Prokaryotic expression and identification of HPV16 E7 protein / 病毒学报

HPV16 E7 fusion protein was expressed in E. coli BL21, and its applied value for HPV was evaluated. HPV16 E7 gene was amplified by PCR, and cloned into prokaryotic expression vector pGEX6p-1. The recombinant plasmid was transformed into E. coli BL21, and HPV16 E7 fusion was expressed through IPTG induction. The expressed product was analyzed by SDS-PAGE and Western blot, subsequently purified according to Glutathione Sepharose 4B purification procedure. An indirect ELISA with the purified fusion protein as the coating antigen was then established to detect E7 serum antibodies from mice immunized with recombinant Listeria monocytogenes delivering HPV16 E7. The results demonstrated that the soluble fusion protein was highly expressed at 25 degrees C after induction with 0.5 mM IPTG. Furthermore, the result of Western blot analysis showed that the fusion protein had good specific reaction with an anti-E7 monoclonal antibody. Indirect ELISA result confirmed that the fusion protein could detect the serum antibodies against E7 with a titer of 1:200. The expressed GST-E7 fusion protein was immunocompetent, which was useful in the research of E7 biological function and therapeutic vaccine.

Construction and immunogenicity of attenuated Salmonella typhimurium stably harbouring DNA vaccine against Newcastle disease virus / 病毒学报

The fusion protein (F) gene of Newcastle disease virus was amplified by polymerase chain reaction (PCR) from the recombinant plasmid pVAX1-F, and subcloned into eukaryotic expression vector pmcDNA3. 1+. The F gene was identified by sequencing. The recombinant plasmid was transformed into attenuated Salmonella typhimurium SL7207, and the recombinant was designated as SL7207 (pmcDNA3. 1-F). In vitro and in vivo experiments showed that the plasmid stability of pmcDNA3. 1-F was apparently higher than that of pcDNA3. 1-F in SL7207. In order to compare the immune response induced by these two re combinant bacteria, BALB/c mice were immunized orally with them at the dosage of 2 x 10(9) CFU respectively. Both SL7207(pcDNA3. 1-F) and SL7207(pmcDNA3. 1-F) initiated F-specific serum and mucosal antibodies in immunized mice. Furthermore, 4-day-old SPF chickens were immunized with SL7207(pcDNA3. 1-F) and SL7207(pmcDNA3. 1-F) at the dosage of 5 x 10(9) CFU and boosted two weeks later with the same dosage. Humoral and intestinal mucosal immune responses were observed and their levels were significantly higher than that of negative and positive controls. The result of protective efficacy showed that the chickens immunized with SL7207(pmcDNA3. 1-F) had the protective rate of 70.0%, higher than that of the SL7207 (pcDNA3. 1-F) with 50.0%. In summary, the DNA vaccine delivered by attenuated Salmonella typhimurium has good immunogenicity. A novel mucosal DNA vaccine has been developed and could be useful for controlling the infection and epidemic of Newcastle disease in the poultry.

Exploration on the Research-oriented Teaching Reform of Microbiology / 微生物学通报

This paper is discussed about course system construction of Microbiology, teaching method, in- struction means and experimental teaching mode. Teaching practice indicated that reform the pattern of Mi- crobiology educational mode can stimulate students’ interest in studying the course, cultivate their inde- pendent ability to solve questions, develop their creative thinking. It is an important way to train high-caliber talents.

Combination of direct-ELISA and PCR for the rapid detection and identification of Salmonella spp / 中华预防医学杂志

<p><b>OBJECTIVE</b>To develop a protocol for the rapid detection of Salmonellae.</p><p><b>METHODS</b>A mono-antibody-based direct-ELISA and PCR methods for the detection of Salmonella were developed previously. This study assessed the accuracy of both direct-ELISA and PCR methods for the rapid detection of Salmonella and set up a new detection protocol.</p><p><b>RESULTS</b>The sensitivity of the PCR method was higher than that of direct-ELISA method. In the 2002 spring physical examination for employees, 1 546 human fecal samples were examined by the combination of direct-ELISA and PCR method. Compared with the results of national standard method, the sensitivity and specificity of direct ELISA was 100% and 97.14%, respectively, while those of PCR method reached both 100%. It also indicated that combination use of two methods could give positive report within 40 hrs, and also achieve high sensitivity and specificity.</p><p><b>CONCLUSIONS</b>Based on the results obtained, a protocol for the rapid detection of Salmonella was developed. The first step is to us direct-ELISA method to screen the large number of samples, and then use PCR method to validate the ELISA positive samples, and the final step is, if needed, is to use the national standard method to determine the serotypes of Salmonellae.</p>

Enhanced Stability of Plasmid pcDNA3.1+ within Salmonella typhimurium by Downregulation of the Ampicillin Resistance Gene Expression / 微生物学通报

The high-copy-number plasmid pcDNA3.1+ is unstable within S almonella typhimurium. A novel plasmid pmcDNA3.1+ was constructed by removin g the promoter sequence of ampicillin resistance gene (bla gene) in plasmid pcDNA3.1+. In contrast to pcDNA3.1+, pmcDNA3.1+ was stable within Salmonel la typhimurium SL7207 in LB medium with or without ampicillin. Further experi ments showed the ?-lactamase activity of Salmonella typhimurium SL7207(pmc DNA3.1+) was apparently lowered than that of Salmonella typhimurium SL7207( pcDNA3.1+) and the high ampicillin concentration was maintained longer in LB me dium culturing Salmonella typhimurium SL7207(pmcDNA3.1+). When mice were a dministered with Salmonella typhimurium SL7207(pmcDNA3.1+) intraperitoneall y, more than 95% of Salmonella cells separated from the spleen still harbore d the plasmid pmcDNA3.1+ 7 days later; but 99% of Salmonella cells lost the plasmid pcDNA3.1+ at day 3 in mice innoculated with Salmonella typhimurium SL7207(pcDNA3.1+). By lowering the expression of bla gene, the rapid deco mposition of ampicillin in LB medium was avoided and the metabolic pressure was relieved for the host cells. This method offers a solution for the problem of t he instability of high-copy-number plasmid within Salmonella typhimurium.