Methods for detection of botulinum neurotoxin
Provided herein is a large immuno-sorbent surface area assay (ALISSA) for rapid and sensitive detection of toxin or enzyme activity. This assay is designed to capture a low number of toxin or enzyme molecules and to measure their intrinsic protease activity via conversion of a fluorogenic or luminescent substrate. The ALISSA is significantly faster and more sensitive than methods routinely utilized in the art. This assay is applicable for use for detection of a variety of toxins or enzymes having proteolytic activity, such as botulinum neurotoxin, bacillus anthracis lethal factor, human chitinases, and aspergillus fumigatus proteases. Also provided are methods for constructing and identifying novel luminescent or fluorescent substrates suitable for use with the ALISSA method.
1. A method for detecting the presence of a botulinum toxin in a sample comprising:
a) exposing the sample putatively containing a botulinum toxin to (i) an enrichment matrix comprising a botulinum-specific antibody that captures botulinum toxin in the sample and (ii) a substrate composition comprising a toxin substrate that is capable of eliciting a detectable fluorogenic signal when modified by the botulinum toxin, the substrate selected from
(SEQ ID NO: 12)
Lys[5-Fam]IleAspGluAlaAsnGlnArgAlaThrLys[DABCYL]X,
wherein X is norleucine;
(SEQ ID NO: 13)
5-Fam-
Lys[5-Fam]IleAspGluAlaAsnGlnArgAlaThrLys[DABCYL]X,
wherein X is norleucine; or
(SEQ ID NO: 14)
5-Fam-LysIleAspGluAlaAsnGlnArgAlaThrLys[DABCYL]Nle,
wherein the exposure occurs under conditions permitting binding of the botulinum toxin to the antibody and modification of the substrate by the botulinum toxin; and
b) detecting the presence of the botulinum toxin by measuring a change in fluorescence in the sample.
2. The method of claim 1 wherein the sample is exposed to the enrichment matrix prior to being exposed to the substrate.
3. The method of claim 1 wherein the toxin retains measurable enzymatic activity subsequent to its binding by the antibody.
4. The method of claim 1 wherein said toxin is botulinum neurotoxin serotype A (BoNT/A).
5. The method of claim 1 wherein the enrichment matrix comprises anti-BoNT/A antibodies bound to bead-immobilized protein A molecules.
6. The method of claim 1 wherein the matrix is an immunosorbent support comprised of loose beads or a fixed column.
7. The method of claim 1 wherein the substrate composition further comprises a control substrate having the sequence:
(SEQ ID NO: 15)
5-Fam-
Lys[5-Fam]IleAspGluAlaAsnGlnGluLeuThrLys[DABCYL]Nle.
8. The method of claim 1 wherein the substrate composition further comprises a substrate that is capable of eliciting a detectable luminogenic signal when modified by the botulinum toxin, the substrate selected from SEQ ID NO:3 or SEQ ID NO:4; and wherein detection of the presence of botulinum toxin is accomplished by measuring a change in light emission in the sample.
9. A method for detecting the presence of a botulinum toxin in a sample comprising:
a) exposing the sample putatively containing a botulinum toxin to (i) an enrichment matrix comprising a botulinum-specific antibody that captures botulinum toxin in the sample and (ii) a substrate composition comprising substrate that is capable of eliciting a detectable fluorogenic signal when modified by the botulinum toxin, the-substrate comprising a control substrate having the sequence 5-Fam-Lys[5-Fam]IleAspGluAlaAsnGlnGluLeuThrLys[DABCYL]Nle (SEQ ID NO:15), wherein the exposure occurs under conditions permitting binding of the botulinum toxin to the antibody and modification of the substrate by the botulinum toxin; and
b) detecting the presence of the botulinum toxin by measuring a change in fluorescence or light emission in the sample.
10. The method of claim 9 wherein the substrate composition further comprises a substrate that is capable of eliciting a detectable fluorogenic signal when modified by the botulinum toxin, the substrate selected from
(SEQ ID NO: 12)
Lys[5-Fam]IleAspGluAlaAsnGlnArgAlaThrLys[DABCYL]X,
wherein X is norleucine;
(SEQ ID NO: 13)
5-Fam-
Lys[5-Fam]IleAspGluAlaAsnGlnArgAlaThrLys[DABCYL]X,
wherein X is norleucine; or
(SEQ ID NO: 14)
5-Fam-LysIleAspGluAlaAsnGlnArgAlaThrLys[DABCYL]Nle.
11. The method of claim 9 wherein the substrate composition further comprises a toxin substrate that is capable of eliciting a detectable luminogenic signal when modified by the botulinum toxin, the substrate selected from SEQ ID NO:3 or SEQ ID NO:4, and wherein detection of the presence of botulinum toxin is accomplished by measuring a change in light emission in the sample.
12. The method of claim 9 wherein the sample is exposed to the enrichment matrix prior to being exposed to the substrate.
13. The method of claim 9 wherein the toxin retains measurable enzymatic activity subsequent to its binding by the antibody.
14. The method of claim 9 wherein said toxin is botulinum neurotoxin serotype A (BoNT/A).
15. The method of claim 9 wherein the enrichment matrix comprises anti-BoNT/A antibodies bound to bead-immobilized protein A molecules.
16. The method of claim 9 wherein the matrix is an immunosorbent support comprised of loose beads or a fixed column.