Study on the safety and immunogenicity of enterotoxigenic Escherichia coli recombinant active vaccine / 中华流行病学杂志

<p><b>OBJECTIVE</b>To study the safety, immunogenicity on the enterotoxige Escherichia coli (E. coli) recombinant active vaccine FE3 and FE16.</p><p><b>METHODS</b>Toxicity and immunogenicity of the vaccine were determined by experiments on enterotoxigenic E. coli toxicity and immunological experiments on rabbits and mice.</p><p><b>RESULTS</b>The results of an toxicological experiments were negative. The agglutination titer of antibodies against the S. flexneri 2a and enterotoxigenic E. coli plamid antigen were all higher than 1:640 and 1:1280 in the sera of rabbits. IgG in the serum went up remarkably, while sIgA against CFA/I was also decteted in the dejecta of mice immunized with active bacteria either orogastrically or intranasally. Simultaneously, sIgA was not detected in the dejecta of mice immunized with inactive bacteria either orogastrically or intranasally.</p><p><b>CONCLUSION</b>The enterotoxigenic E. coli recombinant active vaccine showed good safety and immunogenicity, inducing both humoral and mucosal immunity in mice.</p>

Expression of human mu-opioid receptor cDNA in CHO cell / 生物工程学报

Opioid receptor, is classified into three subtypes, mu, kappa and delta, with the mu-type receptor plays important roles in opioid analgesia and opioid addiction. The cDNA encoding mu-type receptor was obtained by RT-PCR from human brain RNA and was cloned into pcDNA3.1(+). The resultant recombinant plasmid pcDNAMORs were transfected into CHO cells by liposome. After PCR identification, the positive clone were treated with agonist and antiagonist were tested for their competence of signal transduction. CHO cells that contained mu-opioid receptor in the expression vector pcDNA3.1(+) acquired naloxone-blockable high-affinity specific binding of morphine and DAMGO. The concentration of cAMP in CHO cells transfected with pcDNAMOR was reduced after binding to morphine and DAMGO, and increased after binding naloxone. These results indicate that the mu-type receptor expreesd on the CHO cell has similar biological property as the nature receptor. The availability of these specific cell lines will facilitate the drug development and promote our understanding the mechanism underlying opiate addiction.

Construction of the attenuated Salmonella typhimurium strain expressing Helicobacter pylori conservative region of adhesin antigen / 生物工程学报

To construct a non-resistance and attenuated Salmonella typhimurium strain which expresses conservative region of adhesin(AB) of Helicobacter pylori(Hp). The AB gene was amplified by PCR and inserted into the expression vector pYA248 containing asd gene and was introduceded into the delta Cya, delta Crp, delta Asd attenuated Salmonella typhimurium strain by twice transformations, which is a balanced lethal recombinant. Bridged ELISA method was used to measure AB expressed in sonicate and culture supernatant. According to Meacock's way and growth curve, stability of the recombinant is evaluated. Semi-lethal capacity test was used to evaluate the safty of recombinant. Results showed S. typhimurium X4072(pYA248-AB) was constructed successfully, recombinant X4072(pYA248- AB) content of supernatant serum was higher than that of thallus lytic liquor confirmed by bridged ELISA, and after recombinant pYA248- AB cultured 100 generation without selection pressure, all the recombinant germ selected randomly can grow, and the AB antigen was positive by ELISA detection. The growth curve of the recombinant germ showed that the growth state of X4072(pYA248) and X4072(pYA248- AB) were coincidence on the whole, and the survival rate of C57BL/6 was still 100%, 30 days after taking X4072(pYA248- AB) 1.0 x 10(10)cfu. orally. Non-resistance S. typhimurium X4072(pYA248- AB) was constructed successfully. The recombinant plasmid was stable indicated by in vitro experiment. And the recombinant strain was safe confirmed by animal experiment. This live vaccine strain is worthy to be considered as a new live oral vaccine candidate against Hp infection.

Comparion of the expression of CS3 fimbriae in different vector systems / 军事医学科学院院刊

Objective:To choose the best vector for the expression of CS3 fimbriae. Methods: The CS3 operon was cloned into different plasmid vectors such as pUC19 and pTrc99A. The expression of CS3 was monitored by whole-cell ELISA and SDS-PAGE analysis. The assembly of CS3 fimbriae was detected with electron microscopy. Results:The expression level of CS3 fimbriae using plasmid pUC19 as carrying vector was the highest, and the insertion orientation of CS3 gene into the plasmid has a little effect on its expression level. The expression of CS3 fimbriae was confirmed by SDS-PAGE analysis and electron microscopy.Conclusions:The promotor of CS3 itself played the key role in the expression of CS3 fimbriae and the copy number of plasmid was the main factor to affect the expression level.

Utilization of ?-Red Recombination System and Balanced Lethal System to Reconstruct the Plasmid with Antibiotic Resistant Gene Using in Live Vaccine / 微生物学通报

Recombination plasmid pMM085 possessed both immunogens heat-labile enterotoxin(LT) and fimbriae antigen K88 of enterotoxigenic Escherichia coli (ETEC). Althouth vaccine strain MM-3 carrying pMM085 had good effect to protect piglets against diarrhea due to ETEC infections,it was not ideal live vaccine for pMM085 bringing chloramphenicol resistance gene (cat). To solve the problem,the host-plasmid balanced lethal system was introduced which including the replacement of cat gene by asd gene and transformation the new plasmid to the strain X6097 which asd gene was knocked out in its chromosome. Considering pMM085 was a big plasmid (23kb) and traditional genetic manipulations was not easy to carry on,?-Red recombination system was adopt in this work to realize the replacement of cat gene by asd gene. The results indicated that ?-Red recombination system was convenient and efficient to reconstruct big plasmid.

A QUICK AND PRECISION METHOD TO CONSTRUCT ESCHERICHIA COLI HISTIDINE AUXOTROPH / 微生物学通报

Red in vivo recombination is a new kind of genetic engineering technique based on homologous recombination. In this work, plasmid pKD46 which expresses Red recombination proteins is transferred into Escherichia coli strain DH5?.The kanamycine resistant gene is generated by PCR by using primers with homology to hisDCB gene of E.coli chromosome. Thus, the hisDCB gene was replaced with kanamycine resistant gene by the plasmid recombination system, then the resistant gene was eliminated by a helper plasmid encoding the FLP recombinase. At last, a E.coli histidine auxotroph which is sensitive to kanamycine was got. The results indicate that Red in vivo recombination is a convenient method to construct auxotrophs.