Human fusion proteins between interleukin 2 and IgM heavy chain are cytotoxic for cells expressing the interleukin 2 receptor

Cooperativity to increase Turing pattern space for synthetic biology

It is hard to bridge the gap between mathematical formulations and biological implementations of Turing patterns, yet this is necessary for both understanding and engineering these networks with synthetic biology approaches. Here, we model a reaction-diffusion system with two morphogens in a monostable regime, inspired by components that we recently described in a synthetic biology study in mammalian cells.1 The model employs a single promoter to express both the activator and inhibitor genes and produces Turing patterns over large regions of parameter space, using biologically interpretable Hill function reactions. We applied a stability analysis and identified rules for choosing biologically tunable parameter relationships to increase the likelihood of successful patterning. We show how to control Turing pattern sizes and time evolution by manipulating the values for production and degradation relationships. More importantly, our analysis predicts that steep dose-response functions arising from cooperativity are mandatory for Turing patterns. Greater steepness increases parameter space and even reduces the requirement for differential diffusion between activator and inhibitor. These results demonstrate some of the limitations of linear scenarios for reaction-diffusion systems and will help to guide projects to engineer synthetic Turing patterns.

A Recombinant Human scFv Anti-Rh(D) Antibody With Multiple Valences Using a C-Terminal Fragment of C4-Binding Protein

Monomeric recombinant molecules prove generally unsatisfactory for in vivo use. Most biological systems are indeed multivalent either structurally, associating different chains, or functionally, when cross-linked by their ligands. Mimicking natural molecules for immune intervention implies the need for multimerizing systems to create multivalent molecules capable of interfering with physiological processing. A multivalent anti-Rh(D) recombinant protein has been designed by reconstructing the antibody binding site of a human monoclonal anti-Rh(D) antibody as a single chain Fv mini antibody, then multimerizing it by inserting at its C-terminal end the C-terminal part of the C4 binding protein (C4bp) alpha chain, which is responsible for the octamer multimerization of that molecule. This soluble multivalent recombinant molecule was functional, bound red blood cells (RBCs), agglutinated them, and did not activate complement. This demonstration model opens the way for future in vivo use of multivalent molecules associating antibody valences and other functional molecules for cell targeting, imaging, or removal of cells such as Rh(D)-positive RBCs for preventing Rh alloimmunization.

Targeting of antihapten antibodies to activated T cells via an IL-2-hapten conjugate prolongs cardiac graft survival

Antihapten antibodies binding to ligand-hapten conjugates are able to mediate complement mediated lysis in vitro. Based on this observation we propose a new in vivo immunotherapy using molecules that combine a low molecular weight hapten binding to antibodies preexisting in serum and a cell specific ligand. The ligand-hapten conjugates are potential cytotoxic drugs which may (1) be specific for a given target cell, (2) be nonimmunogenic, (3) be of low molecular weight, (4) form soluble complexes with preexisting antibodies resulting in prolonged half life of the drug, and (5) induce a potent antibody mediated rejection of target cells. These novel compounds could be useful for the elimination of certain cell subsets involved in allograft rejection, cancers, infectious diseases, etc., without some of the pitfalls of conventional immunotherapies. The feasibility of this approach was demonstrated in an animal model using a compound consisting of one interleukin 2 and one fluorescein molecule (IL-2-FITC). BALB/c mice (H2d) previously immunized and expressing anti-FITC antibodies were transplanted with a fully mismatched C57BL/6 (H2b) heterotopic heart allograft. Untreated controls rejected their graft by day 9 (MSD = 9 +/- 0.7). Mice with preexisting anti-FITC antibodies treated with IL-2-FITC maintained their grafts for 38.7 +/- 7.1 days (P < 0.02). No prolongation of graft survival was observed in immunized animals that were treated with IL-2 alone (MSD = 10 +/- 1.4). Nonimmunized animals treated with IL-2-FITC rejected their grafts on day 9.4 +/- 1.1. This demonstrates that IL-2-FITC therapy specifically prolonged graft survival in animals with circulating anti-FITC antibodies. The data suggest that a ligand/hapten pair can redirect preexisting antihapten antibodies toward target cells in vivo. Such compounds may be developed for human use as alternatives to polyclonal or monoclonal antibody therapy.

Suppression of cell-mediated and humoral immune responses by an interleukin-2-immunoglobulin fusion protein in mice

Interleukin-2 (IL-2) plays a pivotal role in the cellular and humoral immune responses directed against foreign antigens. We characterized the in vitro and in vivo properties of a chimeric protein consisting of mouse IL-2 fused to the mouse IgG2b Fc domains. This fusion protein binds to IL-2 and Fc receptors and supports IL-2-dependent cell proliferation but does not mediate lysis of IL-2 receptor-positive cells in the presence of murine complement in vitro. However, in vivo the IL2-IgG2b fusion protein suppresses both cellular and humoral immune responses after immunization with sheep erythrocytes. Surprisingly, delayed hypersensitivity is inhibited despite a dramatic increase of splenic CD3+ and NK1.1+ lymphocytes, indicating that altered homing of IL2-IgG2b-activated lymphocytes rather than cytolysis prevents these cells from accumulating in areas of inflammation. Although in vitro the IL2-IgG2b fusion protein does not alter proliferation of B cells in response to mitogenic stimulation, IgM production in response to sheep erythrocytes is profoundly inhibited in mice treated with the IL2-IgG2b fusion protein. Since no side effects are observed, the IL2-IgG2b fusion protein may expand the therapeutic repertoire of reagents used for the treatment of allograft rejection and autoimmune diseases.

Antibodies directed at mouse IL-2-R alpha and beta chains act in synergy to abolish T-cell proliferation in vitro and delayed type hypersensitivity reaction in vivo

The anti-mouse IL-2-R beta chain mAb TM-beta 1 which, by itself, does not affect IL-2-dependent proliferation through the high affinity mouse IL-2 receptor, was shown to cooperate in a synergistic way with a set of anti-IL-2-R alpha chain mAbs both in vitro and in vivo. In vitro, when associated at equimolar concentrations, the TM-beta 1/anti-alpha mAb association was four to ten times more efficient at inhibiting the proliferation of the CTL-L2 cell line than was a similar concentration of anti-alpha mAb alone. In addition, a bispecific antibody in which a Fab' fragment of TM-beta 1 was covalently linked to a Fab' fragment of one of the anti-alpha mAb (5A2) was shown to be as efficient as the TM-beta 1/5A2 association. The association of TM-beta 1 with 5A2 was also tested in vivo in a sheep red blood cell-induced delayed type hypersensitivity (DTH) model. TM-beta 1 which, by itself, had no effect on DTH, induced a two- to threefold decrease in the doses of 5A2 required to suppress this cell-mediated immune reaction.