New Modified Recombinant Botulinum Neurotoxin Type F with Enhanced Potency.

Botulinum neurotoxins (BoNTs) are notorious toxins and powerful agents and can be lethal, causing botulism, but they are also widely used as therapeutics, particularly to treat neuromuscular disorders. As of today, the commercial BoNT treatments available are from native A or B serotypes. Serotype F has shown efficacy in a clinical trial but has scarcely been used, most likely due to its medium duration of effect. Previously, the uniqueness of the light chain of the F7 subtype was identified and reported, showing an extended interaction with its substrates, VAMPs 1, 2 and 3, and a superior catalytic activity compared to other BoNT/F subtypes. In order to more extensively study the properties of this neurotoxin, we engineered a modified F7 chimera, mrBoNT/F7-1, in which all the regions of the neurotoxin were identical to BoNT/F7 except the activation loop, which was the activation loop from BoNT/F1. Use of the activation loop from BoNT/F1 allowed easier post-translational proteolytic activation of the recombinant protein without otherwise affecting its properties. mrBoNT/F7-1 was expressed, purified and then tested in a suite of in vitro and in vivo assays. mrBoNT/F7-1 was active and showed enhanced potency in comparison to both native and recombinant BoNT/F1. Additionally, the safety profile remained comparable to BoNT/F1 despite the increased potency. This new modified recombinant toxin F7 could be further exploited to develop unique therapeutics to address unmet medical needs.

Is standing balance altered in individuals with chronic low back pain? A systematic review.

PURPOSE: To examine the static standing balance of individuals with chronic low back pain when compared to a healthy control group. METHODS: A search of available literature was done using PubMed, SPORTDiscus, CINAHL, and Scopus databases. Studies were included if they contained the following: (1) individuals with chronic low back pain 3 months or longer; (2) healthy control group; (3) quantified pain measurement; and (4) center of pressure measurement using a force plate. Two authors independently reviewed articles for inclusion, and assessed for quality using the Joanna Briggs Institute Critical Appraisal Checklist for Analytical Cross Sectional Studies. Cohen's d effect size was calculated to demonstrate the magnitude of differences between groups. RESULTS: Nine articles were included in this review. Quality scores ranged from 5/8 to 8/8. Although center of pressure measures were nonhomogeneous, subjects with chronic low back pain had poorer performance overall compared to healthy controls. Despite inconsistencies in statistical significance, effect sizes were frequently large, indicating a lack of sufficient power in the included studies. Data were insufficiently reported among certain studies, limiting the ability of direct study comparison. CONCLUSIONS: Results suggest that balance is impaired in individuals with chronic low back pain when compared to healthy individuals. Implications for rehabilitation Static balance is affected in individuals with chronic low back pain. Balance assessments should be completed for individuals with chronic low back pain. Results from balance assessments should be used to indicate areas of improvement and help guide the course of treatment, as well as reassess as treatment progresses.

Purification and Characterization of Recombinant Botulinum Neurotoxin Serotype FA, Also Known as Serotype H.

We have purified and characterized recombinant botulinum neurotoxin serotype FA (BoNT/FA). This protein has also been named as a new serotype (serotype H), but the classification has been controversial. A lack of well-characterized, highly pure material has been a roadblock to study. Here we report purification and characterization of enzymatically active, and of inactive nontoxic, recombinant forms of BoNT/FA as tractable alternatives to purifying this neurotoxin from native Clostridium botulinum. BoNT/FA cleaves the same intracellular target proteins as BoNT/F1 and other F serotype BoNTs; the intracellular targets are vesicle associated membrane proteins (VAMP) 1, 2 and 3. BoNT/FA cleaves the same site in VAMP-2 as BoNT/F5, which is different from the cleavage site of other F serotype BoNTs. BoNT/FA has slower enzyme kinetics than BoNT/F1 in a cell-free protease assay and is less potent at inhibiting ex vivo nerve-stimulated skeletal muscle contraction. In contrast, BoNT/FA is more potent at inhibiting neurotransmitter release from cultured neurons.

High resolution crystal structures of the receptor-binding domain of Clostridium botulinum neurotoxin serotypes A and FA.

The binding specificity of botulinum neurotoxins (BoNTs) is primarily a consequence of their ability to bind to multiple receptors at the same time. BoNTs consist of three distinct domains, a metalloprotease light chain (LC), a translocation domain (HN) and a receptor-binding domain (HC). Here we report the crystal structure of HC/FA, complementing an existing structure through the modelling of a previously unresolved loop which is important for receptor-binding. Our HC/FA structure also contains a previously unidentified disulphide bond, which we have also observed in one of two crystal forms of HC/A1. This may have implications for receptor-binding and future recombinant toxin production.