Development of a Broad-Spectrum Antiserum against Cobra Venoms Using Recombinant Three-Finger Toxins

Three-finger toxins (3FTXs) are the most clinically relevant components in cobra (genus Naja) venoms. Administration of the antivenom is the recommended treatment for the snakebite envenomings, while the efficacy to cross-neutralize the different cobra species is typically limited, which is presumably due to intra-specific variation of the 3FTXs composition in cobra venoms. Targeting the clinically relevant venom components has been considered as an important factor for novel antivenom design. Here, we used the recombinant type of long-chain α-neurotoxins (P01391), short-chain α-neurotoxins (P60770), and cardiotoxin A3 (P60301) to generate a new immunogen formulation and investigated the potency of the resulting antiserum against the venom lethality of three medially important cobras in Asia, including the Thai monocled cobra (Naja kaouthia), the Taiwan cobra (Naja atra), and the Thai spitting cobra (Naja Siamensis) snake species. With the fusion of protein disulfide isomerase and the low-temperature settings, the correct disulfide bonds were built on these recombinant 3FTXs (r3FTXs), which were confirmed by the circular dichroism spectra and tandem mass spectrometry. Immunization with r3FTX was able to induce the specific antibody response to the native 3FTXs in cobra venoms. Furthermore, the horse and rabbit antiserum raised by the r3FTX mixture is able to neutralize the venom lethality of the selected three medically important cobras. Thus, the study demonstrated that the r3FTXs are potential immunogens in the development of novel antivenom with broad neutralization activity for the therapeutic treatment of victims involving cobra snakes in countries.

A Quest for a Universal Plasma-Derived Antivenom Against All Elapid Neurotoxic Snake Venoms

This review describes the research aimed at the development of universal antivenom against elapid neurotoxic snake venoms. The antivenoms produced in Thailand in the 1980s were of low potency, especially against the elapid venoms. This was thought to be due to the low immunogenicity of the α-neurotoxins, which are the most lethal toxins in these venoms. Comparisons of various α-neurotoxin conjugates and polymers, and also different immunological adjuvants, showed that the adjuvant used is the major determinant in the antibody response in horses. The potent Freund's adjuvant was not used due to its severe local side-effect in horses. Therefore, a novel immunization protocol termed 'low dose, low volume multi-site' was developed for use in horses. This immunization protocol has led to the production of highly potent monospecific antivenoms against several elapid and viperid venoms, and two potent polyspecific antivenoms, one against 4 neurotoxic and another against 3 hematotoxic venoms. The immunization protocol has also led to other improvements in antivenom production including: several fold increases in antiserum potency, a reduction in the time required to reach therapeutically useful antibody titers, a 90% reduction in the amount of venom used, and 100% of the horses responding to the immunization program. This development is partly responsible for significant decrease in the Thailand's annual snakebite death toll from a few dozens to mostly nil in recent years. Finally, a simple and novel immunization strategy, using a 'diverse toxin repertoire' composed of numerous elapid toxin fractions as immunogen, was proposed and tested. This immunization procedure has resulted in the successful production of a widely paraspecific antiserum against at least 36 neurotoxic venoms of 28 species encompassing 10 genera and from 20 countries on four continents, and possibly against all elapid venoms with α-neurotoxins as the lethal toxins. These results indicate that, with optimizations of the composition of the 'diverse toxin repertoire', the immunization scheme and antibody fractionation to increase the antivenom neutralizing potency, an effective universal antivenom against the neurotoxic elapid snakes of the world can be produced.

De Novo Venom-Gland Transcriptomics of Spine-Bellied Sea Snake (Hydrophis curtus) from Penang, Malaysia-Next-Generation Sequencing, Functional Annotation and Toxinological Correlation

Envenomation resulted from sea snake bite is a highly lethal health hazard in Southeast Asia. Although commonly caused by sea snakes of Hydrophiinae, each species is evolutionarily distinct and thus, unveiling the toxin gene diversity within individual species is important. Applying next-generation sequencing, this study investigated the venom-gland transcriptome of Hydrophis curtus (spine-bellied sea snake) from Penang, West Malaysia. The transcriptome was de novo assembled, followed by gene annotation and sequence analyses. Transcripts with toxin annotation were only 96 in number but highly expressed, constituting 48.18% of total FPKM in the overall transcriptome. Of the 21 toxin families, three-finger toxins (3FTX) were the most abundantly expressed and functionally diverse, followed by phospholipases A₂. Lh_FTX001 (short neurotoxin) and Lh_FTX013 (long neurotoxin) were the most dominant 3FTXs expressed, consistent with the pathophysiology of envenomation. Lh_FTX001 and Lh_FTX013 were variable in amino acid compositions and predicted epitopes, while Lh_FTX001 showed high sequence similarity with the short neurotoxin from Hydrophis schistosus, supporting cross-neutralization effect of Sea Snake Antivenom. Other toxins of low gene expression, for example, snake venom metalloproteinases and L-amino acid oxidases not commonly studied in sea snake venom were also identified, enriching the knowledgebase of sea snake toxins for future study.

An in vitro α-neurotoxin-nAChR binding assay correlates with lethality and in vivo neutralization of a large number of elapid neurotoxic snake venoms from four continents

The aim of this study was to develop an in vitro assay for use in place of in vivo assays of snake venom lethality and antivenom neutralizing potency. A novel in vitro assay has been developed based on the binding of post-synaptically acting α-neurotoxins to nicotinic acetylcholine receptor (nAChR), and the ability of antivenoms to prevent this binding. The assay gave high correlation in previous studies with the in vivo murine lethality tests (Median Lethal Dose, LD50), and the neutralization of lethality assays (Median Effective Dose, ED50) by antisera against Naja kaouthia, Naja naja and Bungarus candidus venoms. Here we show that, for the neurotoxic venoms of 20 elapid snake species from eight genera and four continents, the in vitro median inhibitory concentrations (IC50s) for α-neurotoxin binding to purified nAChR correlated well with the in vivo LD50s of the venoms (R2 = 0.8526, p < 0.001). Furthermore, using this assay, the in vitro ED50s of a horse pan-specific antiserum against these venoms correlated significantly with the corresponding in vivo murine ED50s, with R2 = 0.6896 (p < 0.01). In the case of four elapid venoms devoid or having a very low concentration of α-neurotoxins, no inhibition of nAChR binding was observed. Within the philosophy of 3Rs (Replacement, Reduction and Refinement) in animal testing, the in vitro α-neurotoxin-nAChR binding assay can effectively substitute the mouse lethality test for toxicity and antivenom potency evaluation for neurotoxic venoms in which α-neurotoxins predominate. This will greatly reduce the number of mice used in toxicological research and antivenom production laboratories. The simpler, faster, cheaper and less variable in vitro assay should also expedite the development of pan-specific antivenoms against various medically important snakes in many parts of the world.

Horse immunization with short-chain consensus α-neurotoxin generates antibodies against broad spectrum of elapid venomous species

Antivenoms are fundamental in the therapy for snakebites. In elapid venoms, there are toxins, e.g. short-chain α-neurotoxins, which are quite abundant, highly toxic, and consequently play a major role in envenomation processes. The core problem is that such α-neurotoxins are weakly immunogenic, and many current elapid antivenoms show low reactivity towards them. We have previously developed a recombinant consensus short-chain α-neurotoxin (ScNtx) based on sequences from the most lethal elapid venoms from America, Africa, Asia, and Oceania. Here we report that an antivenom generated by immunizing horses with ScNtx can successfully neutralize the lethality of pure recombinant and native short-chain α-neurotoxins, as well as whole neurotoxic elapid venoms from diverse genera such as Micrurus, Dendroaspis, Naja, Walterinnesia, Ophiophagus and Hydrophis. These results provide a proof-of-principle for using recombinant proteins with rationally designed consensus sequences as universal immunogens for developing next-generation antivenoms with higher effectiveness and broader neutralizing capacity.

Development and Characterization of Monoclonal Antibodies to Botulinum Neurotoxin Type E

Botulism is a devastating disease caused by botulinum neurotoxins (BoNTs) secreted primarily by Clostridium botulinum. Mouse bioassays without co-inoculation with antibodies are the standard method for the detection of BoNTs, but are not capable of distinguishing between the different serotypes (A-G). Most foodborne intoxications are caused by serotypes BoNT/A and BoNT/B. BoNT/E outbreaks are most often observed in northern coastal regions and are associated with eating contaminated marine animals and other fishery products. Sandwich enzyme-linked immunosorbent assays (ELISAs) were developed for the detection of BoNT/E3. Monoclonal antibodies (mAbs) were generated against BoNT/E3 by immunizing with recombinant peptide fragments of the light and heavy chains of BoNT/E3. In all, 12 mAbs where characterized for binding to both the recombinant peptides and holotoxin, as well as their performance in Western blots and sandwich ELISAs. The most sensitive sandwich assay, using different mAbs for capture and detection, exhibited a limit of detection of 0.2 ng/ml in standard buffer matrix and 10 ng/mL in fish product matrices. By employing two different mAbs for capture and detection, a more standardized sandwich assay was constructed. Development of sensitive and selective mAbs to BoNT/E would help in the initial screening of potential food contamination, speeding diagnosis and reducing use of laboratory animals.

Discovery of a Potential Human Serum Biomarker for Chronic Seafood Toxin Exposure Using an SPR Biosensor

Domoic acid (DA)-producing harmful algal blooms (HABs) have been present at unprecedented geographic extent and duration in recent years causing an increase in contamination of seafood by this common environmental neurotoxin. The toxin is responsible for the neurotoxic illness, amnesic shellfish poisoning (ASP), that is characterized by gastro-intestinal distress, seizures, memory loss, and death. Established seafood safety regulatory limits of 20 μg DA/g shellfish have been relatively successful at protecting human seafood consumers from short-term high-level exposures and episodes of acute ASP. Significant concerns, however, remain regarding the potential impact of repetitive low-level or chronic DA exposure for which there are no protections. Here, we report the novel discovery of a DA-specific antibody in the serum of chronically-exposed tribal shellfish harvesters from a region where DA is commonly detected at low levels in razor clams year-round. The toxin was also detected in tribal shellfish consumers’ urine samples confirming systemic DA exposure via consumption of legally-harvested razor clams. The presence of a DA-specific antibody in the serum of human shellfish consumers confirms long-term chronic DA exposure and may be useful as a diagnostic biomarker in a clinical setting. Adverse effects of chronic low-level DA exposure have been previously documented in laboratory animal studies and tribal razor clam consumers, underscoring the potential clinical impact of such a diagnostic biomarker for protecting human health. The discovery of this type of antibody response to chronic DA exposure has broader implications for other environmental neurotoxins of concern.

Generation of a Broadly Cross-Neutralizing Antibody Fragment against Several Mexican Scorpion Venoms

The recombinant antibody fragments generated against the toxic components of scorpion venoms are considered a promising alternative for obtaining new antivenoms for therapy. Using directed evolution and site-directed mutagenesis, it was possible to generate a human single-chain antibody fragment with a broad cross-reactivity that retained recognition for its original antigen. This variant is the first antibody fragment that neutralizes the effect of an estimated 13 neurotoxins present in the venom of nine species of Mexican scorpions. This single antibody fragment showed the properties of a polyvalent antivenom. These results represent a significant advance in the development of new antivenoms against scorpion stings, since the number of components would be minimized due to their broad cross-neutralization capacity, while at the same time bypassing animal immunization.

Detection of Clostridium tetani Neurotoxins Inhibited In Vivo by Botulinum Antitoxin B: Potential for Misleading Mouse Test Results in Food Controls

The presence of botulinum neurotoxin-producing Clostridia (BPC) in food sources is a public health concern. In favorable environmental conditions, BPC can produce botulinum neurotoxins (BoNTs) outside or inside the vertebrate host, leading to intoxications or toxico-infectious forms of botulism, respectively. BPC in food are almost invariably detected either by PCR protocols targeted at the known neurotoxin-encoding genes, or by the mouse test to assay for the presence of BoNTs in the supernatants of enrichment broths inoculated with the tested food sample. The sample is considered positive for BPC when the supernatant contains toxic substances that are lethal to mice, heat-labile and neutralized in vivo by appropriate polyclonal antibodies raised against purified BoNTs of different serotypes. Here, we report the detection in a food sample of a Clostridium tetani strain that produces tetanus neurotoxins (TeNTs) with the above-mentioned characteristics: lethal for mice, heat-labile and neutralized by botulinum antitoxin type B. Notably, neutralization occurred with two different commercially available type B antitoxins, but not with type A, C, D, E and F antitoxins. Although TeNT and BoNT fold very similarly, evidence that antitoxin B antiserum can neutralize the neurotoxic effect of TeNT in vivo has not been documented before. The presence of C. tetani strains in food can produce misleading results in BPC detection using the mouse test.

The European AntibotABE Framework Program and Its Update: Development of Innovative Botulinum Antibodies

The goal of the AntiBotABE Program was the development of recombinant antibodies that neutralize botulinum neurotoxins (BoNT) A, B and E. These serotypes are lethal and responsible for most human botulinum cases. To improve therapeutic efficacy, the heavy and light chains (HC and LC) of the three BoNT serotypes were targeted to achieve a synergistic effect (oligoclonal antibodies). For antibody isolation, macaques were immunized with the recombinant and non-toxic BoNT/A, B or E, HC or LC, followed by the generation of immune phage-display libraries. Antibodies were selected from these libraries against the holotoxin and further analyzed in in vitro and ex vivo assays. For each library, the best ex vivo neutralizing antibody fragments were germline-humanized and expressed as immunoglobulin G (IgGs). The IgGs were tested in vivo, in a standardized model of protection, and challenged with toxins obtained from collections of Clostridium strains. Protective antibody combinations against BoNT/A and BoNT/B were evidenced and for BoNT/E, the anti-LC antibody alone was found highly protective. The combination of these five antibodies as an oligoclonal antibody cocktail can be clinically and regulatorily developed while their high “humanness” predicts a high tolerance in humans.

Sensitive Immunoassay for Detection and Quantification of the Neurotoxin, Tetramethylenedisulfotetramine

Tetramethylenedisulfotetramine (TETS, tetramine) is a formerly used and highly neurotoxic rodenticide. Its lethality, recent history of intentional use for mass poisoning, and the absence of a known antidote raise public health concerns. Therefore, rapid, high throughput, and sensitive methods for detection and quantification of TETS are critical. Instrumental analysis method such as GC/MS is sensitive but not rapid or high throughput. Therefore, an immunoassay selective to TETS was developed. The assay shows an IC50 of 4.5 ± 1.2 ng/mL, with a limit of detection of 0.2 ng/mL, comparable to GC/MS. Performance of the immunoassay was demonstrated by a recovery study using known concentrations of TETS spiked into buffer and human and mouse serum matrices giving recoveries in the range of 80-120%. The assay demonstrated good correlation in TETS recovery with established GC/MS analysis. The immunoassay was then used to quantify TETS concentration in the serum of mice exposed to 2× LD50 dose of TETS and to monitor kinetics of TETS clearance from blood over a short period of time. TETS concentration in the serum reached 150 ng/mL without significant change over 4 h post-treatment. Results obtained with the immunoassay had good correlation with GC/MS analysis. Overall, this immunoassay is an important tool to rapidly detect and quantify levels of TETS from biological samples with high sensitivity. The assay can be adapted to multiple formats including field or hospital use.

The binding effectiveness of anti-r-disintegrin polyclonal antibodies against disintegrins and PII and PIII metalloproteases: An immunological survey of type A, B and A+B venoms from Mohave rattlesnakes

Snake venoms are known to have different venom compositions and toxicity, but differences can also be found within populations of the same species contributing to the complexity of treatment of envenomated victims. One of the first well-documented intraspecies venom variations comes from the Mohave rattlesnake (Crotalus scutulatus scutulatus). Initially, three types of venoms were described; type A venom is the most toxic as a result of ~45% Mojave toxin in the venom composition, type B lacks the Mojave toxin but contains over 50% of snake venom metalloproteases (SVMPs). Also, type A+B venom contains a combination of Mojave toxin and SVMP. The use of an anti-disintegrin antibody in a simple Enzyme-Linked Immunosorbent Assay (ELISA) can be used to identify the difference between the venoms of the type A, B, and A+B Mohave rattlesnakes. This study implements the use of an anti-recombinant disintegrin polyclonal antibody (ARDPA) for the detection of disintegrins and ADAMs (a disintegrin and metalloproteases) in individual crude snake venoms of Mohave rattlesnakes (Crotalus scutulatus scutulatus) of varying geographical locations. After correlation with Western blots, coagulation activity and LD₅₀ data, it was determined that the antibody allows for a quick and cost-efficient identification of venom types.

Ophiophagus hannah venom: proteome, components bound by Naja kaouthia antivenin and neutralization by N. kaouthia neurotoxin-specific human ScFv

Venomous snakebites are an important health problem in tropical and subtropical countries. King cobra (Ophiophagushannah) is the largest venomous snake found in South and Southeast Asia. In this study, the O. hannah venom proteome and the venom components cross-reactive to N. kaouthia monospecific antivenin were studied. O. hannah venom consisted of 14 different protein families, including three finger toxins, phospholipases, cysteine-rich secretory proteins, cobra venom factor, muscarinic toxin, L-amino acid oxidase, hypothetical proteins, low cysteine protein, phosphodiesterase, proteases, vespryn toxin, Kunitz, growth factor activators and others (coagulation factor, endonuclease, 5’-nucleotidase). N. kaouthia antivenin recognized several functionally different O. hannah venom proteins and mediated paratherapeutic efficacy by rescuing the O. hannah envenomed mice from lethality. An engineered human ScFv specific to N. kaouthia long neurotoxin (NkLN-HuScFv) cross-neutralized the O. hannah venom and extricated the O. hannah envenomed mice from death in a dose escalation manner. Homology modeling and molecular docking revealed that NkLN-HuScFv interacted with residues in loops 2 and 3 of the neurotoxins of both snake species, which are important for neuronal acetylcholine receptor binding. The data of this study are useful for snakebite treatment when and where the polyspecific antivenin is not available. Because the supply of horse-derived antivenin is limited and the preparation may cause some adverse effects in recipients, a cocktail of recombinant human ScFvs for various toxic venom components shared by different venomous snakes, exemplified by the in vitro produced NkLN-HuScFv in this study, should contribute to a possible future route for an improved alternative to the antivenins.

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.

Botulinum neurotoxins and botulism: a novel therapeutic approach

Specific treatment is not available for human botulism. Current remedial mainstay is the passive administration of polyclonal antibody to botulinum neurotoxin (BoNT) derived from heterologous species (immunized animal or mouse hybridoma) together with supportive and symptomatic management. The antibody works extracellularly, probably by blocking the binding of receptor binding (R) domain to the neuronal receptors; thus inhibiting cellular entry of the holo-BoNT. The antibody cannot neutralize the intracellular toxin. Moreover, a conventional antibody with relatively large molecular size (150 kDa) is not accessible to the enzymatic groove and, thus, cannot directly inhibit the BoNT zinc metalloprotease activity. Recently, a 15-20 kDa single domain antibody (V(H)H) that binds specifically to light chain of BoNT serotype A was produced from a humanized-camel VH/V(H)H phage display library. The V(H)H has high sequence homology (>80%) to the human VH and could block the enzymatic activity of the BoNT. Molecular docking revealed not only the interface binding between the V(H)H and the toxin but also an insertion of the V(H)H CDR3 into the toxin enzymatic pocket. It is envisaged that, by molecular linking the V(H)H to a cell penetrating peptide (CPP), the CPP-V(H)H fusion protein would be able to traverse the hydrophobic cell membrane into the cytoplasm and inhibit the intracellular BoNT. This presents a novel and safe immunotherapeutic strategy for botulism by using a cell penetrating, humanized-single domain antibody that inhibits the BoNT by means of a direct blockade of the groove of the menace enzyme.

Camelid single domain antibodies (VHHs) as neuronal cell intrabody binding agents and inhibitors of Clostridium botulinum neurotoxin (BoNT) proteases

Botulinum neurotoxins (BoNTs) function by delivering a protease to neuronal cells that cleave SNARE proteins and inactivate neurotransmitter exocytosis. Small (14 kDa) binding domains specific for the protease of BoNT serotypes A or B were selected from libraries of heavy chain only antibody domains (VHHs or nanobodies) cloned from immunized alpacas. Several VHHs bind the BoNT proteases with high affinity (K(D) near 1 nM) and include potent inhibitors of BoNT/A protease activity (K(i) near 1 nM). The VHHs retain their binding specificity and inhibitory functions when expressed within mammalian neuronal cells as intrabodies. A VHH inhibitor of BoNT/A protease was able to protect neuronal cell SNAP25 protein from cleavage following intoxication with BoNT/A holotoxin. These results demonstrate that VHH domains have potential as components of therapeutic agents for reversal of botulism intoxication.

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.

[Expression, antiserum preparation and bioactivity assays of insect neurotoxin LqhIT2]

According to the codon bias of Pichia pastoris, the mature insect neurotoxin gene LqhIT2 was synthesized based on its amino acid sequence and was cloned to vector of PET-30a (+) and pPIC9K respectively. The fusion protein expressed in Escherichia. coli was induced with IPTG and purified with Ni-NTA His Bind Column. The purified fusion protein was used to immunize BALB/c mice, and antiserum obtained was highly specific with the titer of over 1:128 000. Using the antiserum, high-level expression transformants of P. pastoris were screened by dot blotting. The highest expression of recombinant LqhIT2 was about 9 mg/L in baffled flasks. The fusion protein of LqhIT2 expressed in E. coli was not toxic to locust, but the recombinant LqhIT2 expressed in P. pastoris had insecticidal activity against locust through injection.

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.

Polymorphonuclear leukocytes promote neurotoxicity through release of matrix metalloproteinases, reactive oxygen species, and TNF-α

As the first immune cells to infiltrate the nervous system after traumatic PNS and CNS injury, neutrophils (polymorphonuclear leukocytes, PMNs) may promote injury by releasing toxic soluble factors that may affect neuronal survival. Direct neurotoxicity of matrix metalloproteinases (MMPs), reactive oxygen species (ROS), and cytokines released by PMNs was investigated by culturing dorsal root ganglion (DRG) cells with PMN-conditioned media containing MMP inhibitor (GM6001), ROS scavengers, or tumor necrosis factor alphaR (TNF-alphaR) neutralizing antibody. Although DRGs exposed to PMN-conditioned media had 53% fewer surviving neurons than controls, neuronal cell loss was prevented by GM6001 (20 micromol/L), catalase (1000 U/mL), or TNF-alphaR neutralizing antibody (1.5 microg/mL), elevating survival to 77%, 94%, and 95%, respectively. In accordance with protection by GM6001, conditioned media collected from MMP-9 null PMNs was less neurotoxic than that collected from wild-type PMNs. Additionally, MMP inhibition reduced PMN-derived ROS; removal of ROS reduced PMN-derived MMP-9 activity; and TNF-alpha inhibition reduced both PMN-derived MMP-9 activity and ROS in PMN cultures. Our data provide the first direct evidence that PMN-driven neurotoxicity is dependent on MMPs, ROS, and TNF-alpha, and that these factors may regulate PMN release of these soluble factors or interact with one another to mediate PMN-driven neurotoxicity.

Human immunodeficiency virus type-1 protein Tat induces tumor necrosis factor-alpha-mediated neurotoxicity

HIV-1 infection causes, with increasing prevalence, neurological disorders characterized in part by neuronal cell death. The HIV-1 protein Tat has been shown to be directly and indirectly neurotoxic. Here, we tested the hypothesis that a non-neurotoxic epitope of Tat can, through actions on immune cells, increase neuronal cell death. Tat(1-72) and a mutant Tat(1-72) lacking the neurotoxic epitope (Tat(Delta31-61)) concentration-dependently and markedly increased TNF-alpha production in macrophage-like differentiated human U937 and THP-1 cells, in mouse peritoneal macrophages and in mouse brain microglia. Tat(1-72) was but Tat(Delta31-61) was not neurotoxic when applied directly to neurons. Supernatants from U937 cells treated with either Tat(1-72) or Tat(Delta31-61) were neurotoxic and their immunoneutralization with an anti-TNF-alpha antibody decreased Tat(1-72)- and Tat(Delta31-61)-induced neurotoxicity. Together, these results demonstrate that the neurotoxic epitope of Tat(1-72) is different from the epitope that is indirectly neurotoxic following production of TNF-alpha from immune cells, and suggest that therapeutic interventions against TNF-alpha might be beneficial against HIV-1 associated neurological disorders.

Optimisation of production of a domoic acid-binding scFv antibody fragment in Escherichia coli using molecular chaperones and functional immobilisation on a mesoporous silicate support

Domoic acid is a potent neurotoxin that can lead to amnesic shellfish poisoning in humans through ingestion of contaminated shellfish. We have produced and purified an anti-domoic acid single-chain Fragment variable (scFv) antibody fragment from the Escherichia coli periplasm. Yields of functional protein were increased by up to 100-fold upon co-production of E. coli DnaKJE molecular chaperones but co-overproduction of GroESL led to a reduction in solubility of the scFv. Co-production of the peptidyl-prolyl isomerase trigger factor resulted in accumulation of unprocessed scFv in the E. coli cytoplasm. This was due to an apparent bottleneck in translocation of the cytoplasmic membrane by the recombinant polypeptide. Co-expression of the E. coli disulfide bond isomerase dsbC increased scFv yields by delaying lysis of the host bacterial cells though this effect was not synergistic with molecular chaperone co-production. Meanwhile, use of a cold-shock promoter for protein production led to accumulation of greater amounts of scFv polypeptide which was predominantly in insoluble form and could not be rescued by chaperones. Purification of the scFv was achieved using an optimised metal affinity chromatography procedure and the purified protein bound domoic acid when immobilised on a mesoporous silicate support. The work outlines the potential benefit of applying a molecular chaperone/folding catalyst screening approach to improve antibody fragment production for applications such as sensor development.

Antibodies Against Botulinum Neurotoxin Type A as a Cause of Treatment Failure After the First Detrusor Injection

Botulinum neurotoxins are increasingly used in treatment for hyperactive detrusor and sphincter function. Although reported results are promising, conditions in some patients are refractory. We report what we believe to be the first urologic case of therapy failure possibly induced by botulinum toxin antibodies after just one injection and discuss treatment alternatives based on experience in other fields.

Predicting virulence factors of immunological interest

In this chapter, three prediction servers used for predicting virulence factors, bacterial toxins, and neurotoxins have been described. VICMpred server predicts the functional proteins of gram-negative bacteria that include virulence factors, information molecule, cellular process, and metabolism molecule. BTXpred server allows users to predict bacterial toxins, its release, and further classification of exotoxins. NTXpred server allows prediction of neurotoxins and further classifying them based on their function and source.

Multiagent vaccines vectored by Venezuelan equine encephalitis virus replicon elicits immune responses to Marburg virus and protection against anthrax and botulinum neurotoxin in mice

The development of multiagent vaccines offers the advantage of eliciting protection against multiple diseases with minimal inoculations over a shorter time span. We report here the results of using formulations of individual Venezuelan equine encephalitis (VEE) virus replicon-vectored vaccines against a bacterial disease, anthrax; a viral disease, Marburg fever; and against a toxin-mediated disease, botulism. The individual VEE replicon particles (VRP) expressed mature 83-kDa protective antigen (MAT-PA) from Bacillus anthracis, the glycoprotein (GP) from Marburg virus (MBGV), or the H(C) fragment from botulinum neurotoxin (BoNT H(C)). CBA/J mice inoculated with a mixture of VRP expressing BoNT H(C) serotype C (BoNT/C H(C)) and MAT-PA were 80% protected from a B. anthracis (Sterne strain) challenge and then 100% protected from a sequential BoNT/C challenge. Swiss mice inoculated with individual VRP or with mixtures of VRP vaccines expressing BoNT H(C) serotype A (BoNT/A H(C)), MAT-PA, and MBGV-GP produced antibody responses specific to the corresponding replicon-expressed protein. Combination of the different VRP vaccines did not diminish the antibody responses measured for Swiss mice inoculated with formulations of two or three VRP vaccines as compared to mice that received only one VRP vaccine. Swiss mice inoculated with VRP expressing BoNT/A H(C) alone or in combination with VRP expressing MAT-PA and MBGV GP, were completely protected from a BoNT/A challenge. These studies demonstrate the utility of combining individual VRP vaccines into multiagent formulations for eliciting protective immune responses to various types of diseases.

EGCG mitigates neurotoxicity mediated by HIV-1 proteins gp120 and Tat in the presence of IFN-gamma: role of JAK/STAT1 signaling and implications for HIV-associated dementia

Human immunodeficiency virus (HIV)-1 infection of the central nervous system occurs in the vast majority of HIV-infected patients. HIV-associated dementia (HAD) represents the most severe form of HIV-related neuropsychiatric impairment and is associated with neuropathology involving HIV proteins and activation of proinflammatory cytokine circuits. Interferon-gamma (IFN-gamma) activates the JAK/STAT1 pathway, a key regulator of inflammatory and apoptotic signaling, and is elevated in HIV-1-infected brains progressing to HAD. Recent reports suggest green tea-derived (-)-epigallocatechin-3-gallate (EGCG) can attenuate neuronal damage mediated by this pathway in conditions such as brain ischemia. In order to investigate the therapeutic potential of EGCG to mitigate the neuronal damage characteristic of HAD, IFN-gamma was evaluated for its ability to enhance well-known neurotoxic properties of HIV-1 proteins gp120 and Tat in primary neurons and mice. Indeed, IFN-gamma enhanced the neurotoxicity of gp120 and Tat via increased JAK/STAT signaling. Additionally, primary neurons pretreated with a JAK1 inhibitor, or those derived from STAT1-deficient mice, were largely resistant to the IFN-gamma-enhanced neurotoxicity of gp120 and Tat. Moreover, EGCG treatment of primary neurons from normal mice reduced IFN-gamma-enhanced neurotoxicity of gp120 and Tat by inhibiting JAK/STAT1 pathway activation. EGCG was also found to mitigate the neurotoxic properties of HIV-1 proteins in the presence of IFN-gamma in vivo. Taken together, these data suggest EGCG attenuates the neurotoxicity of IFN-gamma augmented neuronal damage from HIV-1 proteins gp120 and Tat both in vitro and in vivo. Thus EGCG may represent a novel natural copound for the prevention and treatment of HAD.

Prediction of antigenic epitopes of neurotoxin Bmbktx1 from Mesobuthus martensii

Gene therapy or recombinant DNA vaccines targeting multiple antigenic components to direct empower the immune system. Antigenic epitopes on neurotoxin Mesobuthus martensii (Buthus martensii) are important determinant of protection against cardiovascular disorder. Small segments 4-YSSDCRVKCVAM-15, 18-SSGKCINSKC-27 of neuro-toxin protein called the antigenic epitopes is sufficient for eliciting the desired immune response. In analysis predicted antigenic epitopes neurotoxin protein is seen. Immunization cassettes should be capable of immunizing of broad immunity against both humoral and cellular epitope thus giving vaccines the maximum ability to deal with neurotoxin protein of M. martensii. We have predicted a successful immunization.

Role of the pro-inflammatory cytokines TNF-alpha and IL-1beta in HIV-associated dementia

Human immunodeficiency virus-1 (HIV-1)-infected and immune-activated macrophages and microglia secrete neurotoxins. Two of these neurotoxins are the pro-inflammatory cytokines tumour necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta), which are thought to play a major role in inducing neuronal death. Both TNF-alpha and IL-1beta increase the permeability of the blood-brain barrier, through which subsequently HIV-infected monocytes can enter the brain. They both induce over-stimulation of the NMDA-receptor via several pathways, resulting in a lethal neuronal increase in Ca(2+) levels. Additionally, TNF-alpha co-operates with several other proinflammatory mediators to enhance their toxic effects. Although most research has focused on the neurotoxic effects of TNF-alpha and IL-1beta in HAD, there is also evidence that these cytokines can be neuroprotective. In this paper the effect of TNF-alpha and IL-1beta on neuronal life and death in HAD is discussed.

Detection of type A, B, E, and F Clostridium botulinum neurotoxins in foods by using an amplified enzyme-linked immunosorbent assay with digoxigenin-labeled antibodies

An amplified enzyme-linked immunosorbent assay (ELISA) for the detection of Clostridium botulinum complex neurotoxins was evaluated for its ability to detect these toxins in food. The assay was found to be suitable for detecting type A, B, E, and F botulinum neurotoxins in a variety of food matrices representing liquids, solid, and semisolid food. Specific foods included broccoli, orange juice, bottled water, cola soft drinks, vanilla extract, oregano, potato salad, apple juice, meat products, and dairy foods. The detection sensitivity of the test for these botulinum complex serotypes was found to be 60 pg/ml (1.9 50% lethal dose [LD50]) for botulinum neurotoxin type A (BoNT/A), 176 pg/ml (1.58 LD50) for BoNT/B, 163 pg/ml for BoNT/E (4.5 LD50), and 117 pg/ml for BoNT/F (less than 1 LD50) in casein buffer. The test could also readily detect 2 ng/ml of neurotoxins type A, B, E, and F in a variety of food samples. For specificity studies, the assay was also used to test a large panel of type A C. botulinum, a smaller panel of proteolytic and nonproteolytic type B, E, and F neurotoxin-producing Clostridia, and nontoxigenic organisms using an overnight incubation of toxin production medium. The assay appears to be an effective tool for large-scale screening of the food supply in the event of a botulinum neurotoxin contamination event.

[Recombinant antibodies: a new application in scorpion envenomation?]

Serotherapy is the only specific treatment for envenomation. The antibodies are obtained after the purification of serum from hyperimmunised horses and are used after fragmentation in the form of polyclonal Fab or F(ab)'2. The anti-venom sera are heterogeneous, and their protective effect is often weak. The administration of these preparations induces risks of immediate or delayed side effects: hypersensitivity reactions, anaphylactic shock and serum sickness. This observation led us to develop new forms of antibodies produced by molecular engineering, capable of specifically neutralizing the neurotoxins responsible for the toxicity of the venom of Androctonus australis Hector. The recombinant antibody fragments are more homogeneous than conventional antivenoms and perfectly characterized in terms of specific activity. The method used to obtain them eliminates the risk of transmission by non-conventional transmissible agents. The earliest results confirm the importance of these new molecules (scFv recombinant Fab, diabody, triabody) and their ability to neutralize the action of scorpion neurotoxins. They could open the path to a new generation of more homogeneous antivenoms that are better tolerated and have well-characterized intrinsic properties.

Cross-neutralization of the neurotoxicity of Crotalus durissus terrificus and Bothrops jararacussu venoms by antisera against crotoxin and phospholipase A2 from Crotalus durissus cascavella venom

We have previously demonstrated that rabbit antisera raised against crotoxin from Crotalus durissus cascavella venom (cdc-crotoxin) and its PLA2 (cdc-PLA2) neutralized the neurotoxicity of this venom and its crotoxin. In this study, we examined the ability of these antisera to neutralize the neurotoxicity of Crotalus durissus terrificus and Bothrops jararacussu venoms and their major toxins, cdt-crotoxin and bothropstoxin-I (BthTX-I), respectively, in mouse isolated phrenic nerve-diaphragm preparations. Immunoblotting showed that antiserum to cdc-crotoxin recognized cdt-crotoxin and BthTX-I, while antiserum to cdc-PLA2 recognized cdt-PLA2 and BthTX-I. ELISA corroborated this cross-reactivity. Antiserum to cdc-crotoxin prevented the neuromuscular blockade caused by C. d. terrificus venom and its crotoxin at a venom/crotoxin:antiserum ratio of 1:3. Antiserum to cdc-PLA2 also neutralized the neuromuscular blockade caused by C. d. terrificus venom or its crotoxin at venom or toxin:antiserum ratios of 1:3 and 1:1, respectively. The neuromuscular blockade caused by B. jararacussu venom and BthTX-I was also neutralized by the antisera to cdc-crotoxin and cdc-PLA2 at a venom/toxin:antiserum ratio of 1:10 for both. Commercial equine antivenom raised against C. d. terrificus venom was effective in preventing the neuromuscular blockade typical of B. jararacussu venom (venom:antivenom ratio of 1:2), whereas for BthTX-I the ratio was 1:10. These results show that antiserum produced against PLA2, the major toxin in C. durissus cascavella venom, efficiently neutralized the neurotoxicity of C. d. terrificus and B. jararacussu venoms and their PLA2 toxins.

Comparison of electrochemiluminescence assay and ELISA for the detection of Clostridium botulinum type B neurotoxin

We compared the ELISA and electrochemiluminescence (ECL) immunoassay technologies for the detection of botulinum type B neurotoxin (BotNT B), which requires highly sensitive techniques due to its potent biological activity. BotNT B complexes are the naturally secreted form of the toxin, approximately a third of which consists of the neurotoxin itself; they were aliquoted and frozen for this study. Results of both techniques were interpreted with the same standard statistical tests (ANOVA and Tukey). We first compared two commercial assays for BotNT B: the detection limit of the colorimetric ELISA was 1.56 ng/ml BotNT B complexes versus 0.39-0.78 ng/ml in the ECL test. We then used the same monoclonal antibody and the same polyclonal antibody, respectively purified by protein A and protein G chromatography, to optimize an in-house ELISA test and an in-house ECL test, making it possible to directly compare the two technologies without interference due to the properties of the antibodies used in the two tests. The colorimetric in-house ELISA had a detection threshold of 3.12 ng/ml versus the in-house ECL test whose detection threshold was 0.78-1.56 ng/ml. Thus, in both cases, the ECL assay was two to four times more sensitive than the colorimetric ELISA. The ECL assay was also more rapid (2.5 h for the in-house ECL versus 5 h for in-house ELISA with precoated wells). Overall, these elements can be used to compare the qualities of the two technologies, at least for the detection of protein antigens such as toxins.

Neuronal TGF-beta1 mediates IL-9/mast cell interaction and exacerbates excitotoxicity in newborn mice

Intraneocortical injection of ibotenate, a glutamate analog, in newborn mice produces damage mimicking lesions observed in human infants with cerebral palsy. Previous research using this model has demonstrated that pretreatment with IL-9, a Th2 cytokine, significantly exacerbated excitotoxic brain lesions. The goal of this study is to identify the underlying pathophysiological mechanism of lesion formation. Pretreatment with TGF-beta1 produced the same effects as IL-9 on ibotenate-induced lesions. IL-9 effects were abolished when a specific TGF-beta1 neutralizing antibody is administered at the same time. Real-time PCR, Western blot, and immunohistochemistry showed that pretreatment with IL-9 increased TGF-beta1 neocortical expression. In vitro studies using real-time PCR and immunocytochemistry demonstrated that neurons were a major contributor in IL-9-induced increase of TGF-beta1. In c-Kit mast cell-deficient mice, TGF-beta1 failed to exacerbate excitotoxic brain lesions, suggesting a key role of mast cells in TGF-beta1 effects. A specific inhibitor of mast cell degranulation and histamine receptor blockers abrogated TGF-beta1 effects on excitotoxic lesions, providing further evidence of mast cell involvement and the role of mast cell-derived histamine. Finally, in vitro studies using a mast cell line showed that TGF-beta1 increased histamine in the supernatant. In aggregate, these data support the notion that neuronal TGF-beta1 plays a key role in the IL-9/mast cell interaction, which leads to an exacerbation of neonatal excitotoxic damage through an increased extracellular histamine concentration. The identification of this pathway, if confirmed in human neonates, might have important implications for understanding and preventing cerebral palsy.

A strategy for the generation of specific human antibodies by directed evolution and phage display

This study describes the construction of a library of single-chain antibody fragments (scFvs) from a single human donor by individual amplification of all heavy and light variable domains (1.1 x 10(8) recombinants). The library was panned using the phage display technique, which allowed selection of specific scFvs (3F and C1) capable of recognizing Cn2, the major toxic component of Centruroides noxius scorpion venom. The scFv 3F was matured in vitro by three cycles of directed evolution. The use of stringent conditions in the third cycle allowed the selection of several improved clones. The best scFv obtained (6009F) was improved in terms of its affinity by 446-fold, from 183 nm (3F) to 410 pm. This scFv 6009F was able to neutralize 2 LD(50) of Cn2 toxin when a 1 : 10 molar ratio of toxin-to-antibody fragment was used. It was also able to neutralize 2 LD(50) of the whole venom. These results pave the way for the future generation of recombinant human antivenoms.

Immunochemical and biochemical comparisons of equine monovalent and polyvalent snake antivenoms

Although the merit of polyvalent antivenoms is well-recognized, there is still doubt in some medical circles as to the relative efficacy and the propensity to cause adverse reactions of polyvalent (pAV) as compared to monovalent (mAV) antivenoms. Immunochemical and biochemical comparisons of equine polyvalent and monovalent antivenoms prepared under the same immunization protocols were therefore made. These antivenoms were prepared against Naja kaouthia (NK), Ophiophagus hannah (OH) and Bungarus fasciatus (BF) venoms. SDS-PAGE analysis of both types of antivenoms showed similar serum protein profiles. The total amount of immunoglobulin (IgG(T)+IgG) in pAVs was slightly but significantly higher than that of mAVs, while the total serum protein content in mAVs was slightly but significantly higher than that of pAVs. The amounts of total hyperimmune IgG(T), determined by ELISA, were similar in mAVs and pAVs. pAVs contained specific antibodies against the principal NK postsynaptic toxin (NK 3) to the same extent as that observed with the anti-N. kaouthia mAV. The antibodies against OH and BF principal postsynaptic toxins (OH II and BF IX) in pAVs were significantly higher than those of the corresponding anti-O. hannah and anti-B. fasciatus mAVs. These results were in concordance with the comparable in vivo neutralization activities of mAVs and pAV previously reported. The apparent dissociation constant (Kd) of anti-OH II antibody in pAVs was comparable to that of the anti-O. hannah mAVs. The apparent K(d)s of anti-NK 3 and anti-BF IX antibodies in the corresponding mAVs were slightly lower than those in pAVs. The Kd values were all in nM range and were considered to be high affinity binding. It is concluded that pAVs could be prepared with potency and protein contents and thus the propensity to cause adverse reaction that were comparable to those of mAVs.

Biological and enzymatic activities of Micrurus sp. (Coral) snake venoms

The venoms of Micrurus lemniscatus carvalhoi, Micrurus frontalis frontalis, Micrurus surinamensis surinamensis and Micrurus nigrocinctus nigrocinctus were assayed for biological activities. Although showing similar liposome disrupting and myotoxic activities, M. frontalis frontalis and M. nigrocinctus nigrocinctus displayed higher anticoagulant and phospholipase A2 (PLA2) activities. The latter induced a higher edema response within 30 min. Both venoms were the most toxic as well. In the isolated chick biventer cervicis preparation, M. lemniscatus carvalhoi venom blocked the indirectly elicited twitch-tension response (85+/-0.6% inhibition after a 15 min incubation at 5 microg of venom/mL) and the response to acetylcholine (ACh; 55 or 110 microM), without affecting the response to KCl (13.4 mM). In mouse phrenic nerve-diaphragm preparation, the venom (5 microg/mL) produced a complete inhibition of the indirectly elicited contractile response after 50 min incubation and did not affect the contractions elicited by direct stimulation. M. lemniscatus carvalhoi inhibited 3H-L-glutamate uptake in brain synaptosomes in a Ca2+-, but not time, dependent manner. The replacement of Ca2+ by Sr2+ and ethylene glycol-bis(beta-aminoethyl ether) (EGTA), or alkylation of the venom with p-bromophenacyl bromide (BPB), inhibited 3H-L-glutamate uptake. M. lemniscatus carvalhoi venom cross-reacted with postsynaptic alpha-neurotoxins short-chain (antineurotoxin-II) and long-chain (antibungarotoxin) antibodies. It also cross-reacted with antimyotoxic PLA2 antibodies from M. nigrocinctus nigrocinctus (antinigroxin). Our results point to the need of catalytic activity for these venoms to exert their neurotoxic activity efficiently and to their components as attractive tools for the study of molecular targets on cell membranes.

Mechanisms of hypoxic-ischemic injury in the term infant

The pathogenesis of hypoxic-ischemic brain injury in the term infant is multifactorial and complex. Over the past decade the investigative emphasis has turned to cellular and molecular mechanisms of injury, and it has been increasingly recognized that the neonatal brain differs vastly from the adult brain in terms of response to hypoxia-ischemia. This review will discuss the initiation and evolution of brain injury in the term neonate, and the inherent biochemical and physiologic qualities of the neonatal brain that make its response to hypoxia-ischemia unique. Attention will be given to specific areas of investigation including excitotoxicity, oxidative stress, and inflammation. The coalescence of these entities to a final common pathway of hypoxic-ischemic brain injury will be emphasized.

Interleukin-6 produces neuronal loss in developing cerebellar granule neuron cultures

CNS levels of the cytokine interleukin-6 (IL-6) are elevated during CNS injury and disease, but it is unclear if IL-6 contributes to the pathologic process. Our studies show that in a well-characterized CNS developmental model system, primary cultures of rodent cerebellar granule neurons, chronic exposure to IL-6 during neuronal development can result in cell damage and death in a subpopulation of developing granule neurons. Chronic exposure to IL-6 also increased the susceptibility of the granule neurons to a toxic insult produced by excessive activation of NMDA receptors. These results are consistent with a role for IL-6 in the neuropathology observed in the developing CNS during injury and disease.

Anti-sera raised in rabbits against crotoxin and phospholipase A2 from Crotalus durissus cascavella venom neutralize the neurotoxicity of the venom and crotoxin

Crotoxin, the principal neurotoxin in venom of the South American rattlesnakes Crotalus durissus terrificus and Crotalus durissus cascavella, contains a basic phospholipase A2 (PLA2) and an acidic protein, crotapotin. In this work, we examined the ability of rabbit anti-sera against crotoxin and its PLA2 subunit to neutralize the neurotoxicity of venom and crotoxin from C. d. cascavella in mouse phrenic nerve-diaphragm and chick biventer cervicis preparations. Immunoblotting showed that the anti-sera recognized C. d. cascavella crotoxin and PLA2. This was confirmed by ELISA, with both anti-sera having end-point dilutions of 3 x 10(-6). Anti-crotoxin serum neutralized the neuromuscular blockade in phrenic nerve-diaphragm muscle preparations at venom or crotoxin:anti-serum ratios of 1:2 and 1:3, respectively. Anti-PLA2 serum also neutralized this neuromuscular activity at a venom or crotoxin:anti-serum ratio of 1:1. In biventer cervicis preparations, the corresponding ratio for anti-crotoxin serum was 1:3 for venom and crotoxin, and 1:1 and 1:2 for anti-PLA2 serum. The neutralizing capacity of the sera in mouse preparations was comparable to that of commercial anti-serum raised against C. d. terrificus venom. These results show that anti-sera against crotoxin and PLA2 from C. d. cascavella venom neutralized the neuromuscular blockade induced by venom and crotoxin in both nerve-muscle preparations, with the anti-serum against crotoxin being slightly less potent than that against crotoxin.

Engineering of a recombinant Fab from a neutralizing IgG directed against scorpion neurotoxin AahI, and functional evaluation versus other antibody fragments

Antibody-based therapy is the only specific treatment for scorpion envenomation. However, there are still major drawbacks associated with its use; mainly because antivenoms are still prepared from immune equine serum raised against crude venoms, whereas only a limited number of neurotoxins are responsible for the lethality of the venom. Using a murine hybridoma that secretes a well-characterized neutralizing IgG directed to neurotoxins AahI and AahIII from the venom of the scorpion Androctonus australis, we constructed a recombinant Fab (rFab) fragment, which was produced and purified from transformed bacteria. It recognized toxin AahI with a high affinity (KD = 8.2 x 10(-11)) equivalent to the homologous pFab prepared by papain digestion of whole IgG. Although the AahI-neutralizing capacity of protein L-purified rFab was low compared to other recombinant antibody formats (scFv and diabody) investigated in parallel, the antibody engineering approach presented here provides an innovative way to synthesize novel toxin-neutralizing molecules. It may serve as a strategy for designing a new generation of antivenoms.

Basic immunological aspects of botulinum toxin therapy

Previous studies in this laboratory had mapped the immune recognition profile of the regions recognized antibodies (Abs) and by T cells on the protective H(C) domain (C-terminal fragment corresponding to residues 855-1296 of the heavy chain) of botulinum neurotoxin serotype A (BoNT/A). The localization of these regions has several potential applications and has provided a basis for the understanding of immunoresistance to treatment. We briefly outline these localized regions and discuss the impact of these findings on the immunotherapeutic applications of BoNT/A. Immunoresistance to toxin therapy can appear in some patients after a few injections with the toxin. Our epitope mapping studies have shown that several factors can influence the immune response to the toxin. These factors include dose, duration of treatment, frequency of immunization, and quality of the toxin. The immune response to the whole toxin is under genetic control, and the response to each epitope is under separate genetic control. Therefore, the appearance of blocking Abs (i.e., immunoresistance) in patients might be controlled by the major histocompatability of the host. Once a patient becomes immunoresistant to one toxin then switching to another toxin will most often be of limited and short-lived benefit, because the patient becomes rapidly immunoresistant to the second toxin. Finally, because of the considerable structural homology between tetanus neurotoxin (TeNT) and BoNTs, it is possible, although not certain, that a prior active immune response to TeNT might play some role in the early appearance on anti-BoNT Abs in some patients.

Signaling pathways to neuronal damage and apoptosis in human immunodeficiency virus type 1-associated dementia: Chemokine receptors, excitotoxicity, and beyond

Dementia can occur as a debilitating consequence of human immunodeficiency virus-1 (HIV-1) infection. The neuropathology incited by HIV infection involves activation of chemokine receptors, inflammatory factors, and N-methyl-D-aspartate (NMDA) receptor-mediated excitotoxicity, all of which can activate several downstream mechanisms. This article discusses recently identified pathways to neuronal damage triggered by HIV-1 and efforts aimed at development of applicable therapeutic intervention.

Immunized camel sera and derived immunoglobulin subclasses neutralizing Androctonus australis hector scorpion toxins

Scorpion envenoming is a real health problem. The only specific treatment is immunotherapy with antibodies from immunized horses. The severity of scorpion envenoming and the rapid diffusion of the toxins into the blood compartment require an improvement of the present antivenom therapy. In this study, we report successful immunization of dromedaries (Camelus dromedarius) against the small weakly antigenic neurotoxins of Androctonus australis hector scorpion. Camel immune sera was tested for its specific antigenic reactivity and neutralizing capacity against Aah toxic fraction and AahII toxin. We demonstrate that a substantial proportion of polyclonal heavy chain antibodies bind to Aah toxins and in particular to AahII, the most toxic one scorpion venom component. Furthermore, we show that both dromedary sera and heavy chain antibody subclasses are capable of neutralizing the toxicity of Aah toxins in mice.

Bacterial expression, purification and functional characterization of a recombinant chimeric Fab derived from murine mAb BCF2 that neutralizes the venom of the scorpion Centruroides noxius hoffmann

The murine monoclonal antibody BCF2 is able to neutralize the venom of the scorpion Centruroides noxius Hoffmann. A chimeric Fab of BCF2 (chFab-BCF2) comprising the variable regions of murine BCF2 and human constant regions was assembled. chFab-BCF2 was expressed as a soluble and functional protein in the periplasmic space of Escherichia coli. An expression yield of 1 mg/l was reached by combination of late-log-phase induction, rich culture medium, low expression temperature and addition of sucrose (0.3 M) to the culture medium. The addition of sucrose induced secretion of 60% of the protein into the medium. After expression for 23 h, a novel process was used to release the remaining periplasmic protein in situ consisting in the addition of lysozyme and sucrose up to 0.6 M (20%) directly to the culture medium. chFab-BCF2 was recovered by ammonium sulfate precipitation and purified in a single step by affinity chromatography using anti-human anti-F(ab')(2) IgG coupled to Sepharose-proteinG. Pure chFab-BCF2 maintained a similar nanomolar affinity as BCF2 to its cognate antigen, the Na(+)-channel-affecting toxin Cn2. Recombinant chFab-BCF2 was able to neutralize Cn2 in vivo even at a molar ratio of 1:1, as well as the whole venom of C. noxius. Thus, it is a promising candidate to be used as a specific and efficient recombinant antidote against scorpion stings.

Microglia and Alzheimer's disease pathogenesis

The most visible and, until very recently, the only hypothesis regarding the involvement of microglial cells in Alzheimer's disease (AD) pathogenesis is centered around the notion that activated microglia are neurotoxin-producing immune effector cells actively involved in causing the neurodegeneration that is the cause for AD dementia. The concept of detrimental neuroinflammation has gained a strong foothold in the AD arena and is being expanded to other neurodegenerative diseases. This review takes a comprehensive and critical look at the overall evidence supporting the neuroinflammation hypothesis and points out some weaknesses. The current work also reviews evidence for an alternative theory, the microglial dysfunction hypothesis, which, although eliminating some of the shortcomings, does not necessarily negate the amyloid/neuroinflammation theory. The microglial dysfunction theory offers a different perspective on the identity of activated microglia and their role in AD pathogenesis taking into account the most recent insights gained from studying basic microglial biology.

Cardiovascular, haematological and neurological effects of the venom of the Papua New Guinean small-eyed snake (Micropechis ikaheka) and their neutralisation with CSL polyvalent and black snake antivenoms

Cardiovascular and haematological effects of venom of the small-eyed Snake (Micropechis ikaheka) were examined in ventilated anaesthetised piglets. Neurotoxic effects were examined in chick biventer cervicis nerve-muscle preparations. Immunoreactivity of venom was tested against the monovalent antivenom components in a CSL Ltd Venom Detection Kit. Neutralisation was tested in vivo and in vitro with CSL Ltd polyvalent snake and Black Snake (Pseudechis australis) antivenoms. Venom in 0.1% bovine serum albumin in saline was infused into piglets in doses 1-2000 microg/kg. Pulmonary hypertension (P= 0.0007) and depression of cardiac output (P= 0.002) were observed up to 3 h after 150-160 microg/kg. The concentration of plasma free-haemoglobin increased more than 50-fold, indicating haemolysis. Neither coagulopathy nor thrombocytopenia occurred. Creatine phosphokinase and serum potassium levels did not increase suggesting absence of acute rhabdomyolysis. The venom caused post-synaptic neurotoxicty. Immunoreactivity of venom with Black Snake antivenom was observed at very high venom concentrations. Cardiovascular effects were absent and haemolysis was less after venom was pre-incubated at 37 degrees C for 30 min with polyvalent antivenom. Neutralisation by Black Snake antivenom was less effective. The neurotoxicity was neutralised by polyvalent or Black Snake antivenoms. Human envenomation may be treated with CSL Ltd polyvalent snake antivenom.

Interleukin-6, beta-amyloid peptide and NMDA interactions in rat cortical neurons

Neuronal damage in Alzheimer's disease (AD) is thought to involve direct toxicity of beta-amyloid peptide (Abeta) and excitotoxicity involving NMDA receptors (NMDARs) and altered Ca(2+) dynamics. Inflammation agents produced by microglia or astrocytes and associated with senile plaques such as the cytokine interleukin-6 (IL-6) could also contribute. To investigate this possibility, neuronal damage (lactate dehydrogenase assay, LDH, assay) was measured in cultures of rodent cortical neurons chronically treated with IL-6, Abeta or Abeta plus IL-6 and acutely treated with NMDA. Both Abeta and NMDA produced neuronal damage and this effect was larger with combined treatment. IL-6 did not produce significant neuronal damage but the largest neuronal damage was observed in cultures exposed to all three factors. IL-6 and Abeta enhanced Ca(2+) responses to NMDA and combined treatment produced the largest effect. These results are consistent with a role for interactions between Abeta, NMDA and IL-6 in the neuronal loss in AD.

Design and evaluation of a diabody to improve protection against a potent scorpion neurotoxin

Diabodies are recombinant, dimeric, antibody-based molecules composed of two non-covalently associated single-chain antibody fragments that bind to an antigen in a divalent manner. In an attempt to develop more effective therapeutic molecules against scorpion venoms, we designed a diabody derived from monoclonal antibody 9C2, which neutralizes the toxicity of scorpion neurotoxin AahI in mammals. The recombinant diabody produced in the periplasm of Escherichia coli was purified to homogeneity in a single step by protein L-agarose affinity chromatography. It was functional, and possessed a high binding affinity to AahI (8 x 10(-11) M). The bivalence of the diabody was confirmed by size-exclusion chromatography, isoelectrofocussing and electron microscopic observations. Finally, the diabody showed high thermal stability in serum and demonstrated protective activity when injected intraperitoneally in mice experimentally envenomed with toxin AahI. In conclusion, the diabody format gives the 9C2 molecule advantageous properties that are particularly important for potential clinical applications in the treatment of envenomations.