Comparative pathogenomic analysis reveals a highly tetanus toxin-producing clade of Clostridium tetani isolates in Japan

IMPORTANCE

C. tetani is a spore-forming, anaerobic bacterium that produces a toxin causing muscle stiffness and paralysis. Tetanus is preventable with the toxoid vaccine, but it remains a significant public health threat in regions with low vaccine coverage. However, there are relatively few isolates and limited genomic information available worldwide. In Japan, about 100 cases are reported each year, but there have been no nationwide surveys of isolates, and no genomic information from Japanese isolates has been published. In our study, we analyzed the genomes of 151 strains from a limited survey of soil in Kumamoto, Japan. Our findings revealed a high degree of genetic diversity, and we also identified a subset of strains that produced significantly more toxin, which provides new insights into the pathogenesis of tetanus. Our findings lay the foundation for future studies to investigate the distribution and evolution of C. tetani in Japan and neighboring countries.

Tetanus toxin and botulinum neurotoxin-derived fusion molecules are effective bivalent vaccines

Tetanus toxin (TeNT) and botulinum neurotoxins (BoNTs) are neuroprotein toxins, with the latter being the most toxic known protein. They are structurally similar and contain three functional domains: an N-terminal catalytic domain (light chain), an internal heavy-chain translocation domain (HN domain), and a C-terminal heavy chain receptor binding domain (Hc domain or RBD). In this study, fusion functional domain molecules consisting of the TeNT RBD (THc) and the BoNT/A RBD (AHc) (i.e., THc-Linker-AHc and AHc-Linker-THc) were designed, prepared, and identified. The interaction of each Hc domain and the ganglioside receptor (GT1b) or the receptor synaptic vesicle glycoprotein 2 (SV2) was explored in vitro. Their immune response characteristics and protective efficacy were investigated in animal models. The recombinant THc-linker-AHc and AHc-linker-THc proteins with the binding activity had the correct size and structure, thus representing novel subunit vaccines. THc-linker-AHc and AHc-linker-THc induced high levels of specific neutralizing antibodies, and showed strong immune protective efficacy against both toxins. The high antibody titers against the two novel fusion domain molecules and against individual THc and AHc suggested that the THc and AHc domains, as antigens in the fusion functional domain molecules, do not interact with each other and retain their full key epitopes responsible for inducing neutralizing antibodies. Thus, the recombinant THc-linker-AHc and AHc-linker-THc molecules are strong and effective bivalent biotoxin vaccines, protecting against two biotoxins simultaneously. Our experimental design will be valuable to develop recombinant double-RBD fusion molecules as potent bivalent subunit vaccines against bio-toxins. KEY POINTS: • Double-RBD fusion molecules from two toxins had the correct structure and activity. • THc-linker-AHc and AHc-linker-THc efficiently protected against both biotoxins. • Such bivalent biotoxin vaccines based on the RBD are a valuable experimental design.

Does tetanus vaccination contribute to reduced severity of the COVID-19 infection?

We present the hypothesis to the scientific community actively designing clinical trials and recommending public health guidelines to control the pandemic that - "Tetanus vaccination may be contributing to reduced severity of the COVID-19 infection" - and urge further research to validate or invalidate the effectiveness of the tetanus toxoid vaccine against COVID-19. This hypothesis was revealed by an explainable artificial intelligence system unleashed on open public biomedical datasets. As a foundation for scientific rigor, we describe the data and the artificial intelligence system, document the provenance and methodology used to derive the hypothesis and also gather potentially relevant data/evidence from recent studies. We conclude that while correlations may not be reason for causation, correlations from multiple sources is more than a serendipitous coincidence that is worthy of further and deeper investigation.

The temperature of growth and sporulation modulates the efficiency of spore-display in Bacillus subtilis

BACKGROUND

Bacterial spores displaying heterologous antigens or enzymes have long been proposed as mucosal vaccines, functionalized probiotics or biocatalysts. Two main strategies have been developed to display heterologous molecules on the surface of Bacillus subtilis spores: (i) a recombinant approach, based on the construction of a gene fusion between a gene coding for a coat protein (carrier) and DNA coding for the protein to be displayed, and (ii) a non-recombinant approach, based on the spontaneous and stable adsorption of heterologous molecules on the spore surface. Both systems have advantages and drawbacks and the selection of one or the other depends on the protein to be displayed and on the final use of the activated spore. It has been recently shown that B. subtilis builds structurally and functionally different spores when grown at different temperatures; based on this finding B. subtilis spores prepared at 25, 37 or 42 °C were compared for their efficiency in displaying various model proteins by either the recombinant or the non-recombinant approach.

RESULTS

Immune- and fluorescence-based assays were used to analyze the display of several model proteins on spores prepared at 25, 37 or 42 °C. Recombinant spores displayed different amounts of the same fusion protein in response to the temperature of spore production. In spores simultaneously displaying two fusion proteins, each of them was differentially displayed at the various temperatures. The display by the non-recombinant approach was only modestly affected by the temperature of spore production, with spores prepared at 37 or 42 °C slightly more efficient than 25 °C spores in adsorbing at least some of the model proteins tested.

CONCLUSION

Our results indicate that the temperature of spore production allows control of the display of heterologous proteins on spores and, therefore, that the spore-display strategy can be optimized for the specific final use of the activated spores by selecting the display approach, the carrier protein and the temperature of spore production.

The Effect of Differentially Designed Fusion Proteins to Elicit Efficient Anti-human Thyroid Stimulating Hormone Immune Responses

The production of human thyroid stimulating hormone (hTSH) immunoassays requires specific antibodies against hTSH which is a cumbersome process. Therefore, producing specific polyclonal antibodies against engineered recombinant fusion hTSH antigens would be of great significance. The best immunogenic region of the hTSH was selected based on in silico analyses and equipped with two different fusions. Standard methods were used for protein expression, purification, verification, structural evaluation, and immunizations of the white New Zealand rabbits. Ultimately, immunized serums were used for antibody titration, purification and characterization (specificity, sensitivity and cross reactivity). The desired antigens were successfully designed, sub-cloned, expressed, confirmed and used for in vivo immunization. Structural analyses indicated that only the bigger antigen has showed changed 2 dimensional (2D) and 3D structural properties in comparison to the smaller antigen. The raised polyclonal antibodies were capable of specific and sensitive hTSH detection, while the cross reactivity with the other members of the glycoprotein hormone family was minimum and negligible. The fusion which was solely composed of the tetanus toxin epitopes led to better protein folding and was capable of immunizing the host animals resulting into high titer antibody. Therefore, the minimal fusion sequences seem to be more effective in eliciting specific antibody responses.

A novel C3d-containing oligomeric vaccine provides insight into the viability of testing human C3d-based vaccines in mice

The use of C3d, the final degradation product of complement protein C3, as a "natural" adjuvant has been widely examined since the initial documentation of its immunogenicity-enhancing properties as a consequence of binding to complement receptor 2. Subsequently it was demonstrated that these effects are most evident when oligomeric, rather than when monomeric forms of C3d, are linked to various test protein antigens. In this study, we examined the feasibility of enhancing the adjuvant properties of human C3d further by utilizing C4b-binding protein (C4BP) to provide an oligomeric arrayed scaffold fused to the model antigen, tetanus toxin C fragment (TTCF). High molecular weight, C3d-containing oligomeric vaccines were successfully expressed, purified from mammalian cells and used to immunize groups of mice. Surprisingly, anti-TTCF antibody responses measured in these mice were poor. Subsequently we established by in vitro and in vivo analysis that, in the presence of mouse C3, human C3d does not interact with either mouse or even human complement receptor 2. These data confirm the requirement to develop murine versions of C3d based adjuvant compounds to test in mice or that mice would need to be developed that express both human C3 and human CR2 to allow the testing of human C3d based adjuvants in mouse in any capacity.

High Conservation of Tetanus and Botulinum Neurotoxins Cleavage Sites on Human SNARE Proteins Suggests That These Pathogens Exerted Little or No Evolutionary Pressure on Humans

The Genome Aggregation Database presently contains >120,000 human genomes. We searched in this database for the presence of mutations at the sites of tetanus (TeNT) and botulinum neurotoxins (BoNTs) cleavages of the three SNARE proteins: VAMP, SNAP-25 and Syntaxin. These mutations could account for some of the BoNT/A resistant patients. At the same time, this approach was aimed at testing the possibility that TeNT and BoNT may have acted as selective agents in the development of resistance to tetanus or botulism. We found that mutations of the SNARE proteins are very rare and concentrated outside the SNARE motif required for the formation of the SNARE complex involved in neuroexocytosis. No changes were found at the BoNT cleavage sites of VAMP and syntaxins and only one very rare mutation was found in the essential C-terminus region of SNAP-25, where Arg198 was replaced with a Cys residue. This is the P1’ cleavage site for BoNT/A and the P1 cleavage site for BoNT/C. We found that the Arg198Cys mutation renders SNAP-25 resistant to BoNT/A. Nonetheless, its low frequency (1.8 × 10⁻⁵) indicates that mutations of SNAP-25 at the BoNT/A cleavage site are unlikely to account for the existence of BoNT/A resistant patients. More in general, the present findings indicate that tetanus and botulinum neurotoxins have not acted as selective agents during human evolution as it appears to have been the case for tetanus in rats and chicken.

Refinement of ectopic protein expression through the GAL4/UAS system in Bombyx mori: application to behavioral and developmental studies

Silkmoth, Bombyx mori, is one of the important model insects in which transgenic techniques and the GAL4/UAS system are applicable. However, due to cytotoxicity and low transactivation activity of GAL4, effectiveness of the GAL4/UAS system and its application in B. mori are still limited. In the present study, we refined the previously reported UAS vector by exploiting transcriptional and translational enhancers, and achieved 200-fold enhancement of reporter GFP fluorescence in the GAL4/UAS system. Enhanced protein expression of membrane-targeted GFP and calcium indicator protein (GCaMP5G) drastically improved visualization of fine neurite structures and neural activity, respectively. Also, with the refined system, we generated a transgenic strain that expresses tetanus toxin light chain (TeTxLC), which blocks synaptic transmission, under the control of GAL4. Ectopic TeTxLC expression in the sex pheromone receptor neurons inhibited male courtship behavior, proving effectiveness of TeTxLC on loss-of-function analyses of neural circuits. In addition, suppression of prothoracicotropic hormone (PTTH) or insulin-like peptide (bombyxin) secretion impaired developmental timing and growth rate, respectively. Furthermore, we revealed that larval growth is sex-differentially regulated by these peptide hormones. The present study provides important technical underpinnings of transgenic approaches in silkmoths and insights into mechanisms of postembryonic development in insects.

Comparative pathogenomics of Clostridium tetani

Clostridium tetani and Clostridium botulinum produce two of the most potent neurotoxins known, tetanus neurotoxin and botulinum neurotoxin, respectively. Extensive biochemical and genetic investigation has been devoted to identifying and characterizing various C. botulinum strains. Less effort has been focused on studying C. tetani likely because recently sequenced strains of C. tetani show much less genetic diversity than C. botulinum strains and because widespread vaccination efforts have reduced the public health threat from tetanus. Our aim was to acquire genomic data on the U.S. vaccine strain of C. tetani to better understand its genetic relationship to previously published genomic data from European vaccine strains. We performed high throughput genomic sequence analysis on two wild-type and two vaccine C. tetani strains. Comparative genomic analysis was performed using these and previously published genomic data for seven other C. tetani strains. Our analysis focused on single nucleotide polymorphisms (SNP) and four distinct constituents of the mobile genome (mobilome): a hypervariable flagellar glycosylation island region, five conserved bacteriophage insertion regions, variations in three CRISPR (clustered regularly interspaced short palindromic repeats)-Cas (CRISPR-associated) systems, and a single plasmid. Intact type IA and IB CRISPR/Cas systems were within 10 of 11 strains. A type IIIA CRISPR/Cas system was present in two strains. Phage infection histories derived from CRISPR-Cas sequences indicate C. tetani encounters phages common among commensal gut bacteria and soil-borne organisms consistent with C. tetani distribution in nature. All vaccine strains form a clade distinct from currently sequenced wild type strains when considering variations in these mobile elements. SNP, flagellar glycosylation island, prophage content and CRISPR/Cas phylogenic histories provide tentative evidence suggesting vaccine and wild type strains share a common ancestor.

Tetanus toxin production is triggered by the transition from amino acid consumption to peptides

Bacteria produce some of the most potent biomolecules known, of which many cause serious diseases such as tetanus. For prevention, billions of people and countless animals are immunised with the highly effective vaccine, industrially produced by large-scale fermentation. However, toxin production is often hampered by low yields and batch-to-batch variability. Improved productivity has been constrained by a lack of understanding of the molecular mechanisms controlling toxin production. Here we have developed a reproducible experimental framework for screening phenotypic determinants in Clostridium tetani under a process that mimics an industrial setting. We show that amino acid depletion induces production of the tetanus toxin. Using time-course transcriptomics and extracellular metabolomics to generate a 'fermentation atlas' that ascribe growth behaviour, nutrient consumption and gene expression to the fermentation phases, we found a subset of preferred amino acids. Exponential growth is characterised by the consumption of those amino acids followed by a slower exponential growth phase where peptides are consumed, and toxin is produced. The results aim at assisting in fermentation medium design towards the improvement of vaccine production yields and reproducibility. In conclusion, our work not only provides deep fermentation dynamics but represents the foundation for bioprocess design based on C. tetani physiological behaviour under industrial settings.

Clostridium botulinum type D/C intoxication in a dairy cow stock in Saxony-Anhalt (Germany)--report on an innovative diagnostic approach

Botulism in cattle is a rare but serious disease. In Germany there is no obligation to report botulism in animals and therefore a precise morbidity rate is not available. In this manuscript we describe an outbreak of Clostridium (C.) botulinum neurotoxin (BoNT) intoxication in a Saxony-Anhalt dairy cow stock of 286 Holstein-Friesian cows and offspring in spring/summer 2009 and its diagnostic approach. 122 animals showed clinical signs of BoNT intoxication. 115 of the affected animals (40.2% of the herd) independent of age died or had to be euthanized. Therapeutic attempts failed in almost all diseased cows, only four calves and three heifers recovered. Diagnostic samples of several animals (n = 4) (liver, ruminal and intestinal contents) and feed (n = 6) were tested for BoNT genes by polymerase chain reaction (PCR). BoNT gene type D was found in several (n = 8) organ samples. The PCR results allowed a preselection of samples for BoNT that were then tested by the mouse bioassay. Thus, the number of mice being inoculated in the mouse bioassay could be reduced. The mouse bioassay turned out positive (wasp-waist) in three preselected organ samples and the neutralization test of one sample with type-specific antitoxin confirmed the presence of BoNT type D. We succeeded in isolating a C. botulinum strain from a liver sample which was typed as a D/C mosaic strain by sequence analysis of the toxin gene. However, the source of the BoNT intoxication could not be traced back.

Idiotypic DNA vaccination for the treatment of multiple myeloma: safety and immunogenicity in a phase I clinical study

We report on the safety and immunogenicity of idiotypic DNA vaccination in a phase I, non-randomised, open-label study in patients with multiple myeloma. The study used DNA fusion gene vaccines encoding patient-specific single chain variable fragment, or idiotype (Id), linked to fragment C (FrC) of tetanus toxin. Patients in complete or partial response following high-dose chemotherapy and autologous stem cell transplant were vaccinated intramuscularly with 1 mg DNA on six occasions, beginning at least 6 months post-transplant; follow-up was to week 52. Fourteen patients were enrolled on study and completed vaccinations. Idiotypic DNA vaccines were well tolerated with vaccine-related adverse events limited to low-grade constitutional symptoms. FrC- and Id-specific T-cell responses were detected by ex vivo ELISPOT in 9/14 and 3/14 patients, respectively. A boost of pre-existing anti-FrC antibody (Ab) was detected by ELISA in 8/14 patients, whilst anti-Id Ab was generated in 1/13 patients. Overall, four patients (29 %) made an immune response to FrC and Id, with six patients (43 %) responding to FrC alone. Over the 52-week study period, serum paraprotein was undetectable, decreased or remained stable for ten patients (71 %), whilst ongoing CR/PR was maintained for 11 patients (79 %). The median time to progression was 38.0 months for 13/14 patients. Overall survival was 64 % after a median follow-up of 85.6 months.

Equivalent T cell epitope promiscuity in ecologically diverse human pathogens

Background

The HLA (human leukocyte antigen) molecules that present pathogen-derived epitopes to T cells are highly diverse. Correspondingly, many pathogens such as HIV evolve epitope variants in order to evade immune recognition. In contrast, another persistent human pathogen, Mycobacterium tuberculosis, has highly conserved epitope sequences. This raises the question whether there is also a difference in the ability of these pathogens’ epitopes to bind diverse HLA alleles, referred to as an epitope’s binding promiscuity. To address this question, we compared the in silico HLA binding promiscuity of T cell epitopes from pathogens with distinct infection strategies and outcomes of human exposure.

Methods

We used computer algorithms to predict the binding affinity of experimentally-verified microbial epitope peptides to diverse HLA-DR, HLA-A and HLA-B alleles. We then analyzed binding promiscuity of epitopes derived from HIV and M. tuberculosis. We also analyzed promiscuity of epitopes from Streptococcus pyogenes, which is known to exhibit epitope diversity, and epitopes of Bacillus anthracis and Clostridium tetani toxins, as these bacteria do not depend on human hosts for their survival or replication, and their toxin antigens are highly immunogenic human vaccines.

Results

We found that B. anthracis and C. tetani epitopes were the most promiscuous of the group that we analyzed. However, there was no consistent difference or trend in promiscuity in epitopes contained in HIV, M. tuberculosis, and S. pyogenes.

Conclusions

Our results show that human pathogens with distinct immune evasion strategies and epitope diversities exhibit equivalent levels of T cell epitope promiscuity. These results indicate that differences in epitope promiscuity do not account for the observed differences in epitope variation and conservation.

Synaptic activity in serotonergic neurons is required for air-puff stimulated flight in Drosophila melanogaster

Background

Flight is an integral component of many complex behavioral patterns in insects. The giant fiber circuit has been well studied in several insects including Drosophila. However, components of the insect flight circuit that respond to an air-puff stimulus and comprise the flight central pattern generator are poorly defined. Aminergic neurons have been implicated in locust, moth and Drosophila flight. Here we have investigated the requirement of neuronal activity in serotonergic neurons, during development and in adults, on air-puff induced flight in Drosophila.

Methodology/Principal Findings

To target serotonergic neurons specifically, a Drosophila strain that contains regulatory regions from the TRH (Tryptophan Hydroxylase) gene linked to the yeast transcription factor GAL4 was used. By blocking synaptic transmission from serotonergic neurons with a tetanus toxin transgene or by hyperpolarisation with Kir2.1, close to 50% adults became flightless. Temporal expression of a temperature sensitive Dynamin mutant transgene (Shi^ts) suggests that synaptic function in serotonergic neurons is required both during development and in adults. Depletion of IP₃R in serotonergic neurons via RNAi did not affect flight. Interestingly, at all stages a partial requirement for synaptic activity in serotonergic neurons was observed. The status of serotonergic neurons was investigated in the central nervous system of larvae and adults expressing tetanus toxin. A small but significant reduction was observed in serotonergic cell number in adult second thoracic segments from flightless tetanus toxin expressing animals.

Conclusions

These studies show that loss of synaptic activity in serotonergic neurons causes a flight deficit. The temporal focus of the flight deficit is during pupal development and in adults. The cause of the flight deficit is likely to be loss of neurons and reduced synaptic function. Based on the partial phenotypes, serotonergic neurons appear to be modulatory, rather than an intrinsic part of the flight circuit.

Contained and high-level production of recombinant protein in plant chloroplasts using a temporary immersion bioreactor

Chloroplast transformation is a promising approach for the commercial production of recombinant proteins in plants. However, gene containment still remains an issue for the large-scale cultivation of transplastomic plants in the field. Here, we have evaluated the potential of using tobacco transplastomic cell suspensions for the fully contained production of a modified form of the green fluorescent protein (GFP+) and, a vaccine antigen, fragment C of tetanus toxin (TetC). Expression of these proteins in cell suspension cultures (and calli) was much less than in leaves, reaching 0.5%-1.5% of total soluble protein (TSP), but still produced 2.4-7.2 mg/L of liquid culture. Much better expression levels were achieved with a novel protein production platform in which transgenic cell suspension cultures were placed in a temporary immersion bioreactor in the presence of Thidiazuron to initiate shoot formation. GFP+ yield reached 660 mg/L of bioreactor (33% TSP), and TetC accumulated to about 95 mg/L (8% TSP). This new production platform, combining the rapid generation of transplastomic cell suspension cultures and the use of temporary immersion bioreactors, is a promising route for the fully contained low-cost production of recombinant proteins in chloroplasts.

[Production and immunogenicity analysis of conformation-stable fragment-C mutant of tetanus toxin]

Tetanus is caused by tetanus toxin synthesized by Clostridium tetani. Fragment C (Hc), the 50 kDa carboxy-terminal portion of tetanus toxin, is nontoxic but has receptor protein binding activities, which has been evaluated as a potential new recombinant subunit vaccine to replace the traditional formaldehyde inactivated toxoid vaccine. It is easy for wild Hc (HcW) to form inter- and intra-molecular disulfide bonds and the different conformations changes unstably, which brings difficulties for vaccine production technology. In our study, the Cys 869 of HcW was mutated to A1a and the conformation-stable fragment-C mutant of tetanus toxin (HcM) was constructed. The HcM was expressed, fermented and purified and its stability, receptor binding and immunogenicity were evaluated. The result showed that the HcM got high-level expression and was purified to > 95% of purity. The purified HcM was conformation-stable at different temperature for different time and kept the binding activities with one of its receptor GT1b. Mice given three vaccinations by HcM developed a protective immune response and were 100% protected against an intraperitoneal administration of 1 x 10(3) 50% lethal doses (LD50s) of tetanus neurotoxin. All the results showed that the conformation-stable HcM had potent immunogenicity as a recombinant tetanus vaccine candidate with simple production process and similar immunogenicity with HcW. Whether for routine tetanus therapy or for countries to respond to unexpected events (war, earthquake or other disaster), it is of great significance.

Tetanus toxin C-fragment: the courier and the cure?

In many neurological disorders strategies for a specific delivery of a biological activity from the periphery to the central nervous system (CNS) remains a considerable challenge for successful therapy. Reporter assays have established that the non-toxic C-fragment of tetanus toxin (TTC), provided either as protein or encoded by non-viral naked DNA plasmid, binds pre-synaptic motor neuron terminals and can facilitate the retrograde axonal transport of desired therapeutic molecules to the CNS. Alleviated symptoms in animal models of neurological diseases upon delivery of therapeutic molecules offer a hopeful prospect for TTC therapy. This review focuses on what has been learned on TTC-mediated neuronal targeting, and discusses the recent discovery that, instead of being merely a carrier molecule, TTC itself may well harbor neuroprotective properties.

Metaplasticity at single glutamatergic synapses

Optimal function of neuronal networks requires interplay between rapid forms of Hebbian plasticity and homeostatic mechanisms that adjust the threshold for plasticity, termed metaplasticity. Numerous forms of rapid synapse plasticity have been examined in detail. However, the rules that govern synaptic metaplasticity are much less clear. Here, we demonstrate a local subunit-specific switch in NMDA receptors that alternately primes or prevents potentiation at single synapses. Prolonged suppression of neurotransmitter release enhances NMDA receptor currents, increases the number of functional NMDA receptors containing NR2B, and augments calcium transients at single dendritic spines. This local switch in NMDA receptors requires spontaneous glutamate release but is independent of action potentials. Moreover, single inactivated synapses exhibit a lower induction threshold for both long-term synaptic potentiation and plasticity-induced spine growth. Thus, spontaneous glutamate release adjusts plasticity threshold at single synapses by local regulation of NMDA receptors, providing a novel spatially delimited form of synaptic metaplasticity.

Gangliosides as high affinity receptors for tetanus neurotoxin

Tetanus neurotoxin (TeNT) is an exotoxin produced by Clostridium tetani that causes paralytic death to hundreds of thousands of humans annually. TeNT cleaves vesicle-associated membrane protein-2, which inhibits neurotransmitter release in the central nervous system to elicit spastic paralysis, but the molecular basis for TeNT entry into neurons remains unclear. TeNT is a approximately 150-kDa protein that has AB structure-function properties; the A domain is a zinc metalloprotease, and the B domain encodes a translocation domain and C-terminal receptor-binding domain (HCR/T). Earlier studies showed that HCR/T bound gangliosides via two carbohydrate-binding sites, termed the lactose-binding site (the "W" pocket) and the sialic acid-binding site (the "R" pocket). Here we report that TeNT high affinity binding to neurons is mediated solely by gangliosides. Glycan array and solid phase binding analyses identified gangliosides that bound exclusively to either the W pocket or the R pocket of TeNT; GM1a bound to the W pocket, and GD3 bound to the R pocket. Using these gangliosides and mutated forms of HCR/T that lacked one or both carbohydrate-binding pocket, gangliosides binding to both of the W and R pockets were shown to be necessary for high affinity binding to neuronal and non-neuronal cells. The crystal structure of a ternary complex of HCR/T with sugar components of two gangliosides bound to the W and R supported the binding of gangliosides to both carbohydrate pockets. These data show that gangliosides are functional dual receptors for TeNT.

Neurotransmission selectively regulates synapse formation in parallel circuits in vivo

Activity is thought to guide the patterning of synaptic connections in the developing nervous system. Specifically, differences in the activity of converging inputs are thought to cause the elimination of synapses from less active inputs and increase connectivity with more active inputs. Here we present findings that challenge the generality of this notion and offer a new view of the role of activity in synapse development. To imbalance neurotransmission from different sets of inputs in vivo, we generated transgenic mice in which ON but not OFF types of bipolar cells in the retina express tetanus toxin (TeNT). During development, retinal ganglion cells (RGCs) select between ON and OFF bipolar cell inputs (ON or OFF RGCs) or establish a similar number of synapses with both on separate dendritic arborizations (ON-OFF RGCs). In TeNT retinas, ON RGCs correctly selected the silenced ON bipolar cell inputs over the transmitting OFF bipolar cells, but were connected with them through fewer synapses at maturity. Time-lapse imaging revealed that this was caused by a reduced rate of synapse formation rather than an increase in synapse elimination. Similarly, TeNT-expressing ON bipolar cell axons generated fewer presynaptic active zones. The remaining active zones often recruited multiple, instead of single, synaptic ribbons. ON-OFF RGCs in TeNT mice maintained convergence of ON and OFF bipolar cells inputs and had fewer synapses on their ON arbor without changes to OFF arbor synapses. Our results reveal an unexpected and remarkably selective role for activity in circuit development in vivo, regulating synapse formation but not elimination, affecting synapse number but not dendritic or axonal patterning, and mediating independently the refinement of connections from parallel (ON and OFF) processing streams even where they converge onto the same postsynaptic cell.

Generation of plant-derived recombinant DTP subunit vaccine

The current diphtheria-tetanus-pertussis (DTP) pediatric vaccine is produced from the corresponding pathogenic bacteria Corynebacterium diphtheriae, Clostridium tetani and Bordetella pertussis; five injected doses of DTaP (acellular) vaccine are required for every child in the standard US vaccination schedule. Because the vaccine is derived from native live sources, adverse effects are possible and production is complex and costly. To address issues of safety, ease of renewability and expense, we used recombinant technology in an effort to develop a subunit DPT vaccine derived in non-pathogenic plant expression systems. Expression of diphtheria toxin (DT), tetanus fragment-C (TetC) and the non-toxic S1 subunit of pertussis toxin (PTX S1) antigenic proteins in soluble form in low-alkaloid tobacco plants and carrot cell cultures allowed efficient downstream purification to levels suitable for intramuscular injection in BALB/c mice. At working concentrations of 5mug per dose, these preparations induced high levels of antigen-specific IgGs in mouse sera. Our results clearly support the feasibility of producing recombinant pediatric vaccine components in plants.

Expression of a multi-epitope DPT fusion protein in transplastomic tobacco plants retains both antigenicity and immunogenicity of all three components of the functional oligomer

Expression of genes in plant chloroplasts provides an opportunity for enhanced production of target proteins. We report the introduction and expression of a fusion DPT protein containing immunoprotective exotoxin epitopes of Corynebacterium diphtheriae, Bordetella pertussis, and Clostridium tetani in tobacco chloroplasts. Using biolistic-mediated transformation, a plant-optimized synthetic DPT gene was successfully transferred to tobacco plastomes. Putative transplastomic T0 plants were identified by PCR, and Southern blot analysis confirmed homoplasmy in T1 progeny. ELISA assays demonstrated that the DPT protein retained antigenicity of the three components of the fusion protein. The highest level of expression in these transplastomic plants reached 0.8% of total soluble protein. To assess whether the functional recombinant protein expressed in tobacco plants would induce specific antibodies in test animals, a mice feeding experiment was conducted. For mice orally immunized with freeze-dried transplastomic leaves, production of IgG and IgA antibodies specific to each toxin were detected in serum and mucosal tissues.

Fit for purpose? A case study: validation of immunological endpoint assays for the detection of cellular and humoral responses to anti-tumour DNA fusion vaccines

Clinical trials are governed by an increasingly stringent regulatory framework, which applies to all levels of trial conduct. Study critical immunological endpoints, which define success or failure in early phase clinical immunological trials, require formal pre-trial validation. In this case study, we describe the assay validation process, during which the sensitivity, and precision of immunological endpoint assays were defined. The purpose was the evaluation of two multicentre phase I/II clinical trials from our unit in Southampton, UK, which assess the effects of DNA fusion vaccines on immune responses in HLA-A2+ patients with carcinoembryonic antigen (CEA)-expressing malignancies and prostate cancer. Validated immunomonitoring is being performed using ELISA and IFNgamma ELISPOTs to assess humoral and cellular responses to the vaccines over time. The validated primary endpoint assay, a peptide-specific CD8+ IFNgamma ELISPOT, was tested in a pre-trial study and found to be suitable for the detection of low frequency naturally occurring CEA- and prostate-derived tumour-antigen-specific T cells in patients with CEA-expressing malignancies and prostate cancer.

[Expression, purification of tetanus toxin C fragment/cardiotrophin-1 recombinant fusion protein, target delivery to CNS and neurotrophy biology ability]

OBJECTIVE

Expression, purification of tetanus toxin C fragment/cardiotrophin-1 recombinant fusion protein (CT-1/TTC) in BL21 (DE3) E. coli, examined whether tetanus toxin C fragment mediate the cardiotrophin-1 target delivery to the central nervous system and the cardiotrophin-1 has the neurotrophic ability.

METHODS

Induction by IPTG, the fusion protein was expressed and then purified by GST affinity agarose. The interest protein was viewed by SDS-PAGE, further characterized by Western Blot Rat sciatic nerve transected model was selected. Using drug by nerve-regeneration-chamber and intramuscular injection. Execute these animals one week after the operation. The L4-L6 segments of the spinal cord were harvested after transaortic perfusion with 4% paraformaldehyde. The freeze sections of spinal tissues were stained with immunohistochemistry method. And select the new born SD rat sciatic nerve transected model, using CT-1/TTC fusion protein by muscle injection. Execute these animals one week after the operation. The L4-L6 segments of the spinal cord were harvested after transaortic perfusion with 4% paraformaldehyde. The freeze sections of spinal tissues were stained by Nissl's staining.

RESULTS

After induction, the fusion protein was about 15% of the total protein and the soluble part was predominant. Purified by GST fusion protein column, the interest protein's concentration is 2.7 g/L. The CT-1/TTC fusion protein was found in lumbar intumescentia by immunohistochemistry method. And after sciatic nerve transected, the numbers of cornu anterius medullae spinalis motoneurons in L4-L6 segments, compared to CT-1/TTC protein grope, have a lower survival rate.

CONCLUSIONS

The recombinant CT-1/TTC protein can be expressed and purified in BL21 (DE3) E. coli. This fusion protein has two biological activities of targeting delivery to central nervous system and protecting the cornu anterius medullae spinalis motoneurons.

Induction of T cell-mediated immunity using a c-Myb DNA vaccine in a mouse model of colon cancer

Overexpression of the proto-oncogene c-Myb occurs in more than 80% of colorectal cancer (CRC) and is associated with aggressive disease and poor prognosis. To test c-Myb as a therapeutic target in CRC we devised a DNA fusion vaccine to generate an anti-CRC immune response. c-Myb, like many tumor antigens, is weakly immunogenic as it is a "self" antigen and subject to tolerance. To break tolerance, a DNA fusion vaccine was generated comprising wild-type c-Myb cDNA flanked by two potent Th epitopes derived from tetanus toxin. Vaccination was performed targeting a highly aggressive, weakly immunogenic, subcutaneous, syngeneic, colon adenocarcinoma cell line MC38 which highly expresses c-Myb. Prophylactic intravenous vaccination significantly suppressed tumor growth, through the induction of anti-tumor immunity for which the tetanus epitopes were essential. Vaccination generated anti-tumor immunity mediated by both CD4+ and CD8+ T cells and increased infiltration of immune effector cells at the tumor site. Importantly, no evidence of autoimmune pathology in endogenous c-Myb expressing tissues was detected as a consequence of breaking tolerance. In summary, these results establish c-Myb as a potential antigen for immune targeting in CRC and serve to provide proof of principle for the continuing development of DNA vaccines targeting c-Myb to bring this approach to the clinic.

Courtship initiation is stimulated by acoustic signals in Drosophila melanogaster

Finding a mating partner is a critical task for many organisms. It is in the interest of males to employ multiple sensory modalities to search for females. In Drosophila melanogaster, vision is thought to be the most important courtship stimulating cue at long distance, while chemosensory cues are used at relatively short distance. In this report, we show that when visual cues are not available, sounds produced by the female allow the male to detect her presence in a large arena. When the target female was artificially immobilized, the male spent a prolonged time searching before starting courtship. This delay in courtship initiation was completely rescued by playing either white noise or recorded fly movement sounds to the male, indicating that the acoustic and/or seismic stimulus produced by movement stimulates courtship initiation, most likely by increasing the general arousal state of the male. Mutant males expressing tetanus toxin (TNT) under the control of Gr68a-GAL4 had a defect in finding active females and a delay in courtship initiation in a large arena, but not in a small arena. Gr68a-GAL4 was found to be expressed pleiotropically not only in putative gustatory pheromone receptor neurons but also in mechanosensory neurons, suggesting that Gr68a-positive mechanosensory neurons, not gustatory neurons, provide motion detection necessary for courtship initiation. TNT/Gr68a males were capable of discriminating the copulation status and age of target females in courtship conditioning, indicating that female discrimination and formation of olfactory courtship memory are independent of the Gr68a-expressing neurons that subserve gustation and mechanosensation. This study suggests for the first time that mechanical signals generated by a female fly have a prominent effect on males' courtship in the dark and leads the way to studying how multimodal sensory information and arousal are integrated in behavioral decision making.

[Gene cloning, optimized expression and immunogenicity evaluation of tetanus toxin fragment C]

OBJECTIVE

To obtain highly purified tetanus toxin fragment C (TTC) with good immunogenicity.

METHODS

The gene fragment encoding TTC was amplified from Clostridium tetani plasmid DNA by PCR, inserted into the vector pET43.1a (+) and expressed in E. coli BL21(DE3)plysS. After purification using Ni2+-chelate affinity chromatography, the expressed fusion protein was digested by thrombin and the resultant TTC protein was purified with Ni2+-chelate affinity chromatography followed by identification with SDS-PAGE and Western blotting. The purifed TTC protein was then used to immunize mice to test its immunogenecity.

RESULTS

The 1373-bp gene fragment encoding TTC was obtained, and the constructed recombinant expression vector pET43.1a (+)-TTC was successfully expressed in E. coli BL21(DE3)plysS. SDS-PAGE identified a recombinant fusion protein with relative molecular mass (Mr) of 117 000, which accounted for 22% of the total bacterial protein. The TTC protein with Mr of 50 000 was obtained after purification of the thrombin digestion products of the fusion protein, with a purity reaching 95.5%. Both the fusion protein and TTC protein could be recognized by anti-tetanus toxin antibody as shown by Western blotting. The titer of the anti-serum from mice immunized with the TTC protein was 1:25 600, and the anti-serum could specifically bind to tetanus toxin.

CONCLUSION

Highly purified and immunogenetic TTC protein has been successfully obtained, which provides a good model antigen for studying antigen presentation and immune responses in vivo.

Gene activation using FLP recombinase in C. elegans

The FLP enzyme catalyzes recombination between specific target sequences in DNA. Here we use FLP to temporally and spatially control gene expression in the nematode C. elegans. Transcription is blocked by the presence of an "off cassette" between the promoter and the coding region of the desired product. The "off cassette" is composed of a transcriptional terminator flanked by FLP recognition targets (FRT). This sequence can be excised by FLP recombinase to bring together the promoter and the coding region. We have introduced two fluorescent reporters into the system: a red reporter for promoter activity prior to FLP expression and a green reporter for expression of the gene of interest after FLP expression. The constructs are designed using the multisite Gateway system, so that promoters and coding regions can be quickly mixed and matched. We demonstrate that heat-shock-driven FLP recombinase adds temporal control on top of tissue specific expression provided by the transgene promoter. In addition, the temporal switch is permanent, rather than acute, as is usually the case for heat-shock driven transgenes. Finally, FLP expression can be driven by a tissue specific promoter to provide expression in a subset of cells that can only be addressed as the intersection of two available promoters. As a test of the system, we have driven the light chain of tetanus toxin, a protease that cleaves the synaptic vesicle protein synaptobrevin. We show that we can use this to inactivate synaptic transmission in all neurons or a subset of neurons in a FLP-dependent manner.

[PCR-based assembly of the DNA sequence coding for tetanus toxin C fragment]

OBJECTIVE

To develop a PCR-based method for gene assembly of tetanus toxin C fragment (TETC) DNA sequence from a large number of oligodeoxyribonucleotides (oligos).

METHODS

To allow for its cloning and expression in Lactococcus lactis, the TETC gene sequence was designed according to the known TETC gene sequence (GenBank accession number M12739, 367-1719) and the amino acid coding in Lactococcus lactis. The sequence contained 1383 nucleotides (nt) with Sal I site added to its 5' end and Xho I and Hind III sites to its 3' end. There were 209 synonymous codon substitutions in the designed gene sequence as compared with the sequence reported in GenBank for amino acid coding in Lactococcus lactis and elimination of the restriction site of EcoR I and Kpn I. The 1380 nt of the sequence was divided into 68 oligos designated as TETC 1 to TETC 68, each containing 40 nt. A 16 nt oligos designated as TETC 69 was designed as the downstream primer. The TETC 1-24 fragment was acquired using the oligos TETC 1 to TETC 24 by PCR-based gene assembly method, and the TETC 23-46 and TETC45-68 fragments were assembled similarly. The full-length TETC gene was assembled using TETC 1 and TETC 69 as the primers when the 3 fragments were mixed. The target gene was gel-purified and digested with Sal I and Hind III, followed by ligation to the pBluescript II SK(+) and digestion with the same enzymes. The positive clones were confirmed by restriction enzyme excision and sequencing.

RESULTS

Three 500-bp fragments were acquired by PCR-based gene assembly, and the full-length TETC gene was obtained from the 3 fragment mixed at a equal concentration by a second PCR-based gene assembly using TETC 1 and TETC 69 as the primers. The target gene was cloned to pBluescript II SK(+) vector, and sequence analysis of the positive clones indicated that the assembled sequence was identical to the designed coding sequence of TETC gene.

CONCLUSION

PCR-based assembly of the synthesized constitutive gene fragments into the complete sequence can be an effective strategy for synthesis of long DNA sequences in vitro.

Reversible unilateral nigrostriatal pathway inhibition induced through expression of adenovirus-mediated clostridial light chain gene in the substantia nigra

Clostridial light chain (LC) inhibits synaptic transmission by digesting a vesicle-docking protein, synaptobrevin, without killing neurons. We here report the feasibility of creating a rat hemiparkinsonism model through LC gene expression in the substantia nigra (SN), inhibiting nigrostriatal transmission. 40 adult Sprague Dawley rats were divided into four groups for SN injections of PBS, 6-hydroxydopamine (6-OHDA), or adenoviral vectors for the expression of LC (AdLC), or GFP (AdGFP). Amphetamine and apomorphine induced rotations were assessed before and after SN injection, revealing significant rotational alterations at 8 or 10 days after injection in both AdLC and 6-OHDA but not PBS and AdGFP groups. Induced rotation recovered by one month in AdLC rats but persisted in 6-OHDA rats. Histological analysis of the SN revealed LC and GFP expression with corresponding synaptobrevin depletion in the LC, but not the GFP groups. Tyrosine hydroxylase (TH) and dopamine transporter (DAT) immunohistochemistry (IHC) showed markedly decreased staining in ipsilateral SN and striatum in 6-OHDA but not AdLC or AdGFP rats. Similarly, compared with contralateral, ipsilateral striatal dopamine level only decreased in 6-OHDA but not AdLC, AdGFP, or PBS treated rats. Thus, LC expression induces nigral synaptobrevin depletion with resulting inhibition of nigrostriatal synaptic transmission. Unlike 6-OHDA, LC expression inhibits synaptic activity without killing neurons. This approach, therefore, represents a potentially reversible means of nigrostriatal pathway inhibition as a model for Parkinson's disease. Such a model might facilitate transient and controlled nigral inhibition for studying striatal recovery, dopaminergic re-innervation, and normalization of striatal receptors following the recovery of nigrostriatal transmission.

Myostatin DNA vaccine increases skeletal muscle mass and endurance in mice

Myostatin is a transforming growth factor-beta family member that acts as a negative regulator of skeletal muscle growth. In mice, genetic disruption of the myostatin gene leads to a marked increase in body weight and muscle mass. Similarly, pharmacological interference with myostatin in vivo in mdx knockout mice results in a functional improvement of the dystrophic phenotype. Consequently, myostatin is an important therapeutic target for treatment of diseases associated with muscle wasting. To construct a therapeutic DNA vaccine against myostatin, we coupled the foreign, immunodominant T-helper epitope of tetanus toxin to the N terminus of myostatin, and BALB/c mice were immunized with the recombinant vector. Sera from vaccinated mice showed the presence of specific antibodies against the recombinant protein. In addition, body weight, muscle mass, and grip endurance of vaccinated mice were significantly increased. Our study provides a novel, pharmacological strategy for treatment of diseases associated with muscle wasting.

Transgenic tomatoes express an antigenic polypeptide containing epitopes of the diphtheria, pertussis and tetanus exotoxins, encoded by a synthetic gene

A current priority of vaccinology is the development of multicomponent vaccines that protect against several pathogens. The diphtheria-pertussis-tetanus (DPT) vaccine prevents the symptoms of three serious and often fatal diseases due to the exotoxins produced by Corynebacterium diphteriae, Bordetella pertussis and Clostridium tetani. We are attempting to develop an edible DPT multicomponent vaccine in plants, based on the fusion of protective exotoxin epitopes encoded by synthetic genes. By means of Agrobacterium mediated transformation we generated transgenic tomatoes with a plant-optimised synthetic gene encoding a novel polypeptide containing two adjuvant and six DPT immunoprotective exotoxin epitopes joined by peptide linkers. In transformed tomato plants, integration of the synthetic DPT (sDPT) gene detected by PCR was confirmed by Southern blot, and specific transcripts of the expected molecular size were detected by RT-PCR. Expression of the putative polypeptide encoded by the sDPT gene was detected by immunoassay with specific antibodies to the diphtheria, pertussis and tetanus exotoxins. The sDPT gene is therefore integrated, transcribed and translated as the expected recombinant sDPT multiepitope polypeptide in transgenic tomatoes that constitute a potential edible vaccine.

Expression of foreign proteins in a Vibrio cholerae vaccine strain using the stationary phase hemagglutinin/protease promoter

The use of the hemagglutinin(HA)/protease promoter and secretion signals to drive expression and secretion of a foreign antigen in a live genetically attenuated cholera vaccine candidate is demonstrated. A Vibrio cholerae vaccine strain, containing a HA/protease-tetanus toxin C fragment (TCF) fusion, produced soluble-and cell-associated TCF. The fraction of TCF secreted to the culture medium was degraded unless expressed in a HA/protease-defective vaccine strain. Comparison of the hapA promoter with the strong Tac promoter using quantitative real time PCR revealed that at least five times more TCF mRNA was produced when expressed from the hapA promoter.

Reconstruction of a pathway of antigen processing and class II MHC peptide capture

Endocytosed antigens are proteolytically processed and small amounts of peptides captured by class II MHC molecules. The details of antigen proteolysis, peptide capture and how destruction of T-cell epitopes is avoided are incompletely understood. Using the tetanus toxin antigen, we show that the introduction of 3-6 cleavage sites is sufficient to trigger a partially unfolded conformation able to bind to class II MHC molecules. The known locations of T-cell epitopes and protease cleavage sites predict that large domains of processed antigen (8-35 kDa) are captured under these conditions. Remarkably, when antigen is bound to the B-cell antigen receptor (BCR), processing can trigger a concerted 'hand-over' reaction whereby BCR-associated processed antigen is captured by neighbouring class II MHC molecules. Early capture of minimally processed antigen and confinement of the processing and class II MHC loading reaction to the membrane plane may improve the likelihood of T-cell epitope survival in the class II MHC pathway and may help explain the reciprocal relationships observed between B- and T-cell epitopes in many protein antigens and autoantigens.

Primed vesicles can be distinguished from docked vesicles by analyzing their mobility

Neurotransmitters are released from nerve terminals and neuroendocrine cells by calcium-dependent exocytosis of vesicles. Before fusion, vesicles are docked to the plasma membrane and rendered release competent through a process called priming. Electrophysiological methods such as membrane capacitance measurements and carbon fiber amperometry accurately measure the fusion step of exocytosis with high time resolution but provide only indirect information about priming and docking. Total internal reflection fluorescence microscopy (TIRFM) enables the real-time visualization of vesicles, near the plasma membrane, as they undergo changes from one molecular state to the other. We devised a new method to analyze the mobility of vesicles, which not only allowed us to classify the movement of vesicles in three different categories but also to monitor dynamic changes in the mobility of vesicles over time. We selectively enhanced priming by treating bovine chromaffin cells with phorbol myristate acetate (PMA) or by overexpressing Munc13-1 (mammalian Unc) and analyzed the mobility of large dense-core vesicles. We demonstrate that nearly immobile vesicles represent primed vesicles because the pool of vesicles displaying this type of mobility was significantly increased after PMA treatment and Munc13-1 overexpression and decreased during tetanus toxin expression. Moreover, we showed that the movement of docked but unprimed vesicles is restricted to a confined region of approximately 220 nm diameter. Finally, a small third population of undocked vesicles showed a directed and probably active type of mobility. For the first time, we can thus distinguish the molecular state of vesicles in TIRFM by their mobility.

Candidate live, attenuated Salmonella enterica serotype Typhimurium vaccines with reduced fecal shedding are immunogenic and effective oral vaccines

Environmental shedding of genetically manipulated microorganisms is an issue impeding the development of new live vaccines. We have investigated the immunogenicity of a number of novel Salmonella enterica serotype Typhimurium oral vaccine candidates that express the fragment C (TetC) component of tetanus toxin and harbor combinations of additional mutations in genes shdA, misL, and ratB that contribute to the persistence of serotype Typhimurium's colonization of the intestine. Serotype Typhimurium aroA (TetC) derivatives harboring additional mutations in either shdA or misL or combinations of these mutations exhibited a marked decrease in shedding of the vaccine strain in the feces of orally vaccinated mice. However, equivalent levels of anti-TetC and anti-Salmonella lipopolysaccharide immunoglobulin G (IgG), IgG1, IgG2a, and IgA were detected in sera of the vaccinated but not of the control mice. Cellular immune responses to TetC were detected in all vaccinated mice, regardless of the presence of the additional mutations in shdA or misL. Further, immunization with serotype Typhimurium aroA candidate vaccines harboring shdA and misL afforded complete protection against challenge with a virulent strain of serotype Typhimurium.

Differential potencies of effector genes in adult Drosophila

The GAL4/UAS gene expression system in Drosophila has been crucial in revealing the behavioral significance of neural circuits. Transgene products that block neurotransmitter release and induce cell death have been proved to inhibit neural function powerfully. Here we compare the action of the five effector genes shibire(ts1), Tetanus toxin light chain (TNT), reaper, Diphtheria toxin A-chain (DTA), and inwardly rectifying potassium channel (Kir2.1) and show differences in their efficiency depending on the target cells and the timing of induction. Specifically, effectors blocking neuronal transmission or excitability led to adult-induced paralysis more efficiently than those causing cell ablation. We contrasted these differential potencies in adult to their actions during development. Furthermore, we induced TNT expression in the adult mushroom bodies. In contrast to the successful impairment in short-term olfactory memory by shibire(ts1), adult TNT expression in the same set of cells did not lead to any obvious impairment. Altogether, the efficiency of effector genes depends on properties of the targeted neurons. Thus, we conclude that the selection of the appropriate effector gene is critical for evaluating the function of neural circuits.

Inducible expression of retrograde transynaptic genetic tracer in mice

A key step towards understanding the development and function of the central nervous system is by characterizing the connections between neurons. Tetanus toxin C fragment (TTC) is transynaptically and retrogradely transported without the toxin's pathogenic effect, and therefore, recently it has been used as a genetic tracer combined with beta-galactosidase or green fluorescent protein. Here, we introduce a new fusion construct, APTTC, consisting of the truncated human placental alkaline phosphatase with TTC, and generating the transgenic mouse line, (tetracycline operator) tetO-APTTC, for inducible expression of APTTC regulated by tetO. We demonstrate that APTTC is transported retrogradely and transynaptically, and allows us to robustly visualize the inputs of the expressing neurons when transgenetically expressed in mice, exemplified in the striatal neuronal circuit. Therefore, tetO-APTTC transgenic mouse line can be widely used for visualization of neuronal connectivity when combined with mice carrying tetracycline-controlled transactivator (tTA) in any specific neurons.

Impact of plasmid stability on oral DNA delivery by Salmonella enterica serovar Typhimurium

Live attenuated Salmonellae may overcome limitations with conventional methods of DNA immunisation. This study examined the impact of plasmid stability on oral DNA delivery by the attenuated Salmonella enterica serovar Typhimurium vaccine strain BRD509. A DNA vaccine cassette comprising the C fragment of tetanus toxin under control of the cytomegalovirus (CMV) promoter was ligated into plasmid pcDNA3, pUC18, pBBR122, pACYC184, pRSF1010/CAT, pBR322 and pAT153. In vitro and in vivo stability studies revealed that, with the exception of pcDNA3 and pUC18, the plasmids were retained by BRD509. However, pAT153 was the only plasmid to induce a tetanus toxoid-specific antibody response following oral delivery. Plasmid copy number was found to impact on plasmid stability and the induction of antigen-specific humoral responses.

Prime-Boost with Alternating DNA Vaccines Designed to Engage Different Antigen Presentation Pathways Generates High Frequencies of Peptide-Specific CD8+ T Cells

The route for presentation of Ag to CD8+ or CD4+ T cells following DNA vaccination is critical for determining outcome, but the pathways involved are unclear. In this study, we compare two different DNA vaccine designs aimed to elicit CD8+ T cell responses against a specific peptide-epitope either by direct- or cross-presentation. Each carries sequences from tetanus toxin (TT) to provide essential CD4+ T cell help. In the first already proven design, the peptide-epitope is fused to the N-terminal domain of fragment C from TT. This appears to act mainly by cross-presentation. In the second design, the peptide-epitope is encoded by a minigene, with induction of Th responses mediated by coexpression of a hybrid invariant chain molecule, incorporating a single determinant from TT (p30) in exchange for class II-associated invariant chain peptide. This design appears to act mainly via direct presentation from transfected APCs. Both vaccines mediated Th-dependent priming of CD8+ T cells in mice, but the kinetics and level of the responses differed markedly, consistent with engagement of distinct pathways of Ag presentation. Importantly, the vaccines could be combined in an alternating prime-boost regime, in either order, generating substantially expanded memory CD8+ T cells, with potent effector function. Taken together, these results demonstrate that vaccination protocols involving different modes of Ag presentation at prime and boost can significantly improve the effectiveness of immunization.

Distinct functions of neuronal synaptobrevin in developing and mature fly photoreceptors

Neuronal synaptobrevin (n-Syb, alias VAMP2), a synaptic vesicle membrane protein with a central role in neurotransmission, is specifically cleaved by the light chain of tetanus neurotoxin (TNT) that is known to reliably block neuroexocytosis. Here, we study fly photoreceptors transmitting continuous, graded signals to first order interneurons in the lamina, and report consequences of targeted expression of TNT in these cells using the UAS/GAL4 driver/effector system. Expressing the toxin throughout photoreceptor development causes developmental, electrophysiological, and behavioral defects. These can be differentiated by confining toxin expression to shorter developmental periods. Applying a method for controlled temporal and spatial TNT expression, we found that in the early pupa it impaired the development of the retina; in the midpupa, during synapse formation TNT caused a severe hypoplasia of the lamina that persisted into adulthood and left the photoreceptor-interneuron synapses of the lamina without function. Finally, during adulthood TNT neither blocks synaptic transmission in photoreceptors nor depletes the cells of n-Syb. Our study suggests a novel, cell type-specific function of n-Syb in synaptogenesis and it distinguishes between two synapse types: TNT resistant and TNT sensitive ones. These results need to be taken into account if TNT is used for neural circuit analysis.

Reduction of the ganglioside binding activity of the tetanus toxin HC fragment destroys immunogenicity: implications for development of novel tetanus vaccines

In this study, the immunogenicities of the nontoxic H(C) fragment of tetanus toxin and derivatives lacking ganglioside binding activity were compared with that of tetanus toxoid after subcutaneous immunization of mice. Wild-type H(C) (H(C)WT) protein and tetanus toxoid both elicited strong antibody responses against toxoid and H(C) antigens and provided complete protection against toxin challenge. Mutants of H(C) containing deletions essential for ganglioside binding elicited lower responses than H(C)WT. H(C)M115, containing two amino acid substitutions within the ganglioside binding site, provided reduced protection against tetanus toxin challenge compared with H(C)WT, consistent with lower anti-H(C) and anti-toxoid antibody titers. Circular-dichroism spectroscopy and intrinsic fluorescence spectroscopy showed minimal structural perturbation in H(C)M115. We conclude that the presence of the ganglioside binding site within H(C) may be essential for induction of a fully protective anti-tetanus response comparable to that induced by tetanus toxoid by subcutaneous injection.

Expression of HLA-DP0401 molecules for identification of DP0401 restricted antigen specific T cells

Human histocompatibility leukocyte antigen (HLA)-DPA1*0103/DPB1*0401 (DP0401) is the most common HLA class II molecule and is present in approximately 45% of the Caucasian population. In this study, soluble HLA-DP0401 molecules were expressed as "empty'' class II molecules in insect cells. Utilizing these soluble DP molecules and the Tetramer Guided Epitope Mapping (TGEM) approach, the influenza A Puerto Rico/8/34 matrix protein (MP) derived peptide MP(41-60) VLMEWLKTRPILSPLTKGIL and the Clostridium tetani Tetanus Toxin (TT) derived peptide TT(634-653) DKISDVSTIVPYIGPALNIV were identified as the DP0401 restricted MP and TT epitopes, respectively. In addition, T cells specific for the cancer testis antigen NY-ESO-1 and the breast/ovarian cancer over-expressing antigen Her-2/neu were detected in DP0401 subjects by DP0401 tetramers. The availability of HLA-DP0401 tetramers should facilitate the study of DP restricted T cell responses.

Enhanced immunisation and expression strategies using bacterial spores as heat-stable vaccine delivery vehicles

Spores of the gram positive bacterium Bacillus subtilis have been used as oral vaccine vehicles and have been shown to confer protection against tetanus in mice. In this work, we have used tetanus as a model with which to examine different antigen presentation strategies as well as dosing regimes using the TTFC antigen of Clostridium tetani. We show that display of the antigen on the spore surface produces a more pronounced, but less rapid, response than when the antigen is expressed in the germinating spore; though this response has a clear Th1 bias. When using the nasal dosing route ten times less spores were needed to produce the same level of protective antibodies using surface display of TTFC. Expression of the antigen within the germinating spore by contrast enables as little as three oral doses on consecutive days to generate protection with a noticeable Th2 bias. We have also shown that TTFC can be expressed using two routes, using display on the spore surface as well as in the germinating spore. This dual route produced the best responses in terms of magnitude and speed of neutralising response as well as a clear Th1 bias indicating the involvement of cellular as well as humoral responses.

DNA fusion vaccines induce epitope-specific cytotoxic CD8(+) T cells against human leukemia-associated minor histocompatibility antigens

The graft-versus-leukemia effect of allogeneic stem-cell transplantation is believed to be mediated by T-cell recognition of minor histocompatibility antigens on recipient cells. For minor histocompatibility antigens HA-1 and HA-2, normal cell expression is restricted to hemopoietic cells, and boosting the immune response to these antigens may potentiate graft-versus-leukemia effect without accompanying graft-versus-host disease. To increase efficacy, expansion of HA-1- or HA-2-specific CTL before transplantation is desirable. However, primary HA-1- or HA-2-specific CTL expanded in vitro are often of low avidity. An alternative approach is to prime specific CTL responses in vivo by vaccination. Clearly, donor vaccination must be safe and specific. We have developed DNA fusion vaccines able to induce high levels of epitope-specific CTL using linked CD4(+) T-cell help. The vaccines incorporate a domain of tetanus toxin (DOM) fused to a sequence encoding a candidate MHC class I binding peptide. This design generates antitumor CD8(+) T-cell responses and protective immunity in preclinical models. For clinical application, we constructed vaccines encoding HLA-A*0201-restricted peptides from human HA-1 and HA-2, which were fused to DOM, and tested their performance in HLA-A*0201-transgenic mice. Priming induced epitope-specific, IFNgamma-producing CD8(+) T cells with cytotoxic function boosted to high levels with electroporation. Strikingly, these mouse T cells efficiently killed human lymphoblastoid cell lines expressing endogenous HA-1 or HA-2. High avidity is indicated by the independence of cytolysis from CD8/MHC class I interaction. These safe epitope-specific vaccines offer a potential strategy to prime HA-1- or HA-2-specific CTL in transplant donors before adoptive transfer.

Anatomically discrete functional effects of adenoviral clostridial light chain gene-based synaptic inhibition in the midbrain

The gene for the Light Chain fragment of Tetanus Toxin (LC) induces synaptic inhibition by preventing the release of synaptic vesicles. The present experiment applied this approach within the rat midbrain in order to demonstrate that LC gene expression can achieve functionally and anatomically discrete effects within a sensitive brain structure. The deep layers of the superior colliculus/deep mesencephalic nucleus (dSC/DpMe) that are located in the rostral midbrain has been implicated in fear-induced increase of the acoustic startle reflex (fear potentiated startle) but exists in close proximity to neural structures important for a variety of critical functions. The dSC/DpMe of adult rats was injected bilaterally with adenoviral vectors for LC, green fluorescent protein, or vehicle. Synaptobrevin was depleted in brain regions of adenoviral LC expression. LC gene expression in the dSC/DpMe inhibited the increase in startle amplitude seen with the control viral infection, and blocked context-dependent potentiation of startle induced by fear conditioning. Although LC gene expression reduced the absolute amount of cue-specific fear potentiated startle, it did not decrease percent potentiated startle to a cue, nor did it reduce fear-induced contextual freezing, nonspecific locomotor activity, or general health, indicating that its effects were functionally and anatomically specific. Thus, vector-driven LC expression inhibits the function of deep brain nuclei without altering the function of surrounding structures supporting its application to therapeutic neuromodulation.

Motor neurone targeting of IGF-1 prevents specific force decline in ageing mouse muscle

IGF-1 is a potent growth factor for both motor neurones and skeletal muscle. Muscle IGF-1 is known to provide target-derived trophic effects on motor neurones. Therefore, IGF-1 overexpression in muscle is effective in delaying or preventing deleterious effects of ageing in both tissues. Since age-related decline in muscle function stems partly from motor neurone loss, a tetanus toxin fragment-C (TTC) fusion protein was created to target IGF-1 to motor neurones. IGF-1-TTC retains IGF-1 activity as indicated by [(3)H]thymidine incorporation into L6 myoblasts. Spinal cord motor neurones effectively bound and internalized the IGF-1-TTC in vitro. Similarly, IGF-1-TTC injected into skeletal muscles was taken up and retrogradely transported to the spinal cord in vivo, a process prevented by denervation of injected muscles. Three monthly IGF-1-TTC injections into muscles of ageing mice did not increase muscle weight or muscle fibre size, but significantly increased single fibre specific force over aged controls injected with saline, IGF-1, or TTC. None of the injections changed muscle fibre type composition, but neuromuscular junction post-terminals were larger and more complex in muscle fibres injected with IGF-1-TTC, compared to the other groups, suggesting preservation of muscle fibre innervation. This work demonstrates that induced overexpression of IGF-1 in spinal cord motor neurones of ageing mice prevents muscle fibre specific force decline, a hallmark of ageing skeletal muscle.

Efficient production of complement (C3d)3 fusion proteins using the baculovirus expression vector system

Proteins fused to activated complement (C) fragments elicit enhanced immunogenicity. This "natural adjuvant" effect may have important implications when considering novel vaccination approaches. Here we describe both the construction of a novel fusion protein, consisting of a well characterized test antigen fused to multiple copies of the activated complement component (C3d)3, as well as an efficient method for its expression and production in insect cells. Using the inherent biological advantages of the baculovirus expression system, as well as applying specific infection and harvesting modifications, we have optimized the efficiency of protein production. Our modifications allow purification of fusion proteins directly from cell supernatant in a single anion exchange chromatographic step. This alleviates the requirement for the inclusion of protein affinity tags. The integrity of the purified recombinant protein was evaluated by SDS PAGE analysis, reactivity with antibodies, as well as in vivo by administration as an immunogen.

Molecular characterization of Clostridium tetani strains by pulsed-field gel electrophoresis and colony PCR

Pulsed-field gel electrophoresis and PCR were applied for the first time to the molecular characterization of Clostridium tetani. Among five strains tested, one (CN1339) turned out to contain a mixture of two genetically different clones and two (D11 and G761) to contain bacteria differing by the presence or absence of the 74-kb plasmid harboring the tetX gene.