| Present, the gene engineering vaccine is brought into full play more and more effect in presence and control diseases .Which is also the warm spots of life science research. But the expression vector systems that were reported in gene engineering operating are used antibiotic resistance as the stable expressive pressure of exogenous gene. It is easy to screen the cloning when antibiotics are the selection pressure. But the chemical resistant genes drift and scatter to environment uninterrupted, this phenomenon causes the micro-ecology is destroyed. This expression vector systems are not used on human and animals directly, they are far from the food grade. So we have to construct the new expression vector system which is symbol of non-antibiotic resistance and selection pressure. The expression vector system of non-antibiotic resistance is used a bacterial who is defect the house-keeping gene for receptor, cloned homologisation or heterogenesis integrated receptor defects gene in plasmid as the exogenous and stable pressure. They are developed quickly since Nakayama had constructed the Salmonella typhimurium expression vector system of non-antibiotic resistance that was used Asd gene as the selection pressure in 1998. Study on expression vector of food grade is the previous remarks and hot spot. The requirement of stratagem constructions are: the host is micro-organism; the vector adopts food grade selective marker. Now, more full-fledged systems are : Thymidylate synthase, ThyA, (Morona, 1991); Asd Gene (Nakayama, 1998);β-galactosidase (Hashiba, 1992); SSB Gene (Porter, 1990); D-xylose isomerase Gene (Prickly, 1995); Amber mutant (Alison, 1996); Ochre mutant (Chaillou, 1998); Nisin (Sorensen, 1999) and other vegetable factors.Thymidylate synthase, ThyA has the important effect in synthesis of DNA in vivo. It catalysis's dUMP changing into methylation dTMP, and it turns 5, 10-dimethyl tetrahydrofolic acid into 7, 8-dihydrofolic acid. The vicious saltant of Thymidylate synthase undertakes biosynthesis of DNA depending on exogenous thymidylate or exogenous thymidine. If the environment that saltant lives cannot provide enough thymidylate or thymidine, the saltant will dead. Under many circumstances, ThyA vicious saltant could drectly screen from antifolic. Pinter (1998) cloned ThyA gene from fondue lactobacilli and sequenced. R-constructed plasmids of PUC9,PUC18 and PKGS made expression of solubleness protein in ThyAˉE.coli. Ross (1990) cloned ThyA gene, constructed plasmids of pPR101,pPR102, expressed in E. coli.For the success of constructed food grade expression vector systems of lactobacilli, we could clone exogenous gene or related gene that makes for human being and animal into thisv-ector, and introduce into receptor of lactobacilli. Chicken take orally recombine engineering lactobacilli, recombine lactobacilli plant and multiply in chick's intestinal tract stably, recombine antigenand cytokine expressed and realest persistently. That stimulates organism to produce effective immunoprotection. In this experiment, base on the national and international experiments on gene engineering vaccine, we cloned GFP gene with molecular biology and constructed non-antibiotic resistance expression vector of SO7 gene. We translated recombine plasmid in ThyA gene defects acidophilia lactobacilli by electrotransfo-rmation, further detected the protective affection of E.tenella. In the end, we put gene engineering lactobacilli regressed chick's enteron, studied the colonization in chick's cecum. So there results could serve as a basis for further studies on the vivi-vector vaccine of lactobaeilli. |
PDF Full Text Request