Interaction between the two subdomains of the C-terminal part of the botulinum neurotoxin A is essential for the generation of protective antibodies.
The botulinum neurotoxin A C-terminal fragment (Hc), which mediates the binding of the toxin to neuronal cell surface receptors, comprises two subdomains, Hc-N (amino acids 873-1095) and Hc-C (amino acids 1096-1296). In order to define the minimal fragment of Hc carrying protective antigenic properties, Hc, Hc-N and Hc-C have been produced as recombinant proteins in Escherichia coli, and have been tested for their antigenicity in mouse protection assays. Hc, Hc-N and Hc-C induced similar antibody levels as shown by ELISA. However, a single immunization with Hc (10 microg) fully protected mice challenged with 10(3) mouse lethal dose 50 of toxin, whereas Hc-N, Hc-C, or Hc-N plus Hc-C did not give any protection. Triple immunizations with Hc-N or Hc-C were necessary to induce a higher level of protection. Circular dichroism and fluorescence studies showed that the isolated subdomains were folded and stable. However, an intense near-UV dichroic signal was only observed in the Hc spectrum, revealing a highly structured interface between both subdomains. Taken together, the results show that the generation of protective antibodies requires the whole Hc domain and especially the native structure of the interfacial region between Hc-N and Hc-C.
Tavallaie
Mahmood
M
Institut Pasteur Téhéran, Iran.
Chenal
Alexandre
A
Gillet
Daniel
D
Pereira
Yannik
Y
Manich
Maria
M
Gibert
Maryse
M
Raffestin
Stephanie
S
Popoff
Michel R
MR
Marvaud
Jean Christophe
JC
D000818:Animals; D000917:Antibody Formation; D019274:Botulinum Toxins, Type A / Q000737:chemistry* / Q000276:immunology* / Q000633:toxicity; D002942:Circular Dichroism; D003001:Cloning, Molecular; D017931:DNA Primers; D004926:Escherichia coli; D008297:Male; D051379:Mice; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry* / Q000276:immunology* / Q000633:toxicity; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000276:immunology
D017931:DNA Primers; D010446:Peptide Fragments; D011994:Recombinant Proteins; D019274:Botulinum Toxins, Type A