Composition and Molecular Size of Clostridium botulinum Type A Toxin–Hemagglutinin Complex

Abstract

The paper by Lietzow et al. [1] has added an interesting dataset to the literature for Type A neurotoxin (BoNT–A) complex on composition and molecular weight. However, in their work, the authors have left both unanswered questions and difficulties in interpretation of their data concerning the structure and molecular size of the complex. Data previously reported by us [2], have described that the composition of the BoNT–A complex is specific to the producing strain, the method of growth and the method of purification. Schantz and Johnson [3] have also reported these criteria. Comparisons with other publications (for e.g., [4–6]) provide yet further evidence on the importance of these parameters. These aspects need to be very clear in newly published reports, since no comparisons can be made of BoNT–A complexes without this information. For example, there is not one Hall strain of Clostridium botulinum but several [7, 8]. Additionally, the method of production stated by the authors is also unclear, since the cited reference [3] includes several methods; differences in the number of ammonium sulphate crystallisations are described by those workers, to both improve the purity and reduce, in particular, the contamination by nucleic acids. The data reported by Lietzow et al. [1] relating to the size of the BoNT–A complex are unremarkable, showing the expected size at the pH that they have tested, pH 6.0, as approximately 900 kDa. This was published by Schantz and Johnson [3] for their BoNT–A complex over 15 years ago. When the BoNT–A complex meets physiological conditions, the neurotoxin is freed from the complexed proteins in a clearly defined dissociation [9], which is essential for the naked neurotoxin to act in vivo. Therefore, despite the new innovations in analytical technology applied, Lietzow et al. have found only a 4% or less difference when compared to the earlier data, essentially confirming what was already known. The composition of the BoNT–A complex determined by their capillary electrophoresis method shows only the major proteins of the toxin complex. The loadings applied to the analysis are difficult to determine, due to the extensive sample processing used, but appear to be below the detection threshold for the majority of the minor components which are present. In fact, the poor separation of the HA 48 and Light Chain components (which run together) must cast doubt on the appropriateness of this method version for detailed analysis of the BoNT–A complex. Other methods, such as Sodium Dodecyl Sulphate Poly-Acrylamide Gel Electrophoresis (SDS–PAGE) followed by mass spectrometry, are more suitable for fine analysis of the BoNT–A complex [2]. But perhaps what is most surprising about the data set is that this does not relate to the Allergan product, Botox . Nowhere have the authors referred to their product. This is disappointing as many statements have been made in the literature about the size of the Botox toxin complex, yet there is no reference in the scientific literature to provide those facts and details. Lietzow and co-workers appear to have lost this opportunity. Indeed, the production method of Botox toxin complex is believed to be different, in several ways, to that described by Schantz and Johnson [3], as described in information available in the public domain [10]. Their work therefore, regrettably does not help in the A. Pickett (&) K. Perrow (&) Biologicals Science and Technology, Ipsen Biopharm Limited, Wrexham LL13 9UF, UK e-mail: andy.pickett@ipsen.com