From antilymphocyte serum to therapeutic monoclonal antibodies: first experiences with a chimeric CD4 antibody in the treatment of autoimmune disease

Expression of an anti-Pseudomonas aeruginosa lipopolysaccharide core recombinant antibody in Escherichia coli

Antibodies against Pseudomonas aeruginosa LPS are generally protective, however, this protection is usually serotype-specific. Thus the generation of antibodies against the more conserved core-lipid A epitopes has a potential for being more broadly cross reactive. Our laboratory has previously produced several monoclonal antibodies (mAb) against the core region and lipid A region of P. aeruginosa LPS. In this study, we cloned the immunoglobulin genes from mAb 7-4, an antibody with specificity for the inner core region of P. aeruginosa LPS. VH and VL genes of 7-4 were cloned into both of the M13-derived phagemid vectors, pComb3 and pComb8. 14 pComb3/VH/VL and 6 pComb8/VH/VLrecombinant clones were isolated. The presence of recombinant F(ab) molecules in the periplasmic extracts of Escherichia coli was confirmed by Western immunoblots of these extracts with goat anti-mouse F(ab')2 and goat anti-mouse kappa light chain antibodies under non-reduced conditions. Recombinant 7-4 antibody also interacted with LPS prepared from a rough mutant P. aeruginosa strain AK43 in Western immunoblotting, and ELISA as well as with whole cells of AK43 in immunofluorescence. Thus, recombinant 7-4 antibodies expressed in E. coli are structurally and functionally correct.

Prevention of experimental autoimmune encephalomyelitis by MIP-1alpha and MCP-1 naked DNA vaccines

Experimental autoimmune encephalomyelitis (EAE) is a T cell-mediated autoimmune disease of the central nervous system (CNS). RT-PCR verified by Southern blotting and sequencing of PCR products of two C-C chemokines, MIP-1alpha and MCP-1, was performed on brain samples from EAE rats to evaluate mRNA transcription of these chemokines at different stages of disease. mRNA transcription in of each chemokine peaked after the onset of disease and declined during its remission. Each PCR product was then used as a construct for naked DNA vaccination. The subsequent in vivo immune response to MIP-1alpha or MCP-1 DNA vaccines prevented EAE. Immunization of CFA without the encephalitogenic epitope did not elicit an anti-C-C chemokine regulatory response in DNA- vaccinated rats. Thus, modulation of EAE with C-C chemokine DNA vaccines is dependent on targeting chemokines that are highly transcribed at the site of inflammation at the onset of disease.

Augmentation of natural immunity to a pro-inflammatory cytokine (TNF-alpha) by targeted DNA vaccine confers long-lasting resistance to experimental autoimmune encephalomyelitis

TNF-alpha is thought to be a key pro-inflammatory cytokine in T cell-mediated autoimmune diseases, particularly in rheumatoid arthritis (RA) and multiple sclerosis (MS). Experimental autoimmune encephalomyelitis (EAE) serves as an animal model for MS. The current study observes a notable TNF-alpha-specific antibody titer generated during the course of EAE, apparently not sufficient to prevent the development of disease. Administration of TNF-alpha-naked DNA vaccine enhanced the production of TNF-alpha-specific antibody titer and conferred EAE resistance. These antibodies were found to be neutralizing in vitro and capable of inhibiting the development of disease when transferred to other EAE rats. Thus, modulation of EAE with TNF-alpha DNA vaccines enhances the regulation of natural immunity to a self pro-inflammatory cytokine and provides a tool by which the immune system is encouraged to elicit anti-self protective immunity to restrain its own harmful reactivity when such a response is needed.

Clonal characteristics of T cell infiltrates in skin and synovium of patients with psoriatic arthritis

Psoriasis is a chronic inflammatory skin disease that is often complicated by an inflammatory arthritis. Considerable evidence implicates cellular immune responses in psoriatic skin lesions, but the pathogenesis of the associated arthritis has not been elucidated. We analyzed T cell antigen receptor beta chain variable (TCRbetaV) gene repertoires among peripheral blood lymphocytes, skin and synovium of nine patients with psoriatic arthritis. RNase protection assays were used to quantitate the expression levels of 25 TCRbetaV genes, and CDR3 region sequencing was used to further characterize selected expansions. All patients exhibited significant TCRbetaV biases in the peripheral blood and moreover, all had expansions common to both skin and synovium. CDR3 sequencing demonstrated these expansions frequently consisted of oligo- or monoclonal populations. Although no ubiquitous CDR3 nucleotide sequences were identified, two patients shared identical sequences and several highly homologous amino acid motifs were present in skin and synovium among and between individual patients. Findings of common TCRbetaV expansions in diverse inflammatory sites, among multiple afflicted individuals, suggest that these T cell proliferations are driven by engagements with a limited set of conventional antigens. These findings demonstrate an important role for cognate T cell responses in the pathogenesis of psoriatic arthritis, and further suggest the inciting antigen(s) is identical or homologous between afflicted skin and synovium.

Elevated major histocompatibility complex class I expression protects T cells from antibody- and macrophage-mediated deletion

Macrophages are capable of destroying T cells with which they form cellular conjugates. The deletion can be prevented by the simultaneous transmission of costimulatory signals. We show here that T cells with elevated major histocompatibility complex (MHC) class I expression are resistant against macrophage-mediated cytotoxicity. T cells that express the CD45RO isotype, considered memory T cells, exhibit MHC class I antigen at higher density than naive CD45RA T cells and upregulate MHC class I expression promptly when they form cellular conjugates with macrophages. We confirm previous observations that CD45RA T cells are more susceptible to antibody- and macrophage-mediated deletion than memory CD45RO T cells. When MHC class I molecules are masked by specific monoclonal antibody or antibody Fab fragments, CD45RA T cells and CD45RO T cells exhibit equal susceptibility to macrophage cytotoxicity, demonstrating that the difference between CD45RA and CD45RO T cells in their sensitivity to macrophage cytotoxicity is determined by their MHC I expression. Separation of CD4 T cells from CD8 T cells deprives memory CD4 T cells of their resistance against macrophage cytotoxicity, suggesting that memory T cells' resistance against destruction by macrophages is controlled by regulatory T cells.

Long-Lasting Protective Immunity to Experimental Autoimmune Encephalomyelitis Following Vaccination with Naked DNA Encoding C-C Chemokines

DNA vaccination represents a novel means of expressing Ag in vivo for the generation of both humoral and cellular immune responses. The current study uses this technology to elicit protective immunity against experimental autoimmune encephalomyelitis (EAE), a T cell-mediated autoimmune disease of the central nervous system that serves as an experimental model for multiple sclerosis. RT-PCR verified by Southern blotting and sequencing of PCR products of four different C-C chemokines, macrophage-inflammatory protein-1α (MIP-1α), monocyte-chemotactic protein-1 (MCP-1), MIP-1β, and RANTES, were performed on brain samples from EAE rats to evaluate mRNA transcription at different stages of disease. Each PCR product was then used as a construct for naked DNA vaccination. The subsequent in vivo immune response to MIP-1α or MCP-1 DNA vaccines prevented EAE, even if disease was induced 2 mo after administration of naked DNA vaccines. In contrast, administration of the MIP-1β naked DNA significantly aggravated the disease. Generation of in vivo immune response to RANTES naked DNA had no notable effect on EAE. MIP-1α, MCP-1, and MIP-1β mRNA transcription in EAE brains peaked at the onset of disease and declined during its remission, whereas RANTES transcription increased in EAE brains only following recovery. Immunization of CFA without the encephalitogenic epitope did not elicit the anti-C-C chemokine regulatory response in DNA-vaccinated rats. Thus, modulation of EAE with C-C chemokine DNA vaccines is dependent on targeting chemokines that are highly transcribed at the site of inflammation at the onset of disease.

Macrophages may activate or destroy T cells with which they form antigen- or coreceptor-mediated cellular conjugates

The formation of antigen- or mitogen-mediated cellular conjugates with T cells enables macrophages to trigger in T cells costimulatory signals and to facilitate T cell clonal expansion and differentiation. The present study describes T cell death as an alternative consequence of T cell interaction with macrophages. Macrophages initiate the deletion of T cells which they target for conjugate formation through CD4 coreceptors. After suboptimal engagement, the TCR mediates a deletion program. Optimal TCR stimulation induces a rescue program which overrides the deletion program induced by suboptimal antigen receptor ligation or by coreceptor engagement. Evidence is presented suggesting that receptor clustering favors the transmission of activation signals, whereas ligation of nonclustered receptors facilitates T cell deletion.

Immunomodulation of experimental antiphospholipid syndrome

The various therapeutic modalities which are found to be beneficial in experimental antiphospholipid syndrome include: bone marrow transplantation, anti-CD4 monoclonal antibodies, bromocriptine, intravenous immunoglobulins and anti-idiotypes, interleukin-3, and various anti-coagulant and anti-aggregate agents. The advantage of animal models is the ability to evaluate experimental treatments that cannot be tested directly on patients. In this paper, we review the effect of these agents on animal models of antiphospholipid syndrome, their mechanisms of action, and their clinical implications.

Monoclonal antibodies to CD4

Animal models of human autoimmune disease suggest that it should be possible to reinduce self-tolerance in these conditions by the use of T-cell directed therapies, in particular with anti-CD4 monoclonal antibodies (CD4-mAb). Many studies have shown that CD4-mAb can prevent and in a treatment setting suppress activity of these disease models, including collagen-induced arthritis.

A humanized form of a CD4-specific monoclonal antibody exhibits decreased antigenicity and prolonged plasma half-life in rhesus monkeys while retaining its unique biological and antiviral properties

Certain monoclonal antibodies (MAbs) directed against CD4 can efficiently block HIV-1 replication in vitro. To explore CD4-directed passive immunotherapy for prevention or treatment of AIDS virus infection, we previously examined the biological activity of a nondepleting CD4-specific murine MAb, mu5A8. This MAb, specific for domain 2 of CD4, blocks HIV-1 replication at a post-gp120-CD4 binding step. When administered to normal rhesus monkeys, all CD4+ target cells were coated with antibody, yet no cell clearance or measurable immunosuppression occurred. However, strong anti-mouse Ig responses rapidly developed in all monkeys. In the present study, we report a successfully humanized form of mu5A8 (hu5A8) that retains binding to both human and monkey CD4 and anti-AIDS virus activity. When administered intravenously to normal rhesus monkeys, hu5A8 bound to all target CD4+ cells without depletion and showed a significantly longer plasma half-life than mu5A8. Nevertheless, an anti-hu5A8 response directed predominantly against V region determinants did eventually appear within 2 to 4 weeks in most animals. However, when hu5A8 was administered to rhesus monkeys chronically infected with the simian immunodeficiency virus of macaques, anti-hu5A8 antibodies were not detected. Repeated administration of hu5A8 in these animals resulted in sustained plasma levels and CD4+ cell coating with humanized antibody for 6 weeks. These studies demonstrate the feasibility of chronic administration of CD4-specific MAb as a potential means of treating or preventing HIV-1 infection.

Cytotoxic monocytes in the blood of HIV type 1-infected subjects destroy targeted T cells in a CD95-dependent fashion

HIV-1 infection changes the functional balance of macrophages in the body; it inhibits the development of macrophages capable of costimulating T cell responses and it favors the development of macrophages that kill T cells with which they form cellular conjugates. Cytotoxic macrophages destroy CD4 T cells, which they target through CD4-reactive immune-complexed HIV-1 envelope molecules on a large scale. They also destroy T cells that they target through presented antigen or mitogen. We show here that cytotoxic macrophages destroy their cellular targets at least partially in a CD95-dependent process in which T cells first modulate expression of most of their membrane receptors and subsequently die.

Differential functional effects of a humanized anti-CD4 antibody on resting and activated human T cells

A fully humanized immunoglobulin G1 (IgG1) anti-CD4 monoclonal antibody is currently being evaluated in phase I/II clinical trials for rheumatoid arthritis. In order to understand the mode of action of this antibody in vivo, we have carried out a detailed functional analysis in vitro of the effects of this antibody on T-cell activation. The anti-CD4 antibody was found to inhibit both antigen-specific responses involving recognition of human leucocyte antigen (HLA) class II and processed antigenic peptides as well as non-class II dependent responses via anti-CD3 antibodies. The antibody did not cause total blockade of T-cell proliferation, but rather induced a shift in the dose-response curve, decreasing the sensitivity of cells to antigen or anti-CD3-mediated stimulation. The antibody appears to allow at least a partial early signal into the T cell as it does not inhibit the increase in tyrosine phosphorylation induced by anti-CD3 antibodies. A comparison of the intact antibody with that of either the F(ab')2 fragment or an engineered non-Fc receptor (FcR) binding form revealed that the intact antibody was the most effective at inhibiting proliferation of resting peripheral blood CD4+ T cells. However, this difference was only apparent when excess antibody was removed from culture prior to antigen or anti-CD3 mediated stimulation. The intact antibody induced both CD4 down-modulation and increases in CD4-associated tyrosine phosphorylation of resting CD4+ T cells, which were not seen with the non-FcR binding versions, which may account for the enhanced potency of the intact antibody at inhibiting T-cell activation. Interestingly, the anti-CD4 antibody induced a differential effect on activated CD4+ T cell clones compared with resting CD4+ T cells with respect to degree of CD4 cross-linking required to induce functional effects in the T cell. Both intact and non-FcR binding antibodies were equally effective at inhibiting T-cell proliferation of activated T-cell clones. In addition CD4 down-modulation and increased CD4-associated tyrosine phosphorylation were observed with T-cell clones in the absence of secondary cross-linking. Such observations may be of relevance when studying the effects of the antibody at sites of inflammation, where there will be CD4+ T cells of differing activation states as well as varying numbers of FcR positive cells.

Animal models for antiphospholipid syndrome in pregnancy

Experimental models for antipospholipid syndrome (APS) have been established recently in lupus-prone mice and induced in naive mice. The induction of APS is performed by passive infusion or active immunization of antiphospholipid antibodies (aPL) or the cofactor beta 2GP-1. High levels of diverse aPL develop in the animals in conjunction with clinical manifestations similar to the human disease, entailing low fecundity rate, fetal resorptions, thrombocytopenia, prolonged activated partial thromboplastin time, and neurological and behavioral impairments. The pathogenicity of aPL was confirmed in an in vivo thrombosis model. Immunomodulation of APS manifestations and treatment regimens in the experimental models are discussed.

Treatment with a chimeric CD4 monoclonal antibody is associated with a relative loss of CD4+/CD45RA+ cells in patients with rheumatoid arthritis

This study investigates immunogenicity and in vivo effects on T-cells of long-term CD4 monoclonal antibody treatment of patients with rheumatoid arthritis. Patients were treated with several dosage regimens of a chimeric CD4 monoclonal antibody entitled cM-T412 over the course of 1 year. The circulating CD4+ T-cell count sharply decreased after the first cM-T412 injection and slowly recovered after the last injection. Within the CD4+ subset there was a selective depletion of CD45RA+ T cells, HLA-DR+, and CD25+ cells, providing evidence that activated/memory CD4+ cells resist the effect of CD4 monoclonal antibodies. Studies on cytokine production by peripheral blood mononuclear cells cultures in vitro revealed no differential effect on the production of interleukin-4 compared to interferon-gamma, indicating that a shift from a Th1 to a Th2 lymphokine production profile was not achieved. Human anti-monoclonal antibodies (HAMA) were induced in a minority of the patients predominantly after the first treatment course. All the sera containing HAMA specifically inhibited the binding of cM-T412 to T-cells. However, HAMA formation does not interfere with the biological effect of repeated cM-T412 administration since the degree of CD4 depletion following repeated administration of cM-T412 to patients with and without blocking antibodies was similar. We conclude that the currently available data are of critical importance in the interpretation of the obtained clinical experience and for further development of this therapeutic strategy.

TNF-alpha receptor fusion protein prevents experimental auto-immune encephalomyelitis and demyelination in Lewis rats: an overview

To explore the therapeutic use of TNF-alpha inhibitors in human inflammatory demyelinating diseases we examined the effect of a recombinant TNFRp55 protein constructed by fusing TNFRp55 extracellular domain cDNA to a human IgG1 heavy gene fragment containing the hinge and constant domains CH2 and CH3 (TNFRp55-IgG1) in diverse experimental model systems representing inflammation and inflammatory demyelination of encephalitogenic T cells in vivo. In EAE actively induced by immunization of Lewis rats with MBP, a single dose of TNFRp55-IgG1 protected the recipient animals from clinical signs. Interestingly, the treatment neither prevented the formation CNS infiltrations, nor did it alter the cellular composition of the infiltrates. In EAE transferred by MBP specific activated T line cells, a model of inflammatory (not demyelinating) brain disease, the inhibitor's therapeutic effect on clinical disease was also striking achieving almost complete protection even after repeated transfers of encephalitogenic T cells. Finally, the recombinant inhibitor was also protective in Lewis rats with demyelinating experimental autoimmune panencephalitis produced by combined transfer of panencephalitogenic T cells and demyelinating monoclonal antibody specific for MOG. In this system, the T cells are of low encephalitogenic activity, but open the blood-brain barrier for the demyelinating immunoglobulins. The fusion protein treatment, however, prevented the formation of inflammatory lesions and demyelination. The strong therapeutic effect of the recombinant chimeric TNF-alpha inhibitor in three models of myelin specific autoimmunity raises hopes as to TNF-alpha directed therapy of human diseases like MS.

New methods of treatment in an experimental murine model of systemic lupus erythematosus induced by idiotypic manipulation

In this article we have presented our experiences and those of others with various experimental and novel treatments in an experimental model of murine SLE, induced by immunisation with pathogenic anti-DNA antibody (fig 4). Many of the treatments (summarised in the table) were highly effective in ameliorating clinical, serological, and histological manifestations of the disease. According to our results, it seems that hormonal treatments--such as testosterone metabolites, anti-oestrogens, or bromocriptine--as well as immunomodulation with IVIG or anti-CD4 antibodies, hold the most promising potential for application in lupus patients. We believe, therefore, that these types of treatment should receive high priority in human trials. It should be emphasised, however, that the timing of treatment may be critical, since several treatments were effective when used before or during the induction of the disease. This limitation may pose difficulty for human application, since the aetiology of SLE is still obscure and is probably multifactorial38; therefore it is not yet possible to identify patients at risk of developing SLE. Nevertheless, those treatments which proved to be effective might be used early in the course of the disease in lupus patients and hence influence the outcome of the disease, or may even induce partial or complete remission.

Cellular and molecular mechanisms of murine autoimmune myocarditis

Dilated cardiomyopathy is a prevalent cause of progressive heart disease and sudden death, and most patients with cardiomyopathy have a history of viral myocarditis. Coxsackie B3 (CB3) picornaviruses can be detected in as many as 50% of these patients and CB3 infections have been epidemiologically linked to chronic heart disease. Several clinical and experimental studies suggest that chronic stages of disease are mediated by an autoimmune response against heart muscle myosin. Human heart disease can be mimicked in mice using cardiac myosin as autoantigen. Murine cardiac myosin-induced myocarditis is an organ-specific autoimmune disease and mediated by CD4+ T cells that recognize a myosin-specific peptide in association with MHC class II molecules. Here, the recent discovery of autoimmune epitopes derived from the alpha isoform of cardiac myosin, the functional roles of surface receptor and signal transduction molecules, and the molecular mechanisms of target organ susceptibility will be discussed.

The cell surface marker phenotype of macrophages from HIV-1-infected subjects reflects an IL-10-Enriched and IFN-gamma-deprived donor environment

T cells depend on costimulation by accessory cells for an immune response. Costimulatory macrophage activity involves the expression of B7 molecules whose expression is upregulated by interferon-gamma (IFN-gamma) and downregulated by interleukin-10 (IL-10). The expression of low-affinity Fc gamma IIIR (CD16), in contrast, is upregulated in the presence of IL-10 and downregulated in the presence of IFN-gamma. In human immunodeficiency virus-1 (HIV-1) infection, the balance between IFN-gamma and IL-10 expression shifts toward IL-10 predominance. Herein, we compare B7 and CD16 macrophage phenotypes from healthy and from HIV-1-infected patients. Patient macrophages express B7 molecules in lower density than macrophages from healthy donors and are resistant to the upregulation of costimulatory molecule expression. B7 expression can be normalized in patient macrophages by treating them with anti IL-10 monoclonal antibodies (mAb) and IFN-gamma together but not by treatment with either anti-IL-10 mAb or IFN-gamma alone. This finding suggests an excess of IL-10 in HIV-1 infection and an IFN-gamma deficiency, consistent with previous cytokine assessments in HIV-1-infected subjects. The upregulation of CD16 expression was readily induced in patient macrophages by treatment with IL-10 and was inhibited by treatment with IFN-gamma. CD16 expression identifies the subset of cytotoxic macrophages that has been shown to destroy CD4T cells, which they target through CD4-reactive immune-complexed HIV-1 envelope molecules.

Fas (CD95) expression and death-mediating function are induced by CD4 cross-linking on CD4+ T cells

The CD4 receptor contributes to T-cell activation by coligating major histocompatibility complex class II on antigen presenting cells with the T-cell receptor (TCR)/CD3 complex, and triggering a cascade of signaling events including tyrosine phosphorylation of intracellular proteins. Paradoxically, CD3 cross-linking prior to TCR stimulation results in apoptotic cell death, as does injection of anti-CD4 antibodies in vivo of CD4 ligation by HIV glycoprotein (gp) 120. In this report we investigate the mechanism by which CD4 cross-linking induces cell death. We have found that CD4 cross-linking results in a small but rapid increase in levels of cell surface Fas, a member of the tumor necrosis factor receptor family implicated in apoptotic death and maintenance of immune homeostasis. Importantly, CD4 cross-linking triggered the ability of Fas to function as a death molecule. Subsequent to CD4 cross-linking, CD4+ splenocytes cultured overnight became sensitive to Fas-mediated death. Death was Fas-dependent, as demonstrated by cell survival in the absence of plate-bound anti-Fas antibody, and by the lack of CD4-induced death in cells from Fas-defective lymphoproliferative (lpr) mice. We demonstrate here that CD4 regulates the ability of Fas to induce cell death in Cd4+ T cells.

Monocytes in HIV type 1-infected individuals lose expression of costimulatory B7 molecules and acquire cytotoxic activity

Monocytes/macrophages control the function of lymphocytes through positive and negative regulation. They release immunostimulatory cytokines and initiate costimulatory signals in T cells through the expression of B7 molecules. Their negative regulatory functions include the capacity to destroy cells with which they form cellular conjugates. We show here that HIV-1 infection skews monocyte function toward negative regulation by restraining the expression of costimulatory B7 molecules and by enhancing the cytolytic monocyte function. Monocytes that express constitutively B7, a membrane component that facilitates the engagement of costimulatory signals in T cells, lose this marker after HIV-1 infection and become refractory to inducers of B7 expression. The appearance of monocytes with reduced B7 expression is associated with an increased cytolytic monocyte capacity. Monocytes from HIV-1-infected donors destroy antibody-targeted normal lymphocytes more efficiently than do normal monocytes and they destroy CD4+ T cells specifically without the exposure to an exogenous ligand. CD4-reactive HIV-1 envelope molecules, expressed on monocytes as a consequence of infection or of opsonization by antibody, may specifically target CD4+ T lymphocytes for destruction and may thereby contribute to the preferential loss of CD4 T cells in HIV-1-infected individuals.

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.

Repopulation of blood lymphocyte sub-populations in rheumatoid arthritis patients treated with the depleting humanized monoclonal antibody, CAMPATH-1H

Patients with severe rheumatoid arthritis who had failed treatment with conventional therapies were treated with a course of five or 10 daily intravenous infusions of CAMPATH-1H, a humanized antibody against the CD52 antigen, resulting in profound depletion of peripheral blood mononuclear cells. During the subsequent 18 months, lymphocytes were analysed for sub-populations by fluorescence-activated cell sorter (FACS) and for proliferation in response to polyclonal T-cell stimulation with anti-CD3 or staphylococcal enterotoxin B (SEB). Treatment resulted in almost complete depletion of lymphocytes from the blood followed by gradual repopulation. CD16+ natural killer (NK) cells and CD14+ monocytes returned to pretreatment levels within 1-2 months. CD19+ B cells returned to within 50% of pre-treatment levels by day 66 and to within normal range by day 150, whereas CD8+ T cells recovered to 50% of pretreatment levels by day 66, but did not show any further increase during the rest of the study period. The most profound effects were on the CD4+ T lymphocyte sub-population, as the mean CD4+ count did not increase above 20% of pre-treatment level at any time during the study period (550 days), at all the doses tested. The T cells which initially repopulated the blood 1-2 months after treatment, nearly all expressed the activation markers human leucocyte antigen (HLA)-DR and CD45RO, although the percentage of T cells expressing these molecules gradually declined to normal levels over time. Proliferative responses to polyclonal T-cell stimulation (anti-CD3 and SEB) were also significantly reduced in the first few months after treatment, but recovered to pre-treatment levels by day 250. The relationship between these observations and the clinical response is discussed.

Antibody response to islet antigens in anti-CD4/prednisolone immune intervention of type 1 diabetes

Cytoplasmic islet cell antibodies, glutamic acid decarboxylase autoantibodies, spontaneous insulin autoantibodies, and insulin-induced antibodies were analyzed in a 1-year follow-up study of 12 newly diagnosed patients with insulin-dependent diabetes mellitus aged 14 +/- 2 years (range 7-20 years) who had been initially treated with either multiple injections of insulin alone (control group) or, in addition, anti-CD4 monoclonal antibody/prednisolone (treatment group). Despite individual variations in islet cell antibody titers, there were no significant differences in the prevalence or changes in the mean titers between the two groups. Glutamic acid decarboxylase autoantibodies remained almost unchanged, but correlated with levels of islet cell antibodies. While at initiation of treatment only 50% of the patients from both groups had spontaneous insulin autoantibodies, all patients developed insulin-induced antibodies upon conventional insulin therapy during the course of follow-up. This was not related to islet cell antibody or glutamic acid decarboxylase antibody levels. The insulin requirement was markedly reduced through the period of follow-up, but did not significantly differ between the two groups. A correlation between islet cell antibody levels and insulin requirement was observed in the control group but not in the treatment group. Plasma levels of the antibodies were not associated with changes in stimulated C-peptide or hemoglobin A1 concentrations. Activated T-lymphocytes persisted in both groups of patients, but their mean levels were not significantly different. The reason for the absence of statistically significant differences between treatment and control groups could be due to the small number of patients in the study. In conclusion, short-term immune intervention with anti-CD4 monoclonal antibody in addition to insulin therapy did not suppress autoimmune reactions towards the beta cells.

Treatment of severe cutaneous lupus erythematosus with a chimeric CD4 monoclonal antibody, cM-T412

BACKGROUND

Monoclonal CD4 antibodies are among the most potent immunomodulatory agents in various experimental models of autoimmune disease, including murine lupus erythematosus.

OBJECTIVE

The aim of this study was to evaluate the toxicity and therapeutic efficacy of a chimeric monoclonal CD4 antibody, cM-T412, in patients with cutaneous lupus erythematosus (LE).

METHODS

Five patients with severe cutaneous LE lesions received intravenously a total of 275, 400, or 475 mg of cM-T412 in single doses of 20 to 50 mg during a period of 5 to 8 weeks.

RESULTS

CD4 antibody treatment induced a long-lasting decrease in disease activity. It resulted in healing of LE skin lesions, a reconstituted responsiveness to conventional treatment, or both. Despite a substantial depletion of circulating CD4+ T lymphocytes, no clinical signs of immunosuppression were noted.

CONCLUSION

Monoclonal CD4 antibodies should be considered as a novel treatment for the management of severe cutaneous LE.

Structural modification of serum vitamin D3-binding protein and immunosuppression in AIDS patients

A serum glycoprotein, vitamin D3-binding protein (Gc protein), can be converted by beta-galactosidase of stimulated B lymphocytes and sialidase of T lymphocytes to a potent macrophage-activating factor (MAF), a protein with N-acetylgalactosamine as the remaining sugar moiety. Thus, Gc protein is a precursor for MAF. Treatment of purified Gc protein with immobilized beta-galactosidase and sialidase generates an extremely high-titered MAF (GcMAF). When peripheral blood monocytes/macrophages of 46 HIV-infected patients were treated with GcMAF (100 pg/ml), the monocytes/macrophages of all patients were efficiently activated. However, the MAF precursor activity of plasma Gc protein was low in 16 (35%) of of these patients. Loss of the MAF precursor activity appeared to be due to deglycosylation of plasma Gc protein by alpha-N-acetylgalactosaminidase found in the patient blood stream. Levels of plasma alpha-N-acetylgalactosaminidase activity in individual patients had an inverse correlation with the MAF precursor activity of their plasma Gc protein. Thus, precursor activity of Gc protein and alpha-N-acetylgalactosaminidase activity in patient blood can serve as diagnostic and prognostic indices.

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

Basophils and mast cells, as the main effector cells in IgE-mediated type I hypersensitivity, are involved in the elimination of parasites and, according to recent findings, may also play an important role in the defense against bacterial and viral infections. Using a genetic engineering approach we wanted to redirect this potent IgE-mediated defense system against intruding human immune deficiency virus. We constructed a recombinant CD4-IgE molecule, consisting of the two N-terminal domains of CD4 and the CH2-4 domains of the IgE heavy chain, thus providing the IgE with specificity for the gp120 of human immunodeficiency virus (HIV). The binding properties of hybrid CD4-IgE to the high-affinity receptor for IgE (Fc epsilon RI) on basophils as well as to the low-affinity receptor (Fc epsilon RII or CD23) for IgE on lymphoid cells were found to be similar to those of native IgE. At the same time, the CD4 domains of the recombinant molecule retained the gp120 binding specificity with an affinity similar to that of the native CD4. By functional tests, we demonstrated that CD4-IgE armed basophils can be triggered by free HIV and by HIV-infected cells to release their mediators. We further show that HIV-triggered basophils lead to a decreased replication of HIV in susceptible T cells. We, therefore, conclude that the type I hypersensitivity effector cells can be engaged in the elimination of HIV-infected cells, at least in vitro. Because of the strong binding of the CD4-IgE construct to the Fc epsilon RI, we assume that CD4-IgE has a short t1/2 in serum, but may similarly to IgE exhibit prolonged resident time on basophils and mast cells, which are located close to mucosal surfaces or in the connective tissue. Thus CD4-IgE could play an important role in the elimination of HIV also in vivo.

Therapeutic effects of antibodies against adhesion molecules in murine collagen type II-induced arthritis

Adhesion molecules play important roles in immune reactions and inflammatory processes and may constitute attractive targets for immunomodulatory approaches. In this study, blocking mAbs against a series of adhesion molecules were tested for their therapeutic effect on developing arthritis in a mouse model. MAbs were given for a period of 4 weeks at the time of exspected incidence of visible disease symptoms, i.e. 4 weeks after priming with collagen type II. A significant reduction of incidence down to values of 13% and 29% of the controls was obtained with mAbs against CD44 and alpha 4-integrin, respectively, during an observation time of 13 weeks. MAbs against CD4 and LFA-1 resulted only in weaker, non-significant effects or a delay in the incidence. MAbs against other molecules including L-selectin, ICAM-1 or VCAM-1 were not effective. The development of antibodies against collagen type II, collagen type I, proteoglycans and the immunogen, bovine collagen type II was affected by mAb treatment to a different extent. In this case, the anti CD4 mAb was the most effective, followed by the anti alpha 4-antibodies in most cases, whereas anti CD44 showed less clear effects on the development of humoral responses. In a skin delayed type hypersensitivity model analyzed for comparison, mAbs against LFA-1/ICAM-1 and alpha 4-integrin showed the largest effects on ear swelling. These data show that mAbs against several adhesion molecules are able to block selectively distinct aspects of immune reactions, and that CD44 and alpha 4-integrins could be promising targets for an immunotherapy of rheumatoid arthritis with receptor-interfering agents.

Anti-idiotypic monoclonal antibodies (mAb) to an anti-CD4 mAb induce CD4+ T cell depletion in rabbit

We previously produced and characterized the syngeneic anti-idiotypic (Ab2) mAb F11-2302, F16-14D6 and F16-16D7 elicited with the mouse anti-human CD4 mAb HP2/6. We showed that F11-2302, which reacts with an idiotope (id) outside the antigen (Ag) combining site, fails to induce anti-CD4 antibodies (Ab) in mice, whereas mAb F16-14D6 and F16-16D7 to an id within (or closely related to) mAb HP2/6 Ag-combining site induces Ab to CD4 molecule. In the present investigation we extended our analysis to the immune response induced by these three mAb in a xenogeneic system by immunizing three New Zealand White (NZW) rabbits with Ab2 mAb. The latter animals were selected since rabbit CD4 molecules displayed a weak cross-reactivity with the anti-human CD4 mAb HP2/6. An additional rabbit was not immunized and used, together with the F11-2302-immunized one, as control. The three rabbits developed Ab3 Ab highly restricted to their respective immunizing mAb. Although no Ab reacting with human CD4 were detected in the three affinity-purified Ab3 preparations, a marked decrease in the percentage of CD4+ T cells was observed in the rabbits immunized with mAb F16-14D6 and F16-16D7. The results suggest that active specific immunotherapy with selected Ab2 mAb may induce biological effects similar to those generated by the passive administration of anti-CD4 mAb, and the rabbit could be an appropriate xenogeneic host for the testing of potential applications of anti-CD4 Ab2 mAb active immunotherapy in transplantation and autoimmune diseases.

T lymphocytes derived from skin lesions of patients with psoriasis vulgaris express a novel cytokine pattern that is distinct from that of T helper type 1 and T helper type 2 cells

In various immunological disorders the pathomechanisms of tissue damage are causally associated with specific patterns of locally produced cytokines. To study the molecular and cellular mechanisms involved in the manifestation of psoriasis vulgaris we have assessed the cytokine mRNA profile expressed in lesional psoriatic skin and in T cell clones (TCC) that were established from skin lesions of patients with psoriasis. As demonstrated by use of the polymerase chain reaction (PCR), psoriasis lesions consistently exhibit transcription of a complex pattern of cytokines. It includes mediators selectively produced by T lymphocytes [interferon (IFN)-gamma, tumor necrosis factor (TNF)-beta, interleukin (IL)-2, IL-3 and IL-5] as well as cytokines secreted by various cell types [transforming growth factor (TGF)-alpha/-beta, TNF-alpha, IL-6/-8 and granulocyte-macrophage-colony stimulating factor], while IL-4 is missing. With the exception of TGF-alpha, this cytokine profile was also observed in lesional psoriatic T cell clones yielding supernatants mitogenic for keratinocytes in vitro (MTCC), but not in T cell clones yielding supernatants that inhibited keratinocyte proliferation (STCC). The congruent cytokine expression of psoriatic skin lesions and MTCC emphasizes that inflammation in psoriasis is driven by a sofar unrecognized regulatory T cell subset that may serve to control epidermal regeneration and convey immunosurveillance over epithelial surfaces. It is characterized by the combined expression of IFN-gamma, TGF-beta, IL-2 and IL-5 in the absence of IL-4 and by its selective capacity to enhance keratinocyte proliferation. This newly defined combination of regulatory properties of a distinct T cell population cannot be reconciled with an immune response of the T helper cells (TH)0, TH1 or TH2 type.

Suppression of experimental antiphospholipid syndrome and systemic lupus erythematosus in mice by anti-CD4 monoclonal antibodies

OBJECTIVE

To investigate whether anti-CD4 antibodies can suppress experimental antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE) induced by an anti-DNA monoclonal antibody (MAb).

METHODS

BALB/c mice were treated with anti-CD4 MAb either before or 2 months after induction of experimental APS and SLE. Control mice were treated with rat IgG or phosphate buffered saline. Serologic and clinical manifestations of the disease were determined.

RESULTS

Treatment of mice with anti-CD4 before or 2 months after disease induction prevented the development of experimental APS and SLE. The treated mice did not develop leukopenia or proteinuria, and had fewer episodes of fetal resorption. Similarly, the treated mice did not develop elevated erythrocyte sedimentation rate, prolonged activated partial thromboplastin time, or thrombocytopenia, and had significantly lower levels of antibodies to double-stranded DNA, histones, MIV-7, cardiolipin, and phosphatidylserine. Levels of CD4+ cells in the lymph nodes declined temporarily after the treatment and then returned to normal.

CONCLUSION

Anti-CD4 antibodies can prevent experimental APS and SLE. These results may suggest a role for anti-CD4 treatment in human autoimmune diseases.

Deletion of T lymphocytes in human CD4 transgenic mice induced by HIV-gp120 and gp120-specific antibodies from AIDS patients

CD4, a T cell receptor for major histocompatibility complex class II antigen, is a key regulator of immunological reactivities. When engaged together with the T cell antigen receptor, CD4 enhances immune reactions, whereas when ligated independently of the antigen receptor CD4 inhibits the activation of T cells or initiates their deletion. CD4 serves also as a receptor for the human immunodeficiency virus (HIV), which binds the receptor with high avidity through its envelope molecule, gp120. Studies in tissue culture have shown that its affinity to CD4 gives the virus opportunities to utilize CD4-mediated signaling and to manipulate immunocytes. We show here in human CD4 transgenic mice that appropriately cross-linked HIV envelope protein causes massive deletion of HIV-reactive T cells in vivo.

CD4 engagement induces Fas antigen-dependent apoptosis of T cells in vivo

CD4 is a T lymphocyte receptor for major histocompatibility complex class II antigens. It is referred to as coreceptor because it synergizes with the T cell receptor for antigen when both receptors become engaged simultaneously. We show here in mice that when engaged by antibody independently of the T cell antigen receptor, CD4 induces T cells to undergo apoptosis. Several features of this process were identified. The expression of an intact Fas protein is a requirement for CD4-mediated T cell death. Mice homozygous for the lpr mutation which are defective in the expression of Fas and in their ability to delete lymphocytes apoptotically fail to delete anti-CD4-reactive T cells. Sessile anti-CD4-reactive T cells leave their homing environment in lymphoid organs and modulate their cell surface molecules, e.g. CD2, CD3, CD4. A massive influx of lymphoid cells with null-cell phenotype occurs in the blood where they begin to reexpress cell surface markers. With their arrival in the circulation, anti-CD4-reactive T cells develop features of DNA degradation typical of apoptosis. More than one third of the circulating lymphoid cells show apoptotic features 7-8 h after anti-CD4 injection. Their frequency declines subsequently presumably due to their physical disintegration via shedding of apoptotic bodies and phagocytosis. Our data show that when not obliged to the activation process by the antigen receptor, CD4 can mediate deletion signals. Thus, besides functioning as coreceptor with the antigen receptor, CD4 has a function of its own in facilitating the induction of apoptosis.

T cell clones from psoriasis skin lesions can promote keratinocyte proliferation in vitro via secreted products

Psoriasis vulgaris has been recognized lately as an immunologically mediated inflammatory skin disease. To analyze the pathogenetic role of T lymphocytes in the generation of psoriatic skin lesions, 105 T cell clones (TCC) and 10 T cell lines (TCL) were differentially isolated from dermis and epidermis of psoriatic skin specimens. Supernatants prepared from these T cells were studied for their effects on keratinocyte proliferation in vitro. Conditioned media from 14 of 77 epidermal TCC, 7 of which were CD8+, and from 8 of 28 dermal TCC, 5 of which were CD8+, reproducibly enhanced keratinocyte proliferation, with more pronounced mitogenic activities found in dermal TCC. Another 9 epidermal and 3 dermal TCC did not affect keratinocyte growth and supernatants from the remaining clones, as well as from the 5 epidermal and 5 dermal TCL, inhibited keratinocyte replication to varying degrees. Both mitogenic and suppressive activities were largely abolished by addition of an antiserum to interferon-gamma (IFN-gamma), while addition of epidermal growth factor or irradiated psoriatic TCL had little effect on the activities of the supernatants. These studies reveal that a subpopulation of lesional psoriatic T lymphocytes is capable of enhancing keratinocyte proliferation in vitro via secreted products. Their mitogenic capacity most likely requires IFN-gamma, but the ultimate effect is apparently determined by the presence of additional cytokines. Activation of T cells secreting such combinations of factors in vivo may contribute to the keratinocyte alterations characteristic of psoriatic skin lesions.

Human CD4 "internal antigen" mimicry by anti-idiotypic monoclonal antibodies

Of 1019 hybridomas generated from a BALB/c mouse immunized with the syngeneic anti-CD4 monoclonal antibody HP2/6, 3 were found to secrete anti-idiotypic antibodies. Detailed analysis of anti-idiotypic monoclonal antibodies F16-10F6, F16-14D6 and F16-16D7 showed they recognize idiotope(s) not expressed by any of the anti-CD4 monoclonal antibodies tested, including those which inhibit the binding of HP2/6 to CD4 antigen. The idiotope recognized by the three anti-idiotypic antibodies are within (or closely related to) the antigen combining site of the immunizing antibody and distinct and spatially distant from the idiotope defined by monoclonal antibody F11-2302 which was previously shown to be outside the antigen combining site of HP2/6. Although F16-14D6 and F16-16D7 are indistinguishable in isotype, binding titer to idiotopes, fine specificity on a panel of monoclonal antibodies, relation to the combining site and competitive binding, it is likely that they are structurally different and recognize two distinct combining site-related idiotopes on HP2/6, as they display different spectrotypes and induce anti-anti-idiotypic (Ab3) immune sera with different specificities. Analysis of the fine specificity of the two Ab3 immune sera suggest they share idiotopes with HP2/6 and contain antibodies reacting with CD4 antigen. Among the latter, those induced with F16-14D6 display a different CD4 epitope specificity than HP2/6. Hence, anti-idiotypic antibodies F16-14D6 and F16-16D7 behave as "network antigen" for human CD4; idiotope-triggered antibody cascade may have a role in changing the specificities of antibody.

Immunosuppressive therapy of autoimmune diseases

Cyclosporin A, corticosteroids and cyclophosphamide show a remarkable efficacy in a large number of autoimmune diseases. However, their effect is dependent on continuous drug administration with potential risks of drug toxicity and over immunosuppression. Results recently obtained in animal models, particularly with anti-CD3 and anti-CD4 monoclonal antibodies, indicate that reestablishment of tolerance to self antigens is a feasible goal.

Immunosuppressive therapy of autoimmune diseases

Ciclosporin and cyclophosphamide show a remarkable efficacy in most autoimmune diseases. However, their effect is dependent on continuous drug administration with risks of drug toxicity and over immunosuppression. Results recently obtained in animal models, discussed here by Jean François Bach particularly with anti-CD3 and anti-CD4 monoclonal antibodies, indicate that reestablishment of tolerance to self antigens is a feasible goal.