The phosphoinositide pathway of lymphoid cells: labeling after permeabilization by alveolysin, a bacterial sulfhydryl-activated cytolysin.

An improved method allowing incorporation of [3H]myo-inositol into the phosphoinositide pool of human lymphoid cells is described. The procedure devised involves cell permeabilization with a thiol-activated membranolytic toxin, alveolysin, and optimization of the phosphoinositide labeling and extraction. In these conditions 4 to 10% of the added [3H]myo-inositol is found intracellularly and half of this amount (2-5%) is incorporated into the phosphoinositide pool in only 1 h as compared to the classical 0.2 to 0.3% incorporation obtained after 10 to 20 h. The integrity of coupling between receptors and phospholipase C was assessed by the inositol phosphate production after cell stimulation by various agonists.

Decreased whole blood 5-hydroxytryptamine (serotonin) in AIDS patients.

Significantly (p less than 0.001) decreased whole blood unconjugated serotonin levels were detected in AIDS patients as compared to patients with advanced cancers and to healthy individuals.

Development of a quantitative assay for residual host cell proteins in a recombinant subunit vaccine against human respiratory syncytial virus.

We have developed and validated a process-specific immunoligand assay based on the Threshold system for the quantification of residual host cell proteins (HCPs) in a recombinant subunit vaccine candidate against the human respiratory syncytial virus (hRSV). The industrial process of this vaccine produced in Escherichia coli, involved five chromatography steps for the production of clinical-grade batches. The clearance of non-product-related protein throughout the purification process was documented by the evaluation of the HCP content in the chromatographic fractions at each step of the downstream processing. The assay had a detection limit of 0.5 ng/ml of HCP equivalent to 10 parts per million (ppm). The quantification limit was 1.3 ng/ml of HCP, giving a sensitivity range of the assay of 10 to 30 ppm. To our knowledge, this is the first sensitive HCP assay reported for a vaccine.

Synthesis and characterization of respiratory syncytial virus protein G related peptides containing two disulphide bridges.

Respiratory Syncytial Virus (RSV) is the most important cause of bronchiolitis and viral pneumoniae in infants and young children. Approximately 100,000 children are hospitalized in the USA each year as a result of RSV infections. During the research and development of subunit human RSV vaccines, we have produced numerous synthetic peptides and recombinant proteins containing the four cysteines of the highly conserved central region of the G attachment protein. For several of these disulphide bridges containing peptides, all possible oxidizing isomers were synthesized using various oxidising conditions, resulting in different ratios of isomers. Each isolated isomer was fully characterized by RP-HPLC, FZCE and ES-MS after purification by preparative RP-HPLC. The different cysteine pairings were unambiguously established after enzymatic digestion, LC-MS analysis and peptide microsequencing. These synthetic and analytical methods were developed for the characterization of recombinant fusion protein BBG2Na which is currently investigated in clinical phase II and seems to be as a very promising vaccine candidate, and for peptides which were synthesized to be evaluated as conjugate vaccines or as immunochemical tools, after covalent coupling to carrier proteins. Furthermore, these studies allowed us to determine which of the different possible isomers was the most stable and probably the preferred form in native conditions. Finally, the different oxidising and analysis conditions, should be useful for disulphide pairing studies of other peptides and proteins having the same "xCxxCxxxxxCxxxCx" framework, such as G proteins of non-human RSV strains, developed for example as veterinary vaccine candidates.

Adenovirus-mediated gene transfer of pathogen-associated molecular patterns for cancer immunotherapy.

The delivery of stimulatory signals to dendritic cells (DCs) in the tumor microenvironment could be an effective means to break tumor-induced tolerance. The work presented here evaluates the immunostimulatory properties of pathogen-associated molecular patterns (PAMPs), microbial molecules which bind Toll-like receptors and deliver activating signals to immune cells, when expressed in tumor cells using adenoviral (Ad) vectors. In vitro, transduction of A549 tumor cells with Ad vectors expressing either flagellin from Listeria monocytogenes or P40 protein from Klebsiella pneumoniae induced the maturation of human monocyte-derived DCs in co-cultures. In mixed lymphocyte reactions (MLRs), Ad-flagellin and Ad-P40 transduction of tumor cells stimulated lymphocyte proliferation and the secretion of IFN-gamma. In vivo, these vectors were used either as stand-alone immunoadjuvants injected intratumorally or as vaccine adjuvants combined with a tumor antigen-expressing vector. When Ad-PAMPs were administered intratumorally to mice bearing subcutaneous syngeneic B16F0-CAR (cocksackie-adenovirus receptor) melanomas, tumor progression was transiently inhibited by Ad-P40. In a therapeutic vaccine setting, the combination of Ad-MUC1 and Ad-PAMP vectors injected subcutaneously delayed the growth of implanted RenCa-MUC1 tumors and improved tumor rejection when compared with vaccination with Ad-MUC1 alone. These results suggest that Ad-PAMPs could be effective immunoadjuvants for cancer immunotherapy.

Development of novel protein scaffolds as alternatives to whole antibodies for imaging and therapy: status on discovery research and clinical validation.

Recent advances in combinatorial protein engineering have made it possible to develop antibody-based and non-Ig protein scaffolds that can potentially substitute for most whole antibody-associated properties. In theory, many different natural human protein backbones are suitable to be used as recombinant templates for engineering : antibody-derived scaffolds, carrier proteins that display a single binding interface, backbones that provide a rigid core structure suitable for grafting loops or protein scaffolds allowing the incorporation of variable loops in a favorable 3D configuration. In practice however, only a few have yielded the necessary properties to be translated into 'druggable Biologicals'. Amongst these properties, potential broad specificities towards any kind of target, ease of production, small size, good tolerability and low immunogenicity are essential and will be discussed in this review. Intellectual property is another key issue for the development of these protein scaffolds; although circumventing antibody-associated patents is often a major if not primary goal, clear advantages compared to whole antibodies must be presented to translate scaffold discovery into successful therapeutic drug candidates. In this review, a particular emphasis will be given to the most validated scaffolds that have reached the clinical development phase. Although the question of their immunogenicity is still open, preliminary clinical data do not point to any particular adverse immunogenic reactions although these are highly dependent on dosage, administration route and therapeutic indication. Finally, some of the emerging Biotechs developing protein scaffolds have been associated during the last two years with successful acquisitions by Big Pharmas and we will speak on the perspective positions of these proteins within the global Biologicals market.

Selective induction of autocytotoxic activity through the CD3 molecule.

In the present study we show that when certain major histocompatibility complex-alloreactive CD8+ T cell clones with natural killer-like activity are stimulated through their CD3 molecules, in the absence of significant cross-linkage (as provided by Fab' fragments of OKT3 antibodies) they lose their interleukin 2 response. This is attributable to an induction of a nonspecific autocytolytic activity. These results suggest that activation of this process in some cytotoxic cells leads to an overall decrease in CTL activity and constitutes a possible mechanism of suppression of the immune response.

Bradykinin induces actin reorganization and enhances cell motility in HaCaT keratinocytes.

In HaCaT keratinocytes bradykinin-triggered actin reorganization was inhibited by quinacrine, a phospholipase A2 inhibitor, and restored by addition of arachidonic acid. Bradykinin-induced actin breakdown and cortical actin formation were respectively prevented by indomethacin, a cyclooxygenase inhibitor, and nordihydroguaiaretic acid, a lipoxygenase inhibitor. Addition of prostaglandins or leukotrienes, respectively, reversed the effects of inhibitors. This suggested a crucial role for a cyclooxygenase product in actin depolymerization and for a lipoxygenase product in cortical actin formation. Furthermore, we found that bradykinin stimulated HaCaT keratinocyte migration. This event was blocked by quinacrine, indomethacin or nordihydroguaiaretic acid, and restored by addition of prostaglandins or leukotrienes, respectively. We also showed that genistein, a tyrosine kinase inhibitor, inhibited HaCaT cell locomotion. In conclusion, bradykinin modulated actin reorganization and cell motility in keratinocytes, probably by a mechanism involving arachidonic acid metabolites and a tyrosine kinase activity.

Bradykinin induces tyrosine phosphorylation of epidermal growth factor-receptor and focal adhesion proteins in human keratinocytes.

Bradykinin is an inflammatory mediator which activates signalling pathways in human keratinocytes via a receptor linked to a GTP-binding protein. In the HaCaT human keratinocyte cell line, we observed bradykinin-stimulated tyrosine phosphorylation of several cellular proteins with peak response at 15 min. The focal adhesion proteins paxillin and p125FAK were tyrosine phosphorylated in response to bradykinin but not in response to epidermal growth factor. Interestingly, we identified the epidermal growth factor receptor as a novel target for bradykinin-induced tyrosine phosphorylation. The tyrosine kinase inhibitor genistein and the protein kinase C inhibitors staurosporine and Ro31-7549, all blocked bradykinin-induced tyrosine phosphorylation. Our data suggest that stimulation of the bradykinin receptor leads to activation of a tyrosine kinase activity via a protein-kinase-C-dependent pathway in human keratinocytes.

Proliferation of resting lymphocytes is induced by triggering T cells through an epitope common to the three CD18/CD11 leukocyte adhesion molecules.

LFA-1, Mac-1, and p150,95 are a family of functionally important leucocyte integrins that share a common beta-subunit and participate in cellular adhesion. Monoclonal antibody to LFA-1 were described to block T-cell-mediated killing by inhibiting adhesion to target cells and to decrease T cell responses by preventing cell-cell contact. Recently it was demonstrated that LFA-1 molecule was involved in signal transduction. We report here that a monoclonal antibody termed 6.7 reacting with the three members of the leucocyte integrins is able in the presence of monocytes to directly induce the proliferation of resting peripheral blood T cells obtained from normal individuals. These results suggest the possibility that LFA-1 molecules could trigger T lymphocyte activation in addition to their role in homing, growth, and differentiation.

Activation of the CD3/T cell receptor (TcR) complex or of protein kinase C potentiate adenylyl cyclase stimulation in a tumoral T cell line: involvement of two distinct intracellular pathways.

A monoclonal antibody (OKT3) directed against the T cell receptor (TcR)/CD3 molecular complex, as well as a protein kinase C (PKC) activator (phorbol 12-myristate 13-acetate, PMA) were added to a culture of tumoral Jurkat T cells, in order to precise the sequence of intracellular signals leading to T cell activation. The experiments were performed in the presence or in absence of various stimulators of adenylate cyclase (AC) such as forskolin (FK), cholera toxin (CT) or prostaglandin E2 (PGE2). OKT3 increased inositol phosphate (IP) production; in parallel, it induced a slight accumulation of cAMP. The effect was markedly potentiated in presence of FK or CT, and to a lesser extent in the presence of PGE2. FK stimulated adenylate cyclase of Jurkat cell membranes, but the effect was not potentiated by OKT3, suggesting that potentiation of cAMP accumulation requires intact cells and is not mediated by direct receptor coupling. On the other hand, elevated cAMP accumulation induced a negative feedback on IP production. The effect of OKT3 on cAMP was mimicked by A23187, a Ca2+ ionophore, and abolished in the absence of extracellular Ca2+. PMA had the same effect as OKT3 on basal or FK- and CT-induced accumulation of cAMP. In contrast, it inhibited the PGE2 effect on the cyclic nucleotide. After desensitization of PKC by pretreatment with a high concentration of PMA, the phorbol ester was no longer effective. Under those conditions, facilitation by OKT3 of FK-induced accumulation of cAMP was preserved, whereas potentiation by the monoclonal antibody of the PGE2 stimulation of AC was even enhanced. The data indicate that cAMP accumulation indirectly elicited by phospholipase C activation is, at least partly, mediated by IP-dependent Ca2+ mobilization, while PKC is preferentially effective as an inhibitor of PGE2 stimulation.

Characterization of Fc epsilonRI expressing human monocytic cell lines. 1. The role of CD45 on signal transduction in primary monocytes and cell lines.

BACKGROUND: Recently, the high affinity receptor for IgE (Fc epsilonRI), which plays a major role in allergies, has been identified on a number of different antigen-presenting cell types, including human monocytes from atopic and nonatopic donors. In this report human monocytic cell lines were used to test for the expression of Fc epsilonRI, reasoning that a monocytic cell line expressing Fc epsilonRI constitutively would be a useful tool for large scale studies on the regulation of IgE binding and signal transduction. METHODS: Reverse transduction polymerase chain reaction was applied to identify Fc epsilonRI alpha-chain message, flow cytometry to detect Fc epsilonRI surface expression and signal transduction on the cell lines generated by transfection. RESULTS: We report the establishment of monocytic cell lines constitutively expressing Fc epsilonRI (THP1-alpha01 to THP1-alpha40) generated by transfection of the cell line THP1 with a plasmid encoding the Fc epsilonRI alpha-chain only. Fc epsilonRI on the THP1-alpha lines specifically binds IgE and is functional with regard to ligand binding and signal transduction. Comparative studies between the transfectants and primary human monocytes from nonatopic donors demonstrated the regulatory role of the tyrosine phosphatase CD45 on Fc epsilonRI-mediated cell activation. CONCLUSIONS: Monocytic cell lines carry Fc epsilonRI alpha-chain RNA and enhancement by transfection results in surface Fc epsilonRI expression on THP1. Triggering the receptor on the THP1-alpha lines or on human monocytes, which express native Fc epsilonRI, elicits a rapid and transient calcium mobilization, prevented by co-cross-linking of Fc epsilonRI and CD45.

Modulation of Fc gamma receptor-mediated early events by the tyrosine phosphatase CD45 in primary human monocytes. Consequences for interleukin-6 production.

Stimulation of primary human monocytes from several donors by cross-linking of Fc gamma receptor type I (Fc gamma RI) and Fc gamma RII gave rise to calcium mobilization and protein tyrosine phosphorylation. These early events were not observed without cross-linking. CD45, a transmembrane tyrosine phosphatase, when co-cross-linked with either Fc gamma RI or Fc gamma RII, could prevent Fc gamma RI and Fc gamma RII-mediated calcium mobilization and protein tyrosine phosphorylation. When interleukin (IL)-6 production was measured, we noted a strong IL-6 production after activation of primary human monocytes by cross-linking of Fc gamma RI or Fc gamma RII. In contrast to calcium mobilization and tyrosine phosphorylation of proteins, IL-6 production was not affected by co-cross-linking of CD45 with either Fc gamma RI or Fc gamma RII. Interestingly, cross-linking of the CD45 itself was sufficient to induce IL-6 production. Our results show that the CD45 molecule is important in modulating early events following stimulation of primary human monocytes by cross-linking of Fc gamma RI or Fc gamma RII. However, triggering of CD45 alone can also induce IL-6 production, indicating that CD45 ligation itself can give signals and may have an important role in cytokine induction pathways.

Antigen presentation in allergic sensitization.

IgE antibodies, when cross-linked by allergen on the surface of effector cells such as mast cells and basophils, are known to be directly responsible for immediate type hypersensitivity reactions. In addition, IgE may be involved in other, indirect, mechanisms, fundamental to the pathogenesis of allergic diseases, such as enhancement of the antigen capturing capacity of antigen presenting cells. IgE mediated antigen presentation could lead to a continuous activation of the immune system by very low concentrations of allergen. As a result, Th2 cell populations may expand and may induce more B cells to switch to IgE production. Subsequently, the overproduction of IgE and Th2 cells in a patient may explain the clinical observation that certain allergic patients deteriorate from sensitivity to a single group of allergens to sensitivity to multiple groups of allergens. Therefore, control of IgE production is not only important for the treatment of allergic symptoms, but may also regulate deterioration of allergy via the mechanism of CD23/IgE mediated allergen presentation by naive B cells. The role that monocytes, which have recently been found to express Fc epsilon RI, play in the pathogenesis of allergy, remains speculative. We hypothesize that their role may be to remove IgE from the circulation and re-direct the immune response from naive B cells. IgG antibodies which cannot be used for antigen uptake by B cells also direct the immune response to monocytes.

Synthesis, refolding and protective immune responses of a potential antigen for human Respiratory Syncytial Virus vaccine.

The design of new antigens with both high immunogenic and safety properties is of particular interest to vaccine against infectious diseases. In the present study, we describe the synthesis and the refolding of peptide G20 derived from the Human Respiratory Syncytial Virus (hRSV) G-protein. G20 (MEF G140-190 G144-158) is a peptide of 69 amino acids with two disulfide bridges, which comprises multiple protective B-cell epitopes. It was deleted of the T helper cell epitope 184-198 of the RSV G-protein, which was found to induce pulmonary pathology after RSV challenge in mice. Interestingly, we showed in the present study that G20 generated a highly protective antibody response against RSV challenge in Balb/c mice. Therefore, G20 represents a new potential antigen for an RSV vaccine.

Challenge of BALB/c mice with respiratory syncytial virus does not enhance the Th2 pathway induced after immunization with a recombinant G fusion protein, BBG2NA, in aluminum hydroxide.

The polypeptide of aa 130-230 of the G protein (G2Na) of respiratory syncytial virus (RSV) was fused to BB, the albumin-binding region of streptococcal G protein, producing BBG2Na, which induced protective immune responses in rodent models. Evaluation of the immune response in mice immunized with BBG2Na in the adjuvant alhydrogel revealed high amounts of interleukin (IL)-5 and some IL-4 in splenocytes restimulated in vitro. This is compatible with a Th2 response. The activation of the Th2 pathway in such mice was further supported by the detection of IL-5 and G2Na-specific IgE in vivo. Of interest, in contrast to immunization with formalin-inactivated RSV, immunization of mice with BBG2Na followed by intranasal RSV challenge did not lead to increased production of IL-5- or G2Na-specific IgE. However, IgG1- and IgG2a-specific antibodies were boosted. These results demonstrate that the Th2 pathway is not enhanced by RSV challenge in BBG2Na-immunized mice.

Serotonin and human immunodeficiency viruses.

This preliminary study shows, for the first time to our knowledge, decreased whole blood serotonin levels in AIDS patients as compared to healthy controls and cancer patients. The lowest serotonin levels were found in AIDS patients with neuropsychiatric symptoms. Finally the present data suggest an inverse relationship between serotonin level and AIDS severity.

Function and regulation of Fc epsilon RI expression on monocytes from non-atopic donors.

BACKGROUND: The high affinity receptor for IgE (Fc epsilon RI) has recently been identified on antigen presenting cells, i.e. Langerhans cells and monocytes from atopic donors and it was hypothesized that Fc epsilon RI expression levels correlated with allergy. OBJECTIVE: The aims of the study was to investigate the function and expression of Fc epsilon RI on monocytes from non-atopic donors. METHODS: Purified monocytes or peripheral blood mononuclear cells were used to study Fc epsilon RI expression and signal transduction on CD14 positive cells by flow cytometry and/or confocal laser microscopy. RESULTS: Freshly isolated monocytes from healthy individuals (n = 58) were shown to express Fc epsilon RI (median 18%, range 2-66%). No IgE was bound to these receptors in vivo, and in vitro no significant binding of complete IgE molecules could be obtained. IgE positive monocytes from atopic donors were also found to have free Fc epsilon RI incapable of binding IgE in vitro. On all CD14 positive cells free Fc epsilon RI expression was rapidly and completely lost during culture in conventional culture media (IMDM, RPMI) but not in phosphate buffered saline (PBS). Moreover, signal transduction through free Fc epsilon RI appeared to be inhibited. However, both IgE binding and calcium mobilization were restored by treatment of fresh non-atopic monocytes with neuraminidase. Importantly, culturing these monocytes overnight in conventional medium containing 2 micrograms/mL IgE induced a cycloheximide insensitive accumulation of IgE bound to Fc epsilon RI and, in addition, led to cell activation. CONCLUSION: Monocytes from both atopic donors and healthy individuals express Fc epsilon RI, but the previously reported different expression levels between the two groups seem to be directly related to the absence or presence of IgE in the serum. This may be due to the fact that Fc epsilon RI is subjected to a constant turnover process which is slowed down but not prevented by ligand binding. In addition, free Fc epsilon RI on non-atopic monocytes are under control of a neuramindase sensitive structure(s), which influences signal transduction and IgE binding.

The serum albumin-binding region of streptococcal protein G (BB) potentiates the immunogenicity of the G130-230 RSV-A protein.

BBG2Na is a protein comprising residues 130-230 of the respiratory syncytial virus subgroup A (RSV-A) G protein (G2Na) fused to the albumin-binding domain of streptococcal G protein (BB). BBG2Na was cloned, expressed in Escherichia coli and renaturated. In rodent models, this subunit RSV vaccine adjuvanted in Alhydrogel induced specific antibodies and conferred protection to RSV infection. Comparison of the antibody production in a BALB/c mouse model revealed that BBG2Na induced a stronger and earlier G2Na antibody response than G2Na alone, without altering the IgG subclass distribution. To address the role of the BB part, we explored its carrier properties and showed that it is a Th dependent antigen, generating a more potent G2Na-specific B cell memory response and able to generate Th cells that provide help for G2Na antibody production.