Neuregulin-1 modulates the differentiation of neural stem cells in vitro through an interaction with the Swi/Snf complex.

The neuregulin-1 (Nrg-1) gene is translated into several protein isoforms, which are either secreted or membrane-anchored. In vitro, neural stem cells (NSC) express mainly the cystein-rich-domain NRG (CRD-NRG) isoform, a membrane-anchored type III form. This isoform exhibits a cystein-rich-domain, which constitutes a second transmembrane domain and can be cleaved to release both a signaling EGF-containing domain (ECD) at the cell surface and an intracellular domain (ICD). The main goal of this paper was to determine the exact role of ECD and ICD in NSC survival and differentiation. Using an siRNA approach, we demonstrated that CRD-NRG inhibition was followed by a decrease in NSC proliferation and of neuronal or oligodendroglial differentiation. Overexpression of ICD but not ECD was followed by a decrease in NSC proliferation and an increase in neuronal and oligodendroglial differentiation. Moreover, we showed that ICD physically interacted in cultured NSC with BRM and BAF57, two members of the Swi/Snf remodeling complex, and that ICD stimulation of neuronal cell differentiation is dependent on the presence of BAF57.

Comparison of conjugation procedures for the preparation of monoclonal antibody-enzyme conjugates.

Four monoclonal antibodies belonging to different subclasses and with differing isoelectric points were coupled to horseradish peroxidase (HRP) and alkaline phosphatase (AP) using various conjugation procedures. The conjugates were tested by enzyme immunoassay and their efficiency was characterized by the antibody and enzyme concentrations needed to obtain an arbitrary OD value. The suitability of antibody for conjugation through NH2 groups was tested by fluorodinitrobenzene (FDNB). HRP conjugates were produced by two variants of the sodium periodate procedure and two variants of the glutaraldehyde method, as well as by the heterobifunctional linker N-succinimidyl 3-(2-pyridyldithio)propionate (SPDP). Two of the four antibodies were coupled by a third variant of the periodate method, through their carbohydrate moieties. The periodate-mediated conjugations, using sugar moieties on the enzyme, provided the most efficient HRP conjugates, regardless of the antibody subclass or isoelectric point. The glutaraldehyde procedures consistently gave the worst results. AP conjugates were prepared using the same methods. The most efficient and reproducible AP conjugates with all four monoclonal antibodies were obtained using the SPDP procedure. The efficiency of the other methods differed from one antibody to another.

Flow cytometric method for the detection of gpI antigens of varicella zoster virus and evaluation of anti-VZV agents.

Varicella zoster virus (VZV) is responsible for a primary infection (varicella) and, upon reactivation, zoster, which in immunocompromised patients, may both lead to life-threatening disseminated disease. There is a great need for antiviral compounds that are effective inhibitors of VZV replication and for rapid and accurate methods for evaluating viral sensitivity to candidate anti-VZV drugs. With the monoclonal antibody (mAb) (VL8), which is directed against the gpI of VZV, and using the fluorescence-activated cell sorter (FACS) we could readily demonstrate expression of the VZV gpI antigen at 3-4 days after VZV infection. (E)-5-(2-Bromovinyl)-2'-deoxyuridine (BVDU), (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA) and (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMC) were shown to be potent inhibitors of VZV replication by this assay. HPMPA and HPMPC were also active against thymidine kinase-deficient (TK-) VZV whereas BVDU was not. The flow cytometric method based on the use of mAb VL8 may be of considerable help for the early diagnosis of VZV infection and evaluation of viral sensitivity to antiviral drugs.

Protective effects of polyclonal sera and of monoclonal antibodies active to Salmonella minnesota Re595 lipopolysaccharide during experimental endotoxemia.

Mice were passively immunized with sera from blood donors active for rough lipopolysaccharides (LPS), the J5 (Rc chemotype) mutant of Escherichia coli O111:B4, and the Re595 (Re chemotype) mutant of Salmonella minnesota. All protected the mice against lethal challenge with smooth E. coli WF96 LPS, E. coli and Salmonella rough mutant LPS, or free lipid A. Epitopes recognized by monoclonal antibodies (MAbs) reacting with the LPS of S. minnesota Re595 or lipid A were localized in the 2-keto-3-deoxy-D-manno-octulosonic acid (KDO) region and on lipid A. Core-reactive MAbs reacted with their homologous Re LPS and with free lipid A. One, GL11, cross-reacted with the KDO alone. MAbs GL6, GL11, L.4, L.6, and L.8 protected the actinomycin D-sensitized mice against the lethal effects of LPS from E. coli WF96, Salmonella enteritidis, E. coli J5, S. minnesota Re595, and free lipid A. The GL11 antibody was also protective when injected after LPS challenge. These results indicate that antibodies directed against the core glycolipid of S. minnesota Re595 LPS may be useful as an additive form of therapy that may enable decreased mortality during gram-negative bacterial sepsis.

Preparation of reproducible alkaline phosphatase-antibody conjugates for enzyme immunoassay using a heterobifunctional linking agent.

Conjugates of alkaline phosphatase (AP) and mouse monoclonal immunoglobulins G (IgG) were prepared by means of the heterobifunctional linker, N-succinimidyl 3-(2-pyridyldithio)-propionate. The efficiency of such conjugates can be improved by optimizing the degree of substitution of IgG and AP. We have determined conditions yielding better performing conjugates than those synthesized by methods described previously. Moreover, the results obtained with the technique presented here are quite reproducible with all four monoclonal antibodies tested.

Monoclonal antibodies detect M-protein epitopes on the surface of influenza virions.

Various data obtained with activable hydrophobic probes, proteolytic treatments and anti M-protein polyclonal antibodies strongly suggest that M-protein of influenza A is an integral part of the lipid bilayer of native virions and somehow spans at the surface of the virions. Therefore we have looked for the presence of M-protein epitopes on the surface of influenza A virion by using four type A M-protein monoclonal antibodies. We developed a specific and sensitive competition ELISA where intact virions, dodecyl-sulfate disrupted virions and spikeless particles obtained after proteolytic treatment with caseinase C were used to test their ability to inhibit the reaction between these monoclonal antibodies and pure M-protein. Intact virions or SDS disrupted virions prevented three monoclonal antibodies from reacting with the M-protein. Spikeless particles also inhibited the specific binding of two of these antibodies, whereas the other fourth antibody was inhibited by contact with SDS disrupted particles only. Data presented show that at least three distinct M-protein epitopes were detected, of which at least two are exposed on the surface of intact virions. Of these two epitopes, one is inactivated by the proteolytic treatment. The third epitope could only react with its monoclonal antibody when the virus particles were solubilized with SDS. This work provides a clear demonstration that a substantial part of the M-protein spans the lipid bilayer and that the rest, protected by lipids, resists proteolytic enzymes and is prevented from binding with anti M-protein monoclonal antibodies.

Study of the protective effects of hyperimmune immunoglobulins G and M against endotoxin in mice and rats.

We prepared solutions of human IgM and IgG to various lipopolysaccharide (LPS) species. These were then tested, along with solutions of non-LPS specific human IgG or IgM, for their ability to confer passive immunity against experimental endotoxemia in two animal models. The immunoglobulins were first tested for an effect on the lethality induced by seven different LPSs in actinomycin-D sensitized mice, or by three different bacteria in normal mice. When the immunoglobulins were administered 1 h before challenge, a small protective effect was observed. This protection was dependent upon both the anti-LPS agent, the chemical composition of the LPS, or the strain of gram-negative bacteria used for injection. The anti-LPS IgM and IgG preparations reduced the mortality induced by Escherichia coli but not by Serratia marcescens or Klebsiella pneumoniae, indicating protection by strain-specific antibodies. When the antibodies were preincubated with LPS or bacteria for 30 min before administration, almost complete protection was seen. The influence of these immunoglobulin preparations or of human albumin (as a control) on the hypotensive and vascular-permeabilizing effects of LPS in rats was then studied. A dose-dependent inhibitory effect was observed with IgG preparations and albumin. At 200 mg/kg, anti-LPS IgG reduced the effects of LPS, while at 400 mg/kg, both anti-LPS and normal IgG preparations showed protection, as did human albumin used at the same dose. The IgM-enriched preparation worsened the initial hypotensive phase after LPS, whereas the anti-LPS IgM significantly reduced the second phase of the hypotension, but only at the largest dose of 400 mg/kg. In this second model using the rat, a clear difference between the activity of IgG and IgM was thus observed. We conclude that pretreatment with human immunoglobulins from large plasma pools modestly, but significantly, attenuated the effects of murine and rat Gram-negative sepsis, but that protection was incomplete. Our results suggest that single regimen intervention strategies may not be sufficient to influence the course of the disease.