Qingtang Fan

Role of Helicobacter pylori infection in pathogenesis of gastric carcinoma

Gastric cancer (GC) is one of the most common carcinoma and the second leading cause of cancer-related deaths worldwide. Helicobacter pylori (H. pylori) infection causes a series of precancerous lesions like gastritis, atrophy, intestinal metaplasia and dysplasia, and is the strongest known risk factor for GC, as supported by epidemiological, preclinical and clinical studies. However, the mechanism of H. pylori developing gastric carcinoma has not been well defined. Among infected individuals, approximately 10% develop severe gastric lesions such as peptic ulcer disease, 1%-3% progresses to GC. The outcomes of H. pylori infection are determined by bacterial virulence, genetic polymorphism of hosts as well as environmental factors. It is important to gain further understanding of the pathogenesis of H. pylori infection for developing more effective treatments for this common but deadly malignancy. The recent findings on the bacterial virulence factors, effects of H. pylori on epithelial cells, genetic polymorphism of both the bacterium and its host, and the environmental factors for GC are discussed with focus on the role of H. pylori in gastric carcinogenesis in this review.

The AcrAB-TolC Pump Is Involved in Multidrug Resistance in Clinical Shigella flexneri Isolates

The two multiple-antibiotic resistance (Mar) phenotypes (n = 8, respectively) and susceptible isolates (n = 4) of Shigella flexneri from China were characterized involving the efflux pump AcrAB-TolC. The accumulation of ciprofloxacin, acrAB-tolC PCR, and levels of mRNA with northern blots were performed in three groups. Sequencing of acrAB-tolC was performed in selected isolates. An efflux inhibition was performed with Phe-Arg-beta-naphthylamide. The accumulation of ciprofloxacin at steady state in susceptible isolates was significantly higher than that in the two Mar groups (p < 0.05). The level of accumulation in the Mar strains was increased upon the addition of the protonophore carbonyl cyanidem-chlorophenylhydrazone. The expression level of acrA mRNA in the Mar isolates was significantly higher than that in the susceptible isolates (p < 0.05). Mar strain H26 had a single-nucleotide substitution in locus 322(G-->T) of acrA, and Mar 0008 in locus 171(C-->A). The susceptible strain N15 had a base deletion in locus 36 (C) of tolC gene. The role of the inhibitors of efflux pumps was significant in some isolates with the high expression of Mar pump genes. In conclusion, overexpression of acrA gene leads to Mar in clinical isolates of S. flexneri, and ciprofloxacin acquired susceptible to S. flexneri with Phe-Arg-beta-naphthylamide.

Multi-drug Resistance and Characteristic of Integrons in Shigella spp.Isolated from China

OBJECTIVE To investigate the characteristic of integrons and the relationship between integrons and antimicrobial resistance in Shigella spp. METHODS Ninety Shigella strains (83 S. flexneri and 7 S. sonnei) were isolated from the stools of patients in China. Susceptibility to 8 antimicrobials was tested for all isolated strains. PCR, RFLP and sequencing analysis of integrons were applied to all of them. RESULTS High prevalence of multi-drug resistance (95.6%) was identified. Of the isolates 79 (87.8%) carried integrase genes of class 1 integron (3.3%), class 2 integron (10.0%) or both (74.4%). No intI3 was detected in the tested isolates. The prevalence of intI2 was significantly higher in isolates with multi-drug resistance to at least 3 antibiotics than that in isolates with resistance to 2 and less antibiotics (P<0.05). Gene cassettes dfrA17-aadA5, dfrA12-orfF-aadA2 of class 1 integron and dfrA1-sat1-aadA1 of class 2 integron were identified. CONCLUSION The class 2 integron may play a role in the emergence of multi-drug resistance in Shigella spp.

Serum inflammatory cytokine levels correlate with Hand-Foot-Mouth disease severity: A nested serial case-control study

Background Hand-food-mouth disease (HFMD) cases can be fatal. These cases develop rapidly, and it is important to predict the severity of HFMD from mild to fatal and to identify risk factors for mild HFMD. The objective of this study was to correlate the levels of serum inflammatory cytokines with HFMD severity. Methods This study was designed as a nested serial case-control study. The data collected included general information, clinical symptoms and signs, laboratory findings and serum cytokine levels. Results The levels of IL-4, IL-6, IL-10, TNF-α and IFN-γ in patients with severe HFMD were significantly higher than in mild patients during the 2nd to 5th day after disease onset. The levels of IL-4, IL-6, IL-10 and IFN-γ increased from the 2nd day to the 4th day and later decreased. The levels of TNF-α were high on the first two days and subsequently decreased. The changes of IL-10, TNF-α and IFN-γ in the controls were similar for all cases. The levels of IL-4, IL-6 and IL-17 in the controls were not significantly different with the progression of HFMD. Conclusions Our findings indicate that the IL-4, IL-6, IL-10, TNF-α and IFN-γ levels correlate with HFMD severity.

Helicobacter pylori cytotoxin-associated gene A protein upregulates α-enolase expression via Src/MEK/ERK pathway: Implication for progression of gastric cancer

Persistent infection with Helicobacter pylori confers an increased risk for the development of gastric cancer. In our previous investigations, we found that ENO1 was overexpression in cagA-positive H. pylori-infected gastric epithelial AGS cells by proteomic method, in contrast to the isogenic cagA knock out mutant H. pylori-infected cells. ENO1 is a newly identified oncoprotein overexpressed in some cancer. However, the relationship between H. pylori infection and ENO1 expression still remains undefined. The AGS gastric cancer cells were transfected with WT-cagA plasmid and PR-cagA plasmids. Expression of ENO1 mRNA and protein were measured by real-time quantitative PCR and western blot analysis. Signal protein inhibitor treatment was used to investigate the signal pathways. It was found that the ENO1 mRNA and protein overexpression levels were dependent on cagA gene expression and CagA protein phosphorylation. Further analysis revealed that the Src, MEK and ERK pathway was involved in this upregulation effect. Our data suggest that ENO1 was upregulated by CagA protein through activating the Src and MEK/ERK signal pathways, thereby providing a novel mechanism underlying H. pylori-mediated gastric diseases.

Transposition of ISEcp1 modulates blaCTX-M-55-mediated Shigella flexneri resistance to cefalothin

The aim of this study was to uncover the mechanisms underlying Shigella flexneri resistance to cefalothin. In this study, a resistance-related S. flexneri isolate, S. flexneri YDC, was obtained from S. flexneri mel-1998023/zz pre-incubated with cefalothin at a dose of 0.5 × the minimum inhibitory concentration. The ISEcp1 coding element was identified upstream of bla(CTX-M-55) in S. flexneri YDC. To further determine the role of ISEcp1 in S. flexneri resistance, plasmids containing bla(CTX-M-55) recombinant with or without the ISEcp1 sequence were constructed and named as pCTX and pISECTX, respectively. It was shown that Escherichia coli DH5α(pISECTX) was resistant to all β-lactams tested. In contrast, E. coli DH5α(pCTX) was sensitive to all except β-lactams cefazolin and cefalothin. In addition, reverse transcription PCR showed that expression levels of bla(CTX-M-55) were higher in E. coli DH5α(pISECTX). The Clinical and Laboratory Standards Institute (CLSI) assay demonstrated that extended-spectrum β-lactamase was only positively detected in E. coli DH5α(pISECTX) but not in E. coli DH5α(pCTX). Taken together, these results suggest that the translocated ISEcp1 element upstream of bla(CTX-M-55) is required for overexpression of bla(CTX-M-55), leading to cephalosporin resistance.

Production and delivery of Helicobacter pylori NapA in Lactococcus lactis and its protective efficacy and immune modulatory activity

Helicobacter pylori neutrophil-activating protein A subunit (NapA) has been identified as a virulence factor, a protective antigen and a potent immunomodulator. NapA shows unique application potentials for anti-H. pylori vaccines and treatment strategies of certain allergic diseases and carcinomas. However, appropriate production and utilization modes of NapA still remain uncertain to date. This work has established a novel efficient production and utilization mode of NapA by using L. lactis as an expression host and delivery vector, and demonstrated immune protective efficacy and immune modulatory activity of the engineered L. lactis by oral vaccination of mice. It was observed for the first time that H. pylori NapA promotes both polarized Th17 and Th1 responses, which may greatly affect the clinical application of NapA. This report offers a promising anti-H. pylori oral vaccine candidate and a potent mucosal immune modulatory agent. Meanwhile, it uncovers a way to produce and deliver the oral vaccine and immunomodulator by fermentation of food like milk, which might have striking effects on control of H. pylori infection, gastrointestinal cancers, and Th2 bias allergic diseases, including many food allergies.

An engineered food-grade Lactococcus lactis strain for production and delivery of heat-labile enterotoxin B subunit to mucosal sites

BackgroundRecent researches have been focusing on mucosal immune adjuvants, which play the key roles in mucosal immunization and have become the limitation for non-injected vaccine development. Escherichia coli heat-labile enterotoxin B subunit (LTB) was regarded as a promising mucosal adjuvant for its nontoxicity and potent activity. LTB preparation issues have always been recurring, in part owing to that the recombinant LTB expressed by E. coli does not act as its native form.ResultsWe constructed an engineered Lactococcus lactis strain using a food-grade expression system. The LTB secreted by the engineered strain was detected in the culture supernatant, constituting 10.3% of the supernatant proteins, and recognized by mouse anti-LTB antibodies. The engineered strain, co-administered orally to SPF BALB/c mice with a H. pylori vaccine candidate expressing Lpp20 antigen, could significantly enhance the Lpp20-induced mucosal SIgA antibody responses against H. pylori.ConclusionsThis is the first report that LTB was efficiently produced and delivered via using a food-grade lactococcal expression system, which offers a novel production and utilization mode of this crucial mucosal adjuvant. The engineered L. lactis strain secreting LTB has considerable potential for oral vaccine formulation owing to its outstanding safety, adjuvant activity and high-level production.