Pseudomonas exotoxin A: toxoid preparation by photoaffinity inactivation.

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Abstract
A method for toxoid preparation was developed in which toxins expressing enzymatic activity are detoxified by photoaffinity labeling techniques. In the case of P. aeruginosa exotoxin A, the method relies on the affinity of azido-substituted analogs of the substrate (NAD) for the proenzyme form of the toxin. Photolysis of the putative toxin-analog complex results in irreversible inactivation of the toxin without loss of antigenic character. Apparently, this occurs by nitrene insertion into a chemical bond on the toxin molecule. This affinity photoinactivation process should be applicable to other ADP-ribosylating toxins. Inactivated toxins which retain their antigenic characteristics are valuable in vaccine development.