Immunotoxin: A new tool for cancer therapy

Cancer is one of the main reasons of death in the most countries and in Iran. Immunotherapy quickly became one of the best methods of cancer treatment, along with chemotherapy and radiation. “Immunotoxin Therapy” is a promising way of cancer therapy that is mentioned in this field. Immunotoxins are made from a toxin attaching to an antibody target proteins present on cancer cells. The first-generation immunotoxins were made of a full-length toxin attached to whole monoclonal antibodies. But, these immunotoxins could bind to normal cells. DAB389IL2 was the first immunotoxin approved by the Food and Drug Administration. Current trends and researches are ongoing on finding proteins that in combination with immunotoxins have minimal immunogenicity and the most potency for target cell killing.

Macrophage-targeted therapy: CD64-based immunotoxins for treatment of chronic inflammatory diseases

Diseases caused by chronic inflammation (e.g., arthritis, multiple sclerosis and diabetic ulcers) are multicausal, thus making treatment difficult and inefficient. Due to the age-associated nature of most of these disorders and the demographic transition towards an overall older population, efficient therapeutic intervention strategies will need to be developed in the near future. Over the past decades, elimination of activated macrophages using CD64-targeting immunotoxins has proven to be a promising way of resolving inflammation in animal models. More recent data have shown that the M1-polarized population of activated macrophages in particular is critically involved in the chronic phase. We recapitulate the latest progress in the development of IT. These have advanced from full-length antibodies, chemically coupled to bacterial toxins, into single chain variants of antibodies, genetically fused with fully human enzymes. These improvements have increased the range of possible target diseases, which now include chronic inflammatory diseases. At present there are no therapeutic strategies focusing on macrophages to treat chronic disorders. In this review, we focus on the role of different polarized macrophages and the potential of CD64-based IT to intervene in the process of chronic inflammation.

Therapeutic targets and recent advances in protein immunotoxins

Targeted therapy has replaced the conventional methods of disease management with the advances in recombinant technology and increased understanding of molecular mechanisms of diseases. The immunotoxin strategy for diseases like cancer and a variety of autoimmune disorders has been used successfully in the past since its discovery. Since bacterial, fungal and plant toxins have various limitations like toxicity and immunogenicity, studies on fully humanized immunotoxins have gained attraction recently, which reduced toxicity significantly. Improved methods of antibody engineering have led to the emergence of various new formats of immunotoxins. This review summarizes the target moieties used in immunotoxin constructs in different diseases and describes the recent advances in immunotoxin targeting.

Evolution of the HIV-1 env gene in the Rag2-/- gammaC-/- humanized mouse model

Rag2(-/-) gamma(C)(-/-) mice transplanted with human hematopoietic stem cells (DKO-hu-HSC mice) mimic aspects of human infection with human immunodeficiency virus type 1 (HIV-1), including sustained viral replication and CD4(+) T-cell decline. However, the extent of HIV-1 evolution during long-term infection in these humanized mice, a key feature of the natural infection, has not been assessed fully. In this study, we examined the types of genotypic and phenotypic changes in the viral env gene that occur in the viral populations of DKO-hu-HSC mice infected with the CCR5-tropic isolate HIV-1(JRCSF) for up to 44 weeks. The mean rate of divergence of viral populations in mice was similar to that observed in a cohort of humans during a similar period of infection. Many amino acid substitutions were common across mice, including losses of N-linked glycosylation sites and substitutions in the CD4 binding site and in CD4-induced epitopes, indicating common selective pressures between mice. In addition, env variants evolved sensitivity to antibodies directed at V3, suggesting a more open conformation for Env. This phenotypic change was associated with increased CD4 binding efficiency and was attributed to specific amino acid substitutions. In one mouse, env variants emerged that exhibited a CXCR4-tropic phenotype. These sequences were compartmentalized in the mesenteric lymph node. In summary, viral populations in these mice exhibited dynamic behavior that included sequence evolution, compartmentalization, and the appearance of distinct phenotypic changes. Thus, humanized mice offer a useful model for studying evolutionary processes of HIV-1 in a complex host environment.

Optimizing denileukin diftitox (Ontak®) therapy

Denileukin diftitox (Ontak®) is a novel recombinant fusion protein consisting of peptide sequences for the enzymatically active and membrane translocation domain of diphtheria toxin linked to human IL-2. Denileukin diftitox specifically binds to IL-2 receptors on the cell membrane, is internalized via receptor-mediated endocytosis and inhibits protein synthesis by ADP ribosylation of elongation factor 2, resulting in cell death. This article focuses on the clinical trial that led to the US FDA approval of the drug for cutaneous T-cell lymphoma in 1999, and other investigational studies for hematologic malignancies, recurrent and refractory chronic lymphocytic leukemia, non-Hodgkin B-cell lymphoma, graft-versus-host disease and autoimmune disease, demonstrating the activity and adverse effects of the drug.

In vivo administration of plasmid DNA encoding recombinant immunotoxin DT390-IP-10 attenuates experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a T-cell-mediated autoimmune demyelinating disease. The expression of chemokine receptor CXCR3 on activated T cells is crucial to direct the migration of effector cells into the inflammatory sites and initiate EAE. In this study we tested the effect of a novel recombinant immunotoxin targeting CXCR3(+) cells for EAE prevention. The immunotoxin construct DT390-IP-10-SRalpha consisted of interferon gamma-inducible protein 10 (IP-10), a ligand of CXCR3, as the targeting moiety, and a truncated diphtheria toxin (DT390) as the toxic moiety. In vitro transfection of DT390-IP-10-SRalpha into NIH3T3 cells resulted in expression of DT390-IP-10 which proved highly toxic to activated T cells. To evaluate the effect of DT390-IP-10-SRalpha on EAE prevention in vivo, cationic liposome-embedded DT390-IP-10-SRalpha was injected into the muscle of hind limbs of C57BL/6 mice immunized by myelin basic protein (MBP). DT390-IP-10-SRalpha-treated mice showed a delayed onset of EAE and milder symptoms compared to the mice treated with empty control plasmid or PBS alone. Immunohistochemical staining detected significantly reduced infiltrating CXCR3(+) cells in the inflammatory lesions of CNS from immunotoxin treated mice as compared to the controls. This study suggests that targeting CXCR3(+) T cells with recombinant immunotoxin could be achieved in vivo to delay and ameliorate murine EAE.

Clinical experience with denileukin diftitox (ONTAK)

Denileukin diftitox (ONTAK; Seragen Inc, San Diego, CA) is a fusion protein designed to direct the cytocidal action of diphtheria toxin to cells that overexpress the IL-2 receptor. The human IL-2 receptor exists in three isoforms: low (CD25), intermediate (CD122/CD132), and high (CD25/CD122/CD132) affinity. The high-affinity form of this receptor is expressed on activated T lymphocytes, activated B lymphocytes, and activated macrophages. A number of leukemias and lymphomas, including cutaneous T-cell lymphoma, chronic lymphocytic leukemia, and B-cell non-Hodgkin's lymphoma, express a component of the receptor. Ex vivo studies have shown that denileukin diftitox interacts with the high- and intermediate-affinity IL-2 receptor on the cell surface and undergoes internalization. Subsequent cleavage in the endosome releases the diphtheria toxin into the cytosol, which then inhibits cellular protein synthesis, resulting in rapid cell death. This article examines the clinical profile and potential benefits of denileukin diftitox in the treatment of cutaneous T-cell lymphoma and other hematologic disorders.

Monoclonal antibodies for the prevention and treatment of graft-versus-host disease

Acute and chronic graft-versus-host disease (GvHD) remain major obstacles to successful allogeneic hematopoietic stem cell transplantation, contributing substantially to morbidity and non-relapse mortality. Better understanding of the immunopathophysiology of GvHD has identified a number of targets for intervention. Among newly developed agents suitable for the prevention and treatment of GvHD, monoclonal antibodies hold much promise. Monoclonal antibodies currently available, such as infliximab and anti-interferon-gamma (anti-IFN-gamma), are capable of blocking of the action of initiating and effector cytokines. Antibodies directed against activated T cells, including daclizumab, visilizumab and ABX-CBL, may offer more specificity than the more broadly acting pan-T-cell-depleting agents. Finally, the clinical investigation of antibodies to adhesion molecules (such as LFA-1), or distal effector mechanisms (such as FasL) may offer another level of specificity. Many of these monoclonal antibodies have already undergone clinical testing. Campath-1H has been used for the prevention of acute GvHD with success. Daclizumab, infliximab, visilizumab, and ABX-CBL have shown promising activity in steroid-resistant acute GvHD in early clinical testing. This review summarizes current experience with monoclonal antibodies in the management of acute and chronic GvHD. Over the next decade, however, the challenge will be to define the relative place of these antibodies in the therapeutic armamentarium for GvHD and their impact on long-term survival.