Tetanus and tetanus neurotoxin: From peripheral uptake to central nervous tissue targets.

Tetanus is a deadly but preventable disease caused by a protein neurotoxin produced by Clostridium tetani. Spores of C. tetani may contaminate a necrotic wound and germinate into a vegetative bacterium that releases a toxin, termed tetanus neurotoxin (TeNT). TeNT enters the general circulation, binds to peripheral motor neurons and sensory neurons, and is transported retroaxonally to the spinal cord. It then enters inhibitory interneurons and blocks the release of glycine or GABA causing a spastic paralysis. This review attempts to correlate the metalloprotease activity of TeNT and its trafficking and localization into the vertebrate body to the nature and sequence of appearance of the symptoms of tetanus.

Novel fusion proteins for the antigen-specific staining and elimination of B cell receptor-positive cell populations demonstrated by a tetanus toxoid fragment C (TTC) model antigen.

BACKGROUND: In an earlier study we developed a unique strategy allowing us to specifically eliminate antigen-specific murine B cells via their distinct B cell receptors using a new class of fusion proteins. In the present work we elaborated our idea to demonstrate the feasibility of specifically addressing and eliminating human memory B cells. RESULTS: The present study reveals efficient adaptation of the general approach to selectively target and eradicate human memory B cells. In order to demonstrate the feasibility we engineered a fusion protein following the principle of recombinant immunotoxins by combining a model antigen (tetanus toxoid fragment C, TTC) for B cell receptor targeting and a truncated version of Pseudomonas aeruginosa exotoxin A (ETA') to induce apoptosis after cellular uptake. The TTC-ETA' fusion protein not only selectively bound to a TTC-reactive murine B cell hybridoma cell line in vitro but also to freshly isolated human memory B cells from immunized donors ex vivo. Specific toxicity was confirmed on an antigen-specific population of human CD27(+) memory B cells. CONCLUSIONS: This protein engineering strategy can be used as a generalized platform approach for the construction of therapeutic fusion proteins with disease-relevant antigens as B cell receptor-binding domains, offering a promising approach for the specific depletion of autoreactive B-lymphocytes in B cell-driven autoimmune diseases.

The majority of human memory B cells recognizing RhD and tetanus resides in IgM+ B cells.

B cell memory to T cell-dependent (TD) Ags are considered to largely reside in class-switched CD27(+) cells. However, we previously observed that anti-RhD (D) Igs cloned from two donors, hyperimmunized with D(+) erythrocytes, were predominantly of the IgM isotype. We therefore analyzed in this study the phenotype and frequency of D- and tetanus toxoid-specific B cells by culturing B cells in limiting dilution upon irradiated CD40L-expressing EL4.B5 cells and testing the culture supernatant. Most Ag-specific B cells for both TD Ags were found to reside in the IgM-expressing B cells, including CD27(-) B cells, in both hyperimmunized donors and nonhyperimmunized volunteers. Only shortly after immunization a sharp increase in Ag-specific CD27(+)IgG(+) B cells was observed. Next, B cells were enriched with D(+) erythrocyte ghosts and sorted as single cells. Sequencing of IGHV, IGLV, IGKV, and BCL6 genes from these D-specific B cell clones demonstrated that both CD27(-)IgM(+) and CD27(+)IgM(+) B cells harbored somatic mutations, documenting their Ag-selected nature. Furthermore, sequencing revealed a clonal relationship between the CD27(-)IgM(+), CD27(+)IgM(+), and CD27(+)IgG(+) B cell subsets. These data strongly support the recently described multiple layers of memory B cells to TD Ags in mice, where IgM(+) B cells represent a memory reservoir which can re-enter the germinal center and ensure replenishment of class-switched memory CD27(+) B cells from Ag-experienced precursors.

Enhanced immunogenicity of a tricomponent mannan tetanus toxoid conjugate vaccine targeted to dendritic cells via Dectin-1 by incorporating ß-glucan.

In a previous attempt to generate a protective vaccine against Candida albicans, a ß-mannan tetanus toxoid conjugate showed poor immunogenicity in mice. To improve the specific activation toward the fungal pathogen, we aimed to target Dectin-1, a pattern-recognition receptor expressed on monocytes, macrophages, and dendritic cells. Laminarin, a ß-glucan ligand of Dectin-1, was incorporated into the original ß-mannan tetanus toxoid conjugate providing a tricomponent conjugate vaccine. A macrophage cell line expressing Dectin-1 was employed to show binding and activation of Dectin-1 signal transduction pathway by the ß-glucan-containing vaccine. Ligand binding to Dectin-1 resulted in the following: 1) activation of Src family kinases and Syk revealed by their recruitment and phosphorylation in the vicinity of bound conjugate and 2) translocation of NF-κB to the nucleus. Treatment of immature bone marrow-derived dendritic cells (BMDCs) with tricomponent or control vaccine confirmed that the ß-glucan-containing vaccine exerted its enhanced activity by virtue of dendritic cell targeting and uptake. Immature primary cells stimulated by the tricomponent vaccine, but not the ß-mannan tetanus toxoid vaccine, showed activation of BMDCs. Moreover, treated BMDCs secreted increased levels of several cytokines, including TGF-ß and IL-6, which are known activators of Th17 cells. Immunization of mice with the novel type of vaccine resulted in improved immune response manifested by high titers of Ab recognizing C. albicans ß-mannan Ag. Vaccine containing laminarin also affected distribution of IgG subclasses, showing that vaccine targeting to Dectin-1 receptor can benefit from augmentation and immunomodulation of the immune response.

A fully synthetic glycopeptide antitumor vaccine based on multiple antigen presentation on a hyperbranched polymer.

For antitumor vaccines both the selected tumor-associated antigen, as well as the mode of its presentation, affect the immune response. According to the principle of multiple antigen presentation, a tumor-associated MUC1 glycopeptide combined with the immunostimulating T-cell epitope P2 from tetanus toxoid was coupled to a multi-functionalized hyperbranched polyglycerol by "click chemistry". This globular polymeric carrier has a flexible dendrimer-like structure, which allows optimal antigen presentation to the immune system. The resulting fully synthetic vaccine induced strong immune responses in mice and IgG antibodies recognizing human breast-cancer cells.

Results of an international transferability study of the BINACLE (binding and cleavage) assay for in vitro detection of tetanus toxicity.

Tetanus vaccines contain detoxified tetanus neurotoxin. In order to check for residual toxicity, the detoxified material (toxoid) has to be tested in guinea pigs. These tests are time-consuming and raise animal welfare issues. In line with the "3R" principles of replacing, reducing and refining animal tests, the "binding and cleavage" (BINACLE) assay for detection of active tetanus neurotoxin has been developed as a potential alternative to toxicity testing in animals. This in vitro test system can discriminate well between toxic and detoxified toxin molecules based on their receptor-binding and proteolytic characteristics. Here we describe an international study to assess the transferability of the BINACLE assay. We show that all participating laboratories were able to successfully perform the assay. Generally, assay variability was within an acceptable range. A toxin concentration-dependent increase of assay signals was observed in all tests. Furthermore, participants were able to detect low tetanus neurotoxin concentrations close to the estimated in vivo detection limit. In conclusion, the data from this study indicate that the methodology of the BINACLE assay seems to be robust, reproducible and easily transferable between laboratories. These findings substantiate our notion that the method can be suitable for the routine testing of tetanus toxoids.

Ex vivo characterization and isolation of rare memory B cells with antigen tetramers.

Studying human antigen-specific memory B cells has been challenging because of low frequencies in peripheral blood, slow proliferation, and lack of antibody secretion. Therefore, most studies have relied on conversion of memory B cells into antibody-secreting cells by in vitro culture. To facilitate direct ex vivo isolation, we generated fluorescent antigen tetramers for characterization of memory B cells by using tetanus toxoid as a model antigen. Brightly labeled memory B cells were identified even 4 years after last immunization, despite low frequencies ranging from 0.01% to 0.11% of class-switched memory B cells. A direct comparison of monomeric to tetrameric antigen labeling demonstrated that a substantial fraction of the B-cell repertoire can be missed when monomeric antigens are used. The specificity of the method was confirmed by antibody reconstruction from single-cell sorted tetramer(+) B cells with single-cell RT-PCR of the B-cell receptor. All antibodies bound to tetanus antigen with high affinity, ranging from 0.23 to 2.2 nM. Furthermore, sequence analysis identified related memory B cell and plasmablast clones isolated more than a year apart. Therefore, antigen tetramers enable specific and sensitive ex vivo characterization of rare memory B cells as well as the production of fully human antibodies.

Human plasmacytoid dendritic cells phagocytose, process, and present exogenous particulate antigen.

Plasmacytoid dendritic cells (pDCs) play a major role in shaping both innate and adaptive immune responses, mainly via their production of large amounts of type I IFNs. pDCs are considered to primarily present endogenous Ags and are thought not to participate in the uptake and presentation of Ags from the extracellular environment, in contrast to their myeloid counterparts, which efficiently endocytose extracellular particulates. In this study, we show that human pDCs are able to phagocytose and process particulate forms of Ag entrapped in poly(lactic-coglycolic acid) microparticles. Furthermore, pDCs were also able to sense TLR ligands (TLR-Ls) incorporated in these particles, resulting in rapid pDC activation and high IFN-alpha secretion. Combining a tetanus toxoid peptide and TLR-Ls (CpG C and R848) in these microparticles resulted in efficient pDC activation and concomitant Ag-specific T cell stimulation. Moreover, particulate Ag was phagocytosed and presented more efficiently than soluble Ag, indicating that microparticles can be exploited to facilitate efficient delivery of antigenic cargo and immunostimulatory molecules to pDCs. Together, our results show that in addition to their potency to stimulate innate immunity, pDCs can polarize adaptive immune responses against exogenous particulate Ag. These results may have important consequences for the development of new immunotherapeutic strategies exploiting Ag and TLR-Ls encapsulated in microparticles to target APC subsets.

Immunogenicity of Haemophilus influenzae type b conjugate vaccines in Korean infants: a meta-analysis.

A meta-analysis was performed on the immunogenicity of Haemophilus influenzae type b (Hib) conjugate vaccines after 2 (2 and 4 months) and 3 doses (2, 4, and 6 months) in Korean infants. A database search of MEDLINE, KoreaMed, and Korean Medical Database was done. The primary outcome measure was the proportion of infants with anti-polyribosylribitol phosphate (PRP) concentrations > or =1.0 microg/mL. Eight studies including eleven trials were retrieved. One trial reported on the diphtheria toxoid conjugate vaccine (PRP-D) and 2 trials each on the mutant diphtheria toxin (PRP-CRM) and Neisseria meningitidis outer-membrane protein (PRP-OMP) conjugate vaccine. Heterogeneity in study designs between trials on PRP-CRM was noted and one trial reported on a monovalent and another on a combination PRP-OMP vaccine. Thus, a meta-analysis was conducted only on the tetanus toxoid conjugate vaccine (PRP-T). After a primary series of 2 doses and 3 doses, 80.6% (95% confidence interval [CI]; 76.0-85.1%) and 95.7% (95% CI; 94.0-98.0%) of infants achieved an antibody level > or =1.0 microg/mL, respectively. The immunogenic response to the PRP-T vaccine was acceptable after a primary series of 3 doses and also 2 doses. A reduced number of doses as a primary series could be carefully considered in Korean infants.

Epitope-directed processing of specific antigen by B lymphocytes.

Proteolytic processing of specific antigen was studied using Epstein Barr virus transformed B-lymphoblastoid cells expressing membrane IgG against tetanus toxin. As previously reported (Watts, C., and H.W. Davidson. 1988. EMBO (Eur. Mol. Biol. Organ.) J. 7:1937-1945), receptor-mediated endocytosis of monovalent antigen bound at 0 degrees C began immediately upon shifting the cells to 37 degrees C. In contrast, degradation of antigen, assessed either by the release of acid-soluble radiolabel into the incubation medium, or by SDS-PAGE analysis of total cell-associated antigen, proceeded after a lag of 10-20 min. Degradation was abolished by exposure of the cells to metabolic inhibitors, or by incubation at 20 degrees C, and inhibited in a dose-dependent fashion by chloroquine and by the lysosomal protease inhibitors leupeptin, E-64, and pepstatin A. Analysis of the cell-associated radiolabel by SDS-PAGE and autoradiography after incubations at 37 degrees C revealed the time-dependent generation of distinct antigen fragments. Virtually quantitative immunoprecipitation of these fragments was obtained using a monoclonal anti-human IgG antibody, indicating that the antigen/mIg complex is the initial substrate for processing. We show that the pattern of fragmentation observed varies from one B cell line to another (a) depending on the epitope through which the antigen is bound and endocytosed and (b) depending on whether additional epitopes in the antigen are complexed with anti-tetanus Fabs. The implications of these results for the presentation of major histocompatibility complex restricted antigen fragments, and for intracellular trafficking of ligand/receptor complexes are discussed.

High-level Expression of Tetanus Toxin Fragment C in Escherichia coli.

Fragment C is the C-terminal domain of the heavy chain of tetanus toxin that can promote the immune response against the lethal dose of this toxin. Therefore, this portion can be considered as a candidate vaccine against tetanus infection, which occurs by Clostridium tetani. The present study aimed to compare the expression of tetanus toxin fragment C in Escherichia coli BL21 (DE3) pLysS cells having a high tolerance to toxins between two different expression vectors, namely pET22b and pET28a, using the sodium dodecyl sulfate polyacrylamide gel electrophoresis and western blot analyses. After DNA extraction from Harvard CN49205 strain of C. tetani, the gene of interest was amplified using polymerase chain reaction, and then sequenced and cloned into the expression vectors of pET22b and pET28a, transformed into competent BL21 (DE3) pLysS cells, and finally expressed using an optimized protocol. The cells were induced with isopropyl β-D-1-thiogalactopyranoside (IPTG) at four different incubation temperatures (i.e., 37, 33, 30, and 25 °C) and three different incubation times (i.e., 1, 2, and 3 h). Although the SDS-PAGE and western blot analyses confirmed the expression of the recombinant fragment C (r-fragment C) ligated into both of the expression vectors, pET28a showed a higher r-fragment C expression level than the other vector (38.66 mg/L versus 32.33 mg/L, P<0.05). An optimal expression condition was acquired 3 h after 1 mM IPTG induction at 25 °C. The results demonstrated that E. coli BL21 (DE3) pLysS as an expression host in combination with pET-28a as an expression vector was a more compatible expression system to express the fragment C of tetanus toxin, compared to E. coli BL21 (DE3) pLysS/pET-22b expression system. Overall, these results may represent an opportunity to improve the expression system for the production of tetanus toxin vaccine using recombinant protein strategy.

Cyclic OmpC peptidic epitope conjugated to tetanus toxoid as a potential vaccine candidate against shigellosis.

In earlier works we have described that mice immunized with outer membrane protein OmpC survive the challenge with live Shigella flexnerii 3a. We have also identified conformational epitope of this protein, that was recognized by mice antibodies. The aim of current work was to investigate whether synthetic OmpC epitope homologs can elicit immunological response sufficient in protecting mice against shigellosis. Several linear peptides containing RYDERY motif were synthesized and conjugated to poly-lysine. These conjugates appeared to be poor immunogens and to boost the immunological response an addition of the adjuvant (MPL) was required. Unfortunately, the MPL alone caused a very high immunological reaction that was masking response to peptidic epitope. Under those circumstances we used tetanus toxoid (TT) as the carrier protein for the peptides and the agent stimulating immunological response. Series of cyclic peptides, homologs of the OmpC main epitope were synthesized and conjugated to TT. The loop size in cyclic peptides varied by number of glycine residues, i.e., 1-3 residues added to the GLNRYDERYIGK motif. The linear GLNRYDERYIGC-TT was also prepared as the control. The latter conjugate gave the highest immunological response, followed by the cyclic-GGLNRYDERYIGC-TT and cyclic-GLNRYDERYIGC-TT. The third peptide, cyclic-GGGLNRYDERYIGC-TT, gave a very low response, although it was the most resistant to proteolysis. However, antibodies obtained against cyclic-GGLNRYDERYIGC-TT were more potent to recognize both OmpC and Shigella flexnerii 3a cells than the antibodies against linear GLNRYDERYIGC-TT. Furthermore, the monoclonal antibodies raised against linear GLNRYDERYIGC-TT showed 20-fold lower dissociation constant (KD) than the naturally occurring polyclonal antibodies from umbilical cord sera. Monoclonal antibodies also gave a weaker signal in electron microscope than mice and human polyclonal antibodies. In overall, our results point to cyclic peptides as better candidates for a vaccine development, since they are eliciting production of the higher affinity antibodies against Shigella cells and OmpC.

Identification and characterization of subpopulations of lymphocytes in human peripheral blood after fractionation on discontinuous gradients of albumin. The cellular defect in X-linked agammaglobulinemia.

Normal human peripheral blood lymphocytes were separated on discontinuous gradients of 17-35% bovine serum albumin (BSA) into nine fractions. Three subpopulations of lymphocytes were obtained. One occupies the top third of the gradient (fractions 1-3, 17-23% BSA) and is rich in cells characterized by a high spontaneous rate of DNA synthesis and by the ability to give rise to colony-forming units. The middle portion of the gradient (fractions 4 and 5, 23-27% BSA) is rich in thymus-derived (T) lymphocytes identified by their vigorous response to mitogens and by their ability to form rosettes with sheep erythrocytes (E). The third subpopulation at the bottom of the gradient (fractions 6-9, 27-35% BSA) is rich in bone marrow-derived (B) lymphocytes capable of staining with fluorescent antiimmunoglobulin antisera and of forming rosettes with EAC1423. The peripheral blood lymphocytes of five boys with proved X-linked agammaglobulinemia and two with probable X-linked agammaglobulinemia were found to be totally deficient in B lymphocytes (fractions 6-9) and lacked the subpopulation identified by immunofluorescent staining or rosette formation with EAC1423. One boy with proved X-linked agammaglobulinemia and two with probable X-linked agammaglobulinemia possessed a normal amount of circulating B lymphocytes.

Conjugation of PEG-hexadecane markedly increases the immunogenicity of pneumococcal polysaccharide conjugate vaccine.

Streptococcus pneumoniae is a serious Gram-positive pathogen that can lead to an invasive pneumococcal disease with high mortality rate. Pneumococcal capsular polysaccharide (PS) is a key virulence determinant and its immunogenicity can be increased by conjugation with a carrier protein. However, the PS-specific cellular and humoral immunity of pneumococcal conjugate vaccine needs further improvement. Hexadecane (HD) is an element of lipid that decorates the surface of nearly all microbial classes. Polyethylene glycol (PEG)-HD conjugate (PEG-HD) is soluble and can act as an adjuvant. In the present study, a novel pneumococcal polysaccharide conjugate vaccine was prepared by conjugation of tetanus toxoid (TT) portion of PS-TT conjugate (PS-TT) with PEG-HD. As compared with PS-TT, conjugation with PEG-HD led to an 8.0-fold increase in the PS-specific IgG titers. Conjugation with PEG-HD also gave rise to 34.9-, 3.6- and 7.7-fold increase in the IFN-γ, TNF-α and IL-5 levels, respectively. Thus, the conjugated PEG-HD has a stimulatory adjuvant activity to potentiate a robust humoral and cellular immunity. Our proposed conjugate was expected to act as an effective pneumococcal conjugate vaccine for prevention of S. pneumoniae infections.

Generation of an artificial human B cell line test system using Transpo-mAbTM technology to evaluate the therapeutic efficacy of novel antigen-specific fusion proteins.

The antigen-specific targeting of autoreactive B cells via their unique B cell receptors (BCRs) is a novel and promising alternative to the systemic suppression of humoral immunity. We generated and characterized cytolytic fusion proteins based on an existing immunotoxin comprising tetanus toxoid fragment C (TTC) as the targeting component and the modified Pseudomonas aeruginosa exotoxin A (ETA') as the cytotoxic component. The immunotoxin was reconfigured to replace ETA' with either the granzyme B mutant R201K or MAPTau as human effector domains. The novel cytolytic fusion proteins were characterized with a recombinant human lymphocytic cell line developed using Transpo-mAb™ technology. Genes encoding a chimeric TTC-reactive immunoglobulin G were successfully integrated into the genome of the precursor B cell line REH so that the cells could present TTC-reactive BCRs on their surface. These cells were used to investigate the specific cytotoxicity of GrB(R201K)-TTC and TTC-MAPTau, revealing that the serpin proteinase inhibitor 9-resistant granzyme B R201K mutant induced apoptosis specifically in the lymphocytic cell line. Our data confirm that antigen-based fusion proteins containing granzyme B (R201K) are suitable candidates for the depletion of autoreactive B cells.

Synthesis and characterization of Pseudomonas aeruginosa alginate-tetanus toxoid conjugate.

Chronic infection with Pseudomonas aeruginosa is the main proven perpetrator of lung function decline and ultimate mortality in cystic fibrosis (CF) patients. Mucoid strains of this bacterium elaborate mucoid exopolysaccharide, also referred to as alginate. Alginate-based immunization of naïve animals elicits opsonic antibodies and leads to clearance of mucoid P. aeruginosa from the lungs. Alginate was isolated from mucoid P. aeruginosa strain 8821M by repeated ethanol precipitation, dialysis, proteinase and nuclease digestion, and chromatography. To improve immunogenicity, the purified antigen was coupled to tetanus toxoid (TT) with adipic acid dihydrazide (ADH) as a spacer and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDAC) as a linker. The reaction mixture was passed through a Sepharose CL-4B column. The resulting conjugate was composed of TT and large-size alginate polymer at a ratio of about 3 : 1; it was non-toxic and non-pyrogenic, and elicited high titres of alginate-specific IgG. Antisera raised against the conjugate had high opsonic activity against the vaccine strain. The alginate conjugate was also able to protect mice against a lethal dose of mucoid P. aeruginosa. These data indicate that an alginate-based vaccine has significant potential to protect against chronic infection with mucoid P. aeruginosa in the CF host.

A glycoconjugate of Haemophilus influenzae Type b capsular polysaccharide with tetanus toxoid protein: hydrodynamic properties mainly influenced by the carbohydrate.

Three important physical properties which may affect the performance of glycoconjugate vaccines against serious disease are molar mass (molecular weight), heterogeneity (polydispersity), and conformational flexibility in solution. The dilute solution behaviour of native and activated capsular polyribosylribitol (PRP) polysaccharides extracted from Haemophilus influenzae type b (Hib), and the corresponding glycoconjugate made by conjugating this with the tetanus toxoid (TT) protein have been characterized and compared using a combination of sedimentation equilibrium and sedimentation velocity in the analytical ultracentrifuge with viscometry. The weight average molar mass of the activated material was considerably reduced (Mw ~ 0.24 × 10(6) g.mol(-1)) compared to the native (Mw ~ 1.2 × 10(6) g.mol(-1)). Conjugation with the TT protein yielded large polydisperse structures (of Mw ~ 7.4 × 10(6) g.mol(-1)), but which retained the high degree of flexibility of the native and activated polysaccharide, with frictional ratio, intrinsic viscosity, sedimentation conformation zoning behaviour and persistence length all commensurate with highly flexible coil behaviour and unlike the previously characterised tetanus toxoid protein (slightly extended and hydrodynamically compact structure with an aspect ratio of ~3). This non-protein like behaviour clearly indicates that it is the carbohydrate component which mainly influences the physical behaviour of the glycoconjugate in solution.

Mechanisms of Antigen Adsorption Onto an Aluminum-Hydroxide Adjuvant Evaluated by High-Throughput Screening.

The adsorption mechanism of antigen on aluminum adjuvant can affect antigen elution at the injection site and hence the immune response. Our aim was to evaluate adsorption onto aluminum hydroxide (AH) by ligand exchange and electrostatic interactions of model proteins and antigens, bovine serum albumin (BSA), ß-casein, ovalbumin (OVA), hepatitis B surface antigen, and tetanus toxin (TT). A high-throughput screening platform was developed to measure adsorption isotherms in the presence of electrolytes and ligand exchange by a fluorescence-spectroscopy method that detects the catalysis of 6,8-difluoro-4-methylumbelliferyl phosphate by free hydroxyl groups on AH. BSA adsorption depended on predominant electrostatic interactions. Ligand exchange contributes to the adsorption of ß-casein, OVA, hepatitis B surface antigen, and TT onto AH. Based on relative surface phosphophilicity and adsorption isotherms in the presence of phosphate and fluoride, the capacities of the proteins to interact with AH by ligand exchange followed the trend: OVA < ß-casein < BSA < TT. This could be explained by both the content of ligands available in the protein structure for ligand exchange and the antigen's molecular weight. The high-throughput screening platform can be used to better understand the contributions of ligand exchange and electrostatic attractions governing the interactions between an antigen adsorbed onto aluminum-containing adjuvant.

Effect of IVIG Formulation on IgG Binding to Self- and Exo- Antigens In Vitro and In Vivo.

In relation to the recent trials of Intravenous Immunoglobulin (IVIG) in Alzheimer's Disease (AD) it was demonstrated that different IgG preparations contain varying amounts of natural anti-amyloid ß (Aß) antibodies as measured by ELISA. We therefore investigated the relevance of ELISA data for measuring low-affinity antibodies, such as anti-Aß. We analysed the binding of different commercial Immunoglobulin G (IgG) preparations to Aß, actin and tetanus toxoid in different binding assays to further investigate the possible cause for observed differences in binding to Aß and actin between different IgG preparations. We show that the differences of commercial IgG preparations in binding to Aß and actin in ELISA assays are artefactual and only evident in in vitro binding assays. In functional assays and in vivo animal studies the different IVIG preparations exhibited very similar potency. ELISA data alone are not appropriate to analyse and rank the binding capacity of low-affinity antibodies to Aß or other endogenous self-antigens contained in IgG preparations. Additional analytical methods should be adopted to complement ELISA data.

The effect of microfluidization of protein-coated liposomes on protein distribution on the surface of generated small vesicles.

Tetanus toxoid and immunoglobulin G (IgG), model proteins for vaccines and targeting ligands respectively, were covalently coupled to preformed dehydration-rehydration vesicles (DRV) to produce vesicles with surface-bound proteins (DRV-protein) or to preformed small unilamellar vesicles (SUV) which were used to generate DRV with bound protein [(SUV-protein)DRV]. Of the amount of protein employed for coupling (1 mg), 13.8-45.1% was recovered with the liposomes, depending on the type of preparations and the proteins used. Microfluidization of similar DRV-protein or (SUV-protein)DRV for up to 10 cycles led to the formation of smaller vesicles (98-136 mm diameter) which, however, had modestly reduced (estimated as 8.8-21.7%) bound proteins, again depending on the type of preparation and protein used. Treatment of DRV-protein and (SUV-protein) DRV with proteinase revealed that 32.9-45.6% of the total bound protein was exposed on the liposomal surface. With microfluidized liposomes, the proportion of surface-exposed protein increased to 63.1-76.2%. Incubation of intact and microfluidized DRV-IgG and (SUV-IgG) DRV with a protein A-Sepharose 4B CL gel confirmed the presence of IgG on the liposomal surface (47.1-68.4 and 80.5-82.1% of total bound protein respectively). These studies were supplemented with freeze-fracture electron microscopy of (SUV-toxoid)DRV which demonstrated the presence of protein particles (up to 3; 12-14 nm diameter) on the surface of both intact and microfluidized individual liposomes.