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Determination of Antibodies to the Fragments A and B of Diphtheria Toxin.

1[]Wahby AF, 1Ibrahim NH, 2El-Kady EM and 3Hamdi MA.

Departments of 1Molecular Biology and 2Microbial Biotechnology, National Research Center, Cairo and 3Department of Biochemistry, Faculty of Pharmacy, Cairo University.

An indirect ELISA to determine the fraction of anti diphtheria toxoid (DTd) antibody (Ab) reactive with fraction A (FA) and fraction B (FB) of the toxoid is described. In principle, the binding of (DTd) adsorbed onto ELI SA-plates to the corresponding antibodies (Abs) was specifically blocked with horse F(ab)2 to either FA or FB of diphtheria toxin (DT). The unblocked antigenic determinants of the DTd were used for determination of the corresponding Abs in sera from immunized humans and guinea pigs. The results revealed a high correlation between the levels of Abs to the DTd, FA and FB of the toxoid in sera from immunized hosts. In addition, it demonstrates that the use of DT-based immunotoxin alters the ratio of anti-FA/anti-FB. The developed ELI SA is reliable for monitoring of the levels of Abs to the toxic entity of the DT-based immunotoxins.

[] Correspondence: Dr A.F. Wahby, Department of Molecular Biology, National Research Center, Tahrir Street, Dokki, Cairo, Egypt.