High-throughput homogeneous immunoassay readily identifies monoclonal antibody to serovariant clostridial neurotoxins.

High-throughput screening can create the potential ability to screen large numbers of monoclonal antibodies (mAb) in a short time period. A major bottleneck in the hybridoma method for mAb development has historically been the inability to sift through large numbers of hybridoma culture supernatants to identify clones secreting mAbs of the desired specificity. Herein, we develop a homogeneous fluorometric microvolume assay technology (FMAT) and compare it to conventional ELISA screening techniques for monoclonal antibody against soluble protein toxin fragments of the Clostridium botulinum types A, B and E neurotoxin (BoNT) proteins. In total 8,744 hybridoma clones were screened to identify 29 stable hybridomas to neurotoxin binding domain; six of these would have been missed by ELISA alone. Screening of hybridoma supernatants on days 1 and 4 following cloning from semi-solid HAT agarose reveals that FMAT provides a reliable method for screening hybridoma clones to purified protein toxins. The homogeneous FMAT utilizes far less reagent (antigen and hybridoma supernatant) allowing for simultaneous screening against multiple serovariant antigens early in the hybridoma cloning cycle. This reduces costs for reagents and labour by lowering numbers of clones being maintained with undesired specificity. Furthermore, this assay easily accommodates replicate screening which facilitates identification of cross-reactivity to neurotoxin serotypes, thus readily identifying mAb to serovariant antigens. These findings have broad application in accelerating mAb development to serovariant cell-surface or bead bound targets without arraying devices. In summary, FMAT provides a reliable method for the screening of mAbs against C. botulinum neurotoxins.

Trivalent vaccine against botulinum toxin serotypes A, B, and E that can be administered by the mucosal route.

Most reports dealing with vaccines against botulinum toxin have focused on the injection route of administration. This is unfortunate, because a mucosal vaccine is likely to be more efficacious for patients and pose fewer risks to health care workers and to the environment. Therefore, efforts were made to generate a mucosal vaccine that provides protection against the botulinum serotypes that typically cause human illness (serotypes A, B, and E). This work demonstrated that carboxy-terminal peptides derived from each of the three serotypes were able to bind to and penetrate human epithelial barriers in vitro, and there was no cross inhibition of membrane binding and transcytosis. The three polypeptides were then tested in vivo as a trivalent vaccine that could be administered to mice by the intranasal route. The results indicated that the mucosal vaccine evoked high secretory titers of immunoglobulin A (IgA), as well as high circulating titers of IgG and IgA, and it also evoked a high level of resistance to challenge with toxin. The immunoglobulin responses and the levels of resistance to challenge were increased by coadministration of adjuvants, such as chitosan and vitamin E. At least three mechanisms were identified to account for the antibody-induced resistance: (i) blockade of toxin absorption across epithelial cells, (ii) enhanced clearance of toxin from the circulation, and (iii) blockade of toxin action at the neuromuscular junction. These results are a compelling demonstration that a mucosal vaccine against multiple serotypes of botulinum toxin has been identified.