Creation of catalytic antibodies metabolizing organophosphate compounds.

Development of new ways of creating catalytic antibodies possessing defined substrate specificity towards artificial substrates has important fundamental and practical aspects. Low immunogenicity combined with high stability of immunoglobulins in the blood stream makes abzymes potent remedies. A good example is the cocaine-hydrolyzing antibody that has successfully passed clinical trials. Creation of an effective antidote against organophosphate compounds, which are very toxic substances, is a very realistic goal. The most promising antidotes are based on cholinesterases. These antidotes are now expensive, and their production methods are inefficient. Recombinant antibodies are widely applied in clinics and have some advantage compared to enzymatic drugs. A new potential abzyme antidote will combine effective catalysis comparable to enzymes with high stability and the ability to switch on effector mechanisms specific for antibodies. Examples of abzymes metabolizing organophosphate substrates are discussed in this review.

[Expression of the catalytic antibodies in eukaryotic systems].

Expression of recombinant antibodies in mammalian cells is one of key problems in immunobiotechnology. Alternatively, expression of a broad panel of antibodies and of their fragments may be effectively done in yeast cells. We obtained expression strains of the methylotrophic beast Pichia pastoris producing single chain human catalytic antibody A17 (A.17scFv), Fab-fragment (A.17Fab) and full-size light chain (A.17Lch). These antibodies were characterized in terms of functional activity. The capacity to specifically bind and transform organophosphorus compounds has been demonstrated for A.17scFv and A.17Fab. The loss of activity of the antibody light chain when expressed alone indicates that the active site is formed by both heavy and light chains of the antibody. We determined the reversible constant Kd and the first order constant (k2) of the reaction of the covalent modification of A.17scFv and A.17Fab by irreversible inhibitor of the serine proteases p-nitrophenyl 8-methyl-8-azobicyclo[3.2.1]phosphonate (Phosphonate X). Calculated values indicate that activity of the antibodies expressed in yeast is similar to the full-size antibody A17 and single chain antibody A.17 expressed in CHO and E. coli cells respectively.