Molecular immune recognition of botulinum neurotoxin B. The light chain regions that bind human blocking antibodies from toxin-treated cervical dystonia patients. Antigenic structure of the entire BoNT/B molecule

We recently mapped the regions on the heavy (H) chain of botulinum neurotoxin, type B (BoNT/B) recognized by blocking antibodies (Abs) from cervical dystonia (CD) patients who develop immunoresistance during toxin treatment. Since blocking could also be effected by Abs directed against regions on the light (L) chain, we have mapped here the L chain, using the same 30 CD antisera. We synthesized, purified and characterized 32 19-residue L chain peptides that overlapped successively by 5 residues (peptide L32 overlapped with peptide N1 of the H chain by 12 residues). In a given patient, Abs against the L chain seemed less intense than those against H chain. Most sera recognized a limited set of L chain peptides. The levels of Abs against a given region varied with the patient, consistent with immune responses to each epitope being under separate MHC control. The peptides most frequently recognized were: L13, by 30 of 30 antisera (100%); L22, by 23 of 30 (76.67%); L19, by 15 of 30 (50.00%); L26, by 11 of 30 (36.70%); and L14, by 12 of 30 (40.00%). The activity of L14 probably derives from its overlap with L13. The levels of Ab binding decreased in the following order: L13 (residues 169-187), L22 (295-313), L19 (253-271), and L26 (351-369). Peptides L12 (155-173), L18 (239-257), L15 (197-215), L1 (1-19) and L23 (309-327) exhibited very low Ab binding. The remaining peptides had little or no Ab-binding activity. The antigenic regions are analyzed in terms of their three-dimensional locations and the enzyme active site. With the previous localization of the antigenic regions on the BoNT/B H chain, the human Ab recognition of the entire BoNT/B molecule is presented and compared to the recognition of BoNT/A by human blocking Abs.

Enhanced neutralization potency of botulinum neurotoxin antibodies using a red blood cell-targeting fusion protein

Botulinum neurotoxin (BoNT) potently inhibits cholinergic signaling at the neuromuscular junction. The ideal countermeasures for BoNT exposure are monoclonal antibodies or BoNT antisera, which form BoNT-containing immune complexes that are rapidly cleared from the general circulation. Clearance of opsonized toxins may involve complement receptor-mediated immunoadherence to red blood cells (RBC) in primates or to platelets in rodents. Methods of enhancing immunoadherence of BoNT-specific antibodies may increase their potency in vivo. We designed a novel fusion protein (FP) to link biotinylated molecules to glycophorin A (GPA) on the RBC surface. The FP consists of an scFv specific for murine GPA fused to streptavidin. FP:mAb:BoNT complexes bound specifically to the RBC surface in vitro. In a mouse model of BoNT neutralization, the FP increased the potency of single and double antibody combinations in BoNT neutralization. A combination of two antibodies with the FP gave complete neutralization of 5,000 LD50 BoNT in mice. Neutralization in vivo was dependent on biotinylation of both antibodies and correlated with a reduction of plasma BoNT levels. In a post-exposure model of intoxication, FP:mAb complexes gave complete protection from a lethal BoNT/A1 dose when administered within 2 hours of toxin exposure. In a pre-exposure prophylaxis model, mice were fully protected for 72 hours following administration of the FP:mAb complex. These results demonstrate that RBC-targeted immunoadherence through the FP is a potent enhancer of BoNT neutralization by antibodies in vivo.

Injections of Clostridium botulinum neurotoxin A may cause thyroid complications in predisposed persons based on molecular mimicry with thyroid autoantigens

A woman with Hashimoto's thyroiditis, under replacement L-T4, repeatedly experienced, over a 10-year period, elevations of serum TSH after eyelid injections of Clostridium botulinum neurotoxin A (Btx). We hypothesized a link between Btx injections and TSH elevations via molecular mimicry, and aimed to verify our hypothesis. Using an in silico approach, we searched first for amino acid sequence homology between Btx and thyroid autoantigens, and next for HLA binding motifs within homologous segments. We found that (i) Btx and thyroid autoantigens share amino acid sequence homology; (ii) some homologous regions contain epitopes of both Btx and thyroid autoantigens; (iii) some of such regions contain HLA-DR3 and/or HLA-DR7 binding motifs, which predominate over other HLA-DRs. This is relevant because the patient's HLA-DR haplotype was DR3/DR7. In conclusion, clinical and bioinformatics data suggest a possible pathogenetic link between Btx and autoimmune thyroid diseases. Considering the wide and increasing medical and dermocosmetic use of Btx, and the frequently subclinical course of autoimmune thyroid diseases, we think that thyroid "complications" may pass frequently undetected in Btx-treated persons.

Mucosal targeting of a BoNT/A subunit vaccine adjuvanted with a mast cell activator enhances induction of BoNT/A neutralizing antibodies in rabbits

BACKGROUND

We previously reported that the immunogenicity of Hcβtre, a botulinum neurotoxin A (BoNT/A) immunogen, was enhanced by fusion to an epithelial cell binding domain, Ad2F, when nasally delivered to mice with cholera toxin (CT). This study was performed to determine if Ad2F would enhance the nasal immunogenicity of Hcβtre in rabbits, an animal model with a nasal cavity anatomy similar to humans. Since CT is not safe for human use, we also tested the adjuvant activity of compound 48/80 (C48/80), a mast cell activating compound previously determined to safely exhibit nasal adjuvant activity in mice.

METHODS

New Zealand White or Dutch Belted rabbits were nasally immunized with Hcβtre or Hcβtre-Ad2F alone or combined with CT or C48/80, and serum samples were tested for the presence of Hcβtre-specific binding (ELISA) or BoNT/A neutralizing antibodies.

RESULTS

Hcβtre-Ad2F nasally administered with CT induced serum anti-Hcβtre IgG ELISA and BoNT/A neutralizing antibody titers greater than those induced by Hcβtre + CT. C48/80 provided significant nasal adjuvant activity and induced BoNT/A-neutralizing antibodies similar to those induced by CT.

CONCLUSIONS

Ad2F enhanced the nasal immunogenicity of Hcβtre, and the mast cell activator C48/80 was an effective adjuvant for nasal immunization in rabbits, an animal model with a nasal cavity anatomy similar to that in humans.

[Botulinum toxine treatment and the formation of antibodies to botulotoxin in patients with cerebral palsy]

The aim of the study was to search for the association between efficacy of botulinum treatment (dysport) and the formation of antibodies to botulinum toxin in children with cerebral palsy (CP). Fourteen children with CP received dysport, 42 children (29 with CP and 13 patients with paresises of other etiologies) were not treated with this drug. No association between the presence of antibodies in blood serum and efficacy of treatment was found. However, further research of the role of antibody genesis as a factor influencing the formation of reaction to treatment is needed.

Regions of botulinum neurotoxin A light chain recognized by human anti-toxin antibodies from cervical dystonia patients immunoresistant to toxin treatment. The antigenic structure of the active toxin recognized by human antibodies

This work was aimed at determining the BoNT/A L-chain antigenic regions recognized by blocking antibodies in human antisera from cervical dystonia patients who had become immunoresistant to BoNT/A treatment. Antisera from 28 immunoresistant patients were analyzed for binding to each of 32 overlapping synthetic peptides that spanned the entire L-chain. A mixture of the antisera showed that antibodies bound to three peptides, L11 (residues 141-159), L14 (183-201) and L18 (239-257). When mapped separately, the antibodies were bound only by a limited set of peptides. No peptide bound antibodies from all the patients and amounts of antibodies bound to a given peptide varied with the patient. Peptides L11, L14 and L18 were recognized predominantly. A small but significant number of patients had antibodies to peptides L27 (365-383) and L29 (379-397). Other peptides were recognized at very low and perhaps insignificant antibody levels by a minority (15% or less) of patients or had no detectable antibody with any of the sera. In the 3-dimensional structure, antibody-binding regions L11, L14 and L18 of the L-chain occupy surface areas and did not correlate with electrostatic potential, hydrophilicity/hydrophobicity, or temperature factor. These three antigenic regions reside in close proximity to the belt of the heavy chain. The regions L11 and L18 are accessible in both the free light chain and the holotoxin forms, while L14 appears to be less accessible in the holotoxin. Antibodies against these regions could prevent delivery of the L-chain into the neurons by inhibition of the translocation.

Production and characterisation of a neutralising chimeric antibody against botulinum neurotoxin A

Botulinum neurotoxins, produced by Clostridium botulinum bacteria, are the causative agent of botulism. This disease only affects a few hundred people each year, thus ranking it among the orphan diseases. However, botulinum toxin type A (BoNT/A) is the most potent toxin known to man. Due to their potency and ease of production, these toxins were classified by the Centers for Disease Control and Prevention (CDC) as Category A biothreat agents. For several biothreat agents, like BoNT/A, passive immunotherapy remains the only possible effective treatment allowing in vivo neutralization, despite possible major side effects. Recently, several mouse monoclonal antibodies directed against a recombinant fragment of BoNT/A were produced in our laboratory and most efficiently neutralised the neurotoxin. In the present work, the most powerful one, TA12, was selected for chimerisation. The variable regions of this antibody were thus cloned and fused with the constant counterparts of human IgG1 (kappa light and gamma 1 heavy chains). Chimeric antibody production was evaluated in mammalian myeloma cells (SP2/0-Ag14) and insect cells (Sf9). After purifying the recombinant antibody by affinity chromatography, the biochemical properties of chimeric and mouse antibody were compared. Both have the same very low affinity constant (close to 10 pM) and the chimeric antibody exhibited a similar capacity to its parent counterpart in neutralising the toxin in vivo. Its strong affinity and high neutralising potency make this chimeric antibody interesting for immunotherapy treatment in humans in cases of poisoning, particularly as there is a probable limitation of the immunological side effects observed with classical polyclonal antisera from heterologous species.

Current and future botulinum neurotoxin type A preparations in aesthetics: a literature review

Botulinum neurotoxin type A (BTX-A) preparations are well established for cosmetic use. BTX-A inhibits the release of acetylcholine, resulting in temporary muscle paralysis, which has been utilized successfully to treat glabellar frown lines, periorbital wrinkles and other facial enhancement procedures. Two BTX-A products are approved for aesthetic procedures in the United States (U.S.) and Europe, and a next generation of preparations free from complexing proteins has recently been approved in Germany. Despite established efficacy profiles, concerns remain regarding the propensity for immunogenic reactions, which can lead to premature loss of effect and secondary therapy failure. NT 201 is a BTX-A preparation that is free from complexing proteins and is in the advanced stages of aesthetic development. Pivotal clinical studies in therapeutic indications demonstrate noneriority and comparable safety of NT 201 to another available BTX-A preparation. This article reviews the pharmacologic and clinical profiles of BTX-A preparations currently available and in development. Novel BTX-A preparations may offer advantages over existing products in terms of handling and immunogenicity.

Extraction of BoNT/A, /B, /E, and /F with a single, high affinity monoclonal antibody for detection of botulinum neurotoxin by Endopep-MS

Botulinum neurotoxins (BoNTs) are extremely potent toxins that are capable of causing respiratory failure leading to long-term intensive care or death. The best treatment for botulism includes serotype-specific antitoxins, which are most effective when administered early in the course of the intoxication. Early confirmation of human exposure to any serotype of BoNT is an important public health goal. In previous work, we focused on developing Endopep-MS, a mass spectrometry-based endopeptidase method for detecting and differentiating the seven serotypes (BoNT/A-G) in buffer and BoNT/A, /B, /E, and /F (the four serotypes that commonly affect humans) in clinical samples. We have previously reported the success of antibody-capture to purify and concentrate BoNTs from complex matrices, such as clinical samples. However, to check for any one of the four serotypes of BoNT/A, /B, /E, or /F, each sample is split into 4 aliquots, and tested for the specific serotypes separately. The discovery of a unique monoclonal antibody that recognizes all four serotypes of BoNT/A, /B, /E and /F allows us to perform simultaneous detection of all of them. When applied in conjunction with the Endopep-MS assay, the detection limit for each serotype of BoNT with this multi-specific monoclonal antibody is similar to that obtained when using other serotype-specific antibodies.

An evaluation of neutralizing antibody induction during treatment of glabellar lines with a new US formulation of botulinum neurotoxin type A

BACKGROUND

The induction of neutralizing antibodies during the aesthetic application of botulinum neurotoxin type A is rare, but of potential clinical concern. Phase III studies of a new US formulation of botulinum neurotoxin type A, Dysport (BoNTA-ABO [abobotulinumtoxinA]; Medicis Aesthetics, Scottsdale, AZ), have not identified any cases of neutralizing antibody formation during the treatment of glabellar lines in patients who received up to nine treatments.

OBJECTIVE

To provide an in-depth analysis of the potential for induction of neutralizing antibodies in the study population enrolled in phase III trials of BoNTA-ABO in the treatment of glabellar lines.

METHODS

First and last available serum samples from patients in the BoNTA-ABO Glabellar Lines Development Program were screened for BoNTA-ABO antibodies with a radioimmunoprecipitation assay (RIPA), followed by a confirmatory competitive assay (RIPA-C). Confirmed RIPA-C-positive samples were further evaluated for the presence of neutralizing antibodies using a mouse protection assay (MPA), a highly specific bioassay for neutralizing antibodies. We conducted safety and efficacy evaluations, including day 30 responder rate (a rating of no or mild glabellar lines) and duration of response in the last treatment cycle.

RESULTS

Of 1554 patients who received at least one BoNTA-ABO treatment (10 units at five injection points, for a total dose of 50 units/treatment; range one to nine treatments), five (0.32%) were antibody positive on the RIPA-C assay-two at baseline and three at the last treatment cycle. None of the RIPA-C-positive samples tested positive for neutralizing antibodies upon further evaluation using the highly specific MPA. Of note, the RIPA-C-positive group had a responder rate of 100% and a mean response of 103.3 days, while the RIPA-C-negative group had a responder rate of 90% and a mean response of 89.4 days. The safety of BoNTA-ABO did not appear to be altered in the RIPA-C-positive group.

CONCLUSIONS

At the dose and treatment interval used in the correction of glabellar lines, induction of neutralizing antibodies to BoNTA-ABO was not observed. None of the five samples that initially gave positive results in a RIPA-C assay were positive when further evaluated using the MPA. Clinically, RIPA-C-positive status did not correlate with any reduction in efficacy or an altered safety profile, although the small numbers prevent definitive conclusions. These data suggest that the five RIPA-C-positive samples represented false positives.

Long-term safety of repeated administrations of a new formulation of botulinum toxin type A in the treatment of glabellar lines: interim analysis from an open-label extension study

BACKGROUND

A new formulation of botulinum toxin type A (BoNT-A) (Dysport) has recently been approved in the United States for the treatment of glabellar lines.

OBJECTIVE

We sought to evaluate the long-term safety of repeated administrations of this BoNT-A formulation.

METHODS

In all, 768 individuals (1500 planned) from phase III clinical trials received as many as 6 repeated treatments of open-label BoNT-A (50 U) over 17 months, with a minimum of 85 days between treatments. Participants received a telephone call at day 7 postinjection to check for adverse event (AE), with clinical evaluations on days 14 and 30, and monthly until retreatment, study completion, or early termination. Safety end points were AEs, changes in vital signs, and assessment of serum-neutralizing antibodies to BoNT-A.

RESULTS

Of the 285 participants reporting at least one treatment-emergent AE at the interim analysis cutoff, only 74 (26%) reported at least one possibly or probably related event after 2259 treatments with BoNT-A. The incidence of treatment-emergent AEs around the injection sites and eyes was low (< or = 3%). Ten participants (1%) experienced 10 instances of ptosis. No participants developed neutralizing antibodies to BoNT-A or clinically significant changes in vital signs.

LIMITATIONS

This is an interim analysis of a larger multicenter extension study.

CONCLUSIONS

Multiple treatments with BoNT-A (50 U) over 17 months were well tolerated.

Extraction and inhibition of enzymatic activity of botulinum neurotoxins/A1, /A2, and /A3 by a panel of monoclonal anti-BoNT/A antibodies

Botulinum neurotoxins (BoNTs) are extremely potent toxins that are capable of causing death or respiratory failure leading to long-term intensive care. Treatment includes serotype-specific antitoxins, which must be administered early in the course of the intoxication. Rapidly determining human exposure to BoNT is an important public health goal. In previous work, our laboratory focused on developing Endopep-MS, a mass spectrometry-based endopeptidase method for detecting and differentiating BoNT/A–G serotypes in buffer and BoNT/A, /B, /E, and /F in clinical samples. We have previously reported the effectiveness of antibody-capture to purify and concentrate BoNTs from complex matrices, such as clinical samples. Because some antibodies inhibit or neutralize the activity of BoNT, the choice of antibody with which to extract the toxin is critical. In this work, we evaluated a panel of 16 anti-BoNT/A monoclonal antibodies (mAbs) for their ability to inhibit the in vitro activity of BoNT/A1, /A2, and /A3 complex as well as the recombinant LC of A1. We also evaluated the same antibody panel for the ability to extract BoNT/A1, /A2, and /A3. Among the mAbs, there were significant differences in extraction efficiency, ability to extract BoNT/A subtypes, and inhibitory effect on BoNT catalytic activity. The mAbs binding the C-terminal portion of the BoNT/A heavy chain had optimal properties for use in the Endopep-MS assay.

What stands in the way of treating palmar hyperhidrosis as effectively as axillary hyperhidrosis with botulinum toxin type A

Botulinum Toxin type A (BTX-A) has revolutionized the treatment of focal hyperhidrosis (HH) in recent years and has dramatically reduced the invasive surgical techniques that have been performed in the past to control severe focal HH unresponsive to topical therapies. Whereas BTX-A injections are easily performed to control axillary HH with little or no analgesia, pain management is a must during the injection of palmar and plantar HH with BTX-A because of the intense pain generated with the 30 to 40 needle punctures needed on each hand or foot through the densely innervated skin present in those areas. For that reason, many physicians who contentedly treat axillary HH with BTX-A injections, refuse to do so for palmar and plantar HH. Although pain is the major stumbling block deterring patients and physicians from choosing this treatment option, it is not the only one. Many other factors may play a role in deciding whether or not to treat palmar and plantar HH with BTX-A injections. This article reviews these factors and presents some personal data from patients who have already been treated with BTX-A injections on the palms and soles and who came back once or more for repeat treatments when the effect of BTX-A started to fade away. "Jet Anesthesia" was the pain management method used in this group.

Epitope characterization and variable region sequence of f1-40, a high-affinity monoclonal antibody to botulinum neurotoxin type a (Hall strain)

BACKGROUND

Botulism, an often fatal neuroparalytic disease, is caused by botulinum neurotoxins (BoNT) which consist of a family of seven serotypes (A-H) produced by the anaerobic bacterium Clostridium botulinum. BoNT, considered the most potent biological toxin known, is a 150 kDa protein consisting of a 100 kDa heavy-chain (Hc) and a 50 kDa light-chain (Lc). F1-40 is a mouse-derived, IgG1 monoclonal antibody that binds the light chain of BoNT serotype A (BoNT/A) and is used in a sensitive immunoassay for toxin detection. We report the fine epitope mapping of F1-40 and the deduced amino acid sequence of the variable regions of the heavy and light chains of the antibody.

METHODS AND FINDINGS

To characterize the binding epitope of F1-40, three complementary experimental approaches were selected. Firstly, recombinant peptide fragments of BoNT/A light-chain were used in Western blots to identify the epitope domains. Secondly, a peptide phage-display library was used to identify the specific amino acid sequences. Thirdly, the three-dimensional structure of BoNT/A was examined in silico, and the amino acid sequences determined from the phage-display studies were mapped onto the three-dimensional structure in order to visualize the epitope. F1-40 was found to bind a peptide fragment of BoNT/A, designated L1-3, which spans from T125 to L200. The motif QPDRS was identified by phage-display, and was mapped to a region within L1-3. When the three amino acids Q138, P139 and D140 were all mutated to glycine, binding of F1-40 to the recombinant BoNT/A light chain peptide was abolished. Q-138, P-139 and D-140 form a loop on the external surface of BoNT/A, exposed to solvent and accessible to F1-40 binding.

CONCLUSIONS

The epitope of F1-40 was localized to a single exposed loop (ss4, ss5) on the Lc of BoNT. Furthermore amino acids Q138, P139 and D140 forming the tip of the loop appear critical for binding.

Skeletal Muscle Atrophy Induced by Intramuscular Repeated Dose of Botulinum Toxin Type A in Rats

Botulinum toxin type A was intramuscularly administered to Sprague-Dawley rats once a day for 28 days at doses of 1, 3, and 9 ng kg-1 day-1 to investigate the possibility of unanticipated toxicity of repeated dose. A dose-related decrease in body weight gain was noted and lasted throughout the 4-week recovery period. Paralytic gait was a common clinical sign observed in the animals dosed at >or=3 ng kg-1 day-1 and muscle atrophy at 9 ng kg-1 day-1. Decreased creatinine was monitored in both males and females treated at 9 ng kg-1 day-1. Microscopic examination of the quadriceps femoris muscle, the test article application site, confirmed the muscle atrophy with a decrease in myofiber diameter and an increase of myofiber nuclei and intermyofiber connective tissue. Although antibody against botulinum toxin type A was detected in the sera from both males and females at 9 ng kg-1 day-1, no immunogenicity-related changes or lesions were noted. In conclusion, no other side effects of the botulinum toxin type A injection except the decrease in body weight gain and the muscle atrophy at the administration site were noted in the 28-day intramuscular repeated dose study.

[Clinical relevance of botulinum toxin antibodies]

Botulinum toxin antibodies (BT-AB) can be neutralising and non-neutralising, their titres therapy-relevant and non-therapy-relevant. Botulinum toxin (BT) and BT-AB form a functional balance, thus explaining partial and complete therapy failure. Antibody-induced BT therapy failure (ATF) is rare. Clinically it tends to follow a three-phase reaction. Complete ATF occurs in a typical time window. Risk factors for ATF are the amount of BT given at each injection series, duration of the interval between injections, quality of the BT preparation, and individual particularities of the patient's immune system. The detection of BT-AB is complicated. It always needs interpretation and is of major importance for the further treatment strategy.

Enhanced immune responses using plasmid DNA replicon vaccine encoding the Hc domain of Clostridium botulinum neurotoxin serotype A

In current study, the immunogenicity of a plasmid DNA replicon vaccine (pSCARSHc) encoding the Hc domain of Clostridium botulinum neurotoxin serotype A (AHc) was investigated and compared with a conventional plasmid DNA vaccine (pcDNASHc) encoding the same antigen. In vitro, pSCARSHc incorporating Semliki Forest virus (SFV) replicon could express AHc protein and induce apoptosis of transfected cells. Comparison with the conventional plasmid DNA vaccine (pcDNASHc) yielded several interesting results. First, our self-designed pSCARSHc could induce relatively higher AHc-specific antibodies and lymphocyte proliferative responses in immunized Balb/c mice, especially at low doses. Second, while both pSCARSHc and pcDNASHc induced Th2-type immune responses, the ratio of IgG1 to IgG2a was lower in pSCARSHc groups and the Th2- and Th1-type humoral immune responses induced by pSCARSHc were also stronger than that of the pcDNASHc vaccine. Third, it was shown that the sera from pSCARSHc-vaccinated mice conferred more efficient protection than those from pcDNASHc-vaccinated mice by BoNT/A neutralization assay. Finally, mice immunized with pSCARSHc could also elicit more efficient protection against BoNT/A than pcDNASHc. These results indicate that our plasmid DNA replicon vaccine can provide strong immunogenicity and should be a potential alternative strategy to conventional DNA vaccines in developing an efficacious vaccine against C. botulinum neurotoxin serotype A.

A neuronal cell-based botulinum neurotoxin assay for highly sensitive and specific detection of neutralizing serum antibodies

Clostridium botulinum neurotoxin (BoNT) serotypes A and B are widely used as pharmaceuticals to treat various neurological disorders and in cosmetic applications. The major adverse effect of these treatments has been resistance to treatment after multiple injections. Currently, patients receiving BoNT therapies and patients enrolled in clinical trials for new applications and/or new formulations of BoNTs are not routinely monitored for the formation of neutralizing antibodies, since no assay other than the mouse protection procedure is commercially available that reliably tests for the presence of such antibodies. This report presents a highly sensitive and specific neuronal cell-based assay that provides sensitive and specific detection of neutralizing antibodies to BoNT/A.

Formation of neutralizing antibodies in patients receiving botulinum toxin type A for treatment of poststroke spasticity: a pooled-data analysis of three clinical trials

OBJECTIVE

The purpose of this study was to investigate the incidence of neutralizing antibody (NAb) formation in patients with poststroke spasticity treated with a specific formulation of botulinum toxin type A (BoNTA).

METHODS

Data from 3 previous clinical trials of BoNTA in patients with upper and/or lower limb spasticity were pooled and evaluated. Study 1 was a randomized, double-blind, placebo-controlled, multicenter trial of BoNTA in patients aged >/=21 years who had experienced a stroke >6 months before the initiation of the study. Study 2 was an open-label extension of study 1. Study 3 was a randomized, double-blind, multicenter trial of a specific BoNTA formulation in patients aged >/= 21 years who had experienced a stroke >/=6 weeks before study entry. Patients with a fixed contracture of the studied limb were excluded from participation in studies 1 and 2. Serum samples were obtained from each patient before each BoNTA treatment and at the end of each study. The mouse protection assay (MPA) was used for detection of NAbs to BoNTA in serum.

RESULTS

A total of 235 individual patients with post-stroke spasticity were enrolled in the 3 trials, including 126, 111 (all of whom participated in study 1), and 109 in studies 1, 2, and 3, respectively. Study 1 had an equal (50.0%) distribution of male and female patients (63/63). The distribution of male and female patients was 56 (50.5%) and 55 (49.5%), respectively, in study 2, and 55 (50.5%) and 54 (49.5), respectively, in study 3. The mean (SD) ages of patients in studies 1, 2, and 3 were 61.4 (13.8), 61.5 (14.1), and 58.5 (13.9) years, respectively. The MPA was used for detection of NAbs to BoNTA in the serum samples of 191 patients, including 64 from study 1, 111 from study 2 (55 of these patients were placebo recipients and 56 received their first BoNTA injection in study 1), and 72 (a sample was not obtained for 1 patient who had not received an injection) from study 3. The median number of BoNTA treatments received by these patients was 2 (range, 1-4 treatments) over a period lasting from 12 to 42 weeks. The mean dose of BoNTA was 241 U (range, 100-400 U), with a maximum dose of 960 U in any 1 patient. NAbs to BoNTA were detected in the serum sample of 1/191 (0.5%) patient who had participated in studies 1 and 2. Based on muscle-tone scores (3 and 4 for wrist and fingers, respectively) on a 5-point Ashworth Scale (0 = none to 4 = severe), the patient did not appear to exhibit a clinical response to BoNTA at any time during the studies.

CONCLUSION

Formation of NAbs was rare (1/191) in this group of adults with poststroke spasticity from three 12- to 42-week clinical trials who received >/=1 treatment with a specific BoNTA formulation at doses ranging from 100 to 400 U.

Development and comparison of two immunoassay formats for rapid detection of botulinum neurotoxin type A

We have evaluated two formats of immunoassays for the rapid detection of Clostridium botulinum neurotoxin type A (BoNT/A), in assay buffer and various matrices (human serum and nasal swabs, fresh milk, sugar, flour and talcum). The two formats, a vertical-flow strip immunochromatography (ICT) and a small disposable immunoaffinity column (IAC), were selected because they are both rapid and readily usable in the field without sophisticated equipment. We utilised the same critical reagents to develop and optimise both assays, making it possible to compare the corresponding technologies on the same toxin preparations, without interference due to the properties of the antibodies. Results were interpreted using a standard statistical test (ANOVA) and showed little difference of sensitivity between matrices. Though both assays were completed in 40 min, the sensitivity of the IAC, evaluated at 0.45 pM (5 mouse LD50 units/ml), was 40 to 80 times better than that of the ICT. Furthermore, the sensitivity of the IAC assay was improved to 0.09 pM (1 mouse LD50 unit/ml) when performed on a 5-ml volume of human serum. Thus, the IAC appears to be one of the most sensitive and rapid assays for the detection of BoNT/A reported to date and, because it is also highly transportable, it is amongst the best suited for field diagnosis of BoNT/A poisoning.

Neuromuscular paralysis and recovery in mice injected with botulinum neurotoxins A and C

Botulinum neurotoxin type A (BoNT/A) is commonly used in human therapy. This treatment may induce immunoresistance and preliminary evaluation of other botulinum neurotoxin serotypes suggested botulinum neurotoxin type C (BoNT/C) to be a good alternative to BoNT/A. Here, we have further characterized the biological activities of BoNT/C using a variety of experimental approaches. Muscle paralysis and time of recovery of mouse hind limb injected with BoNT/A or BoNT/C were assayed with the Digit Abduction Scoring assay. The extent and duration of paralysis were similar with the two toxin serotypes. Extensor digitorum longus or tibialis anterior muscles were dissected at times of complete paralysis and of complete recovery. Muscle weight and force were significantly reduced in mice injected with BoNT/A and BoNT/C, and some atrophy persisted for a long time. In BoNT/C-treated junctions, nerve terminal sprouting was prominent, indicating that the capacity to extend the field of innervation is not hampered by BoNT/C. BoNT/C induced a marked decrease in the frequency of miniature endplate potentials and in the amplitude of endplate potentials. 3,4-diaminopyridine reversed the effect of BoNT/C by increasing the amplitude of synchronized endplate potentials. The present study shows an extensive similarity in the biological activities of BoNT/A and BoNT/C, further supporting the suggestion that BoNT/C is a valid alternative to BoNT/A.

Trivalent vaccine against botulinum toxin serotypes A, B, and E that can be administered by the mucosal route

Most reports dealing with vaccines against botulinum toxin have focused on the injection route of administration. This is unfortunate, because a mucosal vaccine is likely to be more efficacious for patients and pose fewer risks to health care workers and to the environment. Therefore, efforts were made to generate a mucosal vaccine that provides protection against the botulinum serotypes that typically cause human illness (serotypes A, B, and E). This work demonstrated that carboxy-terminal peptides derived from each of the three serotypes were able to bind to and penetrate human epithelial barriers in vitro, and there was no cross inhibition of membrane binding and transcytosis. The three polypeptides were then tested in vivo as a trivalent vaccine that could be administered to mice by the intranasal route. The results indicated that the mucosal vaccine evoked high secretory titers of immunoglobulin A (IgA), as well as high circulating titers of IgG and IgA, and it also evoked a high level of resistance to challenge with toxin. The immunoglobulin responses and the levels of resistance to challenge were increased by coadministration of adjuvants, such as chitosan and vitamin E. At least three mechanisms were identified to account for the antibody-induced resistance: (i) blockade of toxin absorption across epithelial cells, (ii) enhanced clearance of toxin from the circulation, and (iii) blockade of toxin action at the neuromuscular junction. These results are a compelling demonstration that a mucosal vaccine against multiple serotypes of botulinum toxin has been identified.