Salmonella enterica serovar Paratyphi A-induced immune response in Caenorhabditis elegans depends on MAPK pathways and DAF-16.

Salmonella enterica serovar Paratyphi A (S. Paratyphi A) is a pathogen that can cause enteric fever. According to the recent epidemic trends of typhoid fever, S. Paratyphi A has been the major important causative factor in paratyphoid fever. An effective vaccine for S. Paratyphi A has not been developed, which made it a tricky public health concern. Until now, how S. Paratyphi A interacts with organisms remain unknown. Here using lifespan assay, we found that S. Paratyphi A could infect Caenorhabditis elegans (C. elegans) at 25°C, and attenuate thermotolerance. The immune response of C. elegans was mediated by tir-1, nsy-1, sek-1, pmk-1, mpk-1, skn-1, daf-2 and daf-16, suggesting that S. Paratyphi A could regulate the MAPK and insulin pathways. Furthermore, we observed several phenotypical changes when C. elegans were fed S. Paratyphi A, including an accelerated decline in body movement, reduced the reproductive capacity, shortened spawning cycle, strong preference for OP50, arrested pharyngeal pumping and colonization of the intestinal lumen. The virulence of S. Paratyphi A requires living bacteria and is not mediated by secreting toxin. Using hydrogen peroxide analysis and quantitative RT-PCR, we discovered that S. Paratyphi A could increase oxidative stress and regulate the immune response in C. elegans. Our results sheds light on the infection mechanisms of S. Paratyphi A and lays a foundation for drugs and vaccine development.

[Construction and identification of ureB gene vaccine of H. pylori].

AIM: To clone ureB gene of H.pylori and construct its gene vaccine. METHODS: ureB gene was amplified by PCR from genome of H. pylori 11637 strain and subcloned into pMD18-T vector. The vector digested with restriction enzyme (Sal I and Bgl II) was inserted into pTCAE and transformed into E. coli DH5alpha. The positive recombinant plasmid identified by digesting with restriction enzyme (Sal I and Xho I) and sequencing named pT-ureB. The pT-ureB was transfected into CHO cells by electroporation method. The expression of UreB protein was detected by Western blot. RESULTS: The pT-ureB was obtained by cloning and recombinant DNA technique. The Western blot analysis showed that the expression of UreB protein (M(r)approximately 62,000) was detected in culture supernatant of CHO cells following transfection with pT-ureB. CONCLUSION: UreB DNA vaccine of H. pylori was successfully constructed. The expression of UreB protein can be detected in culture supernatants of transfected CHO cells.

Restriction fragment length polymorphism of adhesin gene hpaA from different Helicobacter pylori strains of Chongqing, China.

AIM: To assess the variability of adhesin gene hpaA between different Helicobacter pylori (H pylori) strains with PCR-restriction fragment length polymorphism (RFLP). METHODS: Twelve different H pylori strains were chosen to amplify the 710-bp segments of gene hpaA. These strains were NCTC11637, SS1; Chongqing clinical isolates CCS9801, CCS9802, CCS9803, CCS9806, CCS9809, CCS9810, CCS9813, which were gained from patients of gastritis; Mongolia gerbil adapted H pylori strains (abbreviation MG), which were gained from the following steps: gastric mucosal specimens of Mongolia gerbils infected by clinical isolate CCS9803 were cultured and detected, the positive H pylori strains were named as the first generation of Mongolia gerbil adapted H pylori strains (abbreviation MG1) and then were subcultured with healthy Mongolia gerbil to generate MG2, in turn to gain the ninth generation (abbreviation MG9). All hpaA segments, obtained from 12 different H pylori strains, were digested by HhaI and HaeIII individually and analyzed by agarose gel electrophoresis. RESULTS: In all 12 strains, the 710-bp PCR products were successfully amplified and products were cloned to pMD18-T vector respectively, then the recombinant plasmids were digested simultaneously with NcoI and XhoI to recover the small fragments. The objective fragments from 12 different H pylori strains digested with Hae III could be seen as 4 types of bands and 5 types with Hha I. According to the hpaA RFLP patterns, the 12 H pylori strains could be divided into 5 groups: group I, NCTC11637 and SS1; group II, CCS9809, which RFLP type digested with HaeIII was the same as strains of group I, but HhaI RFLP showed difference compared with the other groups; group III, CCS9810; group IV, CCS9803; group V: CCS9801, CCS9802, CCS9806, CCS9813, MG1, MG3 and MG9. The sequence data of 12 hpaA segments were analyzed by DNAsis software and it was observed that: (1) The homologies of base pair and amino acid sequence between strains NCTC11637, SS1, CCS9809 were 99.6% and 98.9%, respectively; (2) The homology of base pair and amino acid sequence between CCS9803 and CCS9810 was 97.7% and 99.1%; (3) That of the rest strains, CCS9801, CCS9802, CCS9806, CCS9813, MG1, MG3, MG9 reached 99.4% and 98.4%; (4) The base pair homologies between all hpaA fragments of different sources were higher than 94.6%, therefore the correspondence of deduced amino acid sequence was higher than 96.8% between each other. CONCLUSION: The gene hpaA from different H pylori strains revealed variation, and this might provide an effective method for molecular epidemiological survey of H pylori.

[Immunopotency of the recombinant urease B subunit vaccine of Helicobacter pylori after intranasal administration to mice].

AIM: To observe the immunopotency of the recombinant urease B subunit (rUreB) of Helicobacter pylori after intranasal administration to mice. MDTHODS: BALB/c mice were immunized intranasally with rUreB of 20 microg,10 microg and rUreB plus different adjuvants, such as cholera toxin B subunit (CTB), Escherichia coli heat labile enterotoxin B subunit (LTB) and carbopol respectively, four times at an intervals of 7 days. The serum and washing solution from gastric, intestinal, nasal and tracheal mucosas were collected in 7 days after final immunization. IgG and IgA antibodies specific for rUreB were detected by ELISA. RESULTS: The levels of IgA and IgG antibodies in sera every groups of mice immunized intranasally were significantly increased compared with control group (P<0.01). Only the levels of serum IgG of mice immunized with 20 microg dose were higher than those of mice immunized with 10 microg dose. Carbopol could enhance the level of IgA antibodies in washing solution from mouse gastric mucosa after intranasal immunization. The efficacy of LTB as a nasal mucosal immuno-adjuvant was stronger than that of CTB. CONCLUSION: CTB, LTB and carbopol can play the role of adjuvant in nasal mucosal immunization. Intranasal immunization with rUreB can induce not only serum IgG antibody production but also antibody responses of different mucosa. Thus intranasal inoculation is a convenient, effective and cheap immunization way.