma RI/CD64, Fc gamma RII/CD32, Fc gamma RIII/CD16) have been implicated in a number of diseases. Their functional roles such as capture and clearance of immune complexes, antibody-dependent cell cytotoxicity, or cytokine or inflammatory mediator release, make them potential targets for immuno-intervention. In the present review, we will describe how membrane and soluble human Fc epsilon R and Fc gamma R have been already used as targets/tools for immuno-interventions by using monoclonal and bispecific engineered antibodies. Some therapeutic uses of these molecules both in cancer, infectious, and auto-immune diseases are presented.

AIDS patient monocytes target CD4 T cells for cellular conjugate formation and deletion through the membrane expression of HIV-1 envelope molecules

The human immunodeficiency virus (HIV) causes in humans the acquired immunodeficiency syndrome (AIDS). It replicates at a high rate in lymphoid organs even before it causes clinical symptoms. It binds to CD4 cell surface markers and destroys T lymphocytes that express the receptor. The immune system replenishes CD4 T cells at a formidable rate but, unable to keep up with the losses, allows the CD4 T cell compartment to disintegrate gradually. The net loss of CD4 T cells is an indicator for disease progression. How the virus destroys CD4 T cells and whether their loss accounts for the ensuing immunodeficiency have not been fully explained. We have reported evidence, and confirm here, that HIV-infected subjects deposit on monocytes immune complexes containing the virus or its envelope molecule gp120. Armed with these immune complexes monocytes form specific cellular conjugates with CD4 T cells and kill them. The destruction of normal CD4 T cells by monocytes from AIDS patients can be blocked by soluble CD4 and by free gp120. Normal monocytes and macrophages can be armed with CD4-binding gp120, and so induced to destroy CD4 T cells, by incubating them with gp120 and gp120-specific antibody. CD4-reactive HIV-1 components have a short half-life on the phagocyte surface. Removed from the HIV-infected environment, monocytes clear their surfaces of antibody-complexed viral components within hours, which abrogates their ability to destroy CD4 T cells. Rearming the monocytes with gp120-anti-gp120 complexes restores their capacity to destroy CD4 T cells. The data imply that for uninterrupted deletion of CD4 T cells, monocytes require a continued productive HIV-1 infection of their host.

Immunoadhesins: principles and applications

The prototypic immunoadhesin is an antibody-like molecule that fuses the Fc region of an immunoglobulin and the ligand-binding region of a receptor or adhesion molecule. In this article, we review some important structural and functional principles of immunoadhesins. In addition, we highlight some unique advantages of immunoadhesins as experimental tools in biology, as well as some of their exciting potential applications in medicine.