Production of polyclonal antibody against alkyl hydroperoxide reductase of Helicobacter pylori and its antigenicity

The Diagnostic Tests for Detection of Helicobacter pylori Infection

Helicobacter pylori causes one of the most common infections in human populations. The role of this bacterium in chronic gastritis, gastric ulcer, gastric cancer, as well as extra-digestive diseases such as ischemic heart disease and chronic obstructive pulmonary diseases, is well known. Prevention and control of these diseases can occur by early diagnosis and eradication of H. pylori infection. At present, different methods have been established to detect H. pylori infection. The biopsy-based tests, which are known as invasive methods, such as rapid urease test and histology, have the highest specificity among the others. Similarly, culture of biopsy samples is used for diagnosis of H. pylori infection. It has a high specificity value, and also allows us to perform antibiotic sensitivity testing. On the contrary, polymerase chain reaction and other molecular methods have good sensitivity and specificity, and can be used for detection of H. pylori infection, its virulence factors, and eradication success after treatment. While serological tests are more appropriate for epidemiological studies, their main weakness for clinical use is low specificity. Overall, specificity and sensitivity, cost, usefulness, and limitation of tests should be considered for selection of detection methods of H. pylori in each country.

Clinical proteomics identifies potential biomarkers in Helicobacter pylori for gastrointestinal diseases

The development of gastrointestinal diseases has been found to be associated with Helicobacter pylori (H. pylori) infection and various biochemical stresses in stomach and intestine. These stresses, such as oxidative, osmotic and acid stresses, may bring about bi-directional effects on both hosts and H. pylori, leading to changes of protein expression in their proteomes. Therefore, proteins differentially expressed in H. pylori under various stresses not only reflect gastrointestinal environment but also provide useful biomarkers for disease diagnosis and prognosis. In this regard, proteomic technology is an ideal tool to identify potential biomarkers as it can systematically monitor proteins and protein variation on a large scale of cell’s translational landscape, permitting in-depth analyses of host and pathogen interactions. By performing two-dimensional polyacrylamide gel electrophoresis (2-DE) followed by liquid chromatography-nanoESI-mass spectrometry (nanoLC-MS/MS), we have successfully pinpointed alkylhydroperoxide reductase (AhpC), neutrophil-activating protein and non-heme iron-binding ferritin as three prospective biomarkers showing up-regulation in H. pylori under oxidative, osmotic and acid stresses, respectively. Further biochemical characterization reveals that various environmental stresses can induce protein structure change and functional conversion in the identified biomarkers. Especially salient is the antioxidant enzyme AhpC, an abundant antioxidant protein present in H. pylori. It switches from a peroxide reductase of low-molecular-weight (LMW) oligomers to a molecular chaperone of high-molecular-weight (HMW) complexes under oxidative stress. Different seropositivy responses against LMW or HMW AhpC in H. pylori-infected patients faithfully match the disease progression from disease-free healthy persons to patients with gastric ulcer and cancer. These results has established AhpC of H. pylori as a promising diagnostic marker for gastrointestinal maladies, and highlight the utility of clinical proteomics for identifying disease biomarkers that can be uniquely applied to disease-oriented translational medicine.

Antigenic diversity among Portuguese clinical isolates of Helicobacter pylori

BACKGROUND

 The human gastroduodenal pathogen, Helicobacter pylori, is characterized by an unusual extent of genetic heterogeneity. This dictates differences in the antigenic pattern of strains resulting in heterogeneous human humoral immune responses. Here, we examined the antigenic variability among a group of 10 strains isolated from Portuguese patients differing in age, gender, and H. pylori-associated gastric diseases.

MATERIAL AND METHODS

 Immunoassays were performed on two-dimensional electrophoresis gels obtained for the proteome of each strain, using a commercial pool of antibodies produced in rabbit, against the whole cell lysate of an Australian H. pylori strain. Relevant proteins were identified by mass spectrometry.

RESULTS

Immunoproteomes of the Portuguese strains showed no correlation between the number of antigenic proteins or the antigenic profile, and the disease to which each strain was associated. The Heat shock protein B was the unique immunoreactive protein common to all of them. Additionally, seven proteins were found to be antigenic in at least 80% of strains: enoyl-(acyl-carrier-protein) reductase (NADH); Catalase; Flagellin A; 2 isoforms of alkyl hydroperoxide reductase; succinyl-CoA transferase subunit B; and an unidentified protein. These proteins were present in the proteome of all tested strains, suggesting that differences in their antigenicity are related to antigenic variance.

CONCLUSIONS

 This study showed evidence of the variability of antigenic pattern among H. pylori strains. We believe that this fact contributes to the failure of anti-H. pylori vaccines and the low accuracy of serological tests based on a low number of proteins or antigens of only one strain.

Diagnosis of Helicobacter pylori infection

The articles published this last year in the field of Helicobacter pylori diagnosis reported the development of in vivo histology, small improvements in some invasive methods (urease test, culture, and histology) and new kits for the stool antigen tests. They also contributed to increasing our knowledge, by further exploration into specific conditions for the urea breath test and into the significance of cagA antibodies. The role of serum markers of atrophy was also confirmed. Molecular methods are still being developed for direct genotyping, detection of H. pylori and its clarithromycin resistance, either by polymerase chain reaction or fluorescent in-situ hybridization. For the first time, there was a report on a possible interest of magnetic resonance spectroscopy.