Serum Helicobacter pylori FliD antibody and the risk of gastric cancer

Evaluation of the diagnostic value of FliD, a Helicobacter pylori flagellar protein

Novel immunodominant antigens are urgently required for diagnosis and vaccine of Helicobacter pylori(HP). FliD, an important colonization factor was cloned and expressed(rFliD) to evaluate the levels of specific-IgG, IgM and IgA antibodies in the serum of patients by ELISA. Rabbit anti-rFliD polyclonal antibody (pAb) was obtained by subcutaneous injections of rFliD. The rFliD-specific IFN-γ and IL-4 of peripheral blood mononuclear cells and CD4⁺ T cells from human were analyzed by enzyme-linked immunospot and flow cytometry. We found that the levels of rFliD-specific IgG, IgM and IgA were significantly higher in HP-infected-patients compared with healthy controls. IgG, IgM and IgA had diagnostic sensitivities of 92.6, 89.8 and 83.2%; specificities of 91.1, 88.7 and 64.6%; and areas under the receiver operating curves of 0.97, 0.96 and 0.92, respectively. Furthermore, rFliD-pAb was used in the immunohistochemical analysis of gastritis and gastric cancer tissues from patients infected with HP. The levels of rFliD-specific IFN-γ and IL-4 were significantly elevated in HP-infected patients and exhibited a T helper type 1-dominant subtype. These findings indicate that rFliD exhibits high validity as a biomarker in HP diagnosis and may also be a potent antigen for vaccine design due to its high cellular and humoral immune response.

Expression of the Campylobacter jejuni FliD protein and its reaction to chicken sera

Campylobacter is a leading causative pathogen of acute bacterial gastroenteritis among humans. Contaminated chicken products are regarded as major sources of human infection. The flagellar capping protein (FliD), which plays important roles in colonization and adhesion to the mucosal surface of chicken ceca, is conserved among Campylobacter jejuni strains. In this study, the recombinant C. jejuni FliD protein was expressed, purified and used as a coated protein to examine the prevalence of C. jejuni antibodies in chickens. The anti-FliD antibody was prevalent among chicken serum samples taken from different farms in the diverse regions of Jiangsu province by using enzyme-linked immunosorbent assay. The Campylobacter antibody was present in culture-negative chickens. No strong dose-response relationships were observed between serum FliD antibody levels and Campylobacter cultural status. These results provide a basis for further evaluating FliD as a vaccine candidate for broiler chickens or for examining host-C. jejuni interactions, with implications for improving food safety.

Clinical significance and diagnostic value of serum NSE, CEA, CA19-9, CA125 and CA242 levels in colorectal cancer

The present study investigated the value of combinations of five specific tumor biomarkers for the diagnosis of colorectal cancer (CRC): Neuron-specific enolase (NSE), carcinoembryonic antigen (CEA), cancer antigen (CA)19-9, CA125 and CA242. Associations between these markers and clinicopathological characteristics (including the Tumor-Node-Metastasis stage) were also assessed. Serum levels of the 5 markers were compared between 358 patients with CRC and 298 healthy individuals (CRC and control group, respectively). The NSE concentration of the CRC group was significantly higher compared with the control. Furthermore, patients at clinical stage III+IV exhibited significantly higher NSE levels compared with those at stage I+II. The serum NSE level of N⁺ patients was significantly higher compared with the N⁻ group, and the NSE level of M₁ patients was significantly compared with the M₀ group. NSE level was also significantly associated with tumor stage, lymph node metastasis, distant metastasis and hematochezia. The area under the receiver operating characteristic curve (AUC) for NSE in CRC was 0.766, which was significantly higher than that of the other four markers, which ranged from 0.560–0.682. The AUC of NSE, CEA, CA19-9, CA125, CA242 combined was significantly higher compared with any of the markers individually (range, 0.796–0.858). Therefore, serum NSE may be a good clinical tool for the auxiliary diagnosis of colorectal cancer. Besides, the combination of NSE, CEA, CA19-9, CA125 and CA242 was significantly more sensitive compared with NSE alone. Thus, the combined detection of the 5 tumor markers may be more useful for the diagnosis of CRC.

Clinical significance of serum neuron-specific enolase in gastric adenocarcinoma

As a biomarker, neuron-specific enolase (NSE) has been widely recognized in the diagnosis of benign diseases and malignant tumors. This study aimed to investigate the potential diagnostic value of NSE in patients with gastric adenocarcinoma.Serum levels of the NSE were compared between 219 patients with gastric adenocarcinoma and 298 healthy individuals, NSE and clinicopathological parameters were analyzed. Meanwhile, to evaluate the diagnostic capability of NSE, the receiver operating characteristic (ROC), and area under curve (AUC) was calculated.In the present study, the median serum NSE level of the patient group was 20.770 ng/mL, which was higher than that of the control group 15.625 ng/mL (P < .05). Serum NSE level in patients group compared with healthy control was statistically significant (P < .05). Serum NSE level was associated with pathological tumor-node-metastasis (pTNM) staging, lymph node metastasis, and distant metastasis in patients with gastric adenocarcinoma. Besides, the AUC of NSE in gastric adenocarcinoma was 0.742, which was higher than those of the other 3 markers (0.573-0.644). Besides, the AUC of the combined 4 markers was higher than any individual marker (0.778).Serum NSE detecting may have good value for diagnosis of gastric adenocarcinoma. Besides, the combination of NSE, CEA, CA19-9, and CA242 performed even better than any single marker. Thus, the combined detection of the 4 tumor markers may be more useful for the diagnosis of gastric adenocarcinoma.

Correlation study between serum neuro-specific enolase and gastric and colorectal cancers

This study investigated the diagnostic value of preoperative serum neuro-specific enolase (NSE) in gastric cancer (GC) and colorectal cancer (CRC), and the diagnostic viability of combined serum NSE, carcinoembryonic antigen (CEA), cancer antigen (CA)19-9, and CA242.Patients with GC and CRC, and a healthy control group (n = 666 and 266, respectively) were compared with regard to NSE, CEA, CA19-9, and CA242 serum levels. NSE was analyzed for associations with clinicopathological parameters. To estimate the diagnostic potential of NSE, a receiver operating characteristic curve was constructed and the area under the curve (AUCs) was calculated for different patient subgroups.The median serum NSE level of the tumor group (20.925 ng/mL) was significantly higher than that of the control (15.190 ng/mL). Serum NSE was associated with pathological tumor-node-metastasis staging, lymph node metastasis, distant metastasis, vascular invasion, and nerve infiltration. The area under the receiver operating characteristic curve (AUC) for NSE in GC and CRC (0.769) was higher than for the other 3 markers (0.571-0.680). The AUC of the combined markers was higher than for any of the markers individually (0.778-0.810).The AUC for NSE alone suggests it may be an independent tumor marker, and useful for diagnosis of GC and CRC. However, the AUC for combined NSE, CEA, CA19-9, and CA242 was higher and thus potentially more diagnostic value.

Crystal structure of the flagellar cap protein FliD from Bdellovibrio bacteriovorus

Bdellovibrio bacteriovorus is a predator bacterial species of the Deltaproteobacteria class that requires flagellum-mediated motility to initiate the parasitization of other gram-negative bacteria. The flagellum is capped by FliD, which polymerizes flagellin into a flagellar filament. FliD has been reported to function as a species-specific oligomer, such as a tetramer, a pentamer, or a hexamer, in members of the Gammaproteobacteria class. However, the oligomeric state and structural features of FliD from bacterial species outside the Gammaproteobacteria class are unknown. Based on structural and biochemical analyses, we report here that B. bacteriovorus FliD (bbFliD) forms a tetramer. bbFliD tetramerizes in a circular head-to-tail arrangement by inserting the D2 domain of one subunit into the concave surface of the second subunit generated between the D2 and D3 domains as observed in Serratia marcescens FliD. However, bbFliD adopts a more compact and flat oligomeric structure, which exhibits a more extended tetramerization interface flanked by two additional surfaces due to different intersubunit and interdomain organizations as well as an elongated loop. In conclusion, FliD from B. bacteriovorus, which belongs to the Deltaproteobacteria class, also produces a tetramer similar to FliD from Gammaproteobacterial species but adopts a unique species-specific oligomeric structure.

Structural analysis of the flagellar capping protein FliD from Helicobacter pylori

Helicobacter pylori is a pathogenic flagellated bacterium that infects the gastroduodenal mucosa and causes peptic ulcers in humans. FliD caps the distal end of the flagellar filament and is essential in filament growth. Moreover, FliD has been studied to diagnose and prevent H. pylori infection. Here, we report structure-based molecular studies of H. pylori FliD (hpFliD). A crystal structure of hpFliD at 2.6 Å resolution presents a four-domain (D2-D5) structure, where the D3 domain forms a central platform surrounded by the other three domains (D2, D4, and D5). hpFliD domains D2 and D3 structurally resemble those of FliD orthologs, whereas the D4 and D5 domains are exclusive to hpFliD. Moreover, our ELISA analysis using anti-H. pylori antibodies demonstrated that the hpFliD-specific D4 and D5 domains are highly antigenic compared to the D2 and D3 domains. Collectively, our structural and serological analyses underscore the structural role of hpFliD domains and provide a molecular basis for vaccine and diagnosis development.

Clinical significance and diagnostic capacity of serum TK1, CEA, CA 19-9 and CA 72-4 levels in gastric and colorectal cancer patients

Despite extensive progress in treatment for cancer in recent decades, the early diagnosis for gastric cancer (GC) and colorectal cancer (CRC) remains poor. In this study, we explore the diagnostic value of joint detection of thymidine kinase 1 (TK1), carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA 19-9) and carbohydrate antigen 72-4 (CA 72-4) in the diagnosis of GC and CRC, and to evaluated the relationship between TK1 expression and clinical pathological characteristics in the patients. Serum TK1, CA 19-9, CA 72-4 and CEA levels were measured in 169 patients with GC, 344 patients with CRC and 75 healthy controls using electro-chemiluminescence. The TK1 concentration was significantly higher in patients with cancer than in healthy controls and patients with clinical stage Ⅲ+Ⅳ had higher TK1 levels than clinical stage Ⅰ+Ⅱ (P<0.05). The levels of TK1 is significantly associated with tumor stage, lymph node metastasis, distant metastasis, tumor differentiation and age (P<0.05). When the tumor markers (TK1, CA 19-9 and CA 72-4) were detected respectively, the area under receiver operating characteristics curve (AUC) of TK1 for three cancers was the highest (0.823-0.895). However, the combination of AUC was higher than that for each tumor marker detected respectively (0.934-0.953), and the Hosmer-Lemeshow test showed an adequate model of calibration (P>0.05). Moreover, the AUCs varied significantly between the combination tests and single biomarker tests (Z test, P<0.01). In conclusion, serum TK1 may be an independent tumor marker for GC and CRC patients, and the combination of TK1, CA 19-9 and CA 72-4 and CEA performed even better. This study suggests that combination detection of four tumor markers may prove to be useful for the diagnosis of GC and CRC.