OBJECTIVETo establish the genotype-specific targets plasmids and engineered E.coli strains of botulinum neurotoxins (BoNT) types B and E based on reverse genetics.

METHODSThe gene sequences of BoNT were obtained from GenBank and analyzed using DNAMAN, Lasergene, Vector NTI and BLAST. Two target fragments of BoNT/B and BoNT/E were anchored and then synthesized as 5 and 10 short DNA single strands, respectively. The full-length target sequences were amplified by overlapping PCR and subcloned into pMD 18-T vector, and the recombinant plasmids were identified by restriction enzyme digestion and sequencing.

RESULTSSixty full-length sequences of 4 types of BoNT, namely types A, B, E, and F, were available in GenBank. Two target fragments, BoNT/B of 215 bp and BoNT/E of 360 bp, and their specific primer pairs were anchored after sequence analysis. pMD 18-T-BoNT/B and pMD 18-T-BoNT/E containing these two target sequences were confirmed.

CONCLUSIONThe engineered plasmids and E.coli stains containing the genotype-specific target fragments of BoNT/B and BoNT/E have been constructed successfully.

Base Sequence ; Botulinum Toxins ; genetics ; Botulinum Toxins, Type A ; Clostridium botulinum ; genetics ; isolation & purification ; Gene Targeting ; Genotype ; Molecular Sequence Data ; Polymerase Chain Reaction ; methods ; Sequence Analysis, DNA

To analyze a suspected case of Clostridium botulinum food poisoning in Bayingolin Mongolian Autonomous Prefecture, Xinjiang and to help validating the diagnosis and providing technical support for clinical treatment. The basic information and clinical manifestations of food poisoning cases were investigated by using the epidemiological method of food safety accidents. The botulinum toxin genes in the samples were detected by real-time PCR and inoculation of KM mouse. The enriched bacteria were further purified and validated. PFGE and cluster analysis were performed on five isolates. Clostridium botulinum type A was detected in two homemade fermented bean samples and stool lavage fluid samples of three patients from enriched samples by toxin test and real-time PCR, and were further validated after isolation of Clostridium botulinum. PFGE showed 100% homology among five isolates. Five isolates of bacteria isolated from the stool lavage fluid of three patients and two homemade fermented bean curd were identified as the same source through PFGE. The cause of this food poisoning cases is food pollution of Clostridium botulinum type A.
Animals ; Clostridium botulinum/genetics* ; Feces ; Foodborne Diseases/epidemiology* ; Gerbillinae ; Humans ; Mice

Designed a pair of primers through modifying N-terminal bases (5bps) of gene after ATG but not changing amino acid, and amplified a smaller mutated gene sequnce (468bp) containing two protective antigenic determinants from pBlue-BoNTaHc, N-terminal codon of mutated gene fragment is changed from low to high frenqence in E. coli. Mutated gene was ligated into pGEM-T vector and sequenced, then, cloned into a expression plasmid pBV220. As a result, cloned gene was expressed in insoluble form by temperature inducing (from 30 degrees C to 42 degrees C) in E. coli. Expression product is 40% of total proteins and is of specific binding activity to antibody in ELISA. The successful modification and high level expression of protective fragment of botulinum neurotoxin serotype A(BoNTaHc468) gene is conducive to further study on antitoxin and vaccine.
Bacterial Vaccines ; immunology ; Botulinum Toxins, Type A ; genetics ; immunology ; Clostridium botulinum type A ; immunology ; Enzyme-Linked Immunosorbent Assay ; Escherichia coli ; genetics ; Plasmids ; Polymerase Chain Reaction ; Recombinant Proteins ; biosynthesis

A completely synthetic gene encoding the He domain of Clostridium botulinum neurotoxin serotype A (AHc, 1287 bp, 429 aa, -50 kD) was constructed with oligonucleotides. After expressed in Escherichia coli, soluble product AHc was gained and verified by SDS-PAGE and Western blot analysis. The expressive level of recombinant AHc in E. coli was very high (36%-53% of soluble total proteins) and the purified yield was more than 30 mg/L by one-step purification. Then, the purified AHc was used to vaccinate Balb/c mice, which developed a strong and specific immune response as expected following administration of AHe protein via the subcutaneous route. Results from BoNT/A neutralization assay showed that the serum from mice vaccinated with AHc contained high titer protective antibody. These results showed that the soluble, stable and high-levelly expressive AHc not only could be produced by the prokaryotic expression system built in our lab, but also owned strong immunogenicity to prepare antitoxin for treatment and as sub-unit candidate vaccine for prophylaxis against botulinum toxin serotype A.
Animals ; Antibodies, Bacterial ; blood ; Bacterial Vaccines ; genetics ; immunology ; Botulinum Toxins, Type A ; biosynthesis ; genetics ; immunology ; Botulism ; immunology ; prevention & control ; Clostridium botulinum type A ; genetics ; immunology ; Escherichia coli ; genetics ; metabolism ; Female ; Lymphocyte Activation ; Mice ; Mice, Inbred BALB C ; Recombinant Proteins ; biosynthesis ; genetics ; immunology ; T-Lymphocytes ; immunology ; Vaccines, DNA ; genetics ; immunology