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The Vi capsular polysaccharide vaccine is one of two vaccines against typhoid recommended worldwide and is the vaccine generally used in China. However, in recent years a Salmonella paratyphi A strain that is naturally devoid of capsule has caused frequent outbreaks of typhoid fever in Southern China, leading to the need for identification of additional antigens that could be incorporated into new vaccines. SpaO acts as a major invasion factor of Salmonella enterica spp. and H1a is the unique flagellin subunit ofS. paratyphi A. In this study, the two prokaryotic recombinant antigens, rSpaO and rH1a, were expressed and their immunogenicity was demonstrated by the slide agglutination test and Western blot assays. Using PCR and sequencing analysis as well as ELISA, we find that the spaO and h1a genes are widely distributed in 196 S. paratyphi A isolates (97.5 and 100%, respectively), with high expression frequencies for the SpaO (98.0%) and H1a (100%) antigens. The two genes also show high sequence conservation (similarities from 99.31 to 99.88% for both genes). In sera from 172 paratyphoid A patients, anti-SpaO and anti-H1a IgGs were detectable by ELISA, in 94.8 and 98.8% of patients, respectively. Furthermore, 41.7-66.7% of mice immunized with rSpaO or rH1a alone were protected against subsequent infection, and the protection rate rose to 75.0-91.7% in mice co-immunized with the two antigens. As the spaO and h1a genes of S. paratyphi A are sequence conserved, extensively distributed and highly expressed, the rSpaO and rH1a immunogens should be considered in the development of novel vaccines to prevent S. paratyphi A-caused typhoid fever.

Objective: To determine the frequency of mce gene in Leptospira interrogans, and to investigate the gene transcription levels of L. interrogans before and after infecting cells., Methods: The segments of entire mce genes from 13 L.interrogans strains and 1 L.biflexa strain were amplified by PCR and then sequenced after T-A cloning. A prokaryotic expression system of mce gene was constructed; the expression and output of the target recombinant protein rMce were examined by SDS-PAGE and Western Blot assay. Rabbits were intradermally immunized with rMce to prepare the antiserum, the titer of antiserum was measured by immunodiffusion test. The transcription levels of mce gene in L.interrogans serogroup Icterohaemorrhagiae serovar lai strain 56601 before and after infecting J774A.1 cells were monitored by real-time fluorescence quantitative RT-PCR., Result: mce gene was carried in all tested L.interrogans strains, but not in L.biflexa serogroup Semaranga serovar patoc strain Patoc I. The similarities of nucleotide and putative amino acid sequences of the cloned mce genes to the reported sequences (GenBank accession No: NP712236) were 99.02%-100% and 97.91%-100%, respectively. The constructed prokaryotic expression system of mce gene expressed rMce and the output of rMce was about 5% of the total bacterial proteins. The antiserum against whole cell of L.interrogans strain 56601 efficiently recognized rMce. After infecting J774A.1 cells, transcription levels of the mce gene in L.interrogans strain 56601 were remarkably up-regulated., Conclusion: The constructed prokaryotic expression system of mce gene and the prepared antiserum against rMce provide useful tools for further study of the gene function.

Objective: To study the immunogenicity and immunoprotection of the recombinant expressing product (rSpaO) of S. paratyphi A spaO gene, and to demonstrate the frequencies of spaO gene carrying and expressing in S. paratyphi A isolates., Methods: The spaO gene of a clinical S. paratyphi A strain JH01 was amplified and then cloned. After sequencing of the cloned spaO gene, a prokaryotic expression system of the gene was constructed. SDS-PAGE were applied to examine the rSpaO expression. Ni-NTA affinity chromatography was performed to collect rSpaO. Immunogenicity of rSpaO was determined by Western blot assay. A PCR assay and an ELISA were established to respectively detect the carrying and expressing frequencies of the spaO genes in 98 S. paratyphi A isolates. The immunoprotective effects of rSpaO in S. paratyphi A strain 50001 infected mice were observed., Results: In comparison with the reported corresponding sequences, the nucleotide and putative amino acid sequence homologies of the cloned spaO gene were 99.45%-99.89% and 99.01%-100%, respectively. The expression output of rSpaO was approximately 75% of the total bacterial proteins. S. paratyphi A antiserum could recognize as well as combine with rSpaO. rSpaO could efficiently induce rabbits to produce specific antibody. 94.9% (93/98) of the S. paratyphi A isolates had spaO gene and 91.4% (85/93) of the spaO+ strains could express SpaO. 58.3% and 50.0% of the mice that oral-taken or subcutaneous injected with 500 microg of rSpaO for immunization were survival after challenged by lethal dose of S. paratyphi A strain 50001. When co-immunized with 5 microg rLTB, the survival rates of the mice increased to 88.3% and 75.0%, respectively., Conclusion: The S. paratyphi isolates had relatively high carrying and expressing frequencies of spaO gene. rSpaO showed a fine immunogenicity and a certain immunoprotective effect, which could be used as an antigen candidate for developing genetic engineering vaccine of S. paratyphi.

Objective: To determine the immunoprotective effects of rUreB and rHpaA bivalence genetic engineering vaccine with inner adjuvant of rLTB on BALB/c mice against H.pylori strain SS1 infection., Methods: rUreB, rHpaA, rLTB-rUreB-rHpaA, rLTKA63, rLTB and rLTB were collected by NTA-Ni affinity chromatography. Western blot was applied to demonstrate the immunoreactivity of the recombinant protein antigens. Adjuvant activities of rLTB, rCTB and rLTB-rUreB-rHpaA were determined by GM1-ELISA. H.pylori strain SS1-infected BALB/c mouse modal was established to measure immunoprotective effects of different compositions of antigens and adjuvants. H.pylori in gastric biopsy specimens was examined by routine isolation method and silver staining method. Two ELISAs were established to detect specific S-IgA in gastric juices and specific IgA in sera of the immunized mice., Results: rUreB, rHpaA and rLTB-rUreB-rHpaA were recognized by commercial antibody against whole cell of H.pylori and were able to combine to the bovine GM1. The protective rate in the mice immunized with single rUreB or rHpaA was lower than 70%. When using rUreB or rHpaA plus rLTB or rCTB, the positive rates increased to 75.0%-83.3%. With different combination of antigens and adjuvants, the immunoprotective rate of rLTB-jrUreB-rHpaA was as high as 100%, and then was 91.7% for rUreB+rHpaA+rCTB+rLTKA63 and was 90.9% for rUreB+rHpaA+rLTB. Both the rLTB and rCTB showed remarkable effects to induce specific IgA in sera and specific S-IgA in gastric juices of the immunized mice, and the former showed stronger S-IgA-inducing ability than the latter. The positive rates of specific IgA were basically identical to the corresponding mouse immunoprotective rates. S-IgA positive rates specific to rUreB and rHpaA in rLTB-rUreB-rHpaA immunized mice were 100% and 91.7%, respectively., Conclusion: The rUreB and rHpaA possess qualified immunoreactivity and antigenicity. The rLTB and rCTB can show adjuvant activity of mucosal immunization. The high immunoprotective rate of Helicobacter pylori UreB and HpaA bivalence recombinant vaccine with inner adjuvant in mice is associated with high dosage of rLTB, larger molecular weight of the antigen and the high levels of local specific S-IgA.

Aim: To construct a prokaryotic expression system of a Helicobacter pylori (H pylori) cagA gene fragment and establish enzyme-linked immunosorbent assays (ELISA) for detecting CagA and its antibody, so as to understand the manner in which the infection of CagA-expressing H pylori (CagA(+) H pylori) isolates cause diseases., Methods: H pylori strains in gastric biopsy specimens from 156 patients with positive results in rapid urease test were isolated. PCR was used to detect the frequency of cagA gene in the 109 H pylori isolates and to amplify a 2 148-bp fragment (cagA1) of cagA gene from a clinical strain Y06. A prokaryotic expression system of cagA1 gene was constructed, and the expression of the target recombinant protein (rCagA1) was examined by SDS-PAGE. Western blotting and immunodiffusion assay were employed to determine the immunoreactivity and antigenicity of rCagA1, respectively. Two ELISAs were established to detect CagA expression in 109 H pylori isolates and the presence of CagA antibody in the corresponding patients' sera, and the correlations between infection with CagA(+) H pylori and gastritis as well as peptic ulcer were analyzed., Results: Of all the clinical specimens obtained, 80.8% (126/156) were found to have H pylori isolates and 97.2% of the isolates (106/109) were positive for cagA gene. In comparison with the reported data, the cloned cagA1 fragment possessed 94.83% and 93.30% homologies with the nucleotide and putative amino acid sequences, respectively. The output of rCagA1 produced by the constructed recombinant prokaryotic expression system was approximately 30% of the total bacterial protein. rCagA1 was able to bind to the commercial antibody against the whole-cells of H pylori and to induce the immunized rabbits to produce antibody with an immunodiffusion titer of 1:4. A proportion as high as 92.6% of the H pylori isolates (101/109) expressed CagA and 88.1% of the patients' serum samples (96/109) were CagA antibody-positive. The percentage of CagA(+) H pylori strains (97.9%) isolated from the biopsy specimens of peptic ulcer appeared to be higher than that from gastritis (88.5%), but the difference was not statistically significant (chi (2)=3.48, P>0.05)., Conclusion: rCagA1 produced by the prokaryotic expression system constructed in this study possesses good immunoreactivity and antigenicity, and the established ELISAs can be used to detect CagA of H pylori and its antibody. H pylori isolates show high frequencies of cagA gene and CagA expression, but the infections by CagA(+) H pylori strains are not the most decisive factors to cause gastric diseases.

Aim: To construct a recombinant prokaryotic expression vector inserted with Helicobacter pylori vacA gene and identify the immunity of the expressed recombinant protein, and to determine prevalence of vacA-carrying/VacA expressing H pylori isolates and seroprevalence of specific ant-VacA antibody in H pylori infected patients., Methods: Polymerase chain reaction technique was used to amplify complete vacA gene of H pylori strain NCTC11637 and to detect vacA gene in 109 H pylori isolates. The amplification product of the complete vacA gene was sequenced after T-A cloning. A recombinant expression vector inserted with a complete vacA gene fragment, named as pET32a-vacA, was constructed. Expression of the target recombinant protein VacA (rVacA) was examined by SDS-PAGE. Western blot using commercial antibodies against whole cell of H pylori and an immunodiffusion assay using self-prepared rabbit anti-rVacA antibody were applied to determine immunoreaction and antigenicity of rVacA. Two ELISA methods were established to detect VacA expression in H pylori isolates and the specific anti-VacA antibody in sera from 125 patients infected with H pylori., Results: In comparison with the reported corresponding sequences, homologies of nucleotide and putative amino acid sequences of the cloned vacA gene were 99.82% and 100%, respectively. The constructed recombinant prokaryotic expression system efficiently produced rVacA. rVacA was able to combine with the commercial antibodies against whole cell of H pylori and to induce the immunized rabbit to produce specific antibody with an immunodiffusion titer of 1:4. All tested H pylori isolates carried vacA gene, but only 66.1% expressed VacA protein. Of the serum samples tested, 42.4% were positive for specific anti-VacA antibody., Conclusion: A prokaryotic expression system of H pylori vacA gene was successfully constructed. The expressed rVacA can be used to detect specific anti-VacA antibody in human and to prepare antiserum in animals. The high frequency of vacA gene in H pylori isolates, but with a low frequency of VacA expression and specific anti-VacA antibody in H pylori infected patients implies that VacA is not an ideal antigen for H pylori vaccine.

Objective: To determine cagA/vacA dominant genotypes of Helicobacter pylori in patients suffering from chronic gastritis (CG) or peptic ulcer (PU), and to understand the correlation of different genotype H. pylori infection, coinfection and the gastroduodenal diseases., Methods: H. pylori strains were isolated from antrum and corpus samples on 42 patients with CG and 36 patients with PU. Polymerase chain reaction was used to detect cagA and the s and m regions of vacA in 156 H. pylori isolates from both antrum and corpus. The distribution of H. pylori genotypes and coinfection in CG and PU was analyzed., Results: Almost all of the isolated H. pylori strains were cagA positive. In region of vacA, only one genotype of signal region (s1a) and four genotypes of the middle region (m1, m2, m1b and m1b-m2) were found. The proportions of s1a/m1, s1a/m2, s1a/m1b, s1a/m1b-m2 and coinfection of multiple H. pylori strains in 78 isolates from antrum samples were 6.4%, 55.1%, 26.9%, 1.3% and 3.8%; and the related proportions of those from corpus samples were 6.4%, 53.8%, 25.6%, 3.8% and 5.1%, respectively. Sixteen (20.5%) patients had multiple H. pylori strains with different cagA and vacA genotypes, and multiple samples were better than single sample taken from one stomach to increase the positive proportion of coinfection., Conclusion: cagA(+) s1a/m2 was the dominant genotype of H. pylori in the CG or PU patients followed by cagA(+) s1a/m1b in the Zhejiang area of China. Some of the patients were coinfected with multiple H. pylori strains of different cagA and vacA genotypes. However, there was no significant correlation between the genotypes or mixed infection with multiple strains, CG or PU.

Objective: To determine vacA dominant genotypes of Helicobacter pylori in patients with peptic ulcer (PU) or chronic gastritis (CG)., Methods: H.pylori strains were isolated from mucosa samples of gastric antrum and corpus of patients suffering from PU (n=29) or CG (n=34), 126 strains of H.pylori were selected for PCR to detect s and m regions in vacA gene of the isolates. Parts of the amplification products were sequenced after T A cloning. The correlation between infection or coinfection with different vacA genotypes of H.pylori and different gastroduodenal diseases was further analyzed., Results: The positive amplification products of vacA gene, s and m regions, were found in the DNA samples of all the isolates. In these products, s1a/m1, s1a/m2, s1a/m1b and s1a/m1b m2 genotypes of vacA gene were detected and s1b and s2m1a genotypes absent. Proportions of the s1a/m1, s1a/m2, s1a/m1b and s1a/m1b-m2 genotypes were 7.1% (9/126), 61.9% (78/126), 29.4% (37/126) and 1.6% (2/126), respectively. 17.5% (11/63) of the patients were confirmed to be coinfected with different genotype H.pylori strains. No statistical differences were found in the distribution of different genotype H.pylori strain infection in the gastric diseases (P>0.05). In comparison with the reported sequences of H.pylori strain 60190 with s1a genotype and strain 87-203 with m2 genotype, homologies of the nucleotide sequences of s1a PCR products from 6 strains of H.pylori isolates and m2 PCR products from 4 strains of H.pylori isolates were 93.15% approximate, equals 94.86%and 93.63% approximate, equals 97.61%, respectively., Conclusion: H.pylori with s1a/m2 or s1a/m1b are the dominant genotypes in the PU or GC patients in Zhejiang area. The nucleotide sequences of partial amplification products from the vacA dominant genotypes of H.pylori show high homology compared with the reported sequences. Part of the patients may be coinfected with different vacA genotypes of H.pylori.