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R Aharoni

Publications and source records attributed to R Aharoni.

15 recordsLinked to original sources
PubMed2003

Antibodies to glatiramer acetate do not interfere with its biological functions and therapeutic efficacy.

Glatiramer acetate (GA) previously known as Copolymer 1 (Cop 1), a synthetic amino acid copolymer, suppresses experimental autoimmune encephalomyelitis (EAE) and shows a beneficial effect in relapsing-remitting type of multiple sclerosis (MS). GA acts as a specific immunomodulator by binding to MHC Class II molecules, inducing specific T suppressor (Ts) cells and interfering with T cell responses to myelin antigens. MS patients treated with GA developed GA reactive antibodies, which peaked at three months and decreased at six months. In order to find out whether anti-GA antibodies may neutralize the therapeutic effect of GA, we tested both polyclonal (mouse and human) and monoclonal GA specific antibodies for their ability to interfere with the biological activity of GA in several assay systems. None of the antibodies interfered with GA activities either in vitro (binding to MHC molecules and T cell stimulation) or in vivo (blocking of EAE). Furthermore, 53 samples of sera obtained from 34 MS patients that participated in the open label trial in Israel, and all developed GA specific antibodies, were tested for their ability to inhibit the proliferation response of GA specific Ts cell clone and to interfere with GA competitive inhibition of the response to peptide 84-102 of myelin basic protein (MBP). None of the sera inhibited and some even enhanced the in vitro activities of GA. Furthermore, representative MS sera with high titer of GA reactive antibodies did not neutralize the biological activities of GA and did not inhibit Th2 cytokine secretion by human GA specific clone. These results are consistent with the findings that the therapeutic effect of GA is not affected by GA reactive antibodies and is sustained upon long term treatment.

Animals↗
PubMed2001

Copolymer 1 inhibits manifestations of graft rejection.

BACKGROUND: Copolymer 1 (Cop 1) was previously shown to prevent graft-versus-host disease and interfere in various manifestations of immune rejection. In this study, we tested whether Cop 1 can also hinder the reactivity of host against graft and inhibit graft rejection. METHODS: Cop 1 was tested in two transplantation systems: skin and thyroid grafting assays. The effect of Cop 1 on T cell reactivity was investigated by proliferation and cytokine secretion of spleen and lymph node cells from transplanted mice, as well as the T cell lines generated therefrom. RESULTS: Cop 1 treatment prolonged skin graft survival and inhibited the functional deterioration of thyroid grafts, in various strain combinations, across minor and major histocompatibility barriers, similarly to the potent immunosuppressive drug FK506. Cop 1 inhibited the proliferation of graft-specific T cell lines, as well as their interleukin (IL)-2 and interferon-gamma (IFN-gamma) secretion, when incubated in vitro with the stimulating allogeneic cells. Spleen and lymph node cells from Cop 1-treated mice, as well as the T cell lines generated from them, demonstrated a pronounced inhibition of proliferation and secretion of T helper (Th)1 cytokines in response to graft cells. In addition, cells from Cop 1-treated mice secreted high amounts of Th2 cytokines in response to Cop 1 and small but significant amounts of Th2 cytokines, mainly IL-10, in response to allograft cells. CONCLUSIONS: Cop 1 treatment inhibited the Th1 response to graft and induced a Th2 cytokines secretion in response to both Cop 1 and graft cells, leading to improved survival and function of the transplanted grafts.

Animals↗
PubMed2000

Specific Th2 cells accumulate in the central nervous system of mice protected against experimental autoimmune encephalomyelitis by copolymer 1.

This study addresses the issue of the effect of immunomodulating therapies in the target organ-the central nervous system (CNS)-in the case of multiple sclerosis. Copolymer 1 (Cop 1, Copaxone, glatiramer acetate), an approved drug for the treatment of multiple sclerosis, is a potent inducer of Th2 regulatory cells in both mice and humans. Highly reactive Cop 1-specific T cell lines that secrete IL-4, IL-5, IL-6, IL-10, and transforming growth factor-beta in response to Cop 1 and crossreact with myelin basic protein (MBP) at the level of Th2 cytokine secretion were established from both brains and spinal cords of Cop 1-treated mice. In contrast, no reactivity to the control antigen lysozyme could be obtained in lymphocytes isolated from CNS of mice injected with lysozyme. Adoptively transferred labeled Cop 1-specific suppressor cells were found in brain sections 7 and 10 days after their injection to the periphery, whereas lysozyme-specific cells were absent in the CNS. Hence, Cop 1-induced Th2 cells cross the blood-brain barrier and accumulate in the CNS, where they can be stimulated in situ by MBP and thereby exert therapeutic effects in the diseased organ. This therapeutic effect was manifested, in brains of experimental autoimmune encephalomyelitis-induced mice, by a decrease in the inflammatory cytokine interferon-gamma and by secretion of the anti-inflammatory cytokine IL-10 in response to the autoantigen MBP.

Adjuvants, Immunologic↗
PubMed1999

Copolymer 1 acts against the immunodominant epitope 82-100 of myelin basic protein by T cell receptor antagonism in addition to major histocompatibility complex blocking.

The synthetic random amino acid copolymer Copolymer 1 (Cop 1, Copaxone, glatiramer acetate) suppresses experimental autoimmune encephalomyelitis, slows the progression of disability, and reduces relapse rate in multiple sclerosis (MS). Cop 1 binds to various class II major histocompatibility complex (MHC) molecules and inhibits the T cell responses to several myelin antigens. In this study we attempted to find out whether, in addition to MHC blocking, Cop 1, which is immunologically cross-reactive with myelin basic protein (MBP), inhibits the response to this autoantigen by T cell receptor (TCR) antagonism. Two experimental systems, "prepulse assay" and "split APC assay," were used to discriminate between competition for MHC molecules and TCR antagonism. The results in both systems using T cell lines/clones from mouse and human origin indicated that Cop 1 is a TCR antagonist of the 82-100 epitope of MBP. In contrast to the broad specificity of the MHC blocking induced by Cop 1, its TCR antagonistic activity was restricted to the 82-100 determinant of MBP and could not be demonstrated for proteolipid protein peptide or even for other MBP epitopes. Yet, it was shown for all the MBP 82-100-specific T cell lines/clones tested that were derived from mice as well as from an MS patient. The ability of Cop 1 to act as altered peptide and induce TCR antagonistic effect on the MBP p82-100 immunodominant determinant response elucidates further the mechanism of Cop 1 therapeutic activity in experimental autoimmune encephalomyelitis and MS.

Animals↗
PubMed1999

Binding of random copolymers of three amino acids to class II MHC molecules.

Copolymer 1 [Cop 1, poly(Y,E,A,K)] is a random synthetic amino acid copolymer of L-tyrosine, L-glutamic acid, L-alanine and L-lysine, effective both in suppression of experimental allergic encephalomyelitis and in the treatment of relapsing forms of multiple sclerosis. Cop 1 binds promiscuously and very efficiently to purified human HLA-DR molecules within the peptide-binding groove. In the present study the binding of copolymers composed of three of the four amino acids found in poly(Y,E,A,K) to purified class II MHC molecules was examined. Poly(Y,A,K) and poly(Y,E,A,K) bound to purified human HLA-DR1 or -DR4 molecules with affinity higher than poly(Y,E,A), poly(E,A,K) or poly(Y,E,K), whereas poly(Y,E,A,K) and poly(E,A,K) were the better binders of HLA-DR2 molecules. On the other hand, poly(Y,E,A) and poly(Y,A,K) inhibited the binding of biotinylated poly(Y,E,A,K) to these molecules 10-fold more efficiently than poly(Y,E,K). Finally, poly(Y,E,A), poly(Y,A,K) and poly(E,A,K) were cross-reactive with poly(Y,E,A,K) using YEAK-specific T cell lines and clones of mouse or human origin.

Animals↗
PubMed1998

Bystander suppression of experimental autoimmune encephalomyelitis by T cell lines and clones of the Th2 type induced by copolymer 1.

The synthetic amino acid copolymer, copolymer 1 (Cop 1) induces T suppressor (Ts) lines/clones, which are confined to the Th2 pathway, cross react with myelin basic protein (MBP), but not with other myelin antigens on the level of Th2 cytokine secretion. Nevertheless, Cop 1 Ts cells inhibited the IL-2 response of a proteolipid protein (PLP) specific line. Furthermore, Cop 1 Ts cells ameliorated EAE induced by two unrelated encephalitogenic epitopes of PLP: p139-151 and p178-191, that produced different forms of disease. This bystander suppression demonstrated by the Cop 1 Ts cells may explain the therapeutic effect of Cop 1 in EAE and MS.

Animals↗
PubMed1997

Copolymer 1 induces T cells of the T helper type 2 that crossreact with myelin basic protein and suppress experimental autoimmune encephalomyelitis.

The synthetic amino acid copolymer copolymer 1 (Cop 1) suppresses experimental autoimmune encephalomyelitis (EAE) and is beneficial in multiple sclerosis. To further understand Cop 1 suppressive activity, we studied the cytokine secretion profile of various Cop 1-induced T cell lines and clones. Unlike T cell lines induced by myelin basic protein (MBP), which secreted either T cell helper type 1 (Th1) or both Th1 and Th2 cytokines, the T cell lines/clones induced by Cop 1 showed a progressively polarized development toward the Th2 pathway, until they completely lost the ability to secrete Th1 cytokines. Our findings indicate that the polarization of the Cop 1-induced lines did not result from the immunization vehicle or the in vitro growing conditions, but rather from the tendency of Cop 1 to preferentially induce a Th2 response. The response of all of the Cop 1 specific lines/clones, which were originated in the (SJL/JxBALB/c)F1 hybrids, was restricted to the BALB/c parental haplotype. Even though the Cop 1-induced T cells had not been exposed to the autoantigen MBP, they crossreacted with MBP by secretion of interleukin (IL)-4, IL-6, and IL-10. Administration of these T cells in vivo resulted in suppression of EAE induced by whole mouse spinal cord homogenate, in which several autoantigens may be involved. Secretion of anti-inflammatory cytokines by Cop 1-induced suppressor cells, in response to either Cop 1 or MBP, may explain the therapeutic effect of Cop 1 in EAE and in multiple sclerosis.

Adjuvants, Immunologic↗
PubMed1997

Studies on the mechanism and specificity of the effect of the synthetic random copolymer GLAT on graft-versus-host disease.

Graft-versus-host disease (GVHD), which occurs when donor T-cells recognize multiple minor host histocompatibility antigens as non-self, presents the major limitation to successful allogeneic bone-marrow transplantation. The synthetic random copolymer of the amino acids, L-Glu, L-Lys, L-Ala and L-Tyr, termed GLAT, with promiscuous binding to multiple MHC class II alleles, reduces the incidence, onset and severity of disease in the BIO.D2 --> BALB/c model of lethal GVHD. GLAT inhibited the proliferative response towards host of both spleen cells from mice with GVHD and also of the effector T cell line established from these mice. Administration of GLAT for a limited period after transplantation completely abolished the cytotoxic activity toward host cells exerted by spleen cells from mice with GVHD. Whereas spleen and bone marrow cells from control mice with GVHD secreted IL-2 and INF-gamma when cocultured with host cells, these inflammatory cytokines could not be detected in supernatants of cells from GLAT treated mice. Moreover spleens and bone marrow cells from GLAT treated mice secreted small but significant amounts of IL-4 and IL-6 when cocultured with GLAT, suggesting that GLAT not only inhibits pro-GVHD cytokines but also causes a beneficial effect by inducing secretion of Th2 type cytokines. GLAT binds strongly to MHC molecules of host as well as donor haplotype. D-GLAT, identical to GLAT but composed of D-amino acids is also effective in preventing GVHD. D-GLAT does not cross-react with L-GLAT, but still binds strongly to MHC-class II molecules. These findings indicate that MHC blocking is involved in the therapeutic effect of GLAT on GVHD. The cumulative data demonstrate that GLAT modulates the effector mechanisms involved in GVHD, and can be potentially used for the prevention of GVHD across minor histocompatibility barriers.

Animals↗
PubMed1996

A synthetic random basic copolymer with promiscuous binding to class II major histocompatibility complex molecules inhibits T-cell proliferative responses to major and minor histocompatibility antigens in vitro and confers the capacity to prevent murine graft-versus-host disease in vivo.

Graft-versus-host disease (GVHD) is a T-cell-mediated disease of transplanted donor T cells recognizing host alloantigens. Data presented in this report show, to our knowledge, for the first time that a synthetic copolymer of the amino acids L-Glu, L-Lys, L-Ala, and L-Tyr (molecular ratio, 1.9:6.0:4.7:1.0; Mr, 6000-8500) [corrected], termed GLAT, with promiscuous binding to multiple major histocompatibility complex class II alleles is capable of preventing lethal GVHD in the B10.D2 --> BALB/c model (both H-2d) across minor histocompatibility barriers. Administration of GLAT over a limited time after transplant significantly reduced the incidence, onset, and severity of disease. GLAT also improved long-term survival from lethal GVHD: 14/25 (56%) of experimental mice survived > 140 days after transplant compared to 2/26 of saline-treated or to 1/10 of hen egg lysozyme-treated control mice (P < 0.01). Long-term survivors were documented to be fully chimeric by PCR analysis of a polymorphic microsatellite region in the interleukin 1beta gene. In vitro, GLAT inhibited the mixed lymphocyte culture in a dose-dependent fashion across a variety of major barriers tested. Furthermore, GLAT inhibited the response of nylon wool-enriched T cells to syngeneic antigen-presenting cells presenting minor histocompatibility antigens. Prepulsing of the antigen-presenting cells with GLAT reduced the proliferative response, suggesting that GLAT inhibits antigen presentation.

Animals↗
PubMed1994

Prevention of graft-versus-host disease by peptides binding to class II major histocompatibility complex molecules.

Graft-versus-host disease across minor histocompatibility barriers was induced in two different models by transplanting allogeneic bone marrow and spleen cells into irradiated H-2-compatible recipient mice. In this report, we show that administration of peptides with high binding affinity for the respective class II major histocompatibility complex molecules after transplantation is capable of preventing the development of graft-versus-host disease in two different murine models. The peptides used were myelin basic protein residues 1 through 11 with alanine at position 4 (Ac 1-11[4A]) for I-Au (A alpha uA beta u), and the antigenic core sequence 323 through 339 of ovalbumin with lysine and methionine extension (KM core) for I-As (A alpha sA beta s). In both systems, the mechanism of prevention was found to be major histocompatibility complex-associated, because nonbinding control peptides did not have any effect. Engraftment of allogeneic bone marrow cells was shown by polymerase chain reaction analysis of DNA polymorphisms in a microsatellite region within the murine interleukin-5 gene.

Amino Acid Sequence↗
PubMed1993

T suppressor hybridomas and interleukin-2-dependent lines induced by copolymer 1 or by spinal cord homogenate down-regulate experimental allergic encephalomyelitis.

Suppressor T (Ts) hybridomas and interleukin-2-dependent T cell lines were established from spleens of mice, which had been rendered unresponsive to experimental allergic encephalomyelitis (EAE) either by mouse spinal cord homogenate or by the synthetic suppressant copolymer 1 (Cop 1). The Ts hybridoma supernatants and the Ts line cells specifically suppressed the in vitro response to the encephalitogenic myelin basic protein (BP), as indicated by inhibition of both the proliferation and interleukin-2-secretion responses of a BP-specific T cell line. Moreover, these Ts cells prevented the development of actively induced EAE in vivo. All hybridomas and lines were most effective when injected at the time of disease induction, thus suggesting that they operate as effector suppressor cells, and functionally inhibit encephalitogenic responses. The data presented here suggest that the suppressor cells are stimulated by the protective epitopes included in the BP as well as in the Cop 1 molecules and that they play an active role in the regulation of EAE. The generation of Ts lines and hybridomas, which have been induced by Cop 1, establish the specific stimulation of suppressor cells to EAE as a mechanism underlying the therapeutic activity of Cop 1.

Animals↗
PubMed1991

Cross-reactions and specificities of monoclonal antibodies against myelin basic protein and against the synthetic copolymer 1.

Antibody cross-reactivity is here demonstrated between basic protein (BP), the encephalitogenic molecule of myelin, and copolymer 1 (Cop 1), the synthetic amino acid copolymer, which has a suppressive effect on experimental allergic encephalomyelitis and is effective in reducing the number of relapses in exacerbating-remitting multiple sclerosis. This cross-reactivity is conclusively established using mouse monoclonal antibodies (mAbs). About a third of anti-rat BP mAbs and most of anti-mouse BP mAbs cross-reacted with Cop 1. This cross-reactivity could be demonstrated with anti-BP mAbs of different specificities. In addition, several anti-Cop 1 hybridomas cross-reacted with BP. This cross-reactivity was verified in several assay systems, including competitive inhibition experiments. Moreover, some anti-BP mAbs and anti-Cop 1 mAbs reacted in a heteroclitic manner and favored the cross-reactive antigen over the immunogen. In contrast to the mAbs, no cross-reactivity could be demonstrated with the antisera of immunized mice. This observation may reflect the different B-cell populations expressed in the mAb response as compared to the polyclonal response. Thus, the use of mAbs has uncovered specificities that are not evident in antisera and has revealed pronounced cross-reactivity between BP and Cop 1 at the B-cell level. These results further establish the immunological interrelationships between Cop 1 and BP, demonstrated earlier at the T-cell level.

Animals↗
PubMed1991

Immunomodulation of experimental allergic encephalomyelitis by antibodies to the antigen-Ia complex.

Autoimmune diseases occur when T lymphocytes become activated on recognizing self antigen linked to the autologous class II molecule of the major histocompatibility complex (MHC). The resulting complex of antigen MHC T-cell receptor could be a target for treatment of autoimmune diseases. Studies in which each component is blocked separately might be limited by interference in non-relevant immune responses that either use the same set of T-cell-receptor V gene segments or are linked to the same MHC. We report here an attack by a specific antibody on the unique antigenic site formed by the binding of two components of the trimolecular complex, the autoantigen bound to the self MHC. We tested its effect in experimental allergic encephalomyelitis, an acute neurological autoimmune disease which is widely regarded as a model for autoimmune disorders and which is mediated by CD4+ T cells recognizing myelin basic protein (BP), or its peptides, in association with self Ia. We made monoclonal antibodies which bound only the complex of BP and I-As. These antibodies blocked the proliferative response in vitro to the encephalitogenic determinant of BP and reduced the response to intact BP, without affecting the response to a nonrelevant antigen-purified protein derivative of tuberculin presented on syngeneic macrophages. They also inhibited experimental allergic encephalomyelitis in H-2s mice. Hence, antibodies directed specifically to the autoantigen-Ia complex, may offer a highly selective and effective treatment in autoimmune diseases.

Animals↗
PubMed1988

Specific inhibition of the T-cell response to myelin basic protein by the synthetic copolymer Cop 1.

Cop 1 is a synthetic basic random copolymer of L-alanine, L-glutamic acid, L-lysine, and L-tyrosine in a residue molar ratio of 6.0:1.9:4.7:1.0 and with a molecular weight of 21,000 which proved to be effective in specific suppression of experimental allergic encephalomyelitis and has been proposed as a candidate drug against multiple sclerosis. In the present study we further investigated the mechanism of Cop 1 suppressive activity and tested whether Cop 1 could inhibit the specific T-cell response to myelin basic protein (BP). Eight BP-specific T-cell lines and clones with various H-2 restrictions and antigenic specificities were used. The responses of all these lines and clones to BP, as followed by both cell proliferation and interleukin 2 secretion assays, were affected by Cop 1. For one line, a direct cross proliferation with Cop 1 was observed, whereas in the other seven lines and clones, Cop 1 specifically inhibited the responses to BP in a competitive dose-dependent manner. The inhibition of the response to BP is specific to Cop 1, as D-Cop 1 and another random acidic polymer, poly(Tyr,Glu,Ala) (TGA), both of which were previously demonstrated to be ineffective in suppression of experimental allergic encephalomyelitis, did not inhibit the response to BP. Furthermore, Cop 1 specifically inhibited only the response of the T-cell lines and clones to BP. It did not inhibit their response to the mitogen Con A, nor did it inhibit the responses of the purified protein derivative-specific T-cell line and clone. These results suggest that Cop 1 may be effective in suppression of experimental allergic encephalomyelitis, not only because of the selective stimulation of suppressor T cells, as we have previously demonstrated, but also by specific inhibition of BP-specific effector T cells.

Animals↗