Generation of group-specific antibodies against sulfonamides
Cliquet, P. ; Cox, E. ; Haasnoot, W. ; Schacht, E. ; Goddeeris, B.M. - \ 2003
Journal of Agricultural and Food Chemistry 51 (2003)20. - ISSN 0021-8561 - p. 5835 - 5842.
enzyme-immunoassay - monoclonal-antibodies - sulfamethazine residues - sulfathiazole - elisa - tissue - recognition - antibiotics - milk - meat
To develop a sulfonamide-specific ELISA, different attempts were made to obtain monoclonal antibodies specific for the common structure of sulfonamides. In a first approach, sulfanilamide was linked to albumins using glutaraldehyde or a succinimide ester as cross-linker. A weak immune response or none at all was induced after immunization of mice with those conjugates. High antibody titers were obtained with conjugates where sulfanilamide was linked to albumins or casein (azocasein) with a diazotation reaction. However, the antibodies were only highly specific for the bound sulfanilamide molecule. In a second approach, sulfonamide-protein conjugates were used in which the sulfonamide molecule is linked at its side chain, leaving the common structure of sulfonamides unchanged. Three sulfonamide derivatives (S, TS, and PS, previously described in the literature) containing a carboxyl group in their side chain were linked to proteins using a carbodiimide mediated reaction. Immunization with the S-conjugates led to high antibody titers, but the antibodies were only highly specific for the bound S-molecule. Group-specific antibodies were obtained after immunization with the PS- and TS-conjugates. It was described that immunization with PS-conjugates lead to the recognition of other sulfonamides (sulfamethazine, -merazine, -diazine, and -dimethoxine) that are not well recognized by antibodies induced after immunization with TS-conjugates. Therefore, we tried to guide the immune response in the direction of recognition of the common structure of sulfonamides by immunizing the animals alternately with PS- and TS-conjugates. The polyclonal antibodies of the mice indeed had a broader specificity, but the specificity of the monoclonals obtained after fusion experiments was not influenced. Immunization with TS-conjugates seemed sufficient to obtain sulfonamide-specific monoclonal antibodies. With the best monoclonal (mAb 3B5B10E3) two competitive inhibition (ci) ELISA's were developed: one coated with antigen and the other coated with the monoclonal antibody. Sulfadiazine, -dimethoxine, -thiazole, -pyridine, and -methoxazole were detected in both ELISA's at their MRL-value (100 ppb) in buffer solution. Sulfadiazine, sulfathiazole, and sulfamethoxazole could even be detected at 10 ppb.
Extraction procedure for sulfachloropyridazine in porcine tissues and detection in a sulfonamide-specific enzyme-linked immunosorbent assay (ELISA)
Cliquet, P. ; Cox, E. ; Haasnoot, W. ; Schacht, B. ; Goddeeris, B.M. - \ 2003
Analytica Chimica Acta 494 (2003)1-2. - ISSN 0003-2670 - p. 21 - 28.
sulfamethazine residues - monoclonal-antibodies - animal-tissues - swine urine - immunoassay - sulfathiazole - sulfadimidine - antibiotics - meat - recognition
Sulfonamide-specific polyclonal rabbit antibodies were obtained after immunization with a sulfathiazole derivative (N1-[4-(carboxymethyl)-2-thiazolyl]sulfanilamide = TS) coupled to keyhole lympet hemocyanin. Using these antibodies, two sulfonamide-specific enzyme-linked immunosorbent assays (ELISAs) were developed differing in coating antigen: TS-ovalbumin (TS-ova) and PS-ovalbumin (PS-ova, PS = N1-[4-methyl-5-[2-4-carboxyethyl-1-hydroxyphenyl]-azo-2-pyridyl]sulfanilamide). The detection of sulfamethazine, sulfamerazine, sulfadimethoxine, sulfadiazine, sulfathiazole, sulfapyridine, sulfachloropyridazine and sulfisoxazole in buffer was studied. Higher antibody titers were obtained in the ELISA coated with TS-ova (TS-ciELISA) as compared to the ELISA coated with PS-ova (PS-ciELISA), but the detection of sulfonamides was more sensitive in the PS-ciELISA, allowing the detection of all tested sulfonamides at the maximum residue level (MRL) value (100 ng ml¿1). In a subsequent step, an extraction procedure was developed for the detection of sulfonamides in muscles, kidney, liver and fat by both ELISAs using sulfachloropyridazine as a model. As extraction buffer a carbonate/hydrogen carbonate buffer (pH 10) was chosen in which sulfonamides are highly soluble. Differences in homogenizing techniques (high-speed mixer (Ultraturax) versus vortex) and the effect of kaolin (hydrated aluminum silicate) treatment, to diminish the background signal in the ELISA, were evaluated. The best extraction procedure was the one using a vortex mixer as homogenizer and no kaolin treatment. Sulfachloropyridazine was easily detected at the MRL in all tissues.