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Robust Peptide-Based Diagnostics of Botulinum Toxins


The botulinum neurotoxins (BoNTs; A-G), secreted by the anaerobic bacterium Clostridium botulinum, are highly lethal microbial proteins with an extremely low half-lethal dose of only 1-3 ng/kg in humans. In other words, one hundredth of a milligram (10 ?g) of the toxin could be extremely fatal to an adult; lower doses can result in partial muscle paralysis. Of the seven serotypes (A-G), only types A, B, E, and F are known to be pathogenic in humans. Owing to their high toxicity and to the ease of their production and potential dissemination into air, water, and food supply, the BoNTs are considered among the preeminent bioterrorism threats. As such, the NIAID and CDC have categorized them as Class A threat agents. The benchmark BoNT assay is based on an in vivo mouse lethality assay which can detect the BoNTs at very low levels (10 pg/mL). However, besides being viewed as inhumane and costly to run, the assay results are not available for 2-4 days. This is clearly untenable in a potential bioterrorism situation because, in order to implement suitable therapeutic and prophylactic measures in the event of an intentional release, it is critical that rapid and early diagnosis of neurotoxin intoxication in humans be possible. More pertinently, the assay is more suited for detecting environmental contamination of the toxin than for human biomonitoring. <P>Routine laboratory diagnosis of botulinum intoxication is based on the detection of the neurotoxin in the patient. In vitro diagnostic immunoassays, such as ELISA, enzyme-linked coagulation assay, and IPCR (immunoPCR) methods have been developed for this. <P>However, nearly all such methods are confounded by one or the other of the following requirements: 1) expensive and/or sensitive reagents (antibodies); that require stringent storage (e.g., refrigeration) and delicate assay conditions; 2) protracted assay time; 3) limited sensitiviy of detection; 4) bulky detection equipment (e.g., fluorescence or luminescence plate reader); and/or 5) trained personnel to execute assays. <P>Assays that monitor functional proteolytic activity of the neurotoxins have also been developed, many of which are limited by similar constraints. Consequently, the utility of these for point-of-care diagnosis of BoNT intoxication in humans is limited. <P>This Phase I proposal describes the development of highly robust, short peptide molecules with exquisite affinity for the BoNTs that can serve as antibody replacements in field- deployable diagnostics. The novel discovery approach will find broad impact for designing short peptide affinity reagents to multiple other proteinaceous biothreat agents, including shiga and shiga-like toxins, Staphylococcus and Clostridium enterotoxins, abrin, and ricin. Long term, we envisage the incorporation of short, high-affinity peptides into a highly-sensitive, label-free, multiplexed electrical detection platform, premised on silicon nanowire field-effect transistors, suitable for the generation of low cost, low power, easy-to- use handheld devices for rapid monitoring and detection of toxins produced by pathogenic organisms in humans.

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Public Health Relevance: <br/> The availability of field-deployable, multiplexed diagnostic devices capable of rapidly detecting multiple critical biological threat agents, such as bacterial toxins, in the field is premised on the availability of low cost, robust, and stable capture reagens integrated with a portable but ultrasensitive detection platform. Such a capability will enable prompt treatment and/or preventative strategies to be instituted expeditiously for maximum public health benefit. In addition to toxin monitoring, our proposed multiplexed point-of-care diagnostic platform has valuable ramifications for public health by enabling truly individualized medicine.

Mueller, John
Lynntech, Inc
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