Improvement in laboratory diagnosis of wound botulism and tetanus among injecting illicit-drug users by use of real-time PCR assays for neurotoxin gene fragments

An upsurge in wound infections due to Clostridium botulinum and Clostridium tetani among users of illegal injected drugs (IDUs) occurred in the United Kingdom during 2003 and 2004. A real-time PCR assay was developed to detect a fragment of the neurotoxin gene of C. tetani (TeNT) and was used in conjunction with previously described assays for C. botulinum neurotoxin types A, B, and E (BoNTA, -B, and -E). The assays were sensitive, specific, rapid to perform, and applicable to investigating infections among IDUs using DNA extracted directly from wound tissue, as well as bacteria growing among mixed microflora in enrichment cultures and in pure culture on solid media. A combination of bioassay and PCR test results confirmed the clinical diagnosis in 10 of 25 cases of suspected botulism and two of five suspected cases of tetanus among IDUs. The PCR assays were in almost complete agreement with the conventional bioassays when considering results from different samples collected from the same patient. The replacement of bioassays by real-time PCR for the isolation and identification of both C. botulinum and C. tetani demonstrates a sensitivity and specificity similar to those of conventional approaches. However, the real-time PCR assays substantially improves the diagnostic process in terms of the speed of results and by the replacement of experimental animals. Recommendations are given for an improved strategy for the laboratory investigation of suspected wound botulism and tetanus among IDUs.

SNARE-mediated membrane traffic modulates RhoA-regulated focal adhesion formation

In the present study, we examined the role of soluble NSF attachment protein receptor (SNARE)-mediated membrane traffic in the formation of focal adhesions during cell spreading. CHO-K1 cells expressing a dominant-negative form of N-ethylmaleimide-sensitive factor (E329Q-NSF) were unable to spread as well as control cells and they formed focal adhesions (FAs) that were larger than those in control cells. FA formation was impaired in cells transfected with a dominant-negative form of RhoA, but, significantly, not in cells simultaneously expressing dominant-negative NSF. Treatment of E329Q-NSF-expressing cells with the ROCK inhibitor Y-27632 did inhibit FA formation. The results are consistent with a model of cell adhesion in which SNARE-mediated membrane traffic is required for both the elaboration of lamellipodia and the modulation of biochemical signals that control RhoA-mediated FA assembly.

Highly immunogenic and protective recombinant vaccine candidate expressed in transgenic plants

Vaccine development has been hampered by difficulties in developing new and safe adjuvants, so alternative technologies that offer new avenues forward are urgently needed. The goal of this study was to express a monoclonal recombinant immune complex in a transgenic plant. A recombinant protein consisting of a tetanus toxin C fragment-specific monoclonal antibody fused with the tetanus toxin C fragment was designed and expressed. Immune complex formation occurred between individual fusion proteins to form immune complex-like aggregates that bound C1q and FcgammaRIIa receptor and could be targeted to antigen-presenting cells. Unlike antigen alone, the recombinant immune fusion complexes were highly immunogenic in mice and did not require coadministration of an adjuvant (when injected subcutaneously). Indeed, these complexes elicited antibody titers that were more than 10,000 times higher than those observed in animals immunized with the antigen alone. Furthermore, animals immunized with only 1 mug of recombinant immune complex without adjuvant were fully protected against lethal challenge. This the first report on the use of a genetic fusion between antigen and antibody to ensure an optimal expression ratio between the two moieties and to obtain fully functional recombinant immune complexes as a new vaccine model.

Α genetic fusion construct between the tetanus toxin C fragment and the lysosomal acid hydrolase β-glucuronidase expresses a bifunctional protein with enhanced secretion and neuronal uptake

The neurotropic atoxic fragment of tetanus toxin has been used as a carrier for transporting macromolecules into neurons but all studies to date have tested cytosolic proteins. In this study we investigated the effect of a genetic addition of the tetanus toxin C fragment sequence to a lysosomal enzyme which contains a signal sequence for insertion into the membrane-bound compartment and must be extensively modified in the endoplasmic reticulum (ER) and Golgi to attain functionality. In-frame fusion constructs between the atoxic C fragment and beta-glucuronidase were compared with the wild-type enzyme for: (i) enzymatic activity; (ii) heat stability; (iii) pH dependence; (iv) specific activity; (v) apparent molecular mass and (vi) receptor-mediated uptake by fibroblasts and neurons. The modified proteins had biochemical properties similar to wild-type enzyme but exhibited different enzyme secretion profiles. Addition of the secreted fusion enzyme to cultures of primary neurons showed significantly increased neuronal uptake of the modified protein compared with the wild-type, demonstrating the bifunctionality of the chimeric molecule.

Protection against tetanus toxin using a plant-based vaccine

Plant-expressed vaccines may provide a unique opportunity for generating anti-pathogen immunity, especially in countries where cold storage is lacking. In the following study, we show that soluble protein from tobacco leaves expressing fragment C of tetanus toxin protected mice against a lethal tetanus toxin challenge. More importantly, we show that a single intranasal (i.n.) vaccination was as efficient as oral delivery, inducing high levels of activated CD4(+) T cells and anti-toxin antibody. Unlike the oral route, i.n. delivery did not require the presence of adjuvant (cholera toxin). Indeed, addition of cholera toxin induced bystander immune responses to plant proteins as well. This is the first study documenting protective immunity by a single i.n. dose of plant vaccine. Plant-based vaccines are promising because they are more heat stable, are easy to produce, cheap and do not require needles.

Asparaginase display of polypeptides in the periplasm of Escherichia coli: Potential rapid pepscan technique for antigen epitope mapping

Asparaginase of Escherichia coli, a tetramer of identical subunits, was tested as a vector to display linear peptides on the surface of each enzyme subunit. A recombinant gene encoding a chimeric protein composed of asparaginase, a tetanus toxin peptide (TTP) spacer (831-854 fragment), and the foreign cholesteryl ester transfer protein C-terminal fragment (CETPC) was expressed and targeted to the periplasm of E. coli. The purified chimeric enzyme exhibited approximately 83% activity of the native enzyme, allowing the rapid screening of recombinant clones. In contrast, an asparaginase-CETPC fusion protein without the TTP spacer produced only about 23% activity of the native enzyme. Rats immunized with bacterial cells containing the chimeric enzymes induced CETP-specific immunoresponse. In contrast, rats inoculated with the cells expressing asparaginase only did not generate specific anti-CETP antibodies. Our study showed that asparaginase of E. coli was an effective carrier for displaying foreign peptides or epitopes. Moreover, the use of the TTP spacer appeared to play a critical role in maintaining the catalytic activity of the chimeric enzymes by redirecting the foreign CETPC peptide to the surface of the enzyme. The chimeric enzyme constructs fusing asparaginase with foreign peptides via a TTP spacer could be utilized as a rapid pepscan technique for antigen epitope mapping. The fusion protein of asparaginase-TTP-CETPC could also be useful for the development of a vaccine against atherosclerosis.

Endocytosis and retrograde axonal traffic in motor neurons

Spinal cord motor neurons control voluntary movement by relaying messages that arrive from upper brain centres to the innervated muscles. Despite the importance of motor neurons in human health and disease, the precise control of their membrane dynamics and its effect on motor neuron homoeostasis and survival are poorly understood. In particular, the molecular basis of the co-ordination of specific endocytic events with the axonal retrograde transport pathway is largely unknown. To study these important vesicular trafficking events, we pioneered the use of atoxic fragments of tetanus and botulinum neurotoxins to follow endocytosis and retrograde axonal transport in motor neurons. These neurotoxins bind specifically to pre-synaptic nerve terminals, where they are internalized. Whereas botulinum neurotoxins remain at the neuromuscular junction, tetanus toxin is retrogradely transported along the axon to the cell body, where it is released into the intersynaptic space and is internalized by adjacent inhibitory interneurons. The high neurospecificity and the differential intracellular sorting make tetanus and botulinum neurotoxins ideal tools to study neuronal physiology. In the present review, we discuss recent developments in our understanding of the internalization and trafficking of these molecules in spinal cord motor neurons. Furthermore, we describe the development of a reliable transfection method for motor neurons based on microinjection, which will be extremely useful for dissecting further the molecular basis of membrane dynamics and axonal transport in these cells.

Attenuated Salmonella typhimurium SL3261 as a vaccine vector for recombinant antigen in rabbits

Oral live Salmonella vaccine vectors expressing recombinant guest antigens help stimulate systemic, mucosal, humoral, and cell-mediated immune responses against Salmonella and recombinant antigens. It may be possible to use them effectively against Haemophilus ducreyi, the bacterium that causes chancroid, a sexually transmitted genital ulcer disease. This study aimed to test the feasibility of using oral Salmonella vaccine vectors for the evaluation of chancroid vaccine candidates in the temperature-dependent rabbit model of H. ducreyi infection, an in vivo quantitative virulence assay of inducible immunity. We identified 10(8) to 10(9) CFU to be a safe and immunogenic oral dose range of S. typhimurium SL3261, by monitoring post-administration onset and course of illness and antibody titre by enzyme immunoassay (EIA). We successfully transduced plasmid pTETnir15 into the strain to produce recombinant S. typhimurium SL3261(pTETnir15), successfully expressed tetanus toxin fragment C (TetC) in it, and elicited serum anti-TetC titres of 1:6400 by EIA, 4 weeks after inoculation. The course of experimentally induced H. ducreyi skin lesions in rabbits treated with SL3261(pTETnir15) was similar to that in saline-treated controls. We describe a framework that successfully uses Salmonella as a vector for recombinant control antigen in the rabbit model of H. ducreyi infection, and is suitable for pre-clinical evaluation of Salmonella vector-based H. ducreyi vaccine antigen candidates.

Adenoviral clostridial light chain gene-based synaptic inhibition through neuronal synaptobrevin elimination

Clostridial neurotoxins have assumed increasing importance in clinical application. The toxin's light chain component (LC) inhibits synaptic transmission by digesting vesicle-docking proteins without directly altering neuronal health. To study the properties of LC gene expression in the nervous system, an adenoviral vector containing the LC of tetanus toxin (AdLC) was constructed. LC expressed in differentiated neuronal PC12 cells was shown to induce time- and concentration-dependent digestion of mouse brain synaptobrevin in vitro as compared to control transgene products. LC gene expression in the rat lumbar spinal cord disrupted hindlimb sensorimotor function in comparison to control vectors as measured by the Basso-Beattie-Bresnahan (BBB) scale (P<0.001) and rotarod assay (P<0.003). Evoked electromyography (EMG) showed increased stimulus threshold and decreased response current amplitude in LC gene-transferred rats. At the peak of functional impairment, neither neuronal TUNEL staining nor reduced motor neuron density could be detected. Spontaneous functional recovery was observed to parallel the cessation of LC gene expression. These results suggest that light chain gene delivery within the nervous system may provide a nondestructive means for focused neural inhibition to treat a variety of disorders related to excessive synaptic activity, and prove useful for the study of neural circuitry.

Expressing and purifying an anti-atherosclerosis polypeptide vaccine in Escherichia coli

A chimeric polypeptide of TTP-CETPC was successfully expressed as inclusion bodies in Escherichia coli by fusing it with the C-terminus of asparaginase and a basic amino acid-rich peptide (KR). After partially purified by washing with 0.5% (v/v) Triton X-100 in 10 mM PB, the pellet was solubilized in 8 M urea. The solution was precipitated with single volume and double volumes of cold ethanol for removing impurities. The fusion protein in solution was precipitated with triple volumes of ethanol to increase purity and then hydrolyzed with 50 mM hydrochloric acid at 55 degrees C for 72 h. The TTP-CETPC polypeptide was released after the unique acid-labile aspartylprolyl bond in the fusion protein was cleaved by acid. After impurities were removed by adjusting the hydrolysis solution pH to 9.45 and then to 8.37, the TTP-CETPC polypeptide was further purified by DEAE-cellulose column. The TTP-CETPC containing fractions were eluted at 60-80 mM NaCl. The purified TTP-CETPC cysteines were oxidized to form into intermolecular disulfide bonded dimers for immunizing mice. Specific anti-CETP antibodies in mice serum were assayed by ELISA and Western blot to verify that antibodies against CETP had been successfully induced and lasted for more than seventeen weeks in vivo.

Utilisation du fragment C-terminal de la neurotoxine tétanique pour visualiser et analyser des connexions neuronales et pour le transfert d'une activité biologique associée

The atoxic C-terminal fragment of tetanus neurotoxin or TTC fragment presents similar retrograde and transsynaptic properties to that of holotoxin. Detection of this fragment is easier when it is associated with a fluorescent marker or with beta-galactosidase activity by genetic fusion or chemical conjugation. Thus, these tracers have been used to study and analyse the synaptic connections of a neural network. In this article, we shortly review the various methods used with this aim including: injection of the fusion protein, adenovirus in vivo expression and transgenesis. Since neural activity is essential for neuronal TTC binding and internalization, the functionality of connections can be also evaluated. Moreover, modifications of the retrograde transport can be detected by using this fragment. Thus, TTC fragment is an excellent tracer to analyse the connectivity and functionality of a neural network. The TTC fragment was also soon proposed as potential therapeutic vector to transport and to deliver a biological activity or gene in a neural network. With this aim, the efficiency of a translocation domain to induce the cytosolic release of the associated activity has been evaluated. The use of the TTC fragment to target specifically a neurotrophic factor to neurons and thus avoid secondary effects has been tested with interesting results.

Intranasal immunisation against tetanus with an attenuated Bordetella bronchiseptica vector expressing FrgC: improved immunogenicity using a Bvg-regulated promoter to express FrgC

Mice were immunised intranasally with live Bordetella bronchiseptica aroA strains possessing plasmids encoding fragment C (FrgC) of tetanus toxin. FrgC was expressed either from a constitutive tac promoter (strain GVB120) or the Bvg-dependent fhaB promoter (strain GVB1543). Serum anti-FrgC antibody titres were detected in all mice immunised with GVB1543 and GVB120 but the average titres were higher and the responses to FrgC were more consistent in GVB1543 immunised animals. This was reflected in the protective immunity conferred by the different strains: 100% of GVB1543 immunised mice were protected against tetanus toxin challenge whereas only 60% of animals immunised with GVB120 survived tetanus challenge. Viability of the B. bronchiseptica vector strain was shown to be critical to its efficacy as a vector for FrgC.

BotR/A and TetR are alternative RNA polymerase sigma factors controlling the expression of the neurotoxin and associated protein genes in Clostridium botulinum type A and Clostridium tetani

Clostridium botulinum and Clostridium tetani, respectively, produce potent toxins, botulinum neurotoxin (BoNT) and tetanus neurotoxin (TeTx), which are responsible for severe diseases, botulism and tetanus. Neurotoxin synthesis is a regulated process in Clostridium. The genes botR/A in C. botulinum A and tetR in C. tetani positively regulate expression of BoNT/A and associated non-toxic proteins (ANTPs), as well as TeTx respectively. The botR/A gene lies in close vicinity of the two operons which contain bont/A and antps genes in C. botulinum A, and tetR immediately precedes the tetX gene in C. tetani. We show that BotR/A and TetR function as specific alternative sigma factors rather than positive regulators based on the following results: (i) BotR/A and TetR associated with target DNAs only in the presence of the RNA polymerase core enzyme (Core), (ii) BotR/A and TetR directly bound with the core enzyme, (iii) BotR/A-Core recognized -35 and -10 regions of ntnh-bont/A promoter and (iv) BotR/A and TetR triggered in vitro transcription from the target promoters. In C. botulinum A, bont/A and antps genes are transcribed as bi- and tricistronic operons controlled by BotR/A. BotR/A and TetR are seemingly related to a new subgroup of the sigma70 family that includes TcdR and UviA, which, respectively, regulate production of toxins A and B in C. difficile and bacteriocin in C. perfringens. Sequences of -35 region are highly conserved in the promoter of target toxin genes in C. botulinum, C. tetani, C. difficile and C. perfringens. Overall, a common regulation mechanism probably controls toxin gene expression in these four toxigenic clostridial species.

Sm14 of Schistosoma mansoni in fusion with tetanus toxin fragment C induces immunoprotection against tetanus and schistosomiasis in mice

We have constructed vectors that permit the expression in Escherichia coli of Schistosoma mansoni fatty acid-binding protein 14 (Sm14) in fusion with the nontoxic, but highly immunogenic, tetanus toxin fragment C (TTFC). The recombinant six-His-tagged proteins were purified by nickel affinity chromatography and used in immunization and challenge assays. Animals inoculated with TTFC in fusion with or coadministered with Sm14 showed high levels of tetanus toxin antibodies, while animals inoculated with Sm14 in fusion with or coadministered with TTFC showed high levels of Sm14 antibodies. In both cases, there were no changes in the type of immune response (Th2) obtained with the fusion proteins compared to those obtained with the nonfused proteins. Mice immunized with the recombinant proteins (TTFC in fusion with or coadministered with Sm14) survived the challenge with tetanus toxin and did not show any symptoms of the disease. Control animals inoculated with either phosphate-buffered saline (PBS) or Sm14 died with severe symptoms of tetanus after 24 h. Mice immunized with the recombinant proteins (Sm14 in fusion with or coadministered with TTFC) showed a 50% reduction in worm burden when they were challenged with S. mansoni cercariae, while control animals inoculated with either PBS or TTFC were not protected. The results show that the expression of other antigens in fusion at the carboxy terminus of TTFC is feasible for the development of a multivalent recombinant vaccine.

DNA Fusion Vaccines Induce Targeted Epitope-Specific CTLs against Minor Histocompatibility Antigens from a Normal or Tolerized Repertoire

We have designed DNA fusion vaccines able to induce high levels of epitope-specific CD8(+) T cells, using linked CD4(+) T cell help. Such vaccines can activate effective immunity against tumor Ags. To model performance against minor histocompatibility (H) Ags important in allogeneic hemopoietic stem cell transplantation, responses against the H2D(b)-restricted Uty and Smcy male HY epitopes have been investigated. Vaccination of females induced high levels of tetramer-specific, IFN-gamma-producing CD8(+) T cells against each epitope. Vaccines incorporating a single epitope primed effector CTL able to kill male splenocytes in vitro and in vivo, and HY(Db)Uty-specific vaccination accelerated rejection of syngeneic male skin grafts. Priming against either epitope established long-term memory, expandable by injection of male cells. Expanded CD8(+) T cells remained specific for the priming HY epitope, with responses to the second suppressed. To investigate vaccine performance in a tolerized repertoire, male mice were vaccinated with the fusion constructs. Strikingly, this also generated epitope-specific IFN-gamma-producing CD8(+) T cells with cytotoxic function. However, numbers and avidity were lower than in vaccinated females, and vaccinated males failed to reject CFSE-labeled male splenocytes in vivo. Nevertheless, these findings indicate that DNA fusion vaccines can mobilize CD8(+) T cells against endogenous minor H Ags, even from a profoundly tolerized repertoire. In the transplantation setting, vaccination of donors could prime and expand specific T cells for in vivo transfer. For patients, vaccination could activate a potentially less tolerized repertoire against similar Ags that may be overexpressed by tumor cells, for focused immune attack.

An accelerated assay for the identification of lifespan-extending interventions in Drosophila melanogaster

Recent advances in aging research have uncovered genes and genetic pathways that influence lifespan in such diverse organisms as yeast, nematodes, flies, and mice. The discovery of genes and drugs that affect lifespan has been delayed by the absence of a phenotype other than survivorship, which depends on the measurement of age at death of individuals in a population. The use of survivorship to identify genetic and pharmacological interventions that prolong life is time-consuming and requires a large number of homogeneous animals. Here, we report the development of an assay in Drosophila melanogaster using the expression of molecular biomarkers that accelerates the ability to evaluate potential lifespan-altering interventions. Coupling the expression of an age-dependent molecular biomarker to a lethal toxin reduces the time needed to perform lifespan studies by 80%. The assay recapitulates the effect of the three best known environmental life-span-extending interventions in the fly: ambient temperature, reproductive status, and calorie reduction. Single gene mutations known to extend lifespan in the fly such as Indy and rpd3 also extend lifespan in this assay. We used this assay as a screen to identify drugs that extend lifespan in flies. Lipoic acid and resveratrol were identified as being beneficial in our assay and shown to extend lifespan under normal laboratory conditions. We propose that this assay can be used to screen pharmacological as well as genetic interventions more rapidly for positive effects on lifespan.

Mucosally delivered Salmonella live vector vaccines elicit potent immune responses against a foreign antigen in neonatal mice born to naive and immune mothers

The development of effective vaccines for neonates and very young infants has been impaired by their weak, short-lived, and Th-2 biased responses and by maternal antibodies that interfere with vaccine take. We investigated the ability of Salmonella enterica serovars Typhi and Typhimurium to mucosally deliver tetanus toxin fragment C (Frag C) as a model antigen in neonatal mice. We hypothesize that Salmonella, by stimulating innate immunity (contributing to adjuvant effects) and inducing Th-1 cytokines, can enhance neonatal dendritic cell maturation and T-cell activation and thereby prime humoral and cell-mediated immunity. We demonstrate for the first time that intranasal immunization of newborn mice with 10(9) CFU of S. enterica serovar Typhi CVD 908-htrA and S. enterica serovar Typhimurium SL3261 carrying plasmid pTETlpp on days 7 and 22 after birth elicits high titers of Frag C antibodies, previously found to protect against tetanus toxin challenge and similar to those observed in adult mice. Salmonella live vectors colonized and persisted primarily in nasal tissue. Mice vaccinated as neonates induced Frag C-specific mucosal and systemic immunoglobulin A (IgA)- and IgG-secreting cells, T-cell proliferative responses, and gamma interferon secretion. A mixed Th1- and Th2-type response to Frag C was established 1 week after the boost and was maintained thereafter. S. enterica serovar Typhi carrying pTETlpp induced Frag C-specific antibodies and cell-mediated immunity in the presence of high levels of maternal antibodies. This is the first report that demonstrates the effectiveness of Salmonella live vector vaccines in early life.

Enhancement of antibody responses in DNA vaccination using a vector encoding a universal T-helper cell epitope

DNA vaccination appears as a very promising approach to raise protective antibodies against a variety of proteins from pathogens or tumor cells, but is often hindered by the low immunogenicity of the genetic vectors used for the immunizations. To enhance the humoral response through improvement of the antigenic presentation of newly synthesized proteins upon vaccination, we engineered a plasmid coding for a low immunogenic protein (an scFv, i.e. the single-chain Fragment variable of a well-characterized antibody) fused to a small-size universal T-helper cell epitope derived from tetanus toxin, whose efficiency in classical protein-based immunization protocols has already been demonstrated. We found that immunization of C57Bl/6 mice using this vector greatly enhanced the production not only of specific antibodies recognizing essentially conformational epitopes on the undenatured scFv protein but also of antibodies against linear epitopes on the denatured protein. Since this T-epitope is known to be accommodated by several haplotypes of H-2 molecules in mice, as well as by various class II MHC molecules in humans, the results reported here allow us to conclude that this method could be of general interest for future applications of genetic immunization, including DNA-based vaccinations in humans.

Therapeutic polypeptides based on HBV core 18-27 epitope can induce CD8+ CTL-mediated cytotoxicity in HLA-A2+ human PBMCs

AIM: To explore how to improve the immunogenicity of HBcAg CTL epitope based polypeptides and to trigger an HBV-specific HLA I-restricted CD₈⁺ T cell response in vitro.

METHODS: A new panel of mimetic therapeutic peptides based on the immunodominant B cell epitope of HBV PreS2 18-24 region, the CTL epitope of HBcAg18-27 and the universal T helper epitope of tetanus toxoid (TT) 830-843 was designed using computerized molecular design method and synthesized by Merrifield’s solid-phase peptide synthesis. Their immunological properties of stimulating activation and proliferation of lymphocytes, of inducing T_H1 polarization, CD₈⁺ T cell magnification and HBV-specific CD₈⁺ CTL mediated cytotoxicity were investigated in vitro using HLA-A2⁺ human peripheral blood mononuclear cells (PBMCs) from healthy donors and chronic hepatitis B patients.

RESULTS: Results demonstrated that the therapeutic polypeptides based on immunodominant HBcAg18-27 CTL, PreS2 B- and universal T_H epitopes could stimulate the activation and proliferation of lymphocytes, induce specifically and effectively CD₈⁺ T cell expansion and vigorous HBV-specific CTL-mediated cytotoxicity in human PBMCs.

CONCLUSION: It indicated that the introduction of immunodominant T helper plus B-epitopes with short and flexible linkers could dramatically improve the immunogenicity of short CTL epitopes in vitro.

BotDB: A database resource for the clostridial neurotoxins

BotDB is a database designed to encapsulate the rapidly expanding amount of information about the structure and function of the botulinum (BoNT) and tetanus neurotoxins and to track a variety of basic and applied research efforts. The AceDB management system was chosen for this project because of its flexibility in manipulating semistructured data sets and for its information retrieval query languages. In addition to storing amino and nucleic acid sequences of the clostridial neurotoxin genes and proteins, BotDB provides sequence data for new classes of objects, including neurotoxin mutants, substrates and their mutants, associated nontoxic proteins, and C-fragment vaccine candidates. New data types provide information on detection assays for the neurotoxins and on structural data from X-ray crystallographic and circular dichroism spectroscopic studies. Kinetic parameters from biochemical experiments include reaction rates for substrate cleavage and block of neurotransmission. The structures and kinetic characteristics of presently known chemical inhibitors are also being archived. All of these data are associated with citations of the relevant literature for on-line annotation. Graphics viewer programs are provided to display stored images and three-dimensional representations of protein structures. BotDB is in the alpha test phase of development and will become a publicly available Web site.

Enhanced mucosal delivery of antigen with cell wall mutants of lactic acid bacteria

The potential of recombinant lactic acid bacteria (LAB) to deliver heterologous antigens to the immune system and to induce protective immunity has been best demonstrated by using the C subunit of tetanus toxin (TTFC) as a model antigen. Two types of LAB carriers have mainly been used, Lactobacillus plantarum and Lactococcus lactis, which differ substantially in their abilities to resist passage through the stomach and to persist in the mouse gastrointestinal tract. Here we analyzed the effect of a deficiency in alanine racemase, an enzyme that participates in cell wall synthesis, in each of these bacterial carriers. Recombinant wild-type and mutant strains of L. plantarum NCIMB8826 and L. lactis MG1363 producing TTFC intracellularly were constructed and used in mouse immunization experiments. Remarkably, we observed that the two cell wall mutant strains were far more immunogenic than their wild-type counterparts when the intragastric route was used. However, intestinal TTFC-specific immunoglobulin A was induced only after immunization with the recombinant L. plantarum mutant strain. Moreover, the alanine racemase mutant of either LAB strain allowed induction of a much stronger serum TTFC-specific immune response after immunization via the vagina, which is a quite different ecosystem than the gastrointestinal tract. The design and use of these mutants thus resulted in a major improvement in the mucosal delivery of antigens exhibiting vaccine properties.

DNA fusion gene vaccines against cancer: from the laboratory to the clinic

Vaccination against target antigens expressed by cancer cells has now become a realistic goal. DNA vaccines provide a direct link between identification of genetic markers in tumors and vaccine formulation. Simplicity of manufacture facilitates construction of vaccines against disease subsets or even for individual patients. To engage an immune system that exists to fight pathogens, we have developed fusion gene vaccines encoding tumor antigens fused to pathogen-derived sequences. This strategy activates high levels of T-cell help, the key to induction and maintenance of effective immunity. We have dissected the immunogenic tetanus toxin to obtain specific sequences able to activate antibody, CD4+, or CD8+ T cells to attack selected fused tumor antigens. Principles established in preclinical models are now being tested in patients. So far, objective immune responses against idiotypic antigen of neoplastic B cells have been observed in patients with B-cell malignancies and in normal transplant donors. These responses provide a platform for testing physical methods to improve DNA delivery and strategies to boost responses. For cancer, demands are high, because vaccines have to activate powerful immunity against weak antigens, often in a setting of immune damage or tolerance. Vaccination strategies against cancer and against microbes are sharing knowledge and technology for mutual benefit.

Spontaneous Neural Activity Is Required for the Establishment and Maintenance of the Olfactory Sensory Map

We have developed a genetic approach to examine the role of spontaneous activity and synaptic release in the establishment and maintenance of an olfactory sensory map. Conditional expression of tetanus toxin light chain, a molecule that inhibits synaptic release, does not perturb targeting during development, but neurons that express this molecule in a competitive environment fail to maintain appropriate synaptic connections and disappear. Overexpression of the inward rectifying potassium channel, Kir2.1, diminishes the excitability of sensory neurons and more severely disrupts the formation of an olfactory map. These studies suggest that spontaneous neural activity is required for the establishment and maintenance of the precise connectivity inherent in an olfactory sensory map.

Mucosal and cellular immune responses elicited by recombinant Lactococcus lactis strains expressing tetanus toxin fragment C

The mucosal and cellular responses of mice were studied, following mucosal-route administration of recombinant Lactococcus lactis expressing tetanus toxin fragment C (TTFC), which is a known immunogen protective against tetanus. A TTFC-specific T-cell response with a mixed profile of T-helper (Th) subset-associated cytokines was elicited in the intestine, with a Th2 bias characteristic of a mucosal response. These results correlated with the humoral response, where equivalent titers of anti-TTFC immunoglobulin G1 (IgG1) and IgG2a in serum were accompanied by an elevated IgA-specific response at more than one mucosal site. The route of vaccination had an important role in determining the immune response phenotype, as evidenced by the fact that an IgG1-biased subclass profile was obtained when lactococci were administered parenterally. Stimulation of splenic or mesenteric lymph node cells with lactococci resulted in their proliferation and the secretion of gamma interferon via antigen-specific and innate immune mechanisms. The data therefore provide further evidence of the potential of recombinant lactococcal vaccines for inducing systemic and mucosal immune responses.