Chronic botulism in a Saxony dairy farm: sources, predisposing factors, development of the disease and treatment possibilities.

The aim of this study is to investigate Clostridium botulinum at a Saxony dairy farm with 159 cows and 18 heifers. The animals exhibited clinical symptoms of chronic botulism. To determine the source of the infection, feces, blood, organs, and gastrointestinal fluids of dead or euthanized cows; as well as soil, water, silage and manure were tested for C. botulinum spores and BoNTs using ELISA. BoNT/C and C. botulinum type C were detected in 53% and 3% of tested animals, respectively, while BoNT/D and C. botulinum type D were detected in 18% of the animals. C. botulinum also was detected in organs, gastrointestinal fluids, drinking water and manure. To evaluate possible treatments, animals were given Jerusalem artichoke syrup (JAS), Botulism vaccine (formalinised aluminum hydroxide gel adsorbed toxoid of C. botulinum types C and D) or a suspension of Enterococcus faecalis. After four weeks treatment with JAS, BoNT/C and C. botulinum type C were not detected in feces. In contrast, BoNT/D and C. botulinum type D were not significantly influenced by the JAS treatment. Vaccination with botulism vaccine and the E. faecalis suspension significantly decreased BoNT/D and C. botulinum type D. A significant increase of Enterococci was detected in animals treated with E. faecalis. Interestingly, there was a negative correlation between the detection of both BoNT and C. botulinum with the concentration of Enterococci in feces. Although C. botulinum C and D antibodies increased significantly (p < 0.0001) after vaccination with the botulism vaccine, the reduction of C. botulinum and BoNT in feces did not result in recovery of the animals because they were deficient of trace elements [manganese (Mn), cobalt (Co), copper (Cu) and selenium (Se)]. Animals treated with trace elements recovered. It appears that intestinal microbiota dysbiosis and trace element deficiency could explain the extensive emergence of chronic Botulism.

Binding activity and immunogenic characterization of recombinant C-terminal quarter and half of the heavy chain of botulinum neurotoxin serotype A.

In the present study, we explored and compared the binding activity and immunogenic characterization of the most effective part corresponding to C-terminal quarter of heavy chain of botulinum neurotoxin serotype A (AHc-C) with C-terminal half of heavy chain of botulinum neurotoxin serotype A (AHc). Firstly, the fully soluble AHc-C protein successfully expressed in Escherichia coli by co-expression with thioredoxin (Trx) was shown to bind with ganglioside as the AHc, indicating that the recombinant AHc-C protein retains a functionally active conformation. Furthermore, a solid-phase assay showed that the anti-AHc-C sera effectively inhibited the binding of AHc or AHc-C to the ganglioside GT1b, the first step in BoNT/A intoxication of neurons, as good as the anti-AHc sera. Finally, although the recombinant AHc-C protein still induced a high serum antibody titers and afforded protection level as the mice challenged with active botulinum neurotoxin serotype A, the immunization with AHc protein induced stronger protective potency than the AHc-C protein. The data presented in the report shows that there are the same ganglioside binding activity and different immunogenic characterization between the C-terminal quarter and half of heavy chain of botulinum neurotoxin serotype A. Therefore, the recombinant AHc-C protein can not only be developed into a minimal subunit candidate vaccine for prophylaxis against botulinum neurotoxin serotype A but also be used as a promising tool in the search for binding inhibitors and chimeric vaccines.

Development of an Equine Antitoxin by Immunizing the Halla Horse with the Receptor-Binding Domain of Botulinum Neurotoxin Type A1.

Botulinum neurotoxins (BoNTs), produced by Clostridium botulinum, are the most toxic substances known. However, the number of currently approved medical countermeasures for these toxins is very limited. Therefore, studies on therapeutic antitoxins are essential to prepare for toxin-related emergencies. Currently, more than 10,000 Halla horses, a crossbreed between the native Jeju and Thoroughbred horses, are being raised in Jeju Island of Korea. They can be used for equine antitoxin experiments and production of hyperimmune serum against BoNT/A1. Instead of the inactivated BoNT/A1 toxoid, Halla horse was immunized with the receptor-binding domain present in the C-terminus of heavy chain of BoNT/A1 (BoNT/A1-HCR) expressed in Escherichia coli. The anti-BoNT/A1-HCR antibody titer increased rapidly by week 4, and this level was maintained for several weeks after boosting immunization. Notably, 20 µL of the week 24 BoNT/A1-HCR(-immunized) equine serum showed an in vitro neutralizing activity of over 8 international unit (IU) of a reference equine antitoxin. Furthermore, 20 µL of equine serum and 100 µg of purified equine F(ab')2 showed 100% neutralization of 10,000 LD50 in vivo. The results of this study shall contribute towards optimizing antitoxin production for BoNT/A1, which is essential for emergency preparedness and response.

Botulinum neurotoxin vaccines: past, present, and future.

In the early 1930s, a formalin-inactivated toxoid against botulinum neurotoxin was first tested in humans. In 1965, a pentavalent botulinum toxoid (PBT) received Investigational New Drug (IND) status under the Centers for Disease Control's IND 161 (for at-risk workers), and in 1991 under the United States Army's Office of the Surgeon General IND 3723 (for military deployment). This PBT vaccine has been shown to be safe, with over 20,000 injections given to date, and continues to be used in at-risk individuals. During the past decade, recombinant DNA technology has been employed to develop second-generation vaccines to prevent botulism. Recombinant subunit vaccines utilizing the receptor-binding domains of botulinum neurotoxin (BoNT) have been shown to be safe and efficacious in protecting animal models against BoNT serotypes A, B, C1, D, E, and F. In 2004, the first recombinant subunit vaccine [rBV A/B (Pichia pastoris) vaccine] was tested in humans during a phase I clinical trial. Results from that study demonstrated that the recombinant bivalent vaccine was safe and well tolerated at all dosage levels tested and stimulated serotype-specific neutralizing antibodies among the majority of vaccine recipients.

mRNA mediates passive vaccination against infectious agents, toxins, and tumors.

The delivery of genetic information has emerged as a valid therapeutic approach. Various reports have demonstrated that mRNA, besides its remarkable potential as vaccine, can also promote expression without inducing an adverse immune response against the encoded protein. In the current study, we set out to explore whether our technology based on chemically unmodified mRNA is suitable for passive immunization. To this end, various antibodies using different designs were expressed and characterized in vitro and in vivo in the fields of viral infections, toxin exposure, and cancer immunotherapies. Single injections of mRNA-lipid nanoparticle (LNP) were sufficient to establish rapid, strong, and long-lasting serum antibody titers in vivo, thereby enabling both prophylactic and therapeutic protection against lethal rabies infection or botulinum intoxication. Moreover, therapeutic mRNA-mediated antibody expression allowed mice to survive an otherwise lethal tumor challenge. In conclusion, the present study demonstrates the utility of formulated mRNA as a potent novel technology for passive immunization.

Submolecular recognition profiles in two mouse strains of non-protective and protective antibodies against botulinum neurotoxin A.

We have used a set of synthetic overlapping peptides encompassing the entire heavy (H) chain of botulinum neurotoxin serotype A (BoNT/A) to map, in two mouse strains (BALB/c, H2d, and SJL, H2S), the regions on the H-chain recognized by Abs in the last bleed of non-protective anti-BoNT/A antisera and in the bleed of protective antisera immediately following it in the bleeding schedule. Although the protective antisera bound slightly higher amounts of total (IgG+IgM) Abs, non-protective and protective BALB/c antisera showed similar peptide-binding profiles involving peptides N6/N7, N25, C2/C3, C9/C10/C11, C15, C18, C24, C30, and C31 and, at lower amounts of bound Abs, peptides N19, C6/C7, and C28. IgG+IgM antibodies of the protective SJL antisera recognized peptides N5, N22, and C21, and these peptides were only slightly recognized (N22, C21) or unrecognized (N5) by the non-protective antisera. Additionally, peptides N7/N8, N25, C11, C15, and less so N27/N28 bound two-fold or more Abs from the SJL protective antisera than the non-protective antisera. The Abs bound to peptides C4 and C29 were of relatively lower affinity. Peptides C2/C3, C7, C18/C19, C24, C30, and C31 bound higher amounts of Abs in the SJL protective versus the non-protective antisera, but the differences were less than double. We also mapped the binding profiles of the IgG Abs in these sera. BALB/c and SJL had 13-36-fold higher of IgG Abs that bound to BoNT/A in the protective antisera relative to non-protective antisera. The IgG Abs in the protective antisera of each mouse haplotype bound to the same peptides that bound total Abs in the correlate antiserum. But in both mouse strains, the non-protective Abs showed little or no IgG Abs that bound to these peptides. In the SJL haplotype, the IgG response to peptide N5 was transient, appearing strongly in early protective Abs and disappearing by day 70. It is not clear whether the response to region N5 plays a role in initiating and contributing to the protective activity of the toxin in the SJL strain in the early stages but is not needed in later hyperimmune stages of the Ab response. It is concluded that the switch in BALB/c and SJL mice from non-protective to protective Abs is not associated with major changes in the epitope-recognition profiles. Although some slight differences between non-protective and protective antisera appeared in their levels of Abs that were bound by some peptides, these differences are not sufficient to explain differences in the protection properties. Protection was mostly associated with the immunoglobulin class of the antibodies. IgM antibodies were non-protective, while IgG Abs produced after the switch were protective.

The receptor binding domain of botulinum neurotoxin serotype A (BoNT/A) inhibits BoNT/A and BoNT/E intoxications in vivo.

The receptor binding domain of botulinum neurotoxin (BoNT), also designated the C terminus of the heavy chain (H(C)), is a promising vaccine candidate against botulism. In this study, a highly efficient expression system for the protein was developed in Escherichia coli, which provided yields that were 1 order of magnitude higher than those reported to date (350 mg H(C) per liter). The product was highly immunogenic, protecting mice from a challenge with 10(5) 50% lethal dose (LD(50)) after a single vaccination and generating a neutralizing titer of 49.98 IU/ml after three immunizations. In addition, a single boost with HC increased neutralizing titers by up to 1 order of magnitude in rabbits hyperimmunized against toxoid. Moreover, we demonstrate here for the first time in vivo inhibition of BoNT/A intoxication by H(C)/A, presumably due to a blockade of the neurotoxin protein receptor SV2. Administration of HC/A delayed the time to death from 10.4 to 27.3 h in mice exposed to a lethal dose of BoNT/A (P = 0.0005). Since BoNT/A and BoNT/E partially share SV2 isoforms as their protein receptors, the ability of H(C)/A to cross-inhibit BoNT/E intoxication was evaluated. The administration of H(C)/A together with BoNT/E led to 50% survival and significantly delayed the time to death for the nonsurviving mice (P = 0.003). Furthermore, a combination of H(C)/A and a subprotective dose of antitoxin E fully protected mice against 850 mouse LD(50) of BoNT/E, suggesting complementary mechanisms of protection consisting of toxin neutralization by antibodies and receptor blocking by H(C)/A.

Characterization of new formalin-detoxified botulinum neurotoxin toxoids.

Antigenicities of several formalin-detoxified botulinum neurotoxin preparations were measured by inhibition and sandwich enzyme-linked immunosorbent assay (ELISA), and immunogenicity was studied in mice. The toxoids were derived primarily from the serotype A 150-kDa neurotoxin protein, while one toxoid was derived from the naturally occurring 900-kDa toxin-hemagglutinin complex. Antigenicity was severely compromised in two commercially available toxoids. A variety of new toxoids were synthesized in-house by optimizing formaldehyde reaction conditions. Three of the resulting toxoids were found to be antigenically identical to the native toxin, as measured by inhibition ELISA, in spite of showing a reduction of toxicity by more than 100,000-fold. Sandwich ELISAs indicated that the in-house toxoids were two- to threefold less antigenic than the neurotoxin compared to commercial toxoids, which were about 100-fold less antigenic. Mice were immunized twice, on day 0 and day 14. By day 28, relatively high toxin-specific immunoglobulin G (IgG) titers were detected in animals that had received any of the in-house toxoids, with greater than 99% being IgG1 and the remainder being IgG2. These immunized mice remained asymptomatic after being challenged with 50 to 1,000,000 50% lethal dose (LD(50)) units of the 900-kDa neurotoxin. In contrast, animals immunized with several different batches of commercially available toxoids did not develop measurable toxin-specific antibody titers. However, these mice survived neurotoxin challenges with 2 LD(50) units but died when challenged with 6 LD(50) units. Neutralizing titers measured from pools of sera generated with the in-house toxoid preparations ranged from 2.5 to 5 U/ml. In terms of predicting immunogenicity, inhibition ELISAs comparing each formalin toxoid to the parent toxin provided good insight for screening the new toxoids as well as for estimating their relative in vivo potencies. Inhibition ELISA data indicate that those toxoids that most closely resemble the native toxin are highly immunogenic and protective. The superior quality of these new toxoids makes them useful tools for continued use in ELISA development and for antitoxin production.