Monoclonal antibody-based immunoassay for type A Clostridium botulinum toxin is comparable to the mouse bioassay

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Abstract
A monoclonal antibody (BA11) was produced against G. botulinum type A neurotoxin by the fusion of myeloma cells (P3 NS1/1-Ag4-1) with spleen cells from BALB/c mice immunized with botulinum type A neurotoxoid. The antibody bound specifically to botulinum type A neurotoxin, showing no cross-reactivity with types B and E botulinum toxins or with any of several other bacterial toxins tested. The monoclonal antibody did not bind to botulinum type A neurotoxin which was denatured with sodium dodecyl sulfate and bound only weakly to each of the separated heavy and light subunits of the neurotoxin, suggesting a conformational requirement for the antigenic determinant of the antibody. A sensitive immunoassay for C. botulinum type A toxin with monoclonal antibody BA11 in conjunction with an enzyme amplication system was developed which allows detection of 5-10 mouse 50% lethal doses ml-1 of purified neurotoxin. The assay was equally sensitive when applied to the detection of crude toxin in foodstuffs; the average value for the minimum level of detectable toxin in extracts of tinned salmon or corned beef was 9 .+-. 3.1 mouse 50% lethal doses ml-1.