Major outer membrane protein Omp25 of Brucella suis is involved in inhibition of tumor necrosis factor alpha production during infection of human macrophages

Brucella spp. can establish themselves and cause disease in humans and animals. The mechanisms by which Brucella spp. evade the antibacterial defenses of their host, however, remain largely unknown. We have previously reported that live brucellae failed to induce tumor necrosis factor alpha (TNF-alpha) production upon human macrophage infection. This inhibition is associated with a nonidentified protein that is released into culture medium. Outer membrane proteins (OMPs) of gram-negative bacteria have been shown to modulate macrophage functions, including cytokine production. Thus, we have analyzed the effects of two major OMPs (Omp25 and Omp31) of Brucella suis 1330 (wild-type [WT] B. suis) on TNF-alpha production. For this purpose, omp25 and omp31 null mutants of B. suis (Deltaomp25 B. suis and Deltaomp31 B. suis, respectively) were constructed and analyzed for the ability to activate human macrophages to secrete TNF-alpha. We showed that, in contrast to WT B. suis or Deltaomp31 B. suis, Deltaomp25 B. suis induced TNF-alpha production when phagocytosed by human macrophages. The complementation of Deltaomp25 B. suis with WT omp25 (Deltaomp25-omp25 B. suis mutant) significantly reversed this effect: Deltaomp25-omp25 B. suis-infected macrophages secreted significantly less TNF-alpha than did macrophages infected with the Deltaomp25 B. suis mutant. Furthermore, pretreatment of WT B. suis with an anti-Omp25 monoclonal antibody directed against an epitope exposed at the surface of the bacteria resulted in substancial TNF-alpha production during macrophage infection. These observations demonstrated that Omp25 of B. suis is involved in the negative regulation of TNF-alpha production upon infection of human macrophages.

Production of TNF-alpha by human V gamma 9V delta 2 T cells via engagement of Fc gamma RIIIA, the low affinity type 3 receptor for the Fc portion of IgG, expressed upon TCR activation by nonpeptidic antigen

Human lymphocytes expressing the gammadelta TCR represent a minor T cell subpopulation found in blood. The majority of these cells express Vgamma9Vdelta2 determinants and respond to nonpeptidic phosphoantigens. Several studies have shown that, in vivo, the percentage of Vgamma9Vdelta2 T cells dramatically increases during pathological infection, leading to the hypothesis that they play an important role in the defense against pathogens. However, the specific mechanisms involved in this response remain poorly understood. It has been established that Vgamma9Vdelta2 T cells display potent cytotoxic activity against virus-infected and tumor cells, thereby resembling NK cells. In this study, we show that, upon stimulation by nonpeptidic Ags, Vgamma9Vdelta2 T cells express FcgammaRIIIA (CD16), a receptor that is constitutively expressed on NK cells. CD16 appears to be an activation Ag for Vgamma9Vdelta2 T cells. Indeed, ligation of CD16 on Vgamma9Vdelta2 T cells leads to TNF-alpha production. This TNF-alpha production, which is dependent (like that induced via the TCR-CD3 complex) on the activation of the p38 and extracellular signal-regulated kinase-2 mitogen-activated protein kinases, can be modulated by CD94 NK receptors. Therefore, it appears that Vgamma9Vdelta2 T cells can be physiologically activated by two sequential steps via two different cell surface Ags: the TCR-CD3 complex and the FcgammaRIIIA receptor, which are specific cell surface Ags for T lymphocytes and NK cells, respectively. This strongly suggests that, in the general scheme of the immune response, Vgamma9Vdelta2 T cells represent an important subpopulation of cells that play a key role in the defense against invading pathogens.

Isopentenyl pyrophosphate, a mycobacterial non-peptidic antigen, triggers delayed and highly sustained signaling in human gamma delta T lymphocytes without inducing eown-modulation of T cell antigen receptor

The Vgamma9Vdelta2 T cell subset, which represents up to 90% of the circulating gammadelta T cells in humans, was shown to be activated, via the T cell receptor (TcR), by non-peptidic phosphorylated small organic molecules. These phosphoantigens, which are not presented by professional antigen-presenting cells, induce production of high amounts of interferon-gamma and tumor necrosis factor (TNF-alpha). To date, the specific signals triggered by these antigens have not been characterized. Here we analyze proximal and later intracellular signals triggered by isopentenyl pyrophosphate (IPP), a mycobacterial antigen that specifically stimulates Vgamma9Vdelta2 T cells, and compare these to signals induced by the non-physiological model using an anti-CD3 antibody. During antigenic stimulation we noticed that, except for the proximal p56(lck) signal, which is triggered early, the signals appear to be delayed and highly sustained. This delay, which likely accounts for the delay observed in TNF-alpha production, is discussed in terms of the ability of the antigen to cross-link and recruit transducing molecules mostly anchored to lipid rafts. Moreover, we demonstrate that, in contrast to anti-CD3 antibody, IPP does not induce down-modulation of the TcR.CD3 complex, which likely results in the highly sustained signaling and release of high levels of TNF-alpha.

Optimizing therapeutic strategies to inhibit circulating soluble target molecules with monoclonal antibodies: example of the soluble IL-6 receptors

Therapeutic targeting of soluble molecules such as cytokines can be achieved with monoclonal antibodies (mAb). Anti-IL-6 mAb have been shown to form circulating complexes, resulting in the increase of the half-life of the cytokine in vivo. In IL-6-related diseases, the soluble human IL-6 receptors (shIL-6R), which have been shown to possess strong agonist activity, circulate in the plasma at a high concentration and must be neutralized. Their clearance was studied in mice that had been made to express circulating shIL-6R after i.p. grafting of mouse thymoma cells transfected with a gene coding for shIL-6R, treated with various anti-shIL-6R mAb recognizing different epitopes of the molecule. Injection of one anti-hIL-6R mAb stabilized the short-lived hIL-6R and led to their accumulation. The same result was observed when two mAb directed against two different epitopes of the hIL-6R were used. Clearance of the receptors was only achieved when three mAb specific for three different epitopes were injected. A permanent clearing of the hIL-6R could be obtained by repeated injections of the clearing mixture. No correlation was found between the ability of the mAb to clear the sIL-6R and to immunoprecipitate them in agarose gel. The F(ab')2 fragments lost the clearing ability of the intact mAb. These results clearly show that therapeutic clearance of sIL-6R by mAb need at least three mAb directed against three different epitopes of the molecule, a conclusion which is likely to apply for clearing any soluble target molecule.

The T cell antigen receptor activates phosphatidylinositol 3-kinase-regulated serine kinases protein kinase B and ribosomal S6 kinase 1

The present study has explored T cell antigen receptor-regulated serine kinases in human T cells. The results identify two phosphatidylinositol 3-kinase (PI3K)-controlled serine kinases operating downstream of the T cell receptor (TCR) in primary T cells: (i) protein kinase B whose activation regulates the phosphorylation of glycogen synthase kinase 3 and (ii) ribosomal S6 kinase 1, a kinase with a critical role in the regulation of protein synthesis and cell growth. T cells express two isoforms of S6k1: a 70 kDa cytoplasmic kinase and an 85 kDa isoform that has a classic nuclear localisation. TCR ligation triggers a parallel engagement of both the 70 and 85 kDa isoforms of S6k1 in a response that requires PI3K function.

Tumor necrosis factor-alpha production is differently regulated in gamma delta and alpha beta human T lymphocytes

Tumor necrosis factor-alpha (TNF-alpha) plays a crucial role in the early defense against pathogens. This cytokine is produced by several cell types including T lymphocytes expressing the alphabeta as well as the gammadelta T cell receptor (TcR). In human, the circulating gammadelta T cells, which mostly express Vgamma9Vdelta2 TcR, have been strongly suggested to play an important protective role against infectious agents. These activated cells early produce high amounts of TNF-alpha, which induce a determinant beneficial effect against development of intracellular pathogens; however, sustained production of this cytokine can result in immunopathological diseases. The signals that regulate TNF-alpha production in Vgamma9Vdelta2 T cells are totally unknown. In primary alphabeta T cells, TNF-alpha production was shown to necessitate engagement of the TcR and CD28, and to be independent of the p38 mitogen activated protein kinase pathway. We demonstrate herein that, in contrast to alphabeta T cells, TNF-alpha production in Vgamma9Vdelta2 T lymphocytes is independent of CD28 costimulation and highly dependent on TcR-induced p38 kinase and extracellular signal-regulated kinase 2 pathway activation for optimal cytokine release. Moreover, we bring elements supporting the idea that the "activation threshold" of gammadelta T cells leading to cytokine production is lower than that of alphabeta T cells.

Activation of human Vgamma9Vdelta2 T cells by a Brucella suis non-peptidic fraction impairs bacterial intracellular multiplication in monocytic infected cells

Human gamma delta T cells are considered to play an important role in the early response to infection with intracellular pathogens. Evidence has been presented that the percentage of gamma delta T cells with Vgamma9Vdelta2 phenotype is dramatically increased in the peripheral blood of patients with acute brucellosis. This specific gd T-cell subpopulation is known to be activated by small non-peptidic molecules that can either be produced by the pathogen itself or released from damaged cells after infection. In the present work we provide evidence that Vgamma9Vdelta2 T lymphocytes from peripheral blood mononuclear cells of healthy donors can be specifically activated by non-peptidic low-molecular-weight compound(s) from Brucella suis lysate. Moreover, we show that Vgamma9Vdelta2 T cells activated by this B. suis fraction produce tumour necrosis factor-alpha and interferon-gamma, which reduce bacterial multiplication inside infected cells.

Evidence for a p21(ras)/Raf-1/MEK-1/ERK-2-independent pathway in stimulation of IL-2 gene transcription in human primary T lymphocytes

T cell stimulation leads to triggering of signals transmitted from the cell membrane to the nucleus through TCR/CD3 proteins. Characterization of these signals largely results from the use of cell lines stimulated with anti-CD3 monoclonal antibodies. These studies have established that activation caused a rapid increase in the formation of GTP-bound Ras, which stimulates the mitogen-activated protein kinase pathway involving the extracellular-regulated kinase-2 (ERK-2) and activates the nuclear factor of activated T cells (NF-AT) that regulates interleukin-2 (IL-2) gene transcription. In the present study, we used human primary T cells, and we investigated the intracellular signals triggered by two different anti-CD3 monoclonal antibodies (UCHT1 and X-35), which both strongly induce cell proliferation. We found that, in contrast to the commonly used UCHT1, X-35 activated IL-2 gene transcription without stimulation of the Raf-1/mitogen-activated ERK kinase-1 (MEK-1)/ERK-2 phosphorylation cascade; we also showed that X-35 stimulation, which triggers an ERK-2-independent pathway, does not involve activation of p21(ras). In addition to demonstrating that activation of p21(ras) and of its Raf-1/MEK-1/ERK-2 effector pathway is not an event obligatorily triggered upon TCR/CD3 ligation, these results provide the first evidence of the existence of a p21(ras)/ERK-2-independent pathway for IL-2 gene transcription in human primary T lymphocytes.

Interleukin-6 receptor signaling. I. gp80 and gp130 receptor interaction in the absence of interleukin-6

Interleukin-6 (IL-6) is used as a growth factor by various tumor cells. It binds to a gp80 specific receptor (IL-6R) and then to a gp130 transducing chain. Both receptor chains are released as soluble functional proteins which circulate in biological fluids. To study the physiological role of these soluble receptors, both proteins were purified from human plasma and the kinetic constants of equilibria between IL-6 and its natural soluble IL-6R (sIL-6R) and gp130 receptor (sgp130) were measured using surface plasmon resonance analysis. Unexpectedly, natural sIL-6R and natural sgp130 were found to interact (Kd = 2.8 nM) in the absence of IL-6. No interaction was seen between the recombinant soluble receptors or between either natural soluble receptor and its recombinant partner. This binary complex was not due to copurification of IL-6 and was detected in human plasma of healthy donors. It results from either direct interaction between the two natural soluble receptors or indirect binding mediated by a yet unidentified copurified plasma molecule playing the role of an IL-6 antagonist. Once formed, the binary complex was found to be unable to bind IL-6. Soluble gp130 had already been shown to inhibit IL-6 signaling by inactivating the IL-6/IL-6R complex. In addition we show that, in the absence of IL-6, circulating natural sgp130 is able to inhibit directly the circulating sIL-6R that is a strong synergic molecule of IL-6 signaling.

Dimerization and activation of the common transducing chain (gp130) of the cytokines of the IL-6 family by mAb

The objective of our research was to study the mechanisms of activation of mAb against the gp130 transducer chain common to the IL-6 cytokine family. It has been found that among the 56 anti-gp130 available worldwide, none was able to activate the growth of IL-6-dependent myeloma cell lines. When certain of them were associated in pairs they allowed the cells to grow; alone, they were inhibitory. The same activation was also obtained by cross-linking certain anti-gp130 mAb on the cell membrane with a goat anti-mouse Ig antiserum. A bispecific mAb was prepared by the somatic fusion of two hybridomas secreting two mAb whose association was able to activate gp130 signaling; the bispecific mAb was inactive. The activating mAb were able to support long-term proliferation of the IL-6-dependent myeloma cell lines, which indicates that they are potential valuable growth factors of tumor cells and hematopoietic stem cells. When they were injected into SCID mice, they allowed human IL-6-dependent myeloma cell lines to grow, develop tumors and metastasize. By studying the functional epitopes of the cell membrane gp130 receptors, it was shown that the activating mAb induced gp130 dimerization and STAT3 activation, as did IL-6.

Functional interaction of the gp80 and gp130 IL-6 receptors in human B cell malignancies

IL-6, or cytokines of the IL-6 family using gp130 as transducer chain receptor, have been suggested to play a role in certain B lymphoid neoplasia. The presence of cell membrane gp80 and gp130 IL-6 receptors was studied in 98 patients with various leukaemia and non-Hodgkin's malignant lymphoma using flow cytofluorometry and immunohistology. Except neoplasia of immature B cells which expressed neither of the receptors, the majority of B cell tumours expressed one or both of them, mantle cell lymphoma being found to express the highest density of receptors. Using IL-6-dependent XG myeloma cell lines and mAb recognizing various gp80 and gp130 functional epitopes, it has been shown that IL-6 activation leads to a modified expression of some epitopes. In particular, the decrease or the disappearance of a gp130 epitope called A1 signed gp130 dimerization which is the first step of the gp130 activation pathway. Gp80 and gp130 epitope analysis was achieved in 17 of the patients. In four, an epitope phenotype compatible with a cytokine-induced activation was found. The cells of five B-CLL patients which expressed both gp80 and gp130 receptors were incubated with IL-6 to induce activation. In three of the cases they were found to rearrange their receptors in activated forms but not in the two others, showing that cells able to be activated or not can be found. These results confirm that gp130 signalling might play an important role in the pathogenesis of certain B cell neoplasia.

IFN-alpha is a survival factor for human myeloma cells and reduces dexamethasone-induced apoptosis

IFN-alpha is used as a maintenance therapy in patients with multiple myeloma, but its benefit is a matter of controversy. In vitro studies show that IFN-alpha can both stimulate and inhibit myeloma cell proliferation. We have tested the effect of IFN-alpha on the survival of myeloma cell lines and primary plasma cells. IFN-alpha significantly reduced the apoptosis induced by removal of IL-6 in four IL-6-dependent myeloma cell lines. It also reduced the level of apoptosis induced by dexamethasone in these cell lines as well as in purified primary myeloma cells from seven patients. IFN-alpha promoted the survival of myeloma cells, which, following removal of IL-6, were blocked in G1 and died. However, unlike IL-6, IFN-alpha-treated cells remained mainly blocked in the G1 phase of the cycle. While the effects of IL-6 are mediated through stimulation of its gp130 receptor subunit, the IFN-alpha-induced survival of myeloma cells was independent of gp130 transducer activation (as demonstrated using a neutralizing anti-gp130 Ab). However, the signal transduction cascades activated by these two cytokines share at least some common elements, since stimulation with either IFN-alpha or IL-6 resulted in STAT3 phosphorylation. These results indicate that IFN-alpha promotes the survival, but not the proliferation, of myeloma cells, preventing the apoptosis induced by removal of IL-6 or addition of dexamethasone. This survival factor activity may explain the conflicting reports on the effects of IFN-alpha on myeloma cell proliferation.

A gp130 interleukin-6 transducer-dependent SCID model of human multiple myeloma

Agonist antihuman gp130 transducer monoclonal antibodies (MoAbs) were used in SCID mice to grow myeloma cells whose survival and proliferation is dependent on gp130 transducer activation. The agonist anti-gp130 MoAbs neither bound to murine gp130 nor activated murine cells and, as a consequence, did not induce interleukin-6 (IL-6)-related toxicities in mice. They have a 2-week half-life in vivo when injected in the peritoneum. The agonist antibodies made possible the in vivo growth of exogenous IL-6-dependent human myeloma cells as well as that of freshly explanted myeloma cells from 1 patient with secondary plasma cell leukemia. Tumors occurred 4 to 10 weeks after myeloma cell graft and weighed 3 to 5 g. They grew as solid tumors in the peritoneal cavity and metastasized to the different peritoneal organs: liver, pancreas, spleen, and intestine. Tumoral cells were detected in blood and bone marrow of mice grafted with the XG-2 myeloma cells. Tumoral cells grown in SCID mice had kept the phenotypic characteristics of the original tumoral cells and their in vitro growth required the presence of IL-6 or agonist anti-gp130 MoAbs. Myeloma cells from 4 patients with medullary involvement persisted for more than 1 year as judged by detectable circulating human Ig. However, no tumors were detected, suggesting a long-term survival of human myeloma cells without major proliferation. These observations paralleled those made in in vitro cultures as well as the tumor growth pattern in these patients. This gp130 transducer-dependent SCID model of multiple myeloma should be useful to study various therapeutical approaches in multiple myeloma in vivo.

The myeloma cell antigen syndecan-1 is lost by apoptotic myeloma cells

Syndecan-1 is a cell membrane proteoglycan that binds extracellular matrix components and various growth factors. It is expressed only on malignant plasma cells in bone marrow samples from patients with multiple myeloma (MM). Several reports have suggested that syndecan-1 was present only on a part of the myeloma cells. By using either IL-6-dependent myeloma cell lines or primary myeloma cells stained by annexin V, we report here that syndecan-1 was rapidly lost by myeloma cells undergoing apoptosis. In the same experimental conditions, expression of other cell membrane antigens such as CD38, HLA class-I or CD49d on apoptotic myeloma cells was not affected. In addition, we show that syndecan-1 loss was independent of activation of the gp130 IL-6 transducer. Dexamethasone induced a strong apoptosis of myeloma cells associated with the loss of syndecan-1. Finally, by using freshly-explanted tumoural samples, we show that syndecan-1 rapidly disappeared from myeloma cells in association with induction of apoptosis. In conclusion we showed that syndecan-1 is a marker for viable myeloma cells which is rapidly lost by apoptotic cells. These results emphasize the usefulness of anti-syndecan-1 antibodies to purge tumoural cells from haemopoietic grafts or to purify these cells for further manipulations for immuno or gene therapies.

Major role of the soluble interleukin-6/interleukin-6 receptor complex for the proliferation of interleukin-6-dependent human myeloma cell lines

Interleukin-6 (IL-6) is a proinflammatory cytokine which possesses a central growth factor activity for certain tumor cells such as plasma cells in multiple myeloma (MM). Upon binding of IL-6, soluble IL-6 receptor (sIL-6R) has been shown to retain its affinity for IL-6 and to associate with the signal-transducing gp130 chain. Therefore, contrary to the majority of soluble cytokine receptors, it plays an agonist role in IL-6 signaling. In order to test its physiological importance as compared to that of its membrane counterpart, we studied cells from two myeloma cell lines which need exogenous IL-6 to proliferate and release sIL-6R into their culture supernatant. Using a new culture system where the supernatant recirculated permanently through an anti-IL-6R affinity column, all sIL-6R was removed from the culture medium throughout the culture period. Under these conditions IL-6-dependent cells were unable to grow in the presence of physiological concentrations of IL-6, showing the major role of the sIL-6R for sustaining the proliferation of these cell lines. Increasing IL-6 concentrations well over the physiological values allowed the cells to proliferate again. No effect was seen when sIL-6R was removed from the supernatant of an IL-6-independent myeloma cell line. These results show that the levels of circulating sIL-6R (and thus those of IL-6/sIL-6R complex) are worth looking at in pathologies involving IL-6 hyperactivity.

Expression of the interleukin 6 receptor in primary renal cell carcinoma

AIMS

Interleukin 6 (IL-6) is expressed in the majority of renal cell carcinomas and has an important role in the proliferation of some renal cell carcinoma cell lines. This action is mediated by two membrane proteins, gp80 (the IL-6 receptor; IL-6R), which binds IL-6, and gp130, which transduces the signal. The soluble form of gp80 (sIL-6R) is able to activate gp130 when complexed to the IL-6 molecule. These considerations prompted an investigation of IL-6R expression in this malignancy. IL-6, C reactive protein (CRP), and sIL-6R were also measured in serum and correlated to clinical and pathological features.

METHODS

Immunostaining was performed on cryostat sections from renal cell carcinoma tumours with M91, an anti-IL-6R monoclonal antibody, using the alkaline phosphatase antialkaline phosphatase technique. The proliferation index was measured using the KI-67 monoclonal antibody. CRP, IL-6, and sIL-6R were measured in serum before nephrectomy, using an immunoenzymatic or immunoradiometric assay.

RESULTS

There were significant differences in survival in patients with tumours larger than 8 cm, metastasis at diagnosis, high nuclear grade tumours, detectable serum concentrations of IL-6 (correlated to CRP serum concentration), more than 4% proliferating cells, and the presence of the IL-6R in situ. Furthermore, the serum IL-6 concentration correlated with tumour size and stage. The mean serum sIL-6R concentration was not significantly different from that observed in 40 normal subjects. Tumour IL-6R expression was present in 10 samples. There was a significant association between the presence of the IL-6 receptor in tumours and tumour stage, nuclear grade, proliferation index, and serum IL-6.

CONCLUSIONS

This study revealed the importance of IL-6/CRP and IL-6R expression in situ as potential new prognostic factors and opens the way to new therapeutic strategies in renal cell carcinoma.

Specific inhibition of IL-6 signalling with monoclonal antibodies against the gp130 receptor

A family of cytokines [IL-6, IL-11, oncostatin M (OM), leukaemia inhibitory factor (LIF), ciliary neurotrophic factor (CNTF) and cardiotrophin-1] involved in various inflammatory or tumoral diseases share the same gp130 signal transducer chain. The complex formed with their specific receptors associates with a common transducing gp130 membrane protein (gp130) resulting in the formation of high avidity receptor and activation of tyrosine kinases. With the view of identifying gp130 domains specifically involved in IL-6 signalling, the authors prepared 37 new anti-gp130 mAb and analysed the structure-function relationship of the molecule. By cross-competition ELISA, the mAb were classified in 10 subgroups called A to J. By ELISA and BIAcore analysis, the mAb were found to recognize at least 18 antigenic specificities of the gp130 chain. The mAb reacted against the soluble and the membrane forms of gp130 as well. Their ability to inhibit the proliferation of the human myeloma cell line XG-4 of which the growth is strictly dependent on the presence of either exogenous IL-6, or LIF, or OM, or CNTF was studied. Besides mAb with no evident neutralizing effect (G and H) and mAb which neutralized equally well the activity of all tested cytokines (all mAb of groups A, I and J), some showed a selective effect. Those of group F inhibited also the proliferation induced by the 4 cytokines, but more specifically that dependent on the CNTF. mAb of groups B and E specifically inhibited the growth induced by IL-6, whereas those of group C inhibited that induced by LIF and OM. These results show the presence of different gp130 epitopes specifically involved in the signaling induced by the cytokines of the gp130 family. In ELISA, only mAb of group B and E were found to inhibit the binding of the IL-6-IL-6R complex to gp130, showing that they identified one or two domains of gp130 involved in its interaction with the IL-6-IL-6R complex. Precise identification of this(ese) epitope(s) would be useful to better understand the mechanisms of the IL-6 signalling.

Activation of the gp130 signaling pathway by monoclonal antibodies directed against the gp130 molecule

Six cytokines of the interleukin (IL)-6 family involved in various inflammatory or tumoral diseases share the same gp130 signal transducer chain. We made a panel of anti-gp130 monoclonal antibodies (mAb) to study the structure and function of the gp130 molecule. These mAb recognized different epitopes of the gp130 that we called A to J. Most of the mAb were found to be inhibitors and we studied whether some of them could also induce gp130 activation. When used alone, none of them was able to initiate the proliferation of IL-6-dependent cell lines. However, some particular associations of the mAb were able to induce a proliferative response. mAb B1 could activate the lines in association with F1 or with I2 but not with I1, which in ELISA was similar to I2. In contrast mAb B2, which in ELISA appeared to be very similar to B1, was able to activate the cells in association with I1 but not with F1 or I2. Two other mAb belonging to specificities A and C were found to be activators either in association with I1 only, or with I1 or B2, respectively. These associations of mAb appeared to be nearly as potent activators as IL-6 itself. Although we still have no precise idea of the mechanisms involved, they are interesting tools to study the molecular interactions leading to gp130 activation and, from a practical point of view, valuable growth factors of hematopoietic stem cells.

Identification of a novel antigenic structure of the human receptor for interleukin-6 involved in the interaction with the glycoprotein 130 chain

The receptor for interleukin-6 (IL-6) is characterized by a ligand-binding glycoprotein 80 (gp80) transmembrane chain (IL-6R) which associates with a signal-transducer gp130 chain. We previously raised a series of monoclonal antibodies (mAb) recognizing different epitopes of the human IL-6R and interfering with the function of the receptor. One of them, M182, was able to diminish the proliferation of IL-6-dependent plasmacytoma cell lines although it was found unable to inhibit the binding of IL-6 to its receptor. Using an enzyme-linked immunosorbent assay for measuring the binding of IL-6 IL-6R to the gp130 chain, we showed that M182 was directed against a structure directly involved in the IL-6R gp130 interaction. M182 was able to potentiate the inhibitor effect of anti-IL-6R mAB which interfere with the binding of IL-6, leading to complete inhibition of the proliferation of IL-6-dependent cell lines. M182 was also found to synergize with inhibitory anti-IL-6 mAb. Therefore this structure appears to be an important regulatory domain of the IL-6R and a valuable target for inhibiting IL-6 signalling.

Detection of membrane and soluble interleukin-6 receptor in lymphoid malignancies

We studied the membrane expression of the gp80 chain of IL-6 receptor (IL-6R) by quantitative flow cytometry in chronic lymphocytic leukaemia (CLL) and leukaemic centrocytic lymphoma using a panel of seven monoclonal antibodies. IL-6R was detected in 18/26 CLL cases and 4/7 lymphoma cases, with a mean antigen density < 3000 molecules/cell. Multiple labelling experiments confirmed the IL-6R expression by neoplastic cells. Specific mRNA was found by RT-PCR in neoplastic cells. A specific ELISA test was designed using two anti-IL-6 receptor MAbs to measure the serum soluble IL-6R (sIL-6R) in CLL (n = 48). B-cell non-Hodgkin's lymphoma (NHL; n = 40), and monoclonal gammopathy (MG; n = 32). SIL-6R was higher in CLL (170 +/- 12.6 ng/ml) in NHL (160 +/- 12 ng/ml) and MG patients (183 +/- 23 ng/ml) than in age-matched controls (100 +/- 5.6 ng/ml; P < 0.001) and higher in high-grade than low-grade NHL. No correlation was noted with a previous treatment. Among CLL cases the patients classified as stage B according to the Binet's staging of the disease had the highest sIL-6R values, thus suggesting a link with tumour cell mass.

Effect of anti-ulcer drugs on DNA synthesis in adult normal human hepatocytes in culture

The aim of this work was to investigate the effect of four H2 receptor antagonist, cimetidine, ranitidine, famotidine, nizatidine, and of two proton pump inhibitors, omeprazole and lansoprazole, on the mitotic response of human hepatocytes in primary culture. After plating at subconfluent density, cells were exposed to 0.2 to 20 mumol/L of these drugs for 48 hours, either in the absence or in the presence of epidermal growth factor (EGF). The rate of DNA synthesis was evaluated by [3H]-thymidine incorporation into genomic DNA. Both the basal rate of DNA synthesis and the extent of stimulation by EGF exhibited a wide interindividual variability, and were not correlated with the viability of freshly prepared cells. In contrast, the effects of anti-ulcer drugs on the rate of DNA synthesis were clearly reproducible from one culture to another. H2 receptor antagonists had no significant effect (P > .2) over the entire range of concentration tested, whereas omeprazole and lansoprazole significantly inhibited the rate of DNA synthesis by 60% to 90% at 30 mumol/L (P = .016). This effect was concentration dependent between 2 and 20 mumol/L. Neither of the drugs tested was cytotoxic under the conditions used in this work, as assessed by measurements of the do nov protein synthesis. We conclude that, in contrast to H2 receptor antagonists, omeprazole and lansoprazole are able to interfere with the replicative synthesis of DNA in human hepatocytes in culture, at suprapharmacological concentrations. Whether or not this effect is clinically significant remains to be established.

Immunomodulating IL-6 activity by murine monoclonal antibodies

The human anti-mouse immunoglobulin antibody (HAMA) response, which occurs frequently after injection of murine monoclonal antibodies (MAb) directed against cellular targets, has been reported extensively in several studies. We analysed here HAMA in 12 patients (six with multiple myeloma, MM, and six with metastatic renal cell carcinoma, MRCC) who were treated with B-E8, an IgG1 MAb against interleukin-6 (IL-6). Efficiency of the treatment was evidenced by the drop in the serum levels of C reactive protein (CRP), of which the in vivo production is under the control of IL-6. Three patients with MM and the six patients with MRCC became immunized to the injected MAb. HAMA appeared between days 7 and 15 after the beginning of the treatment. The nine patients made IgG antibodies; four also made IgM. All of immunized patients made anti-idiotype antibodies specific to B-E8. Two of them also developed HAMA directed to murine IgG1 isotype; in these two patients B-E8 MAb cleared rapidly from the circulation with loss of treatment efficiency. In the patients who developed only anti-idiotype antibodies, serum levels of B-E8 remained unchanged and CRP production remained inhibited, indicating that treatment efficiency was not affected by the presence of HAMA. Circulating B-E8 MAb were still able to bind to IL-6 and to inhibit IL-6-independent proliferation despite the presence of anti-idiotypic HAMA. Therefore, in contrast to HAMA against MAb directed against cellular targets, HAMA against anti-IL-6 MAb idiotopes led neither to clearance nor to functional inactivation of the injected MAb.(ABSTRACT TRUNCATED AT 250 WORDS)

IL-6-induced changes in synthesis of alpha 1-acid glycoprotein in human hepatoma Hep3B cells are distinctively regulated by monoclonal antibodies directed against different epitopes of IL-6 receptor (gp80)

The synthesis of the human acute-phase alpha 1-acid glycoprotein (AGP) is primarily controlled by IL-6 and IL-1 in liver cells. In the present study, monoclonal antibodies against human gp80 interleukin-6 receptor (IL-6R) were utilized to study the role of the IL-6R in the control of the IL-6-induced AGP synthesis in the human hepatoma Hep3B cell line. Two of the 4 MAbs used in this study, M164 and M195, identified 2 different epitopes involved in IL-6 binding and two others, M91 and M182, recognized epitopes not involved in IL-6 binding. Dose-response experiments indicated that up to 55% of AGP synthesis was inhibited by 10(5) ng/ml of MAbs 164 or 195 when Hep3B cells were treated by IL-6 for 48h. Kinetics of the inhibition of AGP synthesis after addition of anti-IL-6R indicated that the decrease of the IL-6-induced AGP synthesis by Hep3B cells was obtained immediately after the addition of the anti-IL-6R MAbs. Of the two MAbs not involved in IL-6 binding, M91 was unable to interfere with the IL-6-induced AGP synthesis whereas, surprisingly, M182 decreased it by about 25%. Since M182 was also able to interfere with the proliferative response of an IL-6 dependent plasma cell line, our results suggested that M182 may be directed to a structure involved in the IL-6/IL-6R gp130 complex formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Human anti-mouse antibody response to the injection of murine monoclonal antibodies against IL-6

We analysed human anti-mouse antibodies (HAMA) in 12 patients (six with multiple myeloma (MM) and six with metastatic renal cell carcinoma (MRCC) who were treated with B-E8, an IgG1 MoAb against IL-6. Efficiency of the treatment was evidenced by the drop in the serum levels of C-reactive protein (CRP), the in vivo production of which is under the control of IL-6. Three patients with MM and the six patients with MRCC became immunized to the injected MoAb. HAMA appeared between days 7 and 15 after the beginning of the treatment. The nine patients made IgG antibodies; four also made IgM. All immunized patients made anti-idiotype antibodies specific to B-E8. Two of them also developed HAMA directed to murine IgG1 isotype; in these two patients B-E8 MoAb cleared rapidly from the circulation with loss of treatment efficiency. In the patients who developed only anti-idiotype antibodies, serum levels of B-E8 remained unchanged and CRP production remained inhibited, indicating that treatment remained efficient in the presence of HAMA. Circulating B-E8 MoAbs were still able to bind to IL-6 and to inhibit IL-6-dependent proliferation despite the presence of anti-idiotypic HAMA. Therefore, in contrast to HAMA produced against MoAb directed against cellular targets, HAMA against anti-IL-6 MoAb idiotopes led neither to clearance nor to functional inactivation of the injected MoAb. This was further shown by resuming the B-E8 treatment with success in a patient who still had anti-idiotypic HAMA.

Epitope analysis of human IL-6 receptor gp80 molecule with monoclonal antibodies

Gp80 human IL-6R was studied using 7 murine mAb (M37, M91, M113, M139, M164, M182 and M195) obtained after fusion of splenocytes of Balb/c mice immunised with a mixture of recombinant IL-6 receptor (rIL-6R) and cells from 2 cell lines expressing IL-6R. These were U266, which is IL-6 independent and XG-1 which is IL-6-dependent. In ELISA the 7 mAb reacted against the rIL-6R and against the natural soluble form found in plasma (nIL-6R), which both lack transmembrane and cytoplasmic domains. However, M195 reacted less with the natural than with the recombinant soluble IL-6R. Using FACS analysis, the 7 mAb were shown to bind to U266 cells but not to the Namalva cell line which is deprived of IL-6R. This showed that they all recognised the membrane form of the IL-6R. Three of the anti-IL-6R mAb reacted with rIL-6R by Western blotting. Four different epitopes of the molecule were identified, either by cross-blocking experiments of mAb binding to IL6R in ELISA or by the biosensor Biacore technology. A group of 4 mAb (M37, M113, M139 and M164) and another mAb (M195) identified 2 different epitopes involved in IL-6 binding. These antibodies were able to inhibit the binding of IL-6 to IL-6R and the proliferation of the IL-6-dependent XG-1 cell line. M91 and M182 recognized 2 other epitopes that were not involved in IL-6 binding. As expected, M91 did not inhibit XG-1 proliferation; in contrast, M182 interfered with the proliferative response of the XG-1 cell line.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunoassay for functional human soluble interleukin-6 receptor in plasma based on ligand/receptor interactions

Soluble forms of most cytokine receptors, able to bind effectively to their respective ligands, have now been described. A soluble interleukin-6-binding molecule derived from the gp80 component of the multichain IL-6 receptor can be detected in biological fluids, and can act as an agonist of IL-6 activity. The clinical significance of the soluble receptor levels still remains to be explored. We took advantage of the characterization of an anti-IL-6 monoclonal antibody and of an anti-IL-6R monoclonal antibody that both bound to IL-6/IL-6R complexes to design an immunometric assay for the measurement of soluble IL-6R complexed to IL-6. This reaction scheme was designated as ELIA (enzyme-ligand immunoassay). When exogeneous IL-6 was added in excess to an sIL-6R containing sample, all sIL-6R was present in a complexed form. Thus, the reaction scheme could also be used to determine total sIL-6R concentrations. A recombinant sIL-6R standard was prepared from the supernatant of murine thymoma cells transfected with a gene coding for an extracellular portion of the IL-6 receptor. The assay permitted the precise and reproducible measurement of sIL-6R in serum or plasma. This approach is of general relevance for the determination of soluble cytokine receptors in biological fluids, provided that adequate anti-cytokine and anti-receptor antibodies are available.

Murine anti-interleukin-6 monoclonal antibody therapy for a patient with plasma cell leukemia

A patient with primary plasma cell leukemia resistant to chemotherapy was treated for 2 months with daily intravenous injections of anti-interleukin-6 (IL-6) monoclonal antibodies (MoAbs). The patient's clinical status improved throughout the treatment and no major side effects were observed. Serial monitoring showed blockage of the myeloma cell proliferation in the bone marrow (from 4.5% to 0% myeloma cells in the S-phase in vivo) as well as reduction in the serum calcium, serum monoclonal IgG, and the serum C-reactive protein levels. The serum calcium and serum monoclonal IgG corrected by approximately 30%, whereas the C-reactive protein corrected to undetectable levels during treatment. No major side effects developed, although both platelet and circulating neutrophil counts decreased during anti-IL-6 therapy. A transient immunization was detected 15 days after the initiation of the treatment, which could explain the recovery of myeloma cell proliferation after 2 months of treatment (2% myeloma cells in the S phase). In conclusion, this first anti-IL-6 clinical trial demonstrated the feasibility of injecting anti-IL-6 MoAbs, and also a transient tumor cytostasis and a reduction in IL-6-related toxicities. It gave insight into the major biologic activities of IL-6 in vivo and may serve as a basis for further development of anti-IL-6 therapy in myeloma and other IL-6-related diseases.

Encapsulation of drugs into large unilamellar liposomes prepared by an extemporaneous method

The method we developed for extemporaneous preparation of large unilamellar liposomes (Philippot et al. 1984) was applied to the encapsulation of 12 different antibiotic, anti-asthmatic and anti-inflammatory drugs. The behaviour of these drugs, during encapsulation, assigns them to one of the three classes: hydrophilic, hydrophobic or both. Alone, the first type of compound gave an appreciable encapsulation. However, the entrapment yield depended on the respective charges of the liposome and the drug. The amphiphile molecules tested are permeant and thus did not stay inside the liposomes. Only one of the hydrophobic drugs analysed associated with the liposome membrane lipids with a good yield.

Purification of synthetic oligonucleotides on a weak ion-exchange column

A weak ion-exchange column (PVDI 4000-5) was used to purify oligonucleotides of relatively large size. The purification of polynucleotides was very rapid, they were separated according to size and retained all their properties relevant to genetic engineering experiments.

Analysis of double-stranded poly(A).poly(U) molecules by reversed-phase high-performance liquid chromatography

The behaviour of different batches of synthetic Poly(A).Poly(U) in reversed-phase high-performance liquid chromatography (HPLC) was studied. They consist of large molecules mainly in the form of a double strand. Differences in the elution patterns were correlated with properties detected by conventional methods such as electrophoresis, centrifugation, fusion analysis or enzymatic digestions. Under the present conditions, contamination by products and precursors used during synthesis was detectable, but was absent in most of the preparations. The differences in elution patterns between batches appear to be correlated with the size of the molecules synthesized. The chromatograms suggested that Poly(A).Poly(U) molecules contain single-strand portions at least transiently. The presence of such portions was confirmed by enzymatic digestion with S1 nuclease. The rapidity, reproducibility and ease of reversed-phase HPLC qualify this technique as a tool for routine analysis.

Isolation of biologically active polysomal messenger ribonucleoprotein by centrifugation in cesium sulfate

The ribosomal fraction from HeLa cells treated at elevated temperature was centrifuged in Cs2SO4. 1. The bulk of the RNA labeled in the presence of a low dose of actinomycin D banded at p = 1.36 g/cm3. 2. This fraction contained heterogeneous RNA and proteins with molecular weights close to those of proteins found in polysomal messenger ribonucleoproteins. 3. This ribonucleoprotein bound ribosomes in conditions were deproteinized RNA did not. 4. The binding was inhibited by aurintricarboxylic acid, ethylene diamine tetraacetic acid and sodium deoxycholate, but not by Triton X-100.

[On the protein composition of ribonucleoprotein particles before and after fertilization fo sea urchin eggs (Echinus esculentus)]

Experiments indicate that eggs and embryos of the North Sea sea urchin Echinus esculentus are excellent material to investigate the regulation of protein synthesis before and after fertilization. The dormant egg contains several proteins which are absent from embryos. Such additional proteins have been detected on the small ribosomal subunits, in the salt wash of whole ribosomes, and associated with cytoplasmic messenger ribonucleoprotein particles.