Bacterial Staphylococcal Enterotoxin Research Articles

A DNA Spiegelmer to staphylococcal enterotoxin B.

Bacterial staphylococcal enterotoxin B is involved in several severe disease patterns and it was therefore used as a target for the generation of biologically stable mirror-image oligonucleotide ligands, so called Spiegelmers. The toxin is a 28 kDa protein consisting of 239 amino acids. Since the full-length protein is not accessible to chemical peptide synthesis, a stable domain of 25 amino acids was identified as a suitable selection target. DNA in vitro selection experiments were carried out against the equivalent mirror-image D-peptide domain resulting in high affinity D-DNA aptamers. As expected, the corresponding enantiomeric L-DNA Spiegelmer showed comparable binding characteristics to the L-peptide domain. Moreover, the Spiegelmer bound the whole protein target with only slightly reduced affinity. Dissociation constants of both peptide-oligonucleotide complexes were measured in the range of 200 nM, whereas the Spiegelmer binding to the full-length protein was determined at approximately 420 nM. These data demonstrate the possibility to identify Spiegelmers against large protein targets by a domain approach.

A new screening model for safety evaluation of superantigen–antibody recombinant fusion proteins (mAb Fab-SEA/E) using telemetric monitoring in conscious rabbits

Introduction: Carcinoma recognising monoclonal antibodies (mAb) and mutated forms of the T-cell-activating bacterial staphylococcal enterotoxin A/E (SEA/E) have been combined in single hybrid constructs (mAb Fab-SEA/E). By introducing substitutions in an MHC class II binding site, these harmful toxins can be converted into tolerable immunotoxins. Rabbits and humans are sensitive to SE toxins, and cardiovascular effects in rabbits are similar to those seen in septic shock in man. A new screening model using telemetry in conscious rabbits was applied in the safety evaluation of different mAb Fab-SEA/E constructs administered intravenously. Methods: Telemetry transmitters were implanted in the peritoneal cavity of animals with a pressure catheter in the aorta and electrodes for ECG recording subcutaneously following administration of mAb Fab-SEA/E constructs intravenously. Results: The responses in body temperature, heart rate, and blood pressure varied depending on the treatment regimen and the mutations of the drug given. For example, 25 μg/kg of C215 Fab-SEAmut9 were given as a first treatment cycle on days 1, 5, and 7 and as a second treatment cycle on days 13–15. The first dose induced high fever, whereas the second and third doses induced fever responses more rapidly and were of lower and shorter duration. The second treatment cycle, starting on day 13, did not induce any responses probably due to anti-SEA antibodies formed because of the treatment. Another construct, 5T4 Fab-SEA/E-11 at 50 μg/kg, induced a similar response as C215 Fab-SEAmut9 on days 1, 5, and 7. In this case, the pharmacologic response was still present on days 13–15, though no clinical signs developed or no formation of anti-SEA antibodies occurred. When 50 μg/kg of 5T4 Fab-SEA/E-11 was administered once daily for 4 days, body temperature after the first dose increased slowly during the first 24 h, whereas the second to fourth doses induced more rapid and higher responses. The fourth dose of another compound, K305 Fab-SEA/E-11 (50 μg/kg), induced an even more pronounced response both in magnitude and in duration as well as in adverse clinical signs. Discussion: By using continuous telemetric registration in the rabbit as a tool in superantigen–antibody (mAb Fab-SEA/E) drug selection, it has been possible to evaluate the dynamics of drug-induced immune effects (fever) and concomitant engagement of the cardiovascular system, conditions that are essential before clinical trials can be initiated.