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Infect. Immun., Sep 1997, 3743-3752, Vol 65, No. 9
P Amersdorfer, C Wong, S Chen, T Smith, S Deshpande, R Sheridan, R Finnern and JD Marks
To produce antibodies capable of neutralizing botulinum neurotoxin type A
(BoNT/A), the murine humoral immune response to BoNT/A binding domain
(H(C)) was characterized at the molecular level by using phage antibody
libraries. Mice were immunized with BoNT/A H(C), the spleens were
harvested, and single-chain Fv (scFv) phage antibody libraries were
constructed from the immunoglobulin heavy and light chain variable region
genes. Phage expressing BoNT/A binding scFv were isolated by selection on
immobilized BoNT/A and BoNT/A H(C). Twenty-eight unique BoNT/A H(C) binding
scFv were identified by enzyme-linked immunosorbent assay and DNA
sequencing. Epitope mapping using surface plasmon resonance in a BIAcore
revealed that the 28 scFv bound to only 4 nonoverlapping epitopes with
equilibrium constants (Kd) ranging from 7.3 x 10(-8) to 1.1 x 10(-9) M. In
a mouse hemidiaphragm assay, scFv binding epitopes 1 and 2 significantly
prolonged the time to neuroparalysis, 1.5- and 2.7-fold, respectively,
compared to toxin control. scFv binding to epitopes 3 and 4 showed no
protection against neuroparalysis. A combination of scFv binding epitopes 1
and 2 had an additive effect on time to neuroparalysis, which increased to
3.9-fold compared to the control. The results suggest that there are two
"productive" receptor binding sites on H(C) which lead to toxin
internalization and toxicity. Blockade of these two epitopes with
monoclonal antibodies may provide effective immunoprophylaxis or therapy
against BoNT/A intoxication.
Copyright © 1997, American Society for Microbiology
Molecular characterization of murine humoral immune response to botulinum neurotoxin type A binding domain as assessed by using phage antibody libraries
Department of Anesthesia and Pharmaceutical Chemistry, University of California, San Francisco, 94110, USA.
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