Characteristics of Mitochondrial Transformation into Human Cells

Mitochondria can be incorporated into mammalian cells by simple co-incubation of isolated mitochondria with cells, without the need of transfection reagents or any other type of intervention. This phenomenon was termed mitochondrial transformation, and although it was discovered in 1982, currently little is known regarding its mechanism(s). Here we demonstrate that mitochondria can be transformed into recipient cells very quickly, and co-localize with endogenous mitochondria. The isolated mitochondria interact directly with cells, which engulf the mitochondria with cellular extensions in a way, which may suggest the involvement of macropinocytosis or macropinocytosis-like mechanisms in mitochondrial transformation. Indeed, macropinocytosis inhibitors but not clathrin-mediated endocytosis inhibition-treatments, blocks mitochondria transformation. The integrity of the mitochondrial outer membrane and its proteins is essential for the transformation of the mitochondria into cells; cells can distinguish mitochondria from similar particles and transform only intact mitochondria. Mitochondrial transformation is blocked in the presence of the heparan sulfate molecules pentosan polysulfate and heparin, which indicate crucial involvement of cellular heparan sulfate proteoglycans in the mitochondrial transformation process.

Therapeutic potency of IL2-caspase 3 targeted treatment in a murine experimental model of inflammatory bowel disease

BACKGROUND

Inflammatory bowel disease (IBD) comprises primarily the two disorders - ulcerative colitis and Crohn's disease - that involve deregulated T cell responses. The ever-increasing incidence rate of Crohn's disease and ulcerative colitis during recent decades, combined with the limited efficacy and potential adverse effects of current treatments, explain the real need for seeking more specific and selective methods for treating these diseases.

AIM

To investigate the ability of interleukin 2 (IL2)-caspase 3 chimeric protein, designed to target activated T lymphocytes that express the high-affinity IL2 receptor, to ameliorate the clinical symptoms of acute murine experimental colitis, using a mouse model of dextran sodium sulfate (DSS)-induced colitis.

METHODS

Mice with DSS-induced colitis were treated with IL2-caspase 3 for 7 days and disease severity was assessed in parallel to control, non-treated mice, receiving only daily injections of phosphate-buffered saline. IL2-caspase 3 was tested both for its ability to prevent the development of colitis, and for its therapeutic potential to cure on-going, active acute disease. In addition, colon tissue samples were used for myeloperoxidase assays and RNA isolation followed by polymerase chain reaction to determine mRNA expression levels of specific genes.

RESULTS

Treatment with IL2-caspase 3 dose-dependently ameliorated the disease activity index (DAI) of mice colitis. We achieved up to 78% improvement in DAI with intravenous injections of 15 microg/mouse/day. Furthermore, IL2-caspase 3 decreased neutrophil and macrophage infiltration to the inflamed tissue by up to 57%. IL2-caspase 3 was proven as a therapeutic reagent in another model, where treatment begins only after disease onset. Here we demonstrated a 70% decrease in DAI when compared to non-treated sick mice. A reduction in mRNA expression levels of both IL1 beta and tumour necrosis factor alpha was found in lysates of total colon tissue of treated mice, as compared to sick, untreated mice. We also found that expression levels of Bcl2 were significantly decreased after treatment, while Bax was upregulated in comparison to non-treated mice. Moreover, the Bcl2/Bax ratio, which is elevated in both experimental colitis and in human Crohn's disease, decreased dramatically after treatment.

CONCLUSIONS

IL2-caspase 3 chimeric protein may provide a novel approach to the therapy of human IBD, and a possible suggested treatment for other pathological conditions that involve uncontrolled expansion of activated T cells.

Surface Antigens/Receptors for Targeted Cancer Treatment: The GnRH Receptor / Binding Site for Targeted Adenocarcinoma Therapy

Colon, breast and lung adenocarcinomas - three of the major malignancies occurring in humans, together with ovarian, endometrial, kidney and liver adenocarcinomas, account for more then 50% of cancer-related death. As the number of cancer-related deaths has not decreased in recent years, major efforts are being made to find new and more specific drugs for cancer treatment. One of the approaches developed in recent years for targeted cancer therapy is the construction and use of chimeric proteins. Chimeric cytotoxins are a class of targeted molecules designed to recognize and specifically destroy cells over-expressing specific receptors. These molecules, designed and constructed by gene fusion techniques, comprise both the cell-targeting and the cell-killing moieties. Our laboratory has developed a number of chimeric proteins based on an analog of Gonadotropin Releasing Hormone (GnRH) as their targeting moiety. These chimeras recognize a GnRH-binding site that, we found, was over-expressed on a surprisingly wide variety of cancers, all confined to the adenocarcinoma type. A GnRH analog was fused to a large number of killing moieties, including bacterial or human pro-apoptotic proteins. All GnRH-based chimeric proteins selectively killed adenocarcinoma cells both in vitro and in vivo. Utilizing GnRH-based chimeric proteins for targeted therapy could open up new vistas in the fight against adenocarcinomas in humans. This review summarizes the latest developments in the area of targeted cancer therapy via specific antigens/receptors, as well as our latest findings in targeting GnRH-binding sites using GnRH-based chimeric proteins for specific and targeted adenocarcinoma therapy in humans.

Apoptosis-inducing human-origin Fcepsilon-Bak chimeric proteins for targeted elimination of mast cells and basophils: a new approach for allergy treatment

During the past few years, many chimeric proteins have been developed to specifically target and kill cells expressing specific surface molecules. Generally these molecules carry a bacterial or plant toxin to destroy the unwanted cells. The major obstacle regarding these molecules in their clinical application is the immunogenicity and nonspecific toxicity associated with bacterial or plant toxins. We lately reported a new approach for construction of chimeric proteins: we successfully replaced bacterial or plant toxins with human apoptosis-inducing proteins. The resulting chimeras were shown to specifically induce apoptosis in the target cells. Taking advantage of the human apoptosis inducing proteins Bak and Bax as novel killing components, we have now constructed new chimeric proteins targeted against the human FcepsilonRI, expressed mainly on mast cells and basophils. These cells are the main effectors of the allergic response. Treatment of the target cells with the new chimeric proteins, termed Fcepsilon-Bak/Bax, had a dramatic effect on cell survival, causing apoptosis. The effect was specific to cells expressing the FcepsilonRI of both human and, very unexpectedly, also of mouse origin. Moreover, interaction of the chimeric proteins with the mast cells did not cause degranulation. Fcepsilon-Bak/Bax are new chimeric proteins of human origin and, as such, are expected to be both less immunogenic and less toxic and, thus, may be specific and efficient reagents for the treatment of allergic diseases.

I.V. Administration of L-GNRH-PE66 efficiently inhibits growth of colon adenocarcinoma xenografts in nude mice

When developing new anti-cancer therapeutic treatments, it is crucial to find the correct route of administration and timetable for treatment. Recently, we constructed the L-GnRH-PE66 chimeric protein, which can target and kill adenocarcinoma cells both in vitro and in vivo. We examined the ability of the L-GnRH-PE66 chimeric protein to inhibit tumor growth in colon carcinoma xenografted nude mice, using different routes of administration and various timetables of treatment. In addition, we examined the ability of the chimeric protein to inhibit tumor growth of large tumors that resemble those encountered in human patients in the clinical setting. We found that an i.v. dose of 12.5 microg given every 48 hr was the most efficacious in inhibiting tumor growth. Tumors treated with this concentration of the chimeric protein were 4.4 times smaller in volume and 3.4 times smaller in weight than those in the control groups. This protocol of L-GnRH-PE66 treatment is an improvement on our previously suggested treatment for adenocarcinoma in humans. An i.v. injection every 48 hr is effective, less toxic and less painful. Our results further support the use of L-GnRH-PE66 as an effective treatment for adenocarcinoma in humans.

GnRH-Bik/Bax/Bak chimeric proteins target and kill adenocarcinoma cells; the general use of pro-apoptotic proteins of the Bcl-2 family as novel killing components of targeting chimeric proteins

In recent years chimeric proteins carrying bacterial toxins as their killing moiety, have been developed to selectively recognize and kill cell populations expressing speciific receptors. The involvement of Gonadotropin releasing hormone (GnRH) has been demonstrated in several adenocarcinomas and a GnRH-bacterial toxin chimeric protein (GnRH-PE66) was thus developed and found to specifically target and kill adenocarcinoma cells both in vitro and in vivo. Because of the immunogenicity and the non-specific toxicity of the bacterial toxins, we have developed new chimeric proteins, introducing apoptosis inducing proteins of the Bcl-2 family as novel killing components. Sequences encoding the human Bik, Bak or Bax proteins were fused to the GnRH coding sequence at the DNA level and were expressed in E. coli. GnRH-Bik, GnRH-Bak and GnRH-Bax new chimeric proteins efficiently and specifically inhibited the cell growth of adenocarcinoma cell lines and eventually led to cell death. All three Bcl2-proteins-based chimeric proteins seem to induce apoptosis within the target cells, without any additional cell death stimulus. Apoptosis-inducing-proteins of the Bcl-2 family targeted by the GnRH are novel potential therapeutic reagents for adenocarcinoma treatment in humans. This novel approach could be widely applied, using any molecule that binds a specific cell type, fused to an apoptosis-inducing protein.

Targeted Fc2'-3-PE40 chimeric protein abolishes passive cutaneous anaphylaxis in mice

The alarming increase in the incidence of allergic diseases in the past decade has led to a clear call for more effective treatment. Recently, we reported on the construction of a chimeric protein for targeted elimination of cells expressing FcepsilonRI receptors. This chimeric protein, designated Fc2'-3-PE40, is composed of a Fc fragment of mouse IgE attached to a truncated form of Pseudomonas exotoxin. The Fc2'-3-PE40 chimeric protein was found to be highly cytotoxic to mouse mast cell lines and primary mouse mast cells. We now demonstrate that Fc2'-3-PE40 successfully prevents the development of passive cutaneous anaphylaxis reaction (PCA) in mice. Treatment with Fc2'-3-PE40 for 7 days prevented the PCA reaction in mice by 80% compared with that in control mice given only PBS. Fc2'-3-PE40M, the mutated, enzymatically inactive analogue of Fc2'-3-PE40, did not display this activity. Fc2'-3-PE40 was also effective when given as a single dose 16 h before antigen exposure, resulting in complete inhibition of the PCA reaction. Moreover, treatment with Fc2'-3-PE40 did not cause mast cell degranulation, as the serum histamine values of mice treated with Fc2'-3-PE40 were within the range obtained for control, untreated mice. Thus, the Fc2'-3-PE40 chimeric protein offers a novel approach to the treatment of allergic disorders.

Interleukin 2-Bax: a novel prototype of human chimeric proteins for targeted therapy

During the past few years many chimeric proteins have been developed to target and kill cells expressing specific surface molecules. Generally, these molecules carry a bacterial or plant toxin that destroys the unwanted cells. The major obstacle in the clinical application of such chimeras is their immunogenicity and non-specific toxicity. We have developed a new generation of chimeric proteins, taking advantage of apoptosis-inducing proteins, such as the human Bax protein, as novel killing components. The first prototype chimeric protein, IL2-Bax, directed toward IL2R-expressing cells, was constructed, expressed in Escherichia coli and partially purified. IL2-Bax increased the population of apoptotic cells in a variety of target T cell lines, as well as in human fresh PHA-activated lymphocytes, in a dose-dependent manner and had no effect on cells lacking IL2R expression. The IL2-Bax chimera represents an innovative approach for constructing chimeric proteins comprising a molecule that binds a specific cell type and an apoptosis-inducing protein. Such new chimeric proteins could be used for targeted treatment of human diseases.

A novel antigen-toxin chimeric protein: myelin basic protein-pseudomonas exotoxin (MBP-PE 40) for treatment of experimental autoimmune encephalomyelitis

Myelin basic protein (MBP), is a major component of the central nervous system (CNS) myelin. MBP can stimulate T cells that migrate into the CNS, initiating a cascade of events that result in perivascular infiltration and demyelination. EAE is an inflammatory and demyelinating autoimmune disease of the CNS that serves as a model for the human disease Multiple Sclerosis (MS). Taking advantage of the fact that EAE can be mediated by T cells, able to recognize MBP or its peptides, we developed a new approach to target anti-MBP T cells by fusing an MBP-sequence to a toxin. In the new chimeric protein, an oligonucleotide coding for the guinea pig MBP encephalitogenic moiety (residues 68-88) was fused to a cDNA encoding a truncated form of the PE gene (PE40). The chimeric gene termed MBP-PE was expressed in E. coli and highly purified. MBP-PE chimeric protein was cytotoxic to various anti-MBP T cells. Moreover, treatment with the novel MBP-toxin blocked the clinical signs of EAE as well as CNS inflammation and demyelination. A chimeric protein such as MBP-PE40 presents a novel prototype of chimeric proteins, composed of antigen/peptide-toxin, that could prove to be an efficient and specific immunotherapeutic agent for autoimmune diseases in which a known antigen is involved.

Linker-based GnRH-PE chimeric proteins inhibit cancer growth in nude mice

Since the number of cancer-related deaths has not decreased in recent years, major efforts are being made to find new drugs for cancer treatment. In this report we introduce the gonadotropin releasing hormone-Pseudomonas exotoxin (GnRH-PE) based chimeric proteins L-GnRH-PE66 and L-GnRH-PE40. These proteins are composed of a GnRH moiety attached to modified forms of Pseudomonas exotoxin via a polylinker (gly4ser)2. The chimeric proteins L-GnRH-PE66 and L-GnRH-PE40 have the ability to target and kill adenocarcinoma cell lines in vitro, whereas non-adenocarcinoma cell lines are not affected. We demonstrate that L-GnRH-PE66 and L-GnRH-PE40 efficiently inhibit cancer growth. Nude mice were injected subcutaneously with the SW-48 adenocarcinoma cell line to produce xenograft tumours. When the tumours were established and visible, the animals were injected with chimeric proteins for 10 days. At the end of this period, a reduction of up to 3-fold in tumor size was obtained in the treated mice, as compared with the control group, which received equivalent amounts of GnRH; the difference was even greater 13 days after termination of treatment. Thus, the chimeric proteins L-GnRH-PE66 and L-GnRH-PE40 are promising candidates for treatment of a variety of adenocarcinomas and their use in humans should be considered.

Interleukin-2 (IL-2) receptor alpha, beta and gamma subunit expression as a function of B-cell lineage ontogeny: the use of IL-2-PE66(4Glu) to characterize internalization via IL-2 receptor subunits

Interleukin-2 (IL-2) is a pluripotent cytokine which plays a crucial role in the immune system response. Although the IL-2/IL-2 receptor (IL-2R) system has been well characterized in cells of the T lineage it is less known in B lymphocytes. The authors therefore studied the expression of the IL-2R alpha, beta and gamma subunits in human B-cell lines at different stages of maturation, by the polymerase chain reaction technique. The authors found that the alpha and beta subunits are expressed in the final stages of B-cell lineage maturation, whereas the gamma subunit is constitutively expressed during B-lymphocyte differentiation. The results indicate that the IL-2/IL-2R system, most probably, does not have a role in the early stages of B-cell differentiation, but may be involved only in the final stages of B-cell lineage ontogeny. Moreover, the ability of the different forms of IL-2R to internalize the IL-2 ligand was investigated, using the chimeric protein IL-2-PE66(4Glu). Cell lines bearing the alphagamma, betagamma and alpha betagamma forms of IL-2R were inhibited by the chimeric protein, while those bearing the gamma subunit alone did not respond to the chimera. Thus, internalization of IL-2 is most likely mediated via the alphagamma form of the IL-2R, as shown here for the first time, as well as through the betagamma and alpha betagamma IL-2R forms. However, IL-2 cannot be internalized through the IL-2R gamma subunit alone.

Adenocarcinoma cells are targeted by the new GnRH-PE66 chimeric toxin through specific gonadotropin-releasing hormone binding sites

Luteinizing hormone-releasing hormone, also termed gonadotropin-releasing hormone (GnRH), accounts for the hypothalamic-pituitary gonadal control of human reproduction. The involvement of GnRH has been demonstrated in several carcinomas of hormone-responsive tissues. Exploiting this common feature, we constructed a Pseudomonas exotoxin (PE)-based chimeric toxin (GnRH-PE66) aimed at targeting those cancer cells bearing GnRH binding sites. We report here the strong growth inhibition and killing of a surprisingly wide variety of cancers, confined to the adenocarcinoma type. These cancer cells arising from hormone-responsive tissues, as well as non-responsive ones, express specific GnRH binding sites as indicated by the marked killing of ovarian, breast, endometrial, cervical, colon, lung, hepatic, and renal adenocarcinoma. This cytotoxicity is specific as it could be blocked upon addition of excess GnRH. The specificity of GnRH-PE66 chimeric toxin was also confirmed by GnRH binding assays, and its ability to prevent the formation of colon cancer xenografts in nude mice is presented. Although the functional role of specific GnRH binding sites in human carcinomas remains obscure, GnRH-PE66 displays considerable targeting potential and its use as a therapeutic agent for cancer should be considered.

Targeted elimination of cells expressing the high-affinity receptor for IgE (Fc epsilon RI) by a Pseudomonas exotoxin-based chimeric protein

The interaction between IgE and its high-affinity receptor Fc epsilon RI found on mast cells and basophils is the primary effector pathway in allergic response. To achieve a targeted elimination of cells expressing Fc epsilon RI receptors, we constructed a chimeric protein in which a Fc fragment of mouse IgE is attached to a truncated form of Pseudomonas exotoxin (PE). To prepare the targeting moiety, we used a DNA sequence corresponding to amino acids 301-437, representing 30 residues of domain 2 and domain 3 of the mouse IgE constant region. This sequence was fused at the 5' of a cDNA encoding PE40, a truncated form of PE lacking the cell binding domain. The chimeric protein, termed Fc(2'-3)-PE40, was expressed in Escherichia coli and partially purified. The protein is highly cytotoxic to mouse mast cell lines and bone marrow-derived primary mast cells. This cytotoxicity is specific, as it could be blocked upon addition of whole IgE. Moreover, the protein had no effect on other cell lines of hemopoietic origin. The Fc(2'-3)-PE40 chimeric protein offers a new approach to the treatment of allergic disorders.

B-cell non-Hodgkin's lymphoma: evidence for the t (14;18) translocation in all hematopoietic cell lineages

BACKGROUND

B cells of patients with non-Hodgkin's lymphoma (B-NHL) harbor specific chromosomal translocations, including t(14;18), the most common aberration found in this disease. The translocation involves the immunoglobulin (Ig) heavy-chain joining (JH) region gene on chromosome 14 and the BCL2 gene on chromosome 18, resulting in dysregulated expression of the BCL2 gene. The t(14;18) translocation has been thought to occur in the pre-B-cell stage, during the first event of Ig gene rearrangement.

PURPOSE

This study was conducted to investigate the potential involvement of nonlymphoid lineages in B-NHL.

METHODS

We studied the t(14;18) translocation and other frequently occurring translocations in total bone marrow aspirates of 10 patients with B-NHL, with the use of the fluorescence in situ hybridization (FISH) technique. We also performed cytogenetic analyses on representative bone marrow aspirates from the patients. Moreover, to define which of the major cell lineages present in the bone marrow carry the t(14;18) translocation, we used a series of monoclonal antibodies together with fluorescence-activated cell sorter (FACS) analyses to purify cells positive for CD3 (T cells), CD19 (B cells), CD10 (CALLA-positive cells), CD41a (megakaryocytic cells), CD13 (myeloid cells), and glycophorin A (erythroid cells). The cells of each subgroup underwent FISH analysis with the use of JH and BCL2 probes to detect the t(14;18) translocation. Bone marrow samples obtained from five healthy donors served as controls.

RESULTS

Bone marrow cells from eight of the 10 patients studied carried the t(14;18) translocation. When present, the translocation was observed in many or even all of the cell lineages (lymphoid, myeloid, megakaryocytic, and erythroid) present in the bone marrow, including peripheral blood progenitor stem cells; for seven of the eight patients carrying the translocation, it was found in 96%-100% of the unfractionated bone marrow cells as well as in all of the FACS-purified cell fractions in which it could be detected or studied. Conventional cytogenetic analyses performed on representative bone marrow aspirates confirmed the results obtained by FISH analysis. Cells in control bone marrow samples obtained from the five healthy donors were negative for the t(14;18) translocation by FISH analysis.

CONCLUSIONS

Our findings indicate that the t(14;18) translocation most probably occurs in a very early multilineage progenitor stem cell.

IMPLICATIONS

Given that the t(14;18) chromosomal translocation was found in all types of bone marrow cells when only the B cells were malignant, our results suggest that this translocation is not sufficient to induce neoplastic transformation. This finding underscores the need for the development of new approaches for the detection and surveillance of B-NHL.

Interleukin 2 pseudomonas exotoxin (IL2-PE66(4)Glu) chimeric protein kills B cells from patients with Myasthenia gravis

IL2-PE66(4)Glu is a chimeric cytotoxin consisting of interleukin 2 (IL2) fused to a mutant form of Pseudomonas exotoxin (PE66(4)Glu). The chimeric cytotoxin has been previously shown to be extremely toxic to both phytohemagglutinin blasts and mixed leukocyte reaction blasts prepared from monkey and human lymphocytes. To explore the possible clinical utility of IL2-PE66(4)Glu for autoimmune diseases, particularly in which B cells are involved, we tested fresh B cells from patients with myasthenia gravis for sensitivity to this chimeric cytotoxin. Seventy-six percent (16 of 21) of the B cells tested were markedly sensitive to IL2-PE66(4)Glu-mediated cytotoxicity, with inhibition of protein synthesis ranging from 20 to 92%. B cells from control donors were much less sensitive to IL2-PE66(4)Glu cytotoxicity. Moreover, a control protein lacking IL2 as the targeting moiety of the chimera had no effect toward all B cells tested, thus establishing its specific activity. Our results suggest that IL2-PE66(4)Glu could be an effective tool for selective targeted immunotherapy of myasthenia gravis patients.

Interleukin-2 Pseudomonas exotoxin chimeric protein is cytotoxic to B cell cultures derived from myasthenia gravis patients

IL-2-PE664Glu is a chimeric cytotoxin consisting of interleukin-2 (IL-2) fused to a mutant form of Pseudomonas exotoxin (PE664Glu). The chimeric cytotoxin has been previously shown to be extremely toxic to both phytohaemagglutinin blasts and mixed leukocyte reaction blasts prepared from monkey and human lymphocytes. To explore the possible clinical utility of IL-2-PE664Glu for autoimmune diseases, particularly in which B cells are involved, we tested the sensitivity of B cell lines derived from myasthenia gravis patients to this chimeric cytotoxin. 65% (15 out of 23) of the tested B cell lines were sensitive to IL-2-PE664Glu mediated cytotoxicity. B cell lines from control donors as well as from patients with another autoimmune disease, multiple sclerosis, were much less sensitive to IL-2-PE664Glu cytotoxicity. Moreover, a control protein lacking the IL-2 as the targeting moiety of the chimera, had no effect toward all B cell lines tested, thus establishing its specific activity. A detailed study of the IL-2 receptor of the patients' B cells, using the PCR technique and FACS analysis, showed that the cells express mainly the beta and gamma chains and at a lower level also the alpha-chain of the IL-2 receptor. Our results suggest that IL-2-PE664Glu could be effective for selective targeted immunotherapy of myasthenia gravis patients.

Ocular distribution of the chimeric protein IL2-PE40

A construct of IL-2 and pseudomonas exotoxin (PE40) has been genetically engineered. An aliquot of 100 microliter of the chimeric protein, radiolabelled with I125, was administered to healthy rats by various routes. At different intervals, ocular and non ocular tissues were removed and the levels of the radiolabelled chimeric protein IL-2-PE40 measured. Systemic administration of IL2-PE40 either intravenously (IV) or intraperitoneally (IP) leads to high levels of the drug in the blood, liver and spleen. Little or no radioactivity is observed within the ocular tissues using this route. On the other hand, local administration of the drug either as subtenon injection or as eye drops resulted in a very high concentration of the drug within the conjunctiva, cornea and sclera, with little radioactivity detected systemically. Subtenon injection induced a significant drug level within the optic nerve. With the drops, the chimeric protein was also detected, in low levels, intraocularly.

ABL and BCR genes are not imprinted in androgenetic and gynogenetic human tissues

In the translocation leading to the formation of the Philadelphia chromosome, the hallmark of chronic myeloid leukemia (CML), the translocated chromosome 9 (ABL), is of paternal descent whereas chromosome 22 (BCR) is of maternal origin (1). To study possible imprinting of the human ABL and BCR genes, we used human tissues exclusively endowed with their maternally (benign teratoma) or paternally (complete hydatidiform mole) inherited chromosomes. Using the sensitive PCR technique followed by northern blotting, we demonstrate here that ABL and BCR are expressed to a similar extent in androgenetic and gynogenetic human tissues, thus suggesting that ABL and BCR genes are not imprinted in these human tissues.

Mechanisms of dichotomous action of IL-2-Pseudomonas exotoxin 40 (IL-2-PE40) on cell-mediated and humoral immune response

IL-2-PE40 is a chimeric protein composed of human IL-2 genetically fused to the amino terminus of a modified form of Pseudomonas exotoxin lacking its cell recognition domain. The immunosuppressive efficacy of IL-2-PE40 was demonstrated in several experimental murine transplant and autoimmune models. However, some observations suggested that IL-2-PE40 could not inhibit the humoral response. In this report, we describe the dichotomous effects of IL-2-PE40 on humoral and cell-mediated immune response in a simple, well characterized in vivo model. Although IL-2-PE40 inhibited the cell-mediated delayed type hypersensitivity reaction to SRBC, it increased the humoral immune response to the same Ag. To understand the mechanism of dichotomous action of IL-2-PE40 on the immune response, IL-2R-bearing T cells were treated with IL-2-PE40 in vitro and the cytokine expression was studied at mRNA and protein level. Similar to IL-2, IL-2-PE40 promoted the expression of T helper 1-like (IFN-gamma) as well as T helper 2-like (IL-4, IL-10) cytokines. These in vitro studies show that IL-2-PE40 can induce signal transduction in activated T cells through the IL-2R before exerting its cytotoxic effect. In contrast to DTH reaction, humoral immune response requires T cell help only for a limited period. Therefore, the short-term stimulation of T helper cells by IL-2-PE40 may be sufficient in vivo to mediate a B cell response in the local environment, whereas the DTH reaction and other cell-mediated immune responses are inhibited by the toxin moiety of the chimeric protein.

Mechanisms of dichotomous action of IL-2-Pseudomonas exotoxin 40 (IL-2-PE40) on cell-mediated and humoral immune response

IL-2-PE40 is a chimeric protein composed of human IL-2 genetically fused to the amino terminus of a modified form of Pseudomonas exotoxin lacking its cell recognition domain. The immunosuppressive efficacy of IL-2-PE40 was demonstrated in several experimental murine transplant and autoimmune models. However, some observations suggested that IL-2-PE40 could not inhibit the humoral response. In this report, we describe the dichotomous effects of IL-2-PE40 on humoral and cell-mediated immune response in a simple, well characterized in vivo model. Although IL-2-PE40 inhibited the cell-mediated delayed type hypersensitivity reaction to SRBC, it increased the humoral immune response to the same Ag. To understand the mechanism of dichotomous action of IL-2-PE40 on the immune response, IL-2R-bearing T cells were treated with IL-2-PE40 in vitro and the cytokine expression was studied at mRNA and protein level. Similar to IL-2, IL-2-PE40 promoted the expression of T helper 1-like (IFN-gamma) as well as T helper 2-like (IL-4, IL-10) cytokines. These in vitro studies show that IL-2-PE40 can induce signal transduction in activated T cells through the IL-2R before exerting its cytotoxic effect. In contrast to DTH reaction, humoral immune response requires T cell help only for a limited period. Therefore, the short-term stimulation of T helper cells by IL-2-PE40 may be sufficient in vivo to mediate a B cell response in the local environment, whereas the DTH reaction and other cell-mediated immune responses are inhibited by the toxin moiety of the chimeric protein.

Detection of minimal residual disease state in chronic myelogenous leukemia patients using fluorescence in situ hybridization

Detection of minimal residual disease and relapse remain major problems in chronic myelogenous leukemia (CML) patients following bone marrow transplantation (BMT). In order to disclose the 9;22 Philadelphia translocation, we used a fluorescence in situ hybridization (FISH) technique. BCR and ABL gene fragments were used as probes for the detection of the BCR/ABL fusion product in peripheral blood and bone marrow cells from 11 CML patients in which 5 were post-BMT. The sensitivity and specificity of this approach were compared to conventional cytogenetic and polymerase chain reaction (PCR) methods. FISH demonstrated a high degree of sensitivity (1%) for the detection of the BCR/ABL translocation in these patients. A linear correlation was found between FISH detection of the BCR/ABL fusion product and routine chromosomal analysis (r = 0.995; p < 0.001). Detection of the BCR/ABL signal by FISH was observed in all patients showing a positive PCR signal. A significant reduction in BCR/ABL signal was observed post-transplant (p < 0.001). However, the BCR/ABL translocation was detected in four of five transplanted patients immediately (0.75-2.5 months) following transplant and was found in patients with a low expression of the translocation.

Increased cytotoxicity of interleukin 2-pseudomonas exotoxin (IL2-PE) chimeric proteins containing a targeting signal for lysosomal membranes

IL2-PE40 is a chimeric protein composed of human interleukin 2 (IL2) genetically fused to the amino terminus of a truncated form of pseudomonas exotoxin lacking its cell recognition domain (PE40). IL2-PE40 is extremely cytotoxic to IL2 receptor positive cells. This chimeric protein was found to be an effective and selective immunosuppressive agent for IL2 receptor targeted therapy in many models of disorders of the immune response where activated T-cells play a crucial role. In an attempt to produce an improved IL2-PE40 chimeric protein, we constructed new IL2-PE derivatives. This was done by inserting defined DNA sequences within the chimeric gene encoding IL2-PE40. Inserted sequences represent motifs of other proteins known to be targeted and/or sorted to specific compartments inside or outside the cell. One of the proteins, IL2-PE40(LAP+DUP), containing a targeted signal for lysosomal membrane, was 2-3-fold more active than IL2-PE40. The insertion of the LAP sequence also increased the cytotoxicity of another IL2-PE derivative, IL2-PE664Glu. Our results suggest that a selective targeting of IL2-PE chimeric proteins to lysosomes may enable the proteins to reach the cytosol more efficiently, thus improving its specific cytotoxicity. The LAP (lysosomal alkaline phosphatase) sequence may be used as a common motif for increasing the cytotoxicity of other chimeric proteins to be used for targeted immunotherapy.

Treatment of corneal allograft rejection with the cytotoxin IL-2-PE40

IL-2-PE40 is a recombinant chimeric protein composed of IL-2, fused to a modified pseudomonas exotoxin. This molecule is extremely toxic to activated T cells expressing high-affinity IL-2R. We used this new molecule for selective immunosuppression to treat corneal allograft rejection in the rat, using Fisher and Lewis rats, a strain combination differing only in medial and minor histocompatibility antigens. The effect of IL-2-PE40 on the immunologic response was studied using both a heterotopic corneal graft model and orthotopic grafts. At the dose of 0.31 micrograms/g given intraperitoneally every 12 hr, IL-2-PE40 produced a significant reduction of both total lymph node cells and cytotoxic-T-cell (CTL) activity in draining lymph nodes (DLN) of heterotopically grafted animals. IL-2-PE40 treatment also significantly reduced the clinical rejection score and cumulative rejection rate (CRR) in orthotopic grafts and appears to be a very effective immunosuppressive agent.

Chimeric cytotoxin IL2-PE40 inhibits relapsing experimental allergic encephalomyelitis

IL2-PE40 is a chimeric protein composed of human interleukin-2 (IL2) genetically fused to a modified form of Pseudomonas exotoxin lacking the cell recognition domain. IL2-PE40 is cytotoxic for IL2 receptor-bearing lymphocytes in culture and can inhibit activation of T cells in vivo. IL2-PE40 can significantly diminish antigen-stimulated proliferation of lymphocytes sensitized to myelin basic protein. Intraperitoneal administration of IL2-PE40 not only markedly inhibits the clinical manifestations of adoptively transferred relapsing experimental allergic encephalomyelitis but also dramatically reduces both inflammation and demyelination characteristic of the disease.

Immunospecific suppression of encephalitogenic-activated T lymphocytes by chimeric cytotoxin IL-2-PE40

We examined the action of a chimeric protein, IL-2-PE40, on the development of a T cell-mediated disease of the central nervous system with numerous similarities to multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). EAE is caused by IL-2 receptor-bearing T cells specific for myelin basic protein (BP). We report here that the treatment of Lewis rats with IL-2-PE40 delayed and shortened the course of EAE induced by BP in adjuvant and dramatically prevented EAE mediated by anti-myelin basic protein T line cells. The absence of paralytic signs, the absence of cell infiltration in the central nervous system, and the abatement of cellular immunity to myelin basic protein in the treated rats are direct consequences of the specific mechanism of action of IL-2-PE40. Our data support the notion that IL-2-PE40 may be efficient as an immunosuppressive agent for those disorders in which activated T cells play a crucial role.

Administration of IL-2-PE40 via osmotic pumps prevents adjuvant induced arthritis in rats. Improved therapeutic index of IL-2-PE40 administered by continuous infusion

IL-2-PE40 is a chimeric cytotoxin composed of interleukin 2 (IL-2) fused to a truncated form of Pseudomonas exotoxin (PE) that lacks its binding domain. IL-2-PE40 has been shown to exhibit therapeutic potency in several models in vivo when administered i.p. twice a day. Here we show that the continuous administration of IL-2-PE40 by an osmotic pump specifically prevents the development of adjuvant induced arthritis in rats with an improved therapeutic efficacy as compared to daily repeated i.p. injections. Stabilization of IL-2-PE40 at 37 degrees C for the continuous administration by pumps was achieved by adding NAD, the substrate for the enzyme portion of the chimeric toxin.

IL-2-PE40 prevents the development of tumors in mice injected with IL-2 receptor expressing EL4 transfectant tumor cells

A number of different immunotherapeutic reagents are currently being developed to target IL-2R for the treatment of leukemia, graft rejection, and certain autoimmune diseases. Previously, we have shown that IL-2-PE40, a chimeric protein composed of human IL-2 linked to the N-terminus of a truncated form of Pseudomonas exotoxin (PE), could effectively kill a variety of cell lines in vitro expressing either low, intermediate, or high affinity IL-2R. Here, we demonstrate that IL-2-PE40 can successfully retard or prevent the growth of a lethal ascites tumor or a solid tumor composed of EL4J murine thymoma cells transfected with the p55 murine IL-2R. The transfected line, EL4J-3.4, expresses 1,000 to 3,000 high affinity IL-2R. Survival extension in the ascites model was achieved by initiating treatment either after 4 to 6 h or within 5 days post-tumor injection in both athymic nude and C57BL/6 mice. Similarly, the growth of an aggressive s.c. solid tumor could also be inhibited. Extension of survival was not achieved either by using the truncated toxin alone not attached to IL-2 or by using an IL-2-PE40Asp553 mutant lacking a functional toxin. Survival extension was not caused by IL-2 activated NK or other host effector mechanisms as IL-2-PE40 was unable to prevent the receptor-negative EL4J parental line from forming a lethal ascites or a solid tumor. Thus, IL-2-PE40 is a potent, specific cytolytic reagent that may prove useful in the arsenal of anti-IL-2R immunotherapeutics.

IL-2-PE40 prevents the development of tumors in mice injected with IL-2 receptor expressing EL4 transfectant tumor cells

A number of different immunotherapeutic reagents are currently being developed to target IL-2R for the treatment of leukemia, graft rejection, and certain autoimmune diseases. Previously, we have shown that IL-2-PE40, a chimeric protein composed of human IL-2 linked to the N-terminus of a truncated form of Pseudomonas exotoxin (PE), could effectively kill a variety of cell lines in vitro expressing either low, intermediate, or high affinity IL-2R. Here, we demonstrate that IL-2-PE40 can successfully retard or prevent the growth of a lethal ascites tumor or a solid tumor composed of EL4J murine thymoma cells transfected with the p55 murine IL-2R. The transfected line, EL4J-3.4, expresses 1,000 to 3,000 high affinity IL-2R. Survival extension in the ascites model was achieved by initiating treatment either after 4 to 6 h or within 5 days post-tumor injection in both athymic nude and C57BL/6 mice. Similarly, the growth of an aggressive s.c. solid tumor could also be inhibited. Extension of survival was not achieved either by using the truncated toxin alone not attached to IL-2 or by using an IL-2-PE40Asp553 mutant lacking a functional toxin. Survival extension was not caused by IL-2 activated NK or other host effector mechanisms as IL-2-PE40 was unable to prevent the receptor-negative EL4J parental line from forming a lethal ascites or a solid tumor. Thus, IL-2-PE40 is a potent, specific cytolytic reagent that may prove useful in the arsenal of anti-IL-2R immunotherapeutics.

IL2-PE664Glu, a new chimeric protein cytotoxic to human-activated T lymphocytes

To produce a molecule that will kill activated T cells as well as lymphomas and leukemias expressing interleukin 2 (IL2) receptors, we have created a recombinant chimeric protein in which IL2 is attached in peptide linkage to a truncated mutant form of Pseudomonas exotoxin (PE) (Lorberboum-Galski, H., FitzGerald, D.J.P., Chandhary, V.K., Adhya, S., and Pastan, I. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 1922-1926). Although this molecule was very active on rodent cells, it had lower activity on some human cell types. A new chimeric protein termed IL2-PE664Glu has been constructed that is extremely toxic to both phytohemagglutinin blasts and mixed leukocyte reaction blasts prepared from monkey and human lymphocytes. The chimeric gene encoding this protein was constructed by fusing a cDNA clone for human interleukin 2 to the 5' end of a mutated cDNA encoding a full-length PE molecule. Four amino acids in domain I of PE were changed thus decreasing its nonspecific toxicity. IL2-PE664Glu is a much more active cytotoxic molecule for primate and human-activated T cells than IL2-PE40 which is a chimeric protein that was found to be an effective immunosuppressive agent in rodent models. Our results indicate that IL2-PE664Glu should be evaluated as an immunosuppressive agent for the treatment of human immune disorders in which activated T cells expressing the IL2 receptor are prominent.

Selective immunosuppression of activated T cells with the chimeric toxin IL-2-PE40. Inhibition of experimental autoimmune uveoretinitis

A characteristic of activated T lymphocytes is the expression of high affinity IL-2R. We studied a new method of selective immunosuppression directed against activated T cells by using a chimeric recombinant protein (IL-2-PE40) composed of IL-2 fused to a modified Pseudomonas exotoxin lacking its cell recognition domain. As a model of T cell-mediated disease, we used experimental autoimmune uveoretinitis (EAU) produced in Lewis rats by active immunization with the retinal S-Ag. The treatment protocol consisted of i.p. injection of IL-2-PE40 at 0.25 micrograms/g every 12 h. Controls were PBS, PE40, or IL-2-PE40asp553 a mutant form of the molecule with reduced activity. Treatment with IL-2-PE40 resulted in a significant reduction of the incidence and severity of EAU over controls. The analysis of the effect of i.p. injection of IL-2-PE40 on the popliteal draining lymph nodes of immunized animals showed a marked reduction in the lymphocytes content. Transfer experiments demonstrated that IL-2-PE40 prevented the development of EAU effector T cells. Interestingly, although activated B cells were reported to express IL-2R, there was no significant reduction of antibody production against the immunizing Ag under IL-2-PE40 treatment, suggesting sparing of the B cells.

Selective immunosuppression of activated T cells with the chimeric toxin IL-2-PE40. Inhibition of experimental autoimmune uveoretinitis

A characteristic of activated T lymphocytes is the expression of high affinity IL-2R. We studied a new method of selective immunosuppression directed against activated T cells by using a chimeric recombinant protein (IL-2-PE40) composed of IL-2 fused to a modified Pseudomonas exotoxin lacking its cell recognition domain. As a model of T cell-mediated disease, we used experimental autoimmune uveoretinitis (EAU) produced in Lewis rats by active immunization with the retinal S-Ag. The treatment protocol consisted of i.p. injection of IL-2-PE40 at 0.25 micrograms/g every 12 h. Controls were PBS, PE40, or IL-2-PE40asp553 a mutant form of the molecule with reduced activity. Treatment with IL-2-PE40 resulted in a significant reduction of the incidence and severity of EAU over controls. The analysis of the effect of i.p. injection of IL-2-PE40 on the popliteal draining lymph nodes of immunized animals showed a marked reduction in the lymphocytes content. Transfer experiments demonstrated that IL-2-PE40 prevented the development of EAU effector T cells. Interestingly, although activated B cells were reported to express IL-2R, there was no significant reduction of antibody production against the immunizing Ag under IL-2-PE40 treatment, suggesting sparing of the B cells.

Cardiac allograft survival in mice treated with IL-2-PE40

IL-2-PE40 is a chimeric protein composed of human interleukin 2 (IL-2) genetically fused to the amino terminus of a modified form of Pseudomonas exotoxin lacking its cell recognition domain. IL-2-PE40, which is extremely cytotoxic to IL-2 receptor-positive cells, was examined for its ability to prevent graft rejection in mice in which activation of T cells is prominent. We demonstrate that intraperitoneally administered IL-2-PE40 specifically and significantly prolongs the survival of vascularized heart allografts in mice. The chimeric toxin, IL-2-PE40, offers an alternative approach to the treatment of autoimmune diseases and transplant rejection in humans.

Chimeric cytotoxin IL2-PE40 delays and mitigates adjuvant-induced arthritis in rats

Adjuvant arthritis in rats is a T-cell dependent "autoimmune" disease with close similarities to several forms of human arthritis. Injection of mycobacterial adjuvant leads to T-cell activation and proliferation, processes in which the de novo expression of the interleukin 2 (IL-2) receptor plays a pivotal role. The subsequent massive mononuclear cell infiltration of the joints ultimately results in complete joint destruction. Because activation of the helper/inducer subset of T lymphocytes is critical to the establishment of disease, we reasoned that IL2-PE40, a cytotoxic IL-2-Pseudomonas exotoxin fusion protein that targets the membrane-penetration and ADP-ribosylation domains of the toxin to cells bearing the IL-2 receptor, would be an effective and specific therapy. Adjuvant-injected rats were randomized to treatment with IL2-PE40, phosphate-buffered saline, or either of two control proteins related to IL2-PE40 but lacking either the receptor-binding moiety or an enzymatically active toxin domain and previously demonstrated to lack cytotoxicity in vitro. Intraperitoneal IL2-PE40 given before the establishment of overt clinical disease proved an effective and specific modifier of adjuvant arthritis by clinical, histological, and radiographic criteria. Our data suggest that IL2-PE40 may be effective in those diseases in which activated T-cells play an important role.

Interleukin 2 (IL2) PE40 is cytotoxic to cells displaying either the p55 or p70 subunit of the IL2 receptor

IL2-PE40 is a chimeric protein composed of human interleukin 2 (IL2) genetically fused to the amino terminus of a modified form of pseudomonas exotoxin (PE). Internalization of IL2 via the individual p55 and p70 subunits of the IL2 receptor was studied using IL2-PE40 on several mouse and human cell lines expressing either the p55, the p70, or both IL2 receptor subunits. Internalization was assessed by measuring inhibition of protein synthesis caused by the toxin moiety of IL2-PE40. The results demonstrate that IL2 internalization is mediated by either the p55 receptor subunit or by the p70 subunit but is much more efficient when high affinity receptors composed of both subunits are present. IL2-PE40 is a powerful reagent for studying IL2 receptor interactions and for analyzing pathways of the immune response and its regulation.

IL-2-PE40 is cytotoxic for activated T lymphocytes expressing IL-2 receptors

IL-2-PE40 is a chimeric molecule in which IL-2 is attached to the amino end of modified Pseudomonas exotoxin molecule lacking cell recognition domain. This molecule was extremely toxic for Con A-stimulated spleen cells from mice. Moreover, IL-2-PE40 has suppressive effect against Ag-activated cells; it inhibits the generation of cytotoxic T lymphocyte activity in a MLC. IL-2-PE40 could be a useful agent in IL-2R targeting therapy including immunosuppressive therapy for allograft rejection or some autoimmune diseases.

IL-2-PE40 is cytotoxic for activated T lymphocytes expressing IL-2 receptors

IL-2-PE40 is a chimeric molecule in which IL-2 is attached to the amino end of modified Pseudomonas exotoxin molecule lacking cell recognition domain. This molecule was extremely toxic for Con A-stimulated spleen cells from mice. Moreover, IL-2-PE40 has suppressive effect against Ag-activated cells; it inhibits the generation of cytotoxic T lymphocyte activity in a MLC. IL-2-PE40 could be a useful agent in IL-2R targeting therapy including immunosuppressive therapy for allograft rejection or some autoimmune diseases.

Cytotoxic activity of an interleukin 2-Pseudomonas exotoxin chimeric protein produced in Escherichia coli

A cDNA clone for human interleukin 2 (IL-2) has been fused to the 5' end of a modified Pseudomonas exotoxin (PE) gene that lacks the sequences encoding the cell recognition domain. The chimeric protein IL-2-PE40 was produced in Escherichia coli. It was extremely toxic to IL-2 receptor-positive cells but had no measurable effect on cells lacking the IL-2 receptor. IL-2-PE40 might be a useful cytotoxic agent in the treatment of diseases involving IL-2 receptor-positive cells and in the treatment of allograft rejection.