Construction and characterization of bivalent vaccine candidate expressing HspA and Mr18000 OMP from Helicobacter pylori

Contrasting association of Helicobacter pylori oipA genotype with risk of peptic ulceration and gastric cancer

Helicobacter pylori OipA (outer inflammatory protein A) is an outer membrane protein that involves in the binding and colonization of the bacterium in the stomach. The oipA status is associated with the risk of peptic ulcerations (PUs) and gastric cancer (GC) diseases. However, the association trend with PUs compared to GC is often different and highly challenging. We therefore aimed to determine the presence of this genotype in Iranian strains and assess its association with the risk of PUs and GC in a larger number of samples. A total of 319 strains were obtained from 172 patients with non-atrophic gastritis (NAG), 52 with PUs and 95 with GC. The prevalence of the oipA⁺vs. oipA^- genotype was 67.7% (216/319). The total frequency of the oipA⁺vs. oipA^- genotypes in NAG, PUs, GC, non-peptic ulceration (including NAG and GC), and non-tumor (including NAG and PUs) groups was 121/172 (70.3%), 50/52 (96.2%), 45/95 (47.4%), 166/267 (62.2%), and 171/224 (76.3%), respectively. In multiple logistic regression analysis, the oipA⁺vs. oipA^- genotype showed a strong direct association with PUs; the OR_adj (95% CI) was 18.751 (4.421-79.531), (p = 0.00007). In contrast, it had a significant reverse association with GC; the OR_adj (95% CI) was 0.330 (0.179-0.607), (p = 0.00036). In the present study, we interestingly found a contrasting association of the H. pylori oipA genotype with the risk of PUs and GC in Iran. Therefore, the contrasting effect of this genotype may emphasize its independent role in predicting clinical outcomes.

Helicobacter pylori Recombinant CagA Regulates Th1/Th2 Balance in a BALB/c Murine Model

Purpose:Helicobacter pylori is recognized as one of the prevalent causes of human gastricinfection. In the present study, the role of mixed immunization with H. pylori lipopolysaccharide(LPS) and recombinant cytotoxin-associated gene A (rCagA) as a stimulator of host immuneresponses was determined.

Methods: BALB/c mice were immunized with different formulations by the systemic administrationat 14-day intervals. The effects of the formulations plus CpG adjuvants were assessed before andpost-immunization in separated studies. Moreover, the expression of Th1/Th2 cytokines wasquantified in sera of immunized mice using reverse transcription polymerase chain reaction (RTPCR)test and the protein levels confirmed with enzyme linked immunosorbent assay (ELISA).Finally, the specific antibody levels in sera were studied by ELISA and the tendency of cellularresponse was examined by IgG1/IgG2a ratio.

Results: Data of Western blotting verified the presence of constructed protein. Analysisof lymphocyte proliferation showed that CpG-conjugated rCagA increases lymphocytesproliferation compared to the control group. Also, it was shown that formulations containing LPSand rCagA promote a Th1 response indicated by interferon-gamma expression and induced Th1/Th2 balance. Additionally, the specific IgG1, total IgG and IgG2a levels elevated in response toall treatments. Ultimately, the IgG2a/IgG1 ratio in the mice immunized with rCagA-containingformulations increased.

Conclusion: These results indicated that rCagA protein carried with CpG adjuvant not onlymaintained its antigenicity throughout the experiment but also induced robust Th1-biasedimmune responses. Therefore, it holds promise for the production of an efficient vaccine against H. pylori infection.

Vibriosis in Fish: A Review on Disease Development and Prevention

Current growth in aquaculture production is parallel with the increasing number of disease outbreaks, which negatively affect the production, profitability, and sustainability of the global aquaculture industry. Vibriosis is among the most common diseases leading to massive mortality of cultured shrimp, fish, and shellfish in Asia. High incidence of vibriosis can occur in hatchery and grow-out facilities, but juveniles are more susceptible to the disease. Various factors, particularly the source of fish, environmental factors (including water quality and farm management), and the virulence factors of Vibrio, influence the occurrence of the disease. Affected fish show weariness, with necrosis of skin and appendages, leading to body malformation, slow growth, internal organ liquefaction, blindness, muscle opacity, and mortality. A combination of control measures, particularly a disease-free source of fish, biosecurity of the farm, improved water quality, and other preventive measures (e.g., vaccination) might be able to control the infection. Although some control measures are expensive and less practical, vaccination is effective, relatively cheap, and easily implemented. In this review, the latest knowledge on the pathogenesis and control of vibriosis, including vaccination, is discussed.

Immune effects of a bivalent expressed outer membrane protein to American eels (Anguilla rostrota)

The specific and non-specific immune parameters and protection of American eels (Anguilla rostrata) were evaluated after immunized eels with a bivalent expressed out membrane protein (OMP) of porin Ⅱ of Aeromonas hydrophila and ompS2 of Edwardsiella tarda. One hundred eighty eels were distributed into 3 equal groups and intraperitoneal (i.p) injection with phosphate-buffered saline (PBS group), formalin-killed-whole-cell (FKC) of A. hydrophila and E. tarda (FKC group) or the bivalent OMP (OMP group). The lymphocytes and red blood cells collected on 14, 21 and 42 days post-vaccination were used to evaluate the stimulation index (SI) and the sera collected on 14, 21, 28 and 42 days were used to assize the titers of specific antibody as well as lysozyme activity. Lysozyme activities in skin mucus, suspension of liver and kidney were also recorded on 14, 21 and 28 days. On 28 d post-vaccination, eels from all three groups were challenged by i.p injection of live A. hydrophila or E. tarda. The results show that, compared with the PBS group, proliferation of lymphocytes in OMP group was significantly (P < 0.05) enhanced on 21 days, and the serum titers of anti-A. hydrophila and anti- E. tarda antibody in eels of FKC and OMP group were significant increased (P < 0.05 or P < 0.01) on 14, 21 and 28 days. Activity of the lysozyme in serum, skin mucus, liver and kidney were significant changed (P < 0.05 or P < 0.01) between the three groups. Relative Percent Survival (RPS) after challenged with A. hydrophila on 28 days post immunization in two vaccinated groups vs. PBS group were 50%, and the RPS challenge E. tarda in FKC and OMP vs. PBS group were 50% and 37.5% respectively. These results suggest that American eels immunized with the bivalent OMP would positively affect specific as well as non-specific immune parameters and protect against infection by the two pathogens in freshwater farming.

The rOmp22-HpaA fusion protein confers protective immunity against helicobacter pylori in mice

Helicobacter pylori (H. pylori) plays an essential role in the development of various gastroduodenal diseases; however, no vaccines preventing H. pylori infection have been available now. This study was to evaluate the protective effect of rOmp22-HpaA fusion protein against H. pylori infection in mouse model and to screen the candidate to be used in the development of an oral vaccine against H. pylori. rOmp22, rHpaA, rOmp22+rHpaA, and rOmp22-HpaA groups were used to immunize mice with mLT63 as adjuvant by intragastric route, respectively, four times at 1-week intervals. Two weeks after last immunization, all of the animals were orally challenged with H. pylori NCTC11637 and then were killed after another 2 weeks. The mice gastric tissue of all groups was separated to detect the presence of infection by urease tests, to culture H. pylori, and to observe the histological characteristics. The protective effect against H. pylori challenge in mice immunized with rOmp22-HpaA fusion protein and mLT63 adjuvant was significantly higher than PBS and mLT63 control groups (P < 0.05), but no significant difference was detected among rOmp22, rHpaA, rOmp22+rHpaA, and rOmp22-HpaA groups (P > 0.05). rOmp22-HpaA fusion protein retained immunogenicity and could be used as an antigen candidate in the development of an oral vaccine against H. pylori infection.

Construction of an oral recombinant DNA vaccine from H pylori neutrophil activating protein and its immunogenicity

AIM: To construct a live attenuated Salmonella typhimurium (S. typhimurium) strain harboring the H pylori neutrophil activating protein (HP-NAP) gene as an oral recombinant DNA vaccine, and to evaluate its immunogenicity.

METHODS: By genetic engineering methods, the genomic DNA of H pylori was extracted as a template. The total length of the HP-NAP gene was amplified by polymerase chain reaction (PCR) and cloned into pBT vector for sequencing and BLAST analysis, then subcloned into a eukaryotic expression vector pIRES followed by PCR identification and restriction enzyme digestion. The identified recombinant plasmid pIRES-NAP was transfected into COS-7 cells for target fusion protein expression, and its antigenicity was detected by Western blotting. Then the recombinant plasmid was transformed into a live attenuated S. typhimurium strain SL7207 as an oral vaccine strain, and its immunogenicity was evaluated with animal experiments.

RESULTS: A 435 bp product was cloned using high homology with HP-NAP gene in GenBank (more than 98%). With identification by PCR and restriction enzyme digestion, a recombinant eukaryotic expression plasmid pIRES-NAP containing the HP-NAP gene of H pylori was successfully constructed. The expressed target protein had a specific reaction with H pylorii whole cell antibody and showed a single strip result detected by Western blotting. Oral immunization of mice with recombinant DNA vaccine strain SL7207 (pIRES-NAP) also induced a specific immune response.

CONCLUSION: The successful construction of HP-NAP oral DNA vaccine with good immunogenicity may help to further investigate its immunoprotection effects and develop vaccine against H pylori infection.

Research progress on Helicobacter pylori outer membrane protein

Helicobacter pylori (H pylori), one of the most common bacterial pathogens on human beings, colonizes the gastric mucosa. In its 95 paralogous gene families, there is a large outer membrane protein (OMP) family. It includes 32 members. These OMP are important for the diagnosis, protective immunity, pathogenicity of H pylori and so on. They are significantly associated with high H pylori density, the damage of gastric mucosa, high mucosal IL-8 levels and severe neutrophil infiltration. We introduce their research progress on pathogenicity.

Association of Helicobacter pylori with central serous chorioretinopathy: hypotheses regarding pathogenesis

Central serous chorioretinopathy (CSC) is a serous macular detachment that usually affects young people and leads fortunately to a spontaneous resolution and a good visual prognosis in most patients. Nevertheless, although in a small percentage of subjects only, it may also develop a chronic or progressive disease with widespread decompensation of the retinal pigment epithelium (RPE) and severe vision loss. The aetiopathogenesis of the disease is still not completely understood and no effective treatment is available at this time. However, an interesting association has been recently highlighted between CSC and the Helicobacter pylori infection. In particular, in a first case report recurrences of the disease were always associated with HP-positivity whereas improvements of both retinal findings and visual acuity were significantly correlated with a successful eradication of the bacterium using the conventional antimicrobial triple-therapy. In a second study, the prevalence of HP infection was found to be significantly higher in CSC-affected subjects compared to age- and sex-matched controls from the same country. Much speculation surrounds the role potentially played by HP in determining CSC. In particular, CSC seems not to be more a merely RPE disease but the final result of a general involvement of the choroidal microcirculation. In fact, several vascular abnormalities, such as localized vasoconstriction and impaired fibrinolysis, have been demonstrated during CSC whose "end-points" might be a focal occlusion of the choriocapillaries with decreased foveal choroidal blood flow, secondary RPE defects and serous macular detachment. Moreover, a HP-dependent immune mechanism, based on a "molecular mimicry" between pathogenic antigens expressed on the bacterium and homologous host proteins (e.g., those of the endothelial vascular wall), might also be involved in the pathophysiology of CSC. In this case, a genetically determined susceptibility of the subject could be an important and limiting factor. Although further multicenter, randomized, case-control trials are necessary to confirm the role potentially played by the HP infection in the pathogenesis of CSC, if this hypothesis would be confirmed in the near future, a novel antimicrobial approach to the disease might be possible waiting for a successful vaccine therapy that will surely stimulate the scientific interest of many authors.

Helicobacter pylori outer membrane proteins in diagnosis of Helicobacter pylori infection

AIM: To examine the serological response of patient with various upper gastrointestinal diseases and Helicobacter pylori (H. pylori ) infection to H. pylori outer membrane proteins (OMP) with M_r18 000 and 26 000 acquired by gene recombinant technique, and to determine its diagnostic significance.

METHODS: The recombinant vectors encoding OMP of H. pylori with M_r18 000 and 26 000 identified by restriction enzyme or PCR were used to transform and express in BL21 (DE3) E. coli respectively. After purification with Ni²⁺-NTA agarose resin, the colloid gold kits were prepared with purified recombinant proteins to detect H. pylori infection and disease associated with H. pylori by immunity-marker technology. We selected 150 patients with H. pylori infection and digestive symptoms without previous treatment, including chronic superficial gastritis (n = 60), duodenal ulcer (n = 30), gastric ulcer (n = 30), and gastric cancer (n = 30) during one year. Simultaneously, 33 cases without digestive symptoms and H. pylori infection were used as controls. All sera were collected and the antibody responded to specific proteins of H. pylori was tested with the colloid gold test kit. Taking as reference a combination of standard diagnostic methods (¹³C urea breath test, cultivate) and the classic enzyme-linked immunosorbent assay (ELISA) serological tests was compared with the results of this technique, and the sensitivity, specificity and accuracy of the colloid gold test were evaluated.

RESULTS: After purification with Ni²⁺-NTA agarose resin, the purities of recombinant fusion proteins were all about 95%. The ELISA results showed that recombinant fusion proteins could be recognized by monoclonal antibody of anti-H. pylori with Mr18 000 and 26 000 respectively. The results detected using colloid gold kits were as follows: all patients sera infected with H. pylori showed response to recombinant protein with M_r 26 000 were 94.0%, while 95.0%, 96.7%, 96.7% and 90.0% of patients with H. pylori-infected chronic superficial gastritis, duodenal ulcer, gastric ulcer, and gastric cancer respectively, showed responses. Compared with the serum-based ELISA results in detecting H. pylori-infection, there was no significant difference with the colloid gold kits (P > 0.05). The sensitivity, specificity, and accuracy of the rapid test kit with Mr 26 000 protein were 94.0%, 97.0%, and 94.5%, respectively; To recombinant protein with M_r18 000, 52.0%, 40.0%, 40.0%, 53.3% and 86.7%, of patients with H. pylori-infected chronic superficial gastritis, duodenal ulcer, gastric ulcer, and gastric cancer respectively, showed responses. There were a significant difference (P < 0.05) in the detecting rates of H. pylori infection between gastric cancer (86.7%) and the other diseases (43.3%). The results showed the colloid gold kits with Mr26 000 proteins of H. pylori could be used as a conventional examination method, with similar sensitivity and specificity as other conventional examination method, and simultaneously a significant association was found between the serologic response to M_r 18 000 OMP antigen and malignant outcome of H. pylori infection.

CONCLUSION: The two colloid gold kits with M_r18 000 and 26 000 proteins of H. pylori, can be a useful tool for detecting H. pylori infection, as well as predicting H. pylori related gastrointestinal diseases, such as gastric malignancy and peptic ulcer.

Construction of an oral recombinant DNA vaccine strain of live attenuated Salmonella typhimurium carrying H. pylori neutrophil activating protein

AIM: To construct a live attenuated Salmonella typhimurium (S. typhimurium) strain carrying H. pylori-neutrophil activating protein (HP-NAP) gene as an oral recombinant DNA vaccine.

METHODS: By genetic engineering method, a 435 bp napA gene (encoding HP-NAP) was subcloned into an eukaryotic expression vector pIRES. After sequencing and BLAST analysis, the identified recombinant plasmid was then transformed into a live attenuated S. typhimurium strain SL7207.

RESULTS: By using polymerase chain reaction (PCR) and restriction enzyme digestion, a recombinant eukaryotic expression plasmid pIRES-napA containing napA gene of H. pylori was constructed, and the recombinant plasmid was transformed successfully into the live attenuated S. typhimurium strain SL7207. Most of the H. pylori-napA sequences in recombinant plasmid pIRES-napA were homologized with that of SS1 strain reported by GenBank, and the homology of nucleotide and protein was 98%, respectively.

CONCLUSION: A recombinant live attenuated S. typhimurium strain carrying HP-NAP gene as DNA vaccine is successfully constructed. The results lay the foundation for developing multivalent oral DNA vaccine against H. pylori infection.

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