Human botulism immune globulin for the treatment of infant botulism

Descriptive Epidemiology of Infant Botulism in California: The First 40 Years

OBJECTIVE

To ascertain the descriptive epidemiology of infant botulism, the flaccid paralysis that results when neurotoxigenic Clostridium species produce botulinum toxin (BoNT) in the infant colon, in its first 40 years following initial recognition in California in 1976.

STUDY DESIGN

Cases were defined by laboratory identification of BoNT and/or neurotoxigenic Clostridium species in patients' feces. Parents were interviewed using a structured questionnaire. Descriptive epidemiologic characteristics were compared between 1976-1996 and 1997-2016.

RESULTS

From 1976-2016, 1345 cases of infant botulism occurred in 45 of 58 California counties (6.5 cases/100 000 live-births/year) caused by BoNT types A, B, Ba, Bf, and F; 88% of cases were ≤6 months of age and 51% were female. Cases were white (84.2%), Asian (8.9%), other races (3.8%), and African American (2.8%); 29.4% of cases were Hispanic. More than 99% of cases were hospitalized. Case occurrence peaked in summer-fall. Of 8 designated geographic regions, the Central Coast counties had 3 times the statewide incidence in both 20-year time periods. Breast-fed patients (83%) were more than twice as old at onset as formula-fed patients (median, 4.4 vs 1.7 months, respectively; P < .001). BoNT/A cases were older at onset than BoNT/B cases (median, 3.8 vs 2.9 months, respectively; P < .001).

CONCLUSIONS

Comprehensive continuous surveillance of infant botulism for 40 years in a large, diversely populated state identified fundamental epidemiologic characteristics of this uncommon illness. Unusual features included greater than 99% case hospitalization, absence of male preponderance, and a distinctive age distribution.

Special Delivery: Potential Mechanisms of Botulinum Neurotoxin Uptake and Trafficking within Motor Nerve Terminals

Botulinum neurotoxins (BoNTs) are highly potent, neuroparalytic protein toxins that block the release of acetylcholine from motor neurons and autonomic synapses. The unparalleled toxicity of BoNTs results from the highly specific and localized cleavage of presynaptic proteins required for nerve transmission. Currently, the only pharmacotherapy for botulism is prophylaxis with antitoxin, which becomes progressively less effective as symptoms develop. Treatment for symptomatic botulism is limited to supportive care and artificial ventilation until respiratory function spontaneously recovers, which can take weeks or longer. Mechanistic insights into intracellular toxin behavior have progressed significantly since it was shown that toxins exploit synaptic endocytosis for entry into the nerve terminal, but fundamental questions about host-toxin interactions remain unanswered. Chief among these are mechanisms by which BoNT is internalized into neurons and trafficked to sites of molecular toxicity. Elucidating how receptor-bound toxin is internalized and conditions under which the toxin light chain engages with target SNARE proteins is critical for understanding the dynamics of intoxication and identifying novel therapeutics. Here, we discuss the implications of newly discovered modes of synaptic vesicle recycling on BoNT uptake and intraneuronal trafficking.

Toxemia in Human Naturally Acquired Botulism

Human botulism is a severe disease characterized by flaccid paralysis and inhibition of certain gland secretions, notably salivary secretions, caused by inhibition of neurotransmitter release. Naturally acquired botulism occurs in three main forms: food-borne botulism by ingestion of preformed botulinum neurotoxin (BoNT) in food, botulism by intestinal colonization (infant botulism and intestinal toxemia botulism in infants above one year and adults), and wound botulism. A rapid laboratory confirmation of botulism is required for the appropriate management of patients. Detection of BoNT in the patient's sera is the most direct way to address the diagnosis of botulism. Based on previous published reports, botulinum toxemia was identified in about 70% of food-borne and wound botulism cases, and only in about 28% of infant botulism cases, in which the diagnosis is mainly confirmed from stool sample investigation. The presence of BoNT in serum depends on the BoNT amount ingested with contaminated food or produced locally in the intestine or wound, and the timeframe between serum sampling and disease onset. BoNT levels in patient's sera are most frequently low, requiring a highly sensitive method of detection. Mouse bioassay is still the most used method of botulism identification from serum samples. However, in vitro methods based on BoNT endopeptidase activity with detection by mass spectrometry or immunoassay have been developed and depending on BoNT type, are more sensitive than the mouse bioassay. These new assays show high specificity for individual BoNT types and allow more accurate differentiation between positive toxin sera from botulism and autoimmune neuropathy patients.

BOTOX injection to treat strabismus after infant botulism type B infection

Purpose

The significance of botulinum toxin to ophthalmologists is twofold. Botulism, a medical emergency, frequently presents with ocular findings including blurred vision, diplopia, ptosis, and photophobia as a result of the neurotoxin produced by Clostridium botulinum. However, botulinum toxins also have therapeutic uses for medical conditions including strabismus. The safety and efficacy of Botulinum toxin A in patients with a history of botulism has not been reported.

Observations

We report a 9-week-old infant, diagnosed with type B toxin positive infant botulism treated with human botulism immune globulin, who developed a large angle exotropia. The infant was treated with intramuscular injections of botulinum toxin A to the extraocular muscles resulting in a favorable initial response but ultimately required strabismus surgery. Clinical manifestations and management of botulism are reviewed and botulinum toxin in the treatment of pediatric strabismus is discussed.

Conclusions and importance

This case demonstrates safe administration of onabotulinumtoxinA to an infant with a history of antitoxin-treated botulism, resulting in a transient improvement in control of infantile exotropia.

Characterization of immune response induced against catalytic domain of botulinum neurotoxin type E

Botulinum neurotoxins (BoNTs) represent a family of bacterial toxins responsible for neuroparalytic disease 'botulism' in human and animals. Their potential use as biological weapon led to their classification in category 'A' biowarfare agent by Centers for Disease Control and Prevention (CDC), USA. In present study, gene encoding full length catalytic domain of BoNT/E-LC was cloned, expressed and protein was purified using Ni-NTA chromatography. Humoral immune response was confirmed by Ig isotyping and cell-mediated immunity by cytokine profiling and intracellular staining for enumeration of IFN-γ secreting CD4⁺ and CD8⁺ T cells. Increased antibody titer with the predominance of IgG subtype was observed. An interaction between antibodies produced against rBoNT/E-LC was established that showed the specificity against BoNT/E in SPR assay. Animal protection with rBoNT/E-LC was conferred through both humoral and cellular immune responses. These findings were supported by cytokine profiling and flow cytometric analysis. Splenocytes stimulated with rBoNT/E-LC showed a 3.27 and 2.8 times increase in the IFN-γ secreting CD4⁺ and CD8⁺ T cells, respectively; in immunized group (P < 0.05). Protection against BoNT/E challenge tended to relate with increase in the percentage of rBoNT/E-LC specific IL-2 in the splenocytes supernatant (P = 0.034) and with IFN-γ-producing CD4⁺ T cell responses (P = 0.045). We have immunologically evaluated catalytically active rBoNT/E-LC. Our results provide valuable investigational report for immunoprophylactic role of catalytic domain of BoNT/E.

Fully Human Monoclonal Antibodies Effectively Neutralizing Botulinum Neurotoxin Serotype B

Botulinum neurotoxin (BoNT) is the most potent natural toxin known. Of the seven BoNT serotypes (A to G), types A, B, E, and F cause human botulism. Treatment of human botulism requires the development of effective toxin-neutralizing antibodies without side effects such as serum sickness and anaphylaxis. In this study, we generated fully human monoclonal antibodies (HuMAbs) against serotype B BoNT (BoNT/B1) using a murine–human chimera fusion partner cell line named SPYMEG. Of these HuMAbs, M2, which specifically binds to the light chain of BoNT/B1, showed neutralization activity in a mouse bioassay (approximately 10 i.p. LD₅₀/100 µg of antibody), and M4, which binds to the C-terminal of heavy chain, showed partial protection. The combination of two HuMAbs, M2 (1.25 µg) and M4 (1.25 µg), was able to completely neutralize BoNT/B1 (80 i.p. LD₅₀) with a potency greater than 80 i.p. LD₅₀/2.5 µg of antibodies, and was effective both prophylactically and therapeutically in the mouse model of botulism. Moreover, this combination showed broad neutralization activity against three type B subtypes, namely BoNT/B1, BoNT/B2, and BoNT/B6. These data demonstrate that the combination of M2 and M4 is promising in terms of a foundation for new human therapeutics for BoNT/B intoxication.

Symptomatic treatment of botulism with a clinically approved small molecule

Botulinum neurotoxins (BoNTs) are potent neuroparalytic toxins that cause mortality through respiratory paralysis. The approved medical countermeasure for BoNT poisoning is infusion of antitoxin immunoglobulins. However, antitoxins have poor therapeutic efficacy in symptomatic patients; thus, there is an urgent need for treatments that reduce the need for artificial ventilation. We report that the US Food and Drug Administration-approved potassium channel blocker 3,4-diaminopyridine (3,4-DAP) reverses respiratory depression and neuromuscular weakness in murine models of acute and chronic botulism. In ex vivo studies, 3,4-DAP restored end-plate potentials and twitch contractions of diaphragms isolated from mice at terminal stages of BoNT serotype A (BoNT/A) botulism. In vivo, human-equivalent doses of 3,4-DAP reversed signs of severe respiratory depression and restored mobility in BoNT/A-intoxicated mice at terminal stages of respiratory collapse. Multiple-dosing administration of 3,4-DAP improved respiration and extended survival at up to 5 LD50 BoNT/A. Finally, 3,4-DAP reduced gastrocnemius muscle paralysis and reversed respiratory depression in sublethal models of serotype A-, B-, and E-induced botulism. These findings make a compelling argument for repurposing 3,4-DAP to symptomatically treat symptoms of muscle paralysis caused by botulism, independent of serotype. Furthermore, they suggest that 3,4-DAP is effective for a range of botulism symptoms at clinically relevant time points.

Passive Monoclonal and Polyclonal Antibody Therapies

Passive antibody therapies have a long history of use. In the 19th century, antibodies from xenographic sources of polyclonal antibodies were used to treat infections (diphtheria). They were used often as protection from infectious agents and toxins. Complications related to their use involved development of immune complexes and severe allergic reactions. As a result, human source plasma for polyclonal antibodies became the preferential source for antibodies. They are used to treat infection, remove toxins, prevent hemolytic disease of the newborn, modify inflammatory reactions, and control autoimmune diseases. Continued improvements in processing decreased the transfusion/infusion transmission of infections. In the late 20th century (∼1986), monoclonal antibodies were developed. The first monoclonal antibodies were of xenographic source and were wrought with problems of immunogenicity. These forms of antibodies did not gain favor until chimerization took pace in the mid-1990s and in 1998 two monoclonal antibodies were approved one to treat respiratory syncytial virus and the other for breast cancers. Further development of humanized and then fully human monoclonal antibodies has led to an evolution of therapies with these agents. Monoclonal antibodies are being researched or approved to treat a multitude of diseases to include oncologic, inflammatory, autoimmune, cardiovascular, respiratory, neurologic, allergic, benign hematologic, infections, orthopedic, coagulopathy, metabolic and to decrease morbidity of disease (diminution of pain), modify disease progression, and potentially anatomic development. In this chapter, we will review the history of use of these passive antibody therapies, their mechanism of action, pharmacologic-therapeutic classification, particular medical indication, adverse reactions, and potential future use of these medications.

Acute Neuromuscular Disorders in the Pediatric Intensive Care Unit

BACKGROUND

The neuromuscular disorders encountered in the pediatric intensive care unit (PICU) encompass a broad spectrum of pathologies. These include acute disorders (eg, Guillain-Barre syndrome), acute-on-chronic disorders (eg, myasthenia gravis), progressive disorders (eg, muscular dystrophy), and disorders that develop in the PICU (eg, critical illness myopathy/polyneuropathy). Familiarity with the presenting features of these disorders is of paramount importance in facilitating timely diagnosis.

METHODS

We conducted a retrospective review of the medical records of patients admitted to the PICU or Intermediate Care Program (ICP) at a single tertiary children's hospital from 2006 to 2017 with an acute or acute-on-chronic neuromuscular disorder. We did not include patients with a known progressive neuromuscular disorder or critical illness myopathy/polyneuropathy.

RESULTS

Twenty-four patients were admitted to the PICU/ICP with acute or acute-on-chronic neuromuscular disorders. Diagnosis and indication for ICU/ICP admission were Guillain-Barre syndrome (n = 6; respiratory failure: 3, respiratory monitoring: 2, autonomic instability: 1), myasthenia gravis (n = 5; airway clearance: 3, respiratory failure: 2), acute flaccid myelitis (n = 3; respiratory failure: 2, respiratory monitoring: 1), periodic paralysis (n = 3; intravenous potassium replacement), rhabdomyolysis (n = 3; monitoring for electrolyte derangements), infant botulism (n = 2; respiratory failure), chronic demyelinating polyneuropathy (n = 1; respiratory failure), and congenital myasthenic syndrome (n = 1; apnea). No patients were admitted to the PICU/ICP with a diagnosis of tick paralysis, acute intermittent porphyria, or inflammatory myopathy.

CONCLUSIONS

Although acute and acute-on-chronic neuromuscular disorders are encountered relatively rarely in the PICU, familiarity with the presenting features of these disorders is important in facilitating timely diagnosis. This, in turn, enables the institution of effective management strategies, thereby avoiding complications associated with diagnostic delays.

Neuromuscular Diseases of the Newborn

The peripheral nervous system (PNS) is composed of motor neurons, nerve roots, plexuses, peripheral nerves (motor, sensory and autonomic), neuromuscular junction, and skeletal muscles. Disorders of the PNS in neonates most frequently cause weakness, hypotonia, and contractures, which may be generalized or focal. Since these findings may also occur with brain and spinal cord lesions, key features of the history and neurologic exam, together with diagnostic testing, are helpful in reaching a diagnosis. This review covers the diagnostic approach to PNS disorders in the neonate and includes a discussion of representative diseases of the motor neuron, brachial plexus, peripheral nerves, neuromuscular junction, and muscles. The importance of reaching a precise genetic diagnosis is highlighted with a discussion of current and emerging treatments for neonatal PNS diseases, particularly spinal muscular atrophy.

Targeted 8-hydroxyquinoline fragment based small molecule drug discovery against neglected botulinum neurotoxin type F

OBJECTIVES

Botulinum neurotoxins are highly potent biological warfare agents. The unavailability of countermeasures against these neurotoxins has been a matter of extensive research. However, no clinical therapeutics has come to existence till date. The 8-hydroxyquinoline (8-HQ) scaffold is established privileged compound and its potential as drug candidate against BoNTs is recently being explored.

METHODS

In present work, three course studies were performed involving in silico, in vitro and in vivo cascade to screen 8-HQ small molecule inhibitors against BoNT/F intoxication. ~800 molecules obtained from open repositories were screened in silico and commercially obtained twenty-four 8-HQ derived small molecule inhibitors were evaluated against rBoNT/F light chain through fluorescence thermal shift (FTS) assay. Selected compounds were further evaluated through endopeptidase assay. Further binding affinity analysis was done through surface plasmon resonance (SPR) based Proteon™ XPR 36 system. Finally, the in vivo efficacy of these compounds was evaluated in mice model.

RESULTS

Three compounds NSC1011, NSC1014 and NSC84094 were found to be highly inhibitory after screening of 8-HQ compounds through FTS assay and endopeptidase assay. SPR based protein-small molecule interaction studies showed highest affinity binding of NSC1014 (K_D: 5.58E-06) with BoNT/F-LC. NSC1011, NSC1014, and NSC84094 displayed IC₅₀ of 30.47 ± 6.24, 14.91 ± 2.49 and 17.39 ± 2.74 μM, respectively, in endopeptidase assay. NSC1011 and NSC1014 displayed marked extension of survival time in mice model.

CONCLUSION

NSC1011 and NSC1014 have emerged as promising drug candidate against BoNT/F intoxication displaying higher potential than previously reported compounds.

Antibodies and Vaccines against Botulinum Toxins: Available Measures and Novel Approaches

Botulinum neurotoxin (BoNT) is produced by the anaerobic, Gram-positive bacterium Clostridium botulinum. As one of the most poisonous toxins known and a potential bioterrosism agent, BoNT is characterized by a complex mode of action comprising: internalization, translocation and proteolytic cleavage of a substrate, which inhibits synaptic exocytotic transmitter release at neuro-muscular nerve endings leading to peripheral neuroparalysis of the skeletal and autonomic nervous systems. There are seven major serologically distinct toxinotypes (A-G) of BoNT which act on different substrates. Human botulism is generally caused by BoNT/A, B and E. Due to its extreme lethality and potential use as biological weapon, botulism remains a global public health concern. Vaccination against BoNT, although an effective strategy, remains undesirable due to the growing expectation around therapeutic use of BoNTs in various pathological conditions. This review focuses on the current approaches for botulism control by immunotherapy, highlighting the future challenges while the molecular underpinnings among subtypes variants and BoNT sequences found in non-clostridial species remain to be elucidated.

Identification of Inhibitors against Botulinum Neurotoxins: 8-Hydroxyquinolines Hold Promise

Botulinum neurotoxins (BoNTs) are the most toxic category A biological warfare agents. There is no therapeutics available for BoNT intoxication yet, necessitating the development of a medical countermeasure against these neurotoxins. The discovery of small molecule-based drugs has revolutionized in the last two decades resulting in the identification of several small molecule inhibitors of BoNTs. However, none progressed to clinical trials. 8-Hydroxyquinolines scaffold-based molecules are important 'privileged structures' that can be exploited as inhibitors of a diverse range of targets. In this review, our study of recent reports suggests the development of 8-hydroxyquinoline derived molecules as a potential drug may be on the horizon.

Pediatric Botulism and Use of Equine Botulinum Antitoxin in Children: A Systematic Review

Background

Botulism manifests with cranial nerve palsies and flaccid paralysis in children and adults. Botulism must be rapidly identified and treated; however, clinical presentation and treatment outcomes of noninfant botulism in children are not well described.

Methods

We searched 12 databases for peer-reviewed and non-peer-reviewed reports with primary data on botulism in children (persons <18 years of age) or botulinum antitoxin administration to children. Reports underwent title and abstract screening and full text review. For each case, patient demographic, clinical, and outcome data were abstracted.

Results

Of 7065 reports identified, 184 met inclusion criteria and described 360 pediatric botulism cases (79% confirmed, 21% probable) that occurred during 1929-2015 in 34 countries. Fifty-three percent were male; age ranged from 4 months to 17 years (median, 10 years). The most commonly reported signs and symptoms were dysphagia (53%), dysarthria (39%), and generalized weakness (37%). Inpatient length of stay ranged from 1 to 425 days (median, 24 days); 14% of cases required intensive care unit admission; 25% reported mechanical ventilation. Eighty-three (23%) children died. Median interval from illness onset to death was 1 day (range, 0-260 days). Among patients who received antitoxin (n = 193), 23 (12%) reported an adverse event, including rash, fever, serum sickness, and anaphylaxis. Relative risk of death among patients treated with antitoxin compared with patients not treated with antitoxin was 0.24 (95% confidence interval, .14-.40; P < .0001).

Conclusions

Dysphagia and dysarthria were the most commonly reported cranial nerve symptoms in children with botulism; generalized weakness was described more than paralysis. Children who received antitoxin had better survival; serious adverse events were rare. Most deaths occurred early in the clinical course; therefore, botulism in children should be identified and treated rapidly.

Type F Infant Botulism: Investigation of Recent Clusters and Overview of This Exceedingly Rare Disease

From 1976 to 2016, neurotoxigenic Clostridium baratii type F caused 18 (<0.5%) reported US infant botulism cases. Six cases occurred during 2012-2013; no common source was identified. Type F infant botulism mostly occurs in very young infants and typically presents more rapidly and severely than illness caused by types A and B botulinum neurotoxin.

Botulism in the Pediatric Intensive Care Units in the United States: Interrogating a National Database

Botulism in children can have severe complications necessitating intensive care. The current literature lacks data of children with botulism requiring critical care. We aim to describe the outcomes of pediatric botulism in the pediatric intensive care unit (PICU). Retrospective cohort data from Virtual Pediatric Systems (VPS, LLC, Los Angeles, California), from 2009 to 2016 including all PICU admissions among children with botulism, were analyzed. Characteristics and outcomes were compared with similar studies. A total of 380 children were identified over 8 years. Our cohort had the shortest length of stay (median 4.6 days), the smallest percent requiring mechanical ventilation (40%), and the highest median age (120 days) amongst comparable studies. Length of mechanical ventilation and PICU stay has decreased among children with botulism. Advances in PICU care may have contributed to these improved outcomes.

Targeting virulence factors as an antimicrobial approach: Pigment inhibitors

The fascinating and dangerous colored pathogens contain unique chemically pigmented molecules, which give varied and efficient assistance as virulence factors to the crucial reproduction and growth of microbes. Therefore, multiple novel strategies and inhibitors have been developed in recent years that target virulence factor pigments. However, despite the importance and significance of this topic, it has not yet been comprehensively reviewed. Moreover, research groups around the world have made successful progress against antibacterial infections by targeting pigment production, including our serial works on the discovery of CrtN inhibitors against staphyloxanthin production in Staphylococcus aureus. On the basis of the previous achievements and recent progress of our group in this field, this article will be the first comprehensive review of pigment inhibitors against colored pathogens, especially S. aureus infections, and this article includes design strategies, representative case studies, advantages, limitations, and perspectives to guide future research.

Pharmacokinetics of Human Recombinant Anti-Botulinum Toxin Antibodies in Rats

Botulinum neurotoxins (BoNT) are potential biothreat agents due to their high lethality, potency, and ease of distribution, thus the development of antitoxins is a high priority to the US government. This study examined pre-clinical pharmacokinetic studies in rats of four oligoclonal anti-BoNT mAb-based therapeutics (NTM-1631, NTM-1632, NTM-1633, NTM-1634) for five BoNT serotypes (A, B, E, C, and D). NTM-1631, NTM-1632, and NTM-1633 each consist of three IgG1 mAbs, each with a distinct human or humanized variable region which bind to distinct epitopes on BoNT serotype A, B, or E respectively. NTM-1634 consists of four human immunoglobulin G1 (IgG1) mAbs binding BoNT C/D mosaic toxins. The mechanism of these antitoxins requires that three antibodies simultaneously bind toxin to achieve rapid clearance. Rats (total 378) displayed no adverse clinical signs attributed to antibody treatment from any of the antitoxins. Pharmacokinetic evaluation demonstrated that the individual mAbs are slowly eliminated, exhibiting dose-dependent exposure and long elimination half-lives ranging from 6.5 days to 10 days. There were no consistent differences observed between males and females or among the individual antibodies in each formulation in half-life. Anti-drug antibodies (ADA) were observed, as expected for human antibodies administered to rats. The results presented were used to support the clinical investigation of antibody-based botulism antitoxins.

Medical treatment for botulism

BACKGROUND

Botulism is an acute paralytic illness caused by a neurotoxin produced by Clostridium botulinum. Supportive care, including intensive care, is key, but the role of other medical treatments is unclear. This is an update of a review first published in 2011.

OBJECTIVES

To assess the effects of medical treatments on mortality, duration of hospitalization, mechanical ventilation, tube or parenteral feeding, and risk of adverse events in botulism.

SEARCH METHODS

We searched the Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE, and Embase on 23 January 2018. We reviewed bibliographies and contacted authors and experts. We searched two clinical trials registers, WHO ICTRP and clinicaltrials.gov, on 21 February 2019.

SELECTION CRITERIA

Randomized controlled trials (RCTs) and quasi-RCTs examining the medical treatment of any of the four major types of botulism (infant intestinal botulism, food-borne botulism, wound botulism, and adult intestinal toxemia). Potential medical treatments included equine serum trivalent botulism antitoxin, human-derived botulinum immune globulin intravenous (BIG-IV), plasma exchange, 3,4-diaminopyridine, and guanidine.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methodology.Our primary outcome was in-hospital death from any cause occurring within four weeks from randomization or the beginning of treatment. Secondary outcomes were death from any cause occurring within 12 weeks, duration of hospitalization, duration of mechanical ventilation, duration of tube or parenteral feeding, and proportion of participants with adverse events or complications of treatment.

MAIN RESULTS

A single RCT met the inclusion criteria. Our 2018 search update identified no additional trials. The included trial evaluated BIG-IV for the treatment of infant botulism and included 59 treatment participants and 63 control participants. The control group received a control immune globulin that did not have an effect on botulinum toxin. Participants were followed during the length of their hospitalization to measure the outcomes of interest. There was some violation of intention-to-treat principles, and possibly some between-treatment group imbalances among participants admitted to the intensive care unit and mechanically ventilated, but otherwise the risk of bias was low. There were no deaths in either group, making any treatment effect on mortality inestimable. There was a benefit in the treatment group on mean duration of hospitalization (BIG-IV: 2.60 weeks, 95% confidence interval (CI) 1.95 to 3.25; control: 5.70 weeks, 95% CI 4.40 to 7.00; mean difference (MD) -3.10 weeks, 95% CI -4.52 to -1.68; moderate-certainty evidence); mechanical ventilation (BIG-IV: 1.80 weeks, 95% CI 1.20 to 2.40; control: 4.40 weeks, 95% CI 3.00 to 5.80; MD -2.60 weeks, 95% CI -4.06 to -1.14; low-certainty evidence); and tube or parenteral feeding (BIG-IV: 3.60 weeks, 95% CI 1.70 to 5.50; control: 10.00 weeks, 95% CI 6.85 to 13.15; MD -6.40 weeks, 95% CI -10.00 to -2.80; moderate-certainty evidence), but not on proportion of participants with adverse events or complications (BIG-IV: 63.08%; control: 68.75%; risk ratio 0.92, 95% CI 0.72 to 1.18; absolute risk reduction 0.06, 95% CI 0.22 to -0.11; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

We found low- and moderate-certainty evidence supporting the use of BIG-IV in infant intestinal botulism. A single RCT demonstrated that BIG-IV probably decreases the duration of hospitalization; may decrease the duration of mechanical ventilation; and probably decreases the duration of tube or parenteral feeding. Adverse events were probably no more frequent with immune globulin than with placebo. Our search did not reveal any evidence examining the use of other medical treatments including serum trivalent botulism antitoxin.

Monoclonal Antibody Combinations Prevent Serotype A and Serotype B Inhalational Botulism in a Guinea Pig Model

Botulinum neurotoxins (BoNT) are some of the most toxic proteins known, with a human LD₅₀ of ~1 ng/kg. Equine antitoxin has a half-life in circulation of less than 1 day and is limited to a treatment rather than a prevention indication. The development of monoclonal antibodies (mAbs) may represent an alternative therapeutic option that can be produced at high quantities and of high quality and with half-lives of >10 days. Two different three mAb combinations are being developed that specifically neutralize BoNT serotypes A (BoNT/A) and B (BoNT/B). We investigated the pharmacokinetics of the anti-BoNT/A and anti-BoNT/B antibodies in guinea pigs (Cavia porcellus) and their ability to protect guinea pigs against an aerosol challenge of BoNT/A1 or BoNT/B1. Each antibody exhibited dose-dependent exposure and reached maximum circulating concentrations within 48 h post intraperitoneal or intramuscular injection. A single intramuscular dose of the three mAb combination protected guinea pigs against an aerosol challenge dose of 93 LD₅₀ of BoNT/A1 and 116 LD₅₀ of BoNT/B1 at 48 h post antibody administration. These mAbs are effective in preventing botulism after an aerosol challenge of BoNT/A1 and BoNT/B1 and may represent an alternative to vaccination to prevent type A or B botulism in those at risk of BoNT exposure.

Cryptococcal Meningitis and Anti-virulence Therapeutic Strategies

Fungal infections of the central nervous system are responsible for significant morbidity and mortality. Cryptococcus neoformans (Cn) is the primary cause of fungal meningitis. Infection begins in the lung after inhalation of fungal spores but often spreads to other organs, particularly the brain in immunosuppressed individuals. Cn’s ability to survive phagocytosis and endure the onslaught of oxidative attack imposed by the innate immune response facilitates dissemination to the central nervous system (CNS). Despite the success of Cn at bypassing innate immunity, entry into the heavily protected brain requires that Cn overwhelm the highly restricted blood-brain barrier (BBB). This is a formidable task but mounting evidence suggests that Cn expresses surface-bound and secreted virulence factors including urease, metalloprotease, and hyaluronic acid that can undermine the BBB. In addition, Cn can exploit multiple routes of entry to gain access to the CNS. In this review, we discuss the cellular and molecular interface of Cn and the BBB, and we propose that the virulence factors mediating BBB crossing could be targeted for the development of anti-virulence drugs aimed at preventing fungal colonization of the CNS.

Covalent Modifiers of Botulinum Neurotoxin Counteract Toxin Persistence

Botulinum neurotoxins (BoNTs) are the most potent toxins known to man and a significant threat as weapons of bioterrorism. BoNTs contain a metalloprotease domain that blocks neurotransmitter release in nerve terminals, resulting in a descending, flaccid paralysis with a 5-10% mortality rate. Existing treatment options cannot access or neutralize the toxin following its endocytosis, so there is a clear need to develop novel therapies. Numerous substrate-based and zinc-chelating small-molecule inhibitors have been reported; however, none have progressed to the clinic. This is likely due to the difficulty that reversible inhibitors have in achieving sustained inhibition of the toxin, which has a half-life of months in vivo. An alternative strategy for mitigating BoNT persistence is covalent, irreversible inhibition of toxin function. However, few examples of covalent BoNT inhibitors have been reported. Here, we describe a competition-based screen to identify covalent modifiers of the conserved active-site-adjacent cysteine C165 in the BoNT/A serotype. We found that compounds containing cysteine-reactive electrophiles designed to target cysteine proteases failed to bind C165 while selenide compounds were efficient covalent binders of this cysteine. Importantly, covalent modification at C165 resulted in sustained, irreversible inhibition of BoNT/A protease activity. Covalent selenide inhibitors were nontoxic and protective in a neuronal assay of intoxication, making them promising new scaffolds for the study of the BoNT/A toxin as well as for the design of novel therapy agents.

Antimicrobial Susceptibility of 260 Clostridium botulinum Type A, B, Ba, and Bf Strains and a Neurotoxigenic Clostridium baratii Type F Strain Isolated from California Infant Botulism Patients

Infant botulism is an infectious intestinal toxemia that results from colonization of the infant large bowel by Clostridium botulinum (or rarely, by neurotoxigenic Clostridium baratii or Clostridium butyricum), with subsequent intraintestinal production and absorption of botulinum neurotoxin that then produces flaccid paralysis. The disease is often initially misdiagnosed as suspected sepsis or meningitis, diagnoses that require prompt empirical antimicrobial therapy. Antibiotics may also be needed to treat infectious complications of infant botulism, such as pneumonia or urinary tract infection. Clinical evidence suggests (see case report below) that broad-spectrum antibiotics that are eliminated by biliary excretion may cause progression of the patient's paralysis by lysing C. botulinum vegetative cells in the large bowel lumen, thereby increasing the amount of botulinum neurotoxin available for absorption. The purpose of this antimicrobial susceptibility study was to identify an antimicrobial agent with little or no activity against C. botulinum that could be used to treat infant botulism patients initially diagnosed with suspected sepsis or meningitis, or who acquired secondary infections, without lysing C. botulinum Testing of 12 antimicrobial agents indicated that almost all California infant botulism patient isolates are susceptible to most clinically utilized antibiotics and are also susceptible to newer antibiotics not previously tested against large numbers of C. botulinum patient isolates. No antibiotic with little or no activity against C. botulinum was identified. These findings reinforce the importance of promptly treating infant botulism patients with human botulism immune globulin (BIG-IV [BabyBIG]).

Therapeutic Antibodies for Biodefense

Diseases can be caused naturally by biological agents such as bacteria, viruses and toxins (natural risk). However, such biological agents can be intentionally disseminated in the environment by a State (military context) or terrorists to cause diseases in a population or livestock, to destabilize a nation by creating a climate of terror, destabilizing the economy and undermining institutions. Biological agents can be classified according to the severity of illness they cause, its mortality and how easily the agent can be spread. The Centers for Diseases Control and Prevention (CDC) classify biological agents in three categories (A, B and C); Category A consists of the six pathogens most suitable for use as bioweapons (Bacillus anthracis, Yersinia pestis, Francisella tularensis, botulinum neurotoxins, smallpox and viral hemorrhagic fevers). Antibodies represent a perfect biomedical countermeasure as they present both prophylactic and therapeutic properties, act fast and are highly specific to the target. This review focuses on the main biological agents that could be used as bioweapons, the history of biowarfare and antibodies that have been developed to neutralize these agents.

A Small Molecule-Screening Pipeline to Evaluate the Therapeutic Potential of 2-Aminoimidazole Molecules Against Clostridium difficile

Antibiotics are considered to be the first line of treatment for mild to moderately severe Clostridium difficile infection (CDI) in humans. However, antibiotics are also risk factors for CDI as they decrease colonization resistance against C. difficile by altering the gut microbiota and metabolome. Finding compounds that selectively inhibit different stages of the C. difficile life cycle, while sparing the indigenous gut microbiota is important for the development of alternatives to standard antibiotic treatment. 2-aminoimidazole (2-AI) molecules are known to disrupt bacterial protection mechanisms in antibiotic resistant bacteria such as Pseudomonas aeruginosa, Acinetobacter baumannii, and Staphylococcus aureus, but are yet to be evaluated against C. difficile. A comprehensive small molecule-screening pipeline was developed to investigate how novel small molecules affect different stages of the C. difficile life cycle (growth, toxin, and sporulation) in vitro, and a library of commensal bacteria that are associated with colonization resistance against C. difficile. The initial screening tested the efficacy of eleven 2-AI molecules (compound 1 through 11) against C. difficile R20291 compared to a vancomycin (2 μg/ml) control. Molecules were selected for their ability to inhibit C. difficile growth, toxin activity, and sporulation. Further testing included growth inhibition of other C. difficile strains (CD196, M68, CF5, 630, BI9, M120) belonging to distinct PCR ribotypes, and a commensal panel (Bacteroides fragilis, B. thetaiotaomicron, C. scindens, C. hylemonae, Lactobacillus acidophilus, L. gasseri, Escherichia coli, B. longum subsp. infantis). Three molecules compound 1 and 2, and 3 were microbicidal, whereas compounds 4, 7, 9, and 11 inhibited toxin activity without affecting the growth of C. difficile strains and the commensal microbiota. The antimicrobial and anti-toxin effects of 2-AI molecules need to be further characterized for mode of action and validated in a mouse model of CDI.

Yesterday and Today: The Impact of Research Conducted at Camp Detrick on Botulinum Toxin

Introduction

This review summarizes the research conducted on botulinum toxin (BoTx) from 1943 to 1956 by a small group of Camp Detrick investigators and their staff. A systematic, cross-disciplinary approach was used to develop effective vaccines against this biological warfare threat agent. In response to the potential need for medical countermeasures against BoTx during World War II, the refinement of isolation and purification techniques for BoTx successfully led to the large-scale production of botulinum toxoid vaccines. In addition, the work at Camp Detrick provided the foundation for the subsequent use of BoTx as a tool for studying the trophic regulation of skeletal muscle within motor neuron terminals and, more recently, for elucidation of the intricate details of neurotransmitter release at the molecular level. Indirectly, Camp Detrick investigators also played a significant role in studies that culminated in the use of BoTx as a pharmaceutical product that has been approved by the U.S. Food and Drug Administration for treating movement disorders, autonomic dysfunctions, and other conditions.

Methods

Online literature searches were performed with Google, Google Scholar, PubMed, the bibliography from the Camp Detrick technical library, and at the Defense Technical Information Center. Reference lists in some of the primary research publications and reviews also provided source material. Search terms included botulinum, botulinus, and Camp Detrick. References related to the subsequent impacts of the Camp Detrick results were selected and cited from reviews and primary references in the more recent literature. Notes on toxin nomenclature and potential sources of error in this study are presented.

Results

The literature searches returned 27 citations of Camp Detrick authors, 24 of which were articles in peer-reviewed journals. The publications by these investigators included several disciplines such as biochemistry, immunology, pharmacology, physiology, and toxicology. A fundamental finding was the identification of critical nutritional components for improved growth of Clostridium botulinum and the increased production of BoTx serotype A. The purification processes that were developed at Camp Detrick allowed for the production of crystalline material to be scaled up for the manufacture of toxoid vaccine. Based on the research by Camp Detrick scientists, a toxoid supply of over 1 million units was available to vaccinate ~300,000 troops before the large-scale operations of D-Day.

Conclusions

BoTx research during the period 1943 to 1956 resulted in refinements in the techniques for isolating and purifying the crystalline BoTx type A. These results led to the development and manufacture of a toxoid vaccine that was available in a sufficient quantity to protect ~300,000 warfighters in a large-scale military operation. One of the most important long-term consequences derived from the knowledge gained by the efforts at Camp Detrick was the development in the 1980s of safe and effective therapeutic uses for BoTx type A, the most lethal biological substance known.

Safety and immunogenicity of investigational recombinant botulinum vaccine, rBV A/B, in volunteers with pre-existing botulinum toxoid immunity

OBJECTIVES

We undertook an open-label, uncontrolled study of investigational recombinant botulinum vaccine for botulinum neurotoxin (BoNT) serotypes A and B (rBV A/B) to assess its safety and immunogenicity in healthy volunteers who had been previously immunized with investigational pentavalent botulinum toxoid. Study participants who wished to do so could donate their hyperimmune plasma for production of Human Botulism Immune Globulin Intravenous (BIG-IV, BabyBIG®).

STUDY DESIGN

A single 0.5 ml (mL), 40-microgram intramuscular injection of rBV A/B was administered to study participants. Post-vaccination sera collected at approximately 2-week intervals were evaluated for anti-BoNT/A and anti-BoNT/B neutralizing antibody concentrations (NAC). Local and systemic treatment-emergent adverse events (TEAEs) were identified by clinical and laboratory monitoring for 12 weeks post-vaccination with a final telephone follow-up for additional safety assessment at 6 months. The primary endpoint for immunogenicity was a ≥4-fold rise in NAC in ≥50% of participants by Week 4 post-vaccination.

RESULTS

All 45 enrolled participants completed the study. Forty-two of 45 participants (93.3%) experienced at least one TEAE. Overall, 138 of 218 (63.3%) reported TEAEs were treatment-related, the majority of which were mild injection-site reactions. No serious or unexpected adverse events occurred. The study achieved its primary immunogenicity endpoint with 37/45 (82.2%) participants and 39/45 (86.7%) participants having a ≥4-fold rise in NAC to anti-BoNT/A and to anti-BoNT/B, respectively, by Week 4 post-vaccination.

CONCLUSION

A single 0.5 mL dose of rBV A/B was safe, well-tolerated and immunogenic in participants previously immunized with pentavalent botulinum toxoid. The tolerability and immunogenicity characteristics of rBV A/B vaccination of individuals with existing BoNT immunity support its potential future use to provide occupational protection to botulism laboratory workers. Almost all study participants donated hyperimmune plasma for production of BIG-IV. ClinicalTrials.gov registration number: NCT01701999.

A Single Tri-Epitopic Antibody Virtually Recapitulates the Potency of a Combination of Three Monoclonal Antibodies in Neutralization of Botulinum Neurotoxin Serotype A

The standard of treatment for botulism, equine antitoxin, is a foreign protein with associated safety issues and a short serum half-life which excludes its use as a prophylactic antitoxin and makes it a less-than-optimal therapeutic. Due to these limitations, a recombinant monoclonal antibody (mAb) product is preferable. It has been shown that combining three mAbs that bind non-overlapping epitopes leads to highly potent botulinum neurotoxin (BoNT) neutralization. Recently, a triple human antibody combination for BoNT/A has demonstrated potent toxin neutralization in mouse models with no serious adverse events when tested in a Phase I clinical trial. However, a triple antibody therapeutic poses unique development and manufacturing challenges. Thus, potentially to streamline development of BoNT antitoxins, we sought to achieve the potency of multiple mAb combinations in a single IgG-based molecule that has a long serum half-life. The design, production, and testing of a single tri-epitopic IgG1-based mAb (TeAb) containing the binding sites of each of the three parental BoNT/A mAbs yielded an antibody of nearly equal potency to the combination. The approach taken here could be applied to the design and creation of other multivalent antibodies that could be used for a variety of applications, including toxin elimination.

High level expression and immunochemical characterization of botulinum neurotoxin type F light chain

Botulinum neurotoxins (BoNTs) are the most toxic biological substances known. Their potential use as biological warfare agent results in their classification as category A biowarfare agent by Centers for Disease Control and Prevention (CDC), USA. Presently, there are no approved detection system and pharmacological treatments for BoNT intoxication. Although a toxoid vaccine is available for immuno-prophylaxis, vaccines cannot reverse the effect of pre-translocated toxin. Direct handling of the live BoNTs for developing detection and therapeutics may pose fatal danger. This concern was addressed by purifying the recombinant catalytically active light chain of BoNT/F. BoNT/F-LC gene was amplified from the genomic DNA using specifically designed primers and expressed in Escherichia coli. Expression and purification profile were optimized under different conditions for biologically active light chain production. Specific polyclonal antibodies generated against type F illustrates in vivo neutralization in mice and rabbit. These antibodies play key role in conceiving the development of high throughput SPR based detection system which is a highly precise label free technique for protein interaction analysis. The presented work is first of its kind, signifying the production of highly stable and active rBoNT/F-LC and its immunochemical characterization. The study aids in paving the path towards developing a persistent detection system as well as in presenting comprehended scheme for in vitro small molecule therapeutics analysis.

More Clinical Mimics of Infant Botulism

OBJECTIVE

To ascertain the actual diagnoses of 76 patients (2005-2015) whose clinical presentations so closely resembled infant botulism that the patients were treated with Human Botulism Immune Globulin Intravenous (BIG-IV; BabyBIG), but whose illnesses subsequently were not laboratory confirmed as infant botulism ("clinical mimics" of infant botulism).

STUDY DESIGN

The California Department of Public Health produces BIG-IV and distributes it nationwide as a public service (ie, not-for-profit) orphan drug to treat patients hospitalized with suspected infant botulism. During the study period, admission records and discharge summaries for all patients treated with BIG-IV but who lacked a laboratory-confirmed diagnosis of infant botulism were collected and abstracted. The patients' discharge diagnoses were identified, categorized, and compared with previously reported clinical mimics categories for 32 patients (1992-2005).

RESULTS

From 2005 to 2015, 76 clinical mimic illnesses were identified. These illnesses were distributed into the 5 categories previously reported of (1) probable infant botulism lacking confirmatory testing (26.3%); (2) spinal muscular atrophy (19.7%); (3) miscellaneous (15.8%); (4) metabolic disorders (11.8%); and (5) other infectious diseases (10.6%). Of the 76 clinical mimic illnesses, 15.8% had no alternate diagnosis established and were therefore categorized as undetermined.

CONCLUSIONS

Over the 23 years 1992-2015, patients presenting with illnesses so clinically similar to infant botulism that they were treated with BIG-IV had actual diagnoses that were distributed into 5 main categories. These categories and their individual components constitute a working bedside differential diagnosis of infant botulism.

Efficacy of Human Botulism Immune Globulin for the Treatment of Infant Botulism: The First 12 Years Post Licensure

OBJECTIVES

To report the efficacy of Human Botulism Immune Globulin Intravenous (BIG-IV) in the first 12 years following its licensure in 2003 and to characterize its use nationwide in treating patients with infant botulism.

STUDY DESIGN

Medical records and billing information were collected for US patients treated with BIG-IV from 2003 to 2015. Length of hospital stay (LOS) and hospital charge information for treated patients were compared with the BIG-IV Pivotal Clinical Trial Placebo Group to quantify decreases in LOS and hospital charges.

RESULTS

The use of BIG-IV reduced mean LOS from 5.7 to 2.2 weeks. This shortened hospital stay resulted in a mean decrease in hospital charges of $88 900 per patient. For all US patients 2003-2015, total decreases in LOS and hospital charges were 66.9 years and $86.2 million, respectively. The decrease in mean LOS was time dependent: BIG-IV treatment on hospital days 0-3 reduced mean LOS by 3.7 weeks (P <.001 vs the BIG-IV Pivotal Clinical Trial Placebo Group), on hospital days 4-7 by 2.6 weeks (P <.001 vs the BIG-IV Pivotal Clinical Trial Placebo Group) and on hospital days 8-10 by just 1 week (P = NS). Since licensure, 1192 patients in 48 states and Washington, DC, have been treated with BIG-IV.

CONCLUSIONS

The use of BIG-IV since its licensure in 2003 treated approximately 93% of US patients with laboratory-confirmed infant botulism, and prevented >65 years in hospital stay and >$85 million in hospital charges from occurring. The greatest LOS reduction was achieved when BIG-IV was administered soon after hospital admission. Effective and appropriate use of BIG-IV in the US has continued in the postlicensure period.

3,4-diaminopyridine reverses paralysis in botulinum neurotoxin-intoxicated diaphragms through two functionally distinct mechanisms

Botulinum neurotoxins (BoNTs) are exceedingly potent neurological poisons that prevent neurotransmitter release from peripheral nerve terminals by cleaving presynaptic proteins required for synaptic vesicle fusion. The ensuing neuromuscular paralysis causes death by asphyxiation. Although no antidotal treatments exist to block toxin activity within the nerve terminal, aminopyridine antagonists of voltage-gated potassium channels have been proposed as symptomatic treatments for botulism toxemia. However, clinical evaluation of aminopyridines as symptomatic treatments for botulism has been inconclusive, in part because mechanisms responsible for reversal of paralysis in BoNT-poisoned nerve terminals are not understood. Here we measured the effects of 3,4-diaminopyridine (DAP) on phrenic nerve-elicited diaphragm contraction and end-plate potentials at various times after intoxication with BoNT serotypes A, B, or E. We found that DAP-mediated increases in quantal content promote neurotransmission from intoxicated nerve terminals through two functionally distinguishable mechanisms. First, DAP increases the probability of neurotransmission at non-intoxicated release sites. This mechanism is serotype-independent, becomes less effective as nerve terminals become progressively impaired, and remains susceptible to ongoing intoxication. Second, DAP elicits persistent production of toxin-resistant endplate potentials from nerve terminals fully intoxicated by BoNT/A, but not serotypes B or E. Since this effect appears specific to BoNT/A intoxication, we propose that DAP treatment enables BoNT/A-cleaved SNAP-25 to productively engage in fusogenic release by increasing the opportunity for low-efficiency fusion events. These findings have important implications for DAP as a botulism therapeutic by defining conditions under which DAP may be clinically effective in reversing botulism symptoms.

Disaster Preparedness: Biological Threats and Treatment Options

Biological disasters can be natural, accidental, or intentional. Biological threats have made a lasting impact on civilization. This review focuses on agents of clinical significance, bioterrorism, and national security, specifically Category A agents (anthrax, botulism, plague, tularemia, and smallpox), as well as briefly discusses other naturally emerging infections of public health significance, Ebola virus (also a Category A agent) and Zika virus. The role of pharmacists in disaster preparedness and disaster response is multifaceted and important. Their expertise includes clinical knowledge, which can aid in drug information consultation, patient-specific treatment decision making, and development of local treatment plans. To fulfill this role, pharmacists must have a comprehensive understanding of medical countermeasures for these significant biological threats across all health care settings. New and reemerging infectious disease threats will continue to challenge the world. Pharmacists will be at the forefront of preparedness and response, sharing knowledge and clinical expertise with responders, official decision makers, and the general public.

Efficacy of Antitoxin Therapy in Treating Patients With Foodborne Botulism: A Systematic Review and Meta-analysis of Cases, 1923-2016

Background

Botulism is a rare, potentially severe illness, often fatal if not appropriately treated. Data on treatment are sparse. We systematically evaluated the literature on botulinum antitoxin and other treatments.

Methods

We conducted a systematic literature review of published articles in PubMed via Medline, Web of Science, Embase, Ovid, and Cumulative Index to Nursing and Allied Health Literature, and included all studies that reported on the clinical course and treatment for foodborne botulism. Articles were reviewed by 2 independent reviewers and independently abstracted for treatment type and toxin exposure. We conducted a meta-analysis on the effect of timing of antitoxin administration, antitoxin type, and toxin exposure type.

Results

We identified 235 articles that met the inclusion criteria, published between 1923 and 2016. Study quality was variable. Few (27%) case series reported sufficient data for inclusion in meta-analysis. Reduced mortality was associated with any antitoxin treatment (odds ratio [OR], 0.16; 95% confidence interval [CI], .09-.30) and antitoxin treatment within 48 hours of illness onset (OR, 0.12; 95% CI, .03-.41). Data did not allow assessment of critical care impact, including ventilator support, on survival. Therapeutic agents other than antitoxin offered no clear benefit. Patient characteristics did not predict poor outcomes. We did not identify an interval beyond which antitoxin was not beneficial.

Conclusions

Published studies on botulism treatment are relatively sparse and of low quality. Timely administration of antitoxin reduces mortality; despite appropriate treatment with antitoxin, some patients suffer respiratory failure. Prompt antitoxin administration and meticulous intensive care are essential for optimal outcome.

Therapeutic efficacy of equine botulism antitoxin in Rhesus macaques

Background

There are currently no licensed vaccines available for prevention of botulism in humans. The vaccination is not desirable due to expanding therapeutic indications of botulinum toxins. The only available specific treatment for botulism is antitoxin to remove circulating toxin, thus, preventing further neuronal damage. BAT^® (Botulism Antitoxin Heptavalent (A, B, C, D, E, F, G)—(Equine)) has been developed and its therapeutic efficacy evaluated against botulinum neurotoxin serotype A (BoNT/A) in Rhesus macaques.

Methods and findings

In a post-exposure prophylaxis (PEP) study, animals were exposed to 4x LD₅₀/kg of BoNT/A and administered intravenously with either BAT (1x or 0.1x scaled human dose), or placebo at 4 hours post-exposure. The animals were monitored for 14 days. For the therapeutic intervention studies, animals were exposed to a 1.7x LD₅₀/kg of BoNT/A and treated intravenously with either placebo or BAT at a 1x scaled human dose at the onset of clinical signs. Animals were monitored on an hourly basis for 14 or 21 days. In the PEP study, all animals tolerated equine based antitoxin without any adverse clinical signs. A 100% survival was observed in groups treated with the BAT compared to 0% survival in those treated with the placebo (p<0.001, Fisher’s exact test). BAT antitoxin prevented the development of signs of neurotoxicity of botulinum toxin. In a therapeutic study, treatment with the BAT at scaled 1x human dose after the onset of clinical signs significantly enhanced survival compared to the placebo (46.6% vs. 0%, p<0.0001, Fisher’s exact test). Additionally, treatment with the BAT delayed the progression of signs (muscular weakness, respiratory distress, oral/nasal discharge) of toxin intoxication and reduced the severity of the disease.

Conclusions

A single dose of BAT, when administered to symptomatic monkeys, resulted in a statistically significant survival benefit compared to the placebo. Additionally, BAT completely protected monkeys from the clinical signs of intoxication and subsequent death when administered as PEP treatment. These data in part supported the licensure of BAT under the Animal Rule in the United States by the Food and Drug Administration.

Use-dependent potentiation of voltage-gated calcium channels rescues neurotransmission in nerve terminals intoxicated by botulinum neurotoxin serotype A

Botulinum neurotoxins (BoNTs) are highly potent toxins that cleave neuronal SNARE proteins required for neurotransmission, causing flaccid paralysis and death by asphyxiation. Currently, there are no clinical treatments to delay or reverse BoNT-induced blockade of neuromuscular transmission. While aminopyridines have demonstrated varying efficacy in transiently reducing paralysis following BoNT poisoning, the precise mechanisms by which aminopyridines symptomatically treat botulism are not understood. Here we found that activity-dependent potentiation of presynaptic voltage-gated calcium channels (VGCCs) underlies 3,4-diaminopyridine (3,4-DAP)-mediated rescue of neurotransmission in central nervous system synapses and mouse diaphragm neuromuscular junctions fully intoxicated by BoNT serotype A. Combinatorial treatments with 3,4-DAP and VGCC agonists proved synergistic in restoring suprathreshold endplate potentials in mouse diaphragms fully intoxicated by BoNT/A. In contrast, synapses fully intoxicated by BoNT serotypes D or E were refractory to synaptic rescue by any treatment. We interpret these data to propose that increasing the duration or extent of VGCC activation prolongs the opportunity for low-efficiency fusion by fusogenic complexes incorporating BoNT/A-cleaved SNAP-25. The identification of VGCC agonists that rescue neurotransmission in BoNT/A-intoxicated synapses provides compelling evidence for potential therapeutic utility in some cases of human botulism.

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.

SiMa Cells for a Serotype Specific and Sensitive Cell-Based Neutralization Test for Botulinum Toxin A and E

Botulinum toxins (BoNTs), of which there are seven serotypes, are among the most potent neurotoxins, with serotypes A, B and E causing human botulism. Antitoxins form the first line of treatment for botulism, and functional, highly sensitive in vitro methods for toxin neutralization are needed to replace the current in vivo methods used for determination of antitoxin potency. In this preliminary proof of concept study, we report the development of a neutralization test using the neuroblastoma SiMa cell line. The assay is serotype specific for either BoNT/A or BoNT/E, which both cleave unique sequences on SNAP-25 within SiMa cells. The end point is simple immunodetection of cleaved SNAP-25 from cell lysates with antibodies detecting only the newly exposed sequence on SNAP-25. Neutralizing antibodies prevent the toxin-induced cleavage of SNAP-25. The toxin neutralization assay, with an EC50 of ~2 mIU/mL determined with a standardized reference antiserum, is more sensitive than the mouse bioassays. Relevance was demonstrated with commercial and experimental antitoxins targeting different functional domains, and of known in vivo neutralizing activities. This is the first report describing a simple, specific, in vitro cell-based assay for the detection of neutralizing antibodies against BoNT/A and BoNT/E with a sensitivity exceeding that of the mouse bioassay.

Infant Botulism in the Very Young Neonate: A Case Series

Background  Though botulism is a rare disease overall, all infants younger than 1 year of age are at risk of contracting infant botulism, the most prevalent form reported in the United States. Nonetheless, infant botulism is frequently omitted from the differential diagnosis of the very young neonate exclusively due to age, and the diagnosis is often only considered secondarily after a costly and prolonged work up is undertaken. Delayed diagnosis can lead not only to unnecessary testing but also to prolonged hospital stay and increased morbidity. Case  This case series highlights three critically ill neonates, all younger than 30 days, who presented to our neonatal intensive care unit and were eventually diagnosed with infant botulism. The initial diagnostic dilemma is described for each of these patients and highlights the importance of early recognition of the main symptoms, in addition to consideration of important potential coinciding conditions.

Role of Homologous Fc Fragment in the Potency and Efficacy of Anti-Botulinum Antibody Preparations

The only approved treatment for botulism relies on passive immunity which is mostly based on antibody preparations collected from hyper-immune horses. The IgG Fc fragment is commonly removed from these heterologous preparations to reduce the incidence of hyper-sensitivity reactions. New-generation therapies entering the pipeline are based on a combination of humanized monoclonal antibodies (MAbs), which exhibit improved safety and pharmacokinetics. In the current study, a systematic and quantitative approach was applied to measure the direct contribution of homologous Fc to the potency of monoclonal and polyclonal antitoxin preparations in mice. Homologous Fc increased the potency of three individual anti-botulinum toxin MAbs by up to one order of magnitude. Moreover, Fc fragment removal almost completely abolished the synergistic potency obtained from a combined preparation of these three MAbs. The MAb mixture neutralized a 400-mouse median lethal dose (MsLD₅₀) of botulinum toxin, whereas the F(ab′)₂ combination failed to neutralize 10 MsLD₅₀ of botulinum toxin. Notably, increased avidity did not compensate for this phenomenon, as a polyclonal, hyper-immune, homologous preparation lost 90% of its potency as well upon Fc removal. Finally, the addition of homologous Fc arms to a heterologous pharmaceutical anti-botulinum toxin polyclonal horse F(ab′)₂ preparation improved its efficacy when administered to intoxicated symptomatic mice. Our study extends the aspects by which switching from animal-based to human-based antitoxins will improve not only the safety but also the potency and efficacy of passive immunity against toxins.

Use of human immunoglobulins as an anti-infective treatment: the experience so far and their possible re-emerging role

INTRODUCTION

Pooled human immunoglobulins (IGs) are prepared from plasma obtained from healthy donors as a concentrated antibody-containing solution. In addition, high-titer IGs (hyperimmune) against a specific pathogen can be obtained from vaccinated or convalescing donors. Currently, IGs can be used for the treatment of a variety of infections for which no specific therapy exists or that remain difficult to treat. Moreover, the recent pathogen outbreaks for which there is no approved treatment have renewed attention to the role of convalescent plasma and IGs. Areas covered: In this review, a historical perspective of the use of sera and IGs in humans as anti-infective agents (any viral, bacterial, parasitic infection), excluding immunodeficient patients, is presented from early development to the latest clinical studies. A Medline search was conducted to examine the peer-reviewed literature, with no date limits. Expert commentary: Human pooled plasma-derived IG products benefit from the polyclonal response of every individual donor and from the interindividual variability in such response. The trend to increased availability of vaccines for infectious diseases also opens new potential applications of hyperimmune IGs for emerging or re-emerging infectious diseases (e.g.: Ebola, Zika, Dengue), for the prevention and treatment in the general population, healthcare personnel and caregivers.

Applying Unconventional Secretion in Ustilago maydis for the Export of Functional Nanobodies

Exploiting secretory pathways for production of heterologous proteins is highly advantageous with respect to efficient downstream processing. In eukaryotic systems the vast majority of heterologous proteins for biotechnological application is exported via the canonical endoplasmic reticulum–Golgi pathway. In the endomembrane system target proteins are often glycosylated and may thus be modified with foreign glycan patterns. This can be destructive for their activity or cause immune reactions against therapeutic proteins. Hence, using unconventional secretion for protein expression is an attractive alternative. In the fungal model Ustilago maydis, chitinase Cts1 is secreted via an unconventional pathway connected to cell separation which can be used to co-export heterologous proteins. Here, we apply this mechanism for the production of nanobodies. First, we achieved expression and unconventional secretion of a functional nanobody directed against green fluorescent protein (Gfp). Second, we found that Cts1 binds to chitin and that this feature can be applied to generate a Gfp-trap. Thus, we demonstrated the dual use of Cts1 serving both as export vehicle and as purification tag. Finally, we established and optimized the production of a nanobody against botulinum toxin A and hence describe the first pharmaceutically relevant target exported by Cts1-mediated unconventional secretion.

Different drugs for bad bugs: antivirulence strategies in the age of antibiotic resistance

The rapid evolution and dissemination of antibiotic resistance among bacterial pathogens are outpacing the development of new antibiotics, but antivirulence agents provide an alternative. These agents can circumvent antibiotic resistance by disarming pathogens of virulence factors that facilitate human disease while leaving bacterial growth pathways - the target of traditional antibiotics - intact. Either as stand-alone medications or together with antibiotics, these drugs are intended to treat bacterial infections in a largely pathogen-specific manner. Notably, development of antivirulence drugs requires an in-depth understanding of the roles that diverse virulence factors have in disease processes. In this Review, we outline the theory behind antivirulence strategies and provide examples of bacterial features that can be targeted by antivirulence approaches. Furthermore, we discuss the recent successes and failures of this paradigm, and new developments that are in the pipeline.