ABSTRACT
Protein drugs play an extremely important role in the prevention and treatment of diseases. But the properties of macromolecules hinder their effects on intracellular targets. Among the existing delivery strategies, penetrating peptides are more suitable for clinical research and treatment, and have gradually become the most important tool to deliver protein drugs. Therefore, the development of safe and effective penetrating peptide delivery vehicles is of great significance to the basic research and clinical application of biomedicine. In this paper, a self-releasing intracellular transporter LCA2 based on the enterotoxin A2 domain is designed. This carrier is composed of three parts: a linker, self-releasing enzyme sensitive sites (Cs), and the transmembrane domain LTA2. The fluorescent protein mCherry was used as the model protein to detect the properties of LCA2. The results of electrophoresis showed that the high-purity mCherryLCA2 fusion protein was obtained from the engineered bacteria containing pET24a(+)-ma2 recombinant plasmids, and mCherry could be effectively separated from LCA2 by low concentration trypsin. It was observed under a fluorescence microscope that LCA2 could transport mCherry into different types of cells. Flow cytometry has detected that the transport capacity of LCA2 has certain cellular differences. Confocal microscope fluorescence analysis and Western blotting results showed that the mCherry was transported to the endoplasmic reticulum by the LCA2 carrier, separated from LCA2 by cleavage of enzyme sensitive sites and released into the cell. The CCK-8 results showed that there was no significant change in cell viability within the dose range of 5-40 μg/ mL. These results demonstrate that LCA2 is a safe and effective self-releasing delivery vehicle, which can transport and release active proteins or protein drugs into cells.
ABSTRACT
The distinctive LT siRNAs were designed according to the LT sequence .During the process of cultivation ,siRNA targeting the LT gene ,non‐specific control siRNA ,negative control siRNA and culture medium were added into siRNA group (siRNA‐LT1 group , siRNA‐LT2 group) ,siRNA‐coa3 group ,siRNA‐NC group and blank control group ,respectively ,and three times in each group (1 nmol each time) .After siRNA added at the first time ,bacteria was collected in 45 min (A) ,90 min (B) and 135 min (C) time points .The expression of mRNA in three time points (A ,B and C) were detected by real‐time fluorescence quantitative PCR .The protein level of LT in siRNA‐LT1 group ,siRNA‐LT2 group and blank control group were detected by Western blot in three time points .Results The results of real‐time fluorescence quantitative PCR showed that inhibition of siRNA‐LT1 on the expression of LT mRNA at the three time points(A ,B and C)were 70 .9% ,70 .1% ,72 .5% respectively ,and inhibition of siRNA‐LT2 on the ex‐pression of LT mRNA at the three time points(A ,B and C)were 70 .1% ,69 .2% and 70 .5% respectively .In the three time points (A ,B and C)the inhibition rate of the expression of LT mRNA in siRNA‐LT1 group and siRNA‐LT2 group were statistically lower than that in the siRNA‐NC group ,siRNA‐coa3 group and blank control group (P<0 .05) .The results of Western blot showed that in siRNA‐LT1 group the inhibitory rate of expression of LT protein in the three time points were 43 .1% ,18 .4% and 5 .0% ,re‐spectively ;in the siRNA‐LT2 group were 38 .2% ,15 .4% and 30 .1% ,respectively .Conclusion The specific siRNA could inhibit the expression of LT gene in vitro .
ABSTRACT
Objective To establish a triplex TaqMan real-time PCR system containing internal amplification control(IAC)to detect cholera toxin gene ctxA and enterotoxigenic Escherichia coli(ETEC)heat-labile enterotoxin gene elt. Methods Primers and probes were designed based on the sequences of ctxA,elt and IAC. Both sensitivity and specificity were analyzed and interactions between different reactions were evaluated. Results This system showed that the sensitivity of ctxA was 94 copies/reaction while the elt 79 copies/reaction and the amplification efficiency were 94.7%and 98.1%,respectively. Under the ratio of copy numbers on gene ctxA to elt as between 1∶1-1∶10, when both targets were detected,with impact was less on each other. However,when the amount of elt or ctxA was 100 times of IAC,the amplification of IAC was significantly inhibited. Conclusion This system showed both satisfactory sensitivity and specificity, thus could be used to detect pathogenic bacteria in diarrhea stools. The detection of IAC could prompt the presence of PCR inhibitors in samples being tested.
ABSTRACT
Objective To establish a triplex TaqMan real-time PCR system containing internal amplification control(IAC)to detect cholera toxin gene ctxA and enterotoxigenic Escherichia coli(ETEC)heat-labile enterotoxin gene elt. Methods Primers and probes were designed based on the sequences of ctxA,elt and IAC. Both sensitivity and specificity were analyzed and interactions between different reactions were evaluated. Results This system showed that the sensitivity of ctxA was 94 copies/reaction while the elt 79 copies/reaction and the amplification efficiency were 94.7%and 98.1%,respectively. Under the ratio of copy numbers on gene ctxA to elt as between 1∶1-1∶10, when both targets were detected,with impact was less on each other. However,when the amount of elt or ctxA was 100 times of IAC,the amplification of IAC was significantly inhibited. Conclusion This system showed both satisfactory sensitivity and specificity, thus could be used to detect pathogenic bacteria in diarrhea stools. The detection of IAC could prompt the presence of PCR inhibitors in samples being tested.
ABSTRACT
Objective To evaluate the immunogenicity of group A and C meningococcal polysaccharides conjugates using different proteins as carriers. Methods Heat-labile enterotoxin B subunit (LTB)pentamer form was expressed in E. coli. The target protein was identified and purified by cation-exchange chromatography. Then biological activity of rLTB was tested using GM1-ELISA. GCMP was conjugated to rLTB with the chemical method (ADH). Furthermore, the mice were immunized with GAMp-TT/GCMP-TT conjugates and GAMP-TT/GCMP-rLTB conjugates via peritoneal. Finally the anti-polysaccharide antibody was detected. Results The GAMP-TT/GCMP-rLTB conjugate elicits remarkably higher serum antibodies in mice than GAMP-TT/GCMP-TT conjugate. Conclusion These results indicated that polysaccharide conjugates using different proteins as carriers were superior to those using only one protein as carrier.
ABSTRACT
In the present study, the expression, purification, toxicity detection and the adjuvant effect of the heat-labile enterotoxin in non-toxic mutant mLT63 of Escherichia coli were investigated, in which the inductive expression was performed under optimal condition for inductive expression and the toxicity of the products obtained from inductive expression were tested for toxicity after being purified and concentrated with affinity chromatography. BALB/c mice were immunized orally with the mutant mLT63 associated with Helicobacter pylori (Hp) subunit vaccine UreB, Omp11. After immunization, the specific antibody levels in serum, extract from gastric tissues and fecal extract were determind by means of ELISA assay and the results were subjected to statistical analysis. It was demonstrated that the mutant mLT63 of heat-labile entrotoxin of E.coli constructed in our laboratory devoided of any toxic effect as revealed by the rabbit ileal loop assay, but its adjuvant effect could be demonstrated in the associated immunization of mice with Hp subunit vaccine UreB and Omp11.
ABSTRACT
Enterotoxigenic Escherichia coli (ETEC) is an important pathogen responsible for secretory diarrhoea. The production of heat labile enterotoxin (LT), by ETEC, is largely responsible for the pathogenesis of diarrhoea. In the present study we investigated the effect of stress factors such as temperature, pH, osmotic stress and nutritional limitation on the production of LT by ETEC using in-house GMI-ELISA. Four strains of E. coli consisting, one standard strain MTCC 723 and three clinical isolates were used in the study. Maximum amount of LT (OD 3.285) was produced at 37 0 C followed by 40 0 C (OD 3.305). Growth of E. coli in medium with pH 8.6 resulted in maximum amount of LT production (OD 3.489). LT was not detectable when bacteria were grown in medium with pH ≤7.2 and ≥ 9.2. Sodium chloride concentration of 0.2 M stimulated maximum amount of LT production. Maximum amount of LT was produced when the bacteria were grown in medium containing 2.5g/l of glucose. All the stress factors had a significant effect on the LT production by E. coli , though quantitative differences in the various strains were observed.
ABSTRACT
Objective To construct a fusion expression vector with subunit B of Escherichia coli heat labile enterotoxin. Methods Gene encoding LTB without stop codon obtained by PCR was introduced to a linker and was recombined on vector Pinpoint Xa I through Eco RⅠ and Eco RⅤ sites and then fused with ureB. The recombinant was used to transform E. coli JM109. The expression of LTB was analyzed by SDS PAGE and Western blotting. Results The fusion expression plasmid was successfully constructed. The subunit B of urease of Helicobacter pylori (Hp) fusogenic protein with LTB with the ability to bind GM 1 and the reactogenicity with polyclonal antibodies against Hp was harvested. Conclusion The successfully constructed vector provides experimental base for the studies of intramolecular adjuvant vaccine.
ABSTRACT
Objective To investigate the fermentation conditions for the heat-labile enterotoxin B subunit (LTB) of genetic recombinant E.coli. Methods The effects of different kinds of media, the range of pH, the induction time, the glucose concentration, and the fed-batch on LTB level in 10-liter fermenter under the condition of cascade controlling dissolved oxygen content were analyzed. Results Under the established conditions, the cell output per liter was 40.5g, and the expression level was 30.6%. Conclusion The results indicate that the stable fermentation technology with high efficiency has been established.