New advances in the production of edible plant vaccines: chloroplast expression of a tetanus vaccine antigen, TetC

Vaccines are a proven method of controlling disease. However there are issues with the delivery and administration of vaccines. A particular problem is that the majority of vaccines currently used are injected, which can be unsafe if needles are reused in areas where blood-borne diseases are prevalent. Vaccines targeting the mucosal immune system avoid many of the problems associated with injections. One potential form of mucosal vaccine is based on the expression of vaccine antigens in plants. Current research in this area has focused on the expression of immunogens from the plant's nuclear genome but low expression levels generally achieved using this system have limited progress. In recent work we have used the model antigen, TetC, which confers resistance to Tetanus infection, to demonstrate the feasibility of expressing vaccine antigens at high levels in the plant chloroplast.

A survival motor neuron:tetanus toxin fragment C fusion protein for the targeted delivery of SMN protein to neurons

Spinal muscular atrophy (SMA) is a degenerative disorder of spinal motor neurons caused by homozygous mutations in the survival motor neuron (SMN1) gene. Because increased tissue levels of human SMN protein (hSMN) in transgenic mice reduce the motor neuron loss caused by murine SMN knockout, we engineered a recombinant SMN fusion protein to deliver exogenous hSMN to the cytosolic compartment of motor neurons. The fusion protein, SDT, is comprised of hSMN linked to the catalytic and transmembrane domains of diphtheria toxin (DTx) followed by fragment C of tetanus toxin (TTC). Following overexpression in Escherichia coli, SDT possessed a subunit molecular weight of approximately 130 kDa as revealed by both SDS-PAGE and immunoblot analyses with anti-SMN, anti-DTx, and anti-TTC antibodies. Like wild-type SMN, purified SDT showed specific binding in vitro to an RG peptide derived from Ewing's sarcoma protein. The fusion protein also bound to cultured primary neurons in amounts similar to those achieved by TTC. Unlike the case with TTC, however, immunolabeling of SDT-treated neurons with anti-TTC and anti-SMN antibodies showed staining restricted to the cell surface. Results from cytotoxicity studies in which the DTx catalytic domain of SDT was used as a reporter protein for internalization and membrane translocation activity suggest that the SMN moiety of the fusion protein is interfering with one or both of these processes. While these studies indicate that SDT may not be useful for SMA therapy, the use of the TTC:DTx fusion construct to deliver other passenger proteins to the neuronal cytosol should not be ruled out.

[Production of recombinant fragments of the Clostridium tetani neurotoxin for the development of new immune-prophylaxis preparations against tetanus]

Tetanus belongs to dangerous infection diseases, whose effective prevention can be ensured by vaccines. The acting substance of tetanus vaccines, presently in use, is a partially purified and deprived-of-lethal-action Clostridium tetani neurotoxin. The construction of a subunit preparation on the basis of toxin fragments obtained through gene engineering could be a method aimed at promoting the quality of the used tetanus vaccines. With this goal in mind, we built, within the present case study, the expressing genetic constructions and obtained, in the pure form, an extensive tetanus-vaccine chain with its C-terminal (Hc) fragment, hydride peptides, containing the Hc-fragment and C-terminal fragment of toxin B C. difficile, as well as Hc-fragment and S3 collagen-binding domain of collagenase C. histolyticum. The thus obtained proteins can be used in testing their immunogenic and protective properties, while the conducted study could be a basis for further research of a new-generation vaccine against tetanus and other human infection diseases.

Reversible suppression of glutamatergic neurotransmission of cerebellar granule cells in vivo by genetically manipulated expression of tetanus neurotoxin light chain

We developed a novel technique that allowed reversible suppression of glutamatergic neurotransmission in the cerebellar network. We generated two lines of transgenic mice termed Tet and TeNT mice and crossed the two transgenic lines to produce the Tet/TeNT double transgenic mice. In the Tet mice, the tetracycline-controlled reverse activator (rtTA) was expressed selectively in cerebellar granule cells by the promoter function of the GABA(A) receptor alpha6 subunit gene. In the TeNT mice, the fusion gene of tetanus neurotoxin light chain (TeNT) and enhanced green fluorescent protein (EGFP) was designed to be induced by the interaction of doxycycline (DOX)-activated rtTA with the tetracycline-responsive promoter. The Tet/TeNT mice grew normally even after DOX treatment and exhibited a restricted DOX-dependent expression of TeNT in cerebellar granule cells. Along with this expression, TeNT proteolytically cleaved the synaptic vesicle protein VAMP2 (also termed synaptobrevin2) and reduced glutamate release from granule cells. Both cleavage of VAMP2/synaptobrevin2 and reduction of glutamate release were reversed by removal of DOX. Among the four genotypes generated by heterozygous crossing of Tet and TeNT mice, only Tet/TeNT mice showed DOX-dependent reversible motor impairments as analyzed with fixed bar and rota-rod tests. Reversible suppression of glutamatergic neurotransmission thus can be manipulated with spatiotemporal accuracy by DOX treatment and removal. These transgenic mice will serve as an animal model to study the cerebellar function in motor coordination and learning.

In vitro and in vivo stability of recombinant plasmids in a vaccine strain of Salmonella enterica var. Typhimurium

This study examined the ability of different plasmid vectors encoding H(C) fragment, the non-toxic binding portion of tetanus toxin, to be stably retained by Salmonella enterica var. Typhimurium (Salmonella typhimurium) vaccine strain BRD509 and, upon immunisation, to induce an antibody response against the carried antigen. The H(C) fragment expression cassette containing the transcription/translation signals, H(C) fragment open reading frame and the downstream TrpA terminator, was excised from pTETtac4 and incorporated into the plasmids pIC20H, pBR322, pACYC184 and pRSF1010. The resulting constructs were transferred into attenuated S. typhimurium, BRD509, and the level of H(C) fragment expression was examined by Western blot analysis. The relative stability of each plasmid in S. typhimurium was determined in vitro in the absence of antibiotic selection, and in vivo following immunisation. The ability of each H(C) fragment-expressing strain to induce lipopolysaccharide- and tetanus toxoid-specific antibody responses was assayed by an enzyme-linked immunosorbent assay. These studies showed that all the vaccine vector constructs, except the S. typhimurium carrying the expression vector based on pIC20H, were able to elicit a high titre immune response. The level of tetanus toxoid-specific antibody induced by S. typhimurium directly correlated with the level of in vitro and in vivo stability of the H(C) fragment expression plasmid carried by the bacterium, and not with an increased copy number of the parent plasmid vector.

Blocking sensory inputs to identified antennal glomeruli selectively modifies odorant perception in Drosophila

Neural coding of sensory input is a major unsolved issue in neuroscience. Current experimental methods rely on neural activity recording or visualization following sensory stimulation. Most of them, however, do not include behavioral correlates on the actual perception by the animal. We present a novel approach to address olfaction and coding in adult Drosophila. Sensory input was selectively blocked in two subsets of sensory neurons that project to different, albeit overlapping, groups of central targets, by means of tetanus toxin expressed under the control of the yeast transcription factor Gal4. Glomeruli DL1, DL2, VM1, and VM4 were tested following stimulation with benzaldehyde, ethyl acetate, propionic acid, butanol, or acetone at various concentrations. The behavioral response was found to be modified in an odorant-specific and a concentration-dependent manner. Sensory input to DL2 and, to a minor extent, VM1 and/or VM4, appear to be required for benzaldehyde perception, while acetone is processed through DL1. None of these glomeruli, however, seem necessary for butanol perception. In addition, sexual differences were observed for some stimuli. These results demonstrate the behavioral relevance of odor representation as maps of glomerular activity generated in the antennal lobes following specific sensory input. The strategy used here should be useful to characterize olfactory coding, as new and selective Gal4 lines become available.

Targeted expression of tetanus toxin reveals sets of neurons involved in larval locomotion in Drosophila

The Drosophila larva is widely used for studies of neuronal development and function, yet little is known about the neuronal basis of locomotion in this model organism. Drosophila larvae crawl over a plain substrate by performing repetitive waves of forward peristalsis alternated by brief episodes of head swinging and turning. To identify sets of central and peripheral neurons required for the spatial or temporal pattern of larval locomotion, we blocked neurotransmitter release from defined populations of neurons by targeted expression of tetanus toxin light chain (TeTxLC) with the GAL4/UAS system. One hundred fifty GAL4 lines were crossed to a UAS-TeTxLC strain and a motion-analysis system was used to identify larvae with abnormal movement patterns. Five lines were selected that show discrete locomotor defects (i.e., increased turning and pausing) and these defects are correlated with diverse sets of central neurons. One line, 4C-GAL4, caused an unusual circling behavior that is correlated with approximately 200 neurons, including dopaminergic and peptidergic interneurons. Expression of TeTxLC in all dopaminergic and serotonergic but not in peptidergic neurons, caused turning deficits that are similar to those of 4C-GAL4/TeTxLC larvae. The results presented here provide a basis for future genetic studies of motor control in the Drosophila larva.

Targeted gene expression in Drosophila dopaminergic cells using regulatory sequences from tyrosine hydroxylase

Dopamine (DA) is the only catecholaminergic neurotransmitter in the fruit fly Drosophila melanogaster. Dopaminergic neurons have been identified in the larval and adult central nervous system (CNS) in Drosophila and other insects, but no specific genetic tool was available to study their development, function, and degeneration in vivo. In Drosophila as in vertebrates, the rate-limiting step in DA biosynthesis is catalyzed by the enzyme tyrosine hydroxylase (TH). The Drosophila TH gene (DTH) is specifically expressed in all dopaminergic cells and the corresponding mutant, pale (ple), is embryonic lethal. We have performed ple rescue experiments with modified DTH transgenes. Our results indicate that partially redundant regulatory elements located in DTH introns are required for proper expression of this gene in the CNS. Based on this study, we generated a GAL4 driver transgene, TH-GAL4, containing regulatory sequences from the DTH 5' flanking and downstream coding regions. TH-GAL4 specifically expresses in dopaminergic cells in embryos, larval CNS, and adult brain when introduced into the Drosophila genome. As a first application of this driver, we observed that in vivo inhibition of DA release induces a striking hyperexcitability behavior in adult flies. We propose that TH-GAL4 will be useful for studies of the role of DA in behavior and disease models in Drosophila.

Expression of tetanus toxin Fragment C in tobacco chloroplasts

Fragment C (TetC) is a non-toxic 47 kDa polypeptide fragment of tetanus toxin that can be used as a subunit vaccine against tetanus. Expression of TetC in Escherichia coli and yeast was dependent on the availability of synthetic genes that were required to improve translation efficiency and stabilize the mRNA. To explore the feasibility of producing TetC in tobacco leaves, we attempted expression of both the bacterial high-AT (72.3% AT) and the synthetic higher-GC genes (52.5% AT) in tobacco chloroplasts. We report here that the bacterial high-AT mRNA is stable in tobacco chloroplasts. Significant TetC accumulation was obtained from both genes, 25 and 10% of total soluble cellular protein, respectively, proving the versatility of plastids for expression of unmodified high-AT and high-GC genes. Mucosal immunization of mice with the plastid- produced TetC induced protective levels of TetC antibodies. Thus, expression of TetC in chloroplasts provides a potential route towards the development of a safe, plant-based tetanus vaccine for nasal and oral applications.

Identification of a binding site for ganglioside on the receptor binding domain of tetanus toxin

The carboxyl-terminal region of the tetanus toxin heavy chain (H(C) fragment) binds to di- and trisialylgangliosides on neuronal cell membranes. To determine which amino acids in tetanus toxin are involved in ganglioside binding, homology modeling was performed using recently resolved X-ray crystallographic structures of the tetanus toxin H(C) fragment. On the basis of these analyses, two regions in tetanus toxin that are structurally homologous with the binding domains of other sialic acid and galactose-binding proteins were targeted for mutagenesis. Specific amino acids within these regions were altered using site-directed mutagenesis. The amino acid residue tryptophan 1288 was found to be critical for binding of the H(C) fragment to ganglioside GT1b. Docking of GD1b within this region of the toxin suggested that histidine 1270 and aspartate 1221 were within hydrogen bonding distance of the ganglioside. These two residues were mutagenized and found also to be important for the binding of the tetanus toxin H(C) fragment to ganglioside GT1b. In addition, the H(C) fragments mutagenized at these residues have reduced levels of binding to neurites of differentiated PC-12 cells. These studies indicate that the amino acids tryptophan 1288, histidine 1270, and aspartate 1221 are components of the GT1b binding site on the tetanus toxin H(C) fragment.

Protection against tetanus toxin after intragastric administration of two recombinant lactic acid bacteria: impact of strain viability and in vivo persistence

Non-pathogenic lactic acid bacteria (LAB) are attractive as live carriers to deliver protective antigens to the mucosal immune system. Both persisting and non-persisting strains of lactic acid bacteria have been evaluated and seem to work equally well by the systemic and nasal routes of administration. However, it is not known if persistence and viability of the strain play a critical role when immunizing by the oral route. To address this question, recombinant LAB strains, able to persist (Lactobacillus plantarum NCIMB8826/pMEC127) or not (Lactococcus lactis MG1363/pMEC46) in the gastro-intestinal tract of mice and producing equivalent amounts of the tetanus toxin fragment C (TTFC) were compared to each other. A very strong ELISA TTFC-specific and protective humoral response was elicited by either live or UV-inactivated recombinant Lb. plantarum strains. In a similar protocol, recombinant Lc. lactis seemed to be somewhat less efficient than the former host. It is thus tempting to propose that the difference in the capacity of the bacterial vector to persist in the gastro-intestinal tract impacts on its immunogenicity and on the level of protection it may induce. Protection was slightly superior after administration of live strains.

Hybrid tetanus toxin C fragment-diphtheria toxin translocation domain allows specific gene transfer into PC12 cells

To study the mechanism by which genes can efficiently be transferred into specific cell types, we have constructed several novel, single-chain multicomponent proteins by recombining the nontoxic C fragment of tetanus toxin and the translocation domain of diphtheria toxin together with the DNA-binding fragment of GAL4 transcription factor, for transportation of plasmid DNA into neuronal cells. The C fragment of tetanus toxin provided neuronal selectivity, the translocation domain of diphtheria toxin permitted endosomal escape, and the GAL4 domain provided binding to DNA. To assess the cellular tasks of each component in gene transfer, different combinations of these fragments were produced by polymerase chain reaction, expressed in Escherichia coli, and purified under native conditions from the soluble proteins. We show that only fusion proteins bearing the C fragment of tetanus toxin bind to gangliosides and, followed by their specific binding to differentiated PC12 cells, are internalized within 10 min. These proteins delivered the green fluorescence protein gene to PC12 cells, with the highest transfection efficiency achieved with proteins containing both the C fragment and the translocation domain. Addition of chloroquine elevated the transfection efficiency, which was further increased by incorporation of a nuclear localization signal in the delivery system. In addition, the effect of different DNA-condensing materials (poly-L-lysine, protamine, lysine(n=8)-trytophan(n=2)-lysine(n=8)) on gene transfer was investigated.

In vivo neuronal tracing with GFP-TTC gene delivery

The retrograde transport and transynaptic transfer properties of the nontoxic tetanus toxin C-fragment (TTC) can be used to visualize specific neural pathways or to deliver biomolecules in the central nervous system (CNS). Here we tested different delivery techniques to explore the potential use of a new GFP-TTC fusion construct for use as a genetic tracer in vivo. Plasmids encoding GFP-TTC were targeted to brain regions using intracerebral grafted transfected cells or adenoviral transduction. Transport was monitored using GFP fluorescence. We show that following GFP-TTC synthesis in grafted transfected cells, the TTC fragment alone, with no signal peptide, is necessary and sufficient to provide secretion and uptake of the fusion protein into neighboring neurons around the injection site. Using an adenoviral vector to express the fusion protein into brain neurons, we show that transduced neurons can deliver the fusion protein specifically into connected neurons, demonstrating that synaptic transfer in the CNS can be visualized with GFP-TTC.

Use of a rationally attenuated Bordetella bronchiseptica as a live mucosal vaccine and vector for heterologous antigens

Inactivation of the aroA gene of Bordetella bronchiseptica severely impaired its ability to colonise the respiratory tract of mice. The B. bronchiseptica aroA mutant was investigated as a live vaccine and vector for heterologous antigens. The B. bronchiseptica aroA mutant expressing the non-toxic fragment C (FrgC) of tetanus toxin (strain GVB120) was used to immunise mice intranasally. Immunised mice produced a strong serum and mucosal antibody response to B. bronchiseptica and serum anti-FrgC antibodies. Upon challenge with wild type B. bronchiseptica, immunised mice rapidly reduced the numbers of B. bronchiseptica in their respiratory tract, although clearance was more pronounced in the lower than in the upper respiratory tract. Immunisation with GVB120 protected approximately 40% of mice from tetanus toxin challenge. As far as we are aware, this is the first description of a recombinant B. bronchiseptica strain being used as a live vaccine vector for heterologous antigens.

Comparison of the immune responses induced by local immunizations with recombinant Lactobacillus plantarum producing tetanus toxin fragment C in different cellular locations

Lactobacillus plantarum NCIMB8826 was selected as a bacterial carrier for the development of live mucosal vaccines. This strain was reported to display interesting pharmaco-kinetic properties when fed to human volunteers and is also able to persist in the mouse intestine. The non-toxic C fragment of tetanus toxin (TTFC) was used as a model antigen. Recombinant strains producing TTFC in three cellular locations, intracellular, secreted or cell-surface exposed were compared to each other by immunizing mice through the subcutaneous, intranasal and intragastric routes. The three types of constructs were able to induce strong specific immune responses against TTFC by all routes tested. While cell-surface presentation required lower antigen doses to be immunogenic, the highest IgG serum antibody titers were obtained with the strain producing large amounts of TTFC in the cytoplasm.

Vaccination with DNA encoding a single-chain TCR fusion protein induces anticlonotypic immunity and protects against T-cell lymphoma

The clonotypic T-cell antigen receptor (TCR) provides unique Valpha and Vbeta sequences with potential as idiotypic targets for immunoregulation. For T-cell malignancies, vaccination with the TCR could induce therapeutic anti-idiotypic responses. To facilitate this approach, we have developed DNA vaccines that include the genes encoding TCR sequences from a T-cell lymphoma (TCL). To combine requirements for stable folding with a simple minimized single-chain construction, we used a three-domain ValphaVbetaCbeta sequence. To promote anti-TCR immunity, we fused a pathogen-derived sequence from tetanus toxin to the 3'-end of the single-chain TCR. The fusion gene vaccine induced anti-idiotypic antibodies and generated protection against the TCL. The critical requirement for the conformational integrity of the delivered TCR antigen was highlighted by the observation that DNA fusion vaccines containing either ValphaVbeta or VbetaCbeta sequences failed to generate antibodies reactive with the native TCR or provide protection. This is the first report of a DNA vaccine able to induce anti-idiotypic immunity against TCL, and it presents a simple strategy for selectively eliminating T-cell clones in vivo.

Embryonic assembly of a central pattern generator without sensory input

Locomotion depends on the integration of sensory information with the activity of central circuitry, which generates patterned discharges in motor nerves to appropriate muscles. Isolated central networks generate fictive locomotor rhythms (recorded in the absence of movement), indicating that the fundamental pattern of motor output depends on the intrinsic connectivity and electrical properties of these central circuits. Sensory inputs are required to modify the pattern of motor activity in response to the actual circumstances of real movement. A central issue for our understanding of how locomotor circuits are specified and assembled is the extent to which sensory inputs are required as such systems develop. Here we describe the effects of eliminating sensory function and structure on the development of the peristaltic motor pattern of Drosophila embryos and larvae. We infer that the circuitry for peristaltic crawling develops in the complete absence of sensory input; however, the integration of this circuitry into actual patterns of locomotion requires additional information from the sensory system. In the absence of sensory inputs, the polarity of movement is deranged, and backward peristaltic waves predominate at the expense of forward peristalsis.

Targeted expression of tetanus neurotoxin interferes with behavioral responses to sensory input in Drosophila

Targeted inactivation of neurons by expression of toxic gene products is a useful tool to assign behavioral functions to specific neurons or brain structures. Of a variety of toxic gene products tested, tetanus neurotoxin light chain (TNT) has the least severe side effects and can completely block chemical synapses. By using the GAL4 system to drive TNT expression in a subset of chemo- and mechanosensory neurons, we detected walking and flight defects consistent with blocking of relevant sensory information. We also found, for the first time, an olfactory behavioral phenotype associated with blocking of a specific subset of antennal chemoreceptors. Similar behavioral experiments with GAL4 lines expressing in different subsets of antennal chemoreceptors should contribute to an understanding of olfactory coding in Drosophila. To increase the utility of the GAL4 system for such purposes, we have designed an inducible system that allows us to circumvent lethality caused by TNT expression during early development.

Antibody modulation of antigen presentation: positive and negative effects on presentation of the tetanus toxin antigen via the murine B cell isoform of FcgammaRII

Tetanus toxin has been a valuable model antigen to study the MHC class II-restricted antigen processing pathway and is also frequently used to provide T helper determinants in vaccine formulations. To date most basic studies on the processing of this antigen have utilized human T and B cell clones. As a first step towards extending studies on this antigen into the murine system we have generated a panel of T cell clones and mAb in H-2(b) and H-2(d) mice. We investigated the presentation of tetanus toxin C fragment (TTCF) by the murine B cell lines LB27.4 (H-2(dxb)), A20 (H-2(d)) and IIA1.6 (H-2(d)) and the extent to which this could be modulated by the addition of mAb. One mAb, 10G5, induced strikingly enhanced presentation of T cell determinants located in the N-terminal region of TTCF while other antibodies inhibited presentation of these and other epitopes. The enhancing effects of the 10G5 antibody were blocked by the anti-FcR antibody 2.4G2 and were not observed in the FcR-negative IIA1.6 cell line. Interestingly, both FcgammaRIIB1 and FcgammaRIIB2 isoforms of FcgammaRII were able to restore antibody enhanced presentation in IIA1.6 cells but only if the cytoplasmic tails were intact. These results show that the B cell isoform of FcgammaRII (FcgammaRIIB1) can mediate capture and presentation of some antigen/antibody complexes and might play a role in BCR-independent antigen presentation in vivo.

New strategies for vaccination and imunomodulation in NHL

Knowledge of the genetic changes which occur in cancer cells is stimulating research aimed towards new therapies. Immunotherapeutic approaches, particularly antibody therapy, are already finding a place in treatment of hematological malignancies. Vaccination will build on experience in the field of infectious diseases, and it should be possible to design vehicles to deliver the expanding range of tumour antigens to the immune system. For DNA vaccines, fusion genes have the potential to activate and direct immune effector pathways. One candidate antigen for B-cell malignancies is the clonal idiotypic immunoglobulin and we have designed a fusion vaccine encoding idiotypic sequence fused to a sequence from a powerful antigen from tetanus toxin. This promotes protective immunity against lymphoma in models, and is now in clinical trial. One challenge is to bring patients into remission without significant damage to immune capacity. Another is to rethink the nature of clinical trials so that more pilot studies of efficacy can be carried out. There is no evidence so far of toxicity due to injection of DNA, but for antigens which are expressed by normal cells, the line between attack on tumour and autoimmunity will have to be carefully drawn.

Tetanus toxin fragment C-specific priming by intranasal infection with recombinant Bordetella pertussis

As an alternative to parenteral administration, mucosal administration offers several advantages including the ease of administration, safety and the ability to induce mucosal immunity. As a first step towards nasal administration of important childhood vaccines, we have previously developed attenuated Bordetella pertussis strains able to protect mice against pertussis upon nasal vaccination. Since pertussis vaccines are generally combined with tetanus and diphtheria vaccines, we constructed recombinant B. pertussis strains producing the non-toxic protective tetanus toxin fragment C (TTFC). TTFC was genetically fused to the N-terminal domain of the B. pertussis filamentous haemagglutinin. The hybrid gene was introduced into B. pertussis both on a multi-copy replicative plasmid and as a single copy inserted into the chromosome of a pertussis toxin-producing strain and a toxin-deficient attenuated strain. The hybrid protein was secreted by the recombinant strains. However, the recombinant multi-copy plasmid was unstable in vivo, and immunisation could only be carried out with the strains containing the single-copy chromosomal integration. Both the toxin-producing and the toxin-deficient recombinant B. pertussis strains were able to prime mice for the production of anti-TTFC serum antibodies upon intranasal administration, suggesting the feasibility of using recombinant attenuated B. pertussis for the development of combined childhood vaccines.

DNA fusion vaccines against B-cell tumors

DNA vaccination is currently being explored as a potential strategy for combatting cancer. However, tumor antigens are often weak and the immune system of patients may be compromised. For B-cell tumors, immunoglobulin idiotypic antigens provide defined targets but are poorly immunogenic. Fusion of a sequence derived from tetanus toxin to the genes encoding idiotypic determinants has proved highly effective in activating protective anti-tumor immunity. DNA fusion vaccines containing immuno-enhancing sequences can augment and direct immune attack on a range of target antigens. Gene-based fusion vaccines offer ease of manipulation and flexible design to activate effective attack on cancer.

Neuronal Targeting of Cardiotrophin-1 by Coupling with Tetanus Toxin C Fragment

Cardiotrophin-1 (CT-1) is a potent neurotrophic factor for motoneurons but its clinical use in motor neuron diseases is precluded by side effects on the heart and liver. We explored the possibility of targeting CT-1 to neurons by coupling with the tetanus toxin fragment TTC. Genetic fusion proteins between CT-1 or GFP and TTC were produced in Escherichia coli and assayed in vitro. In contrast to uncoupled CT-1 or GFP, TTC-coupled proteins bound with high affinity to cerebral neurons and spinal cord motoneurons and were rapidly internalized. Glia, hepatocytes, or cardiomyocytes did not show detectable binding or uptake of TTC-coupled proteins. Similar to CT-1, TTC-coupled CT-1 induced IL-6 secretion by KB cells, activated Reg-2 gene expression, and promoted motoneuron survival in a dose-dependent manner. In vivo studies will test whether TTC-coupled CT-1 might be targeted to degenerating spinal cord or brain-stem motoneurons and migrate trans-synaptically to cortical motoneurons, which are also affected in amyotrophic lateral sclerosis.

Defining the role of Drosophila lateral neurons in the control of circadian rhythms in motor activity and eclosion by targeted genetic ablation and PERIOD protein overexpression

The ventral lateral neurons (LNvs) of the Drosophila brain that express the period (per) and pigment dispersing factor (pdf) genes play a major role in the control of circadian activity rhythms. A new P-gal4 enhancer trap line is described that is mostly expressed in the LNvs This P-gal4 line was used to ablate the LNvs by using the pro-apoptosis gene bax, to stop PER protein oscillations by overexpressing per and to block synaptic transmission with the tetanus toxin light chain (TeTxLC). Genetic ablation of these clock cells leads to the loss of robust 24-h activity rhythms and reveals a phase advance in light-dark conditions as well as a weak short-period rhythm in constant darkness. This behavioural phenotype is similar to that described for disconnected1 (disco1) mutants, in which we show that the majority of the individuals have a reduced number of dorsally projecting lateral neurons which, however, fail to express PER. In both LNv-ablated and disco1 flies, PER cycles in the so-called dorsal neurons (DNs) of the superior protocerebrum, suggesting that the weak short-period rhythm could stem from these PDF-negative cells. The overexpression of per in LNs suppresses PER protein oscillations and leads to the disruption of both activity and eclosion rhythms, indicating that PER cycling in these cells is required for both of these rhythmic behaviours. Interestingly, flies overexpressing PER in the LNs do not show any weak short-period rhythms, although PER cycles in at least a fraction of the DNs, suggesting a dominant role of the LNs on the behavioural rhythms. Expression of TeTxLC in the LNvs does not impair activity rhythms, which indicates that the PDF-expressing neurons do not use synaptobrevin-dependent transmission to control these rhythms.