No abstract

The emergence of antibiotic-resistant Helicobacter pylori is of concern in the treatment of H. pylori-associated gastroduodenal diseases. As the organism was reported to bind gastric mucin, we used porcine gastric mucin as substrate to assess the antiadhesive property of polysaccharides derived from Spirulina (PS), a commercially available microalga, against the binding of H. pylori to gastric mucin. Results show that polysaccharides prevented H. pylori from binding to gastric mucin optimally at pH 2.0, without affecting the viability of either bacteria or gastric epithelial cells, thus favouring its antiadhesive action in a gastric environment. Using ligand overlay analysis, polysaccharide was demonstrated to bind H. pylori alkyl hydroperoxide reductase (AhpC) and urease, which have shown here to possess mucin-binding activity. An in vivo study demonstrated that bacteria load was reduced by >90% in BALB/c mice treated with either Spirulina or polysaccharides. It is thus suggested that polysaccharides may function as a potential antiadhesive agent against H. pylori colonization of gastric mucin.

Outer inflammatory protein A (OipA) is an important virulence factor associated with gastric cancer and ulcer development; however, the results have not been well established and turned out to be controversial. This study aims to elucidate the role of OipA in Helicobacter pylori infection using clinical strains harbouring oipA "on" and "off" motifs. Proteomics analysis was performed on AGS cell pre-infection and postinfection with H. pylori oipA "on" and "off" strains, using liquid chromatography/mass spectrometry. AGS apoptosis and cell cycle assays were performed. Moreover, expression of vacuolating cytotoxin A (VacA) was screened using Western blotting. AGS proteins that have been suggested previously to play a role or associated with gastric disease were down-regulated postinfection with oipA "off" strains comparing to oipA "on" strains. Furthermore, oipA "off" and ΔoipA cause higher level of AGS cells apoptosis and G0/G1 cell-cycle arrest than oipA "on" strains. Interestingly, deletion of oipA increased bacterial VacA production. The capability of H. pylori to induce apoptosis and suppress expression of proteins having roles in human disease in the absence of oipA suggests that strains not expressing OipA may be less virulent or may even be protective against carcinogenesis compared those expressing OipA. This potentially explains the higher incidence of gastric cancer in East Asia where oipA "on" strains predominates.

Aim:Helicobacter pylori causes peptic ulcer disease and gastric cancer. Western studies suggest that polymorphisms in the virulence factors caga and vaca may determine the ability of bacteria to cause gastroduodenal diseases. Differences in the caga EPIYA motifs and polymorphisms of the signal (s), middle (m) and intermediate (i) regions of vaca are thought to be important. The aim of this study was to compare the polymorphisms of caga and vaca of H. pylori isolated from the Chinese, Malay and Indian populations living in Singapore.Method: A total of 104 H. pylori isolates obtained from patients with dyspeptic symptoms were analysed. Of the 104 patients, 80 were Chinese, 9 Malays and 15 Indians. DNA was extracted from the isolates and the vaca allelic types and caga EPIYA motifs were determined by polymerase chain reaction (PCR) and sequencing, respectively. results: Differences in the vaca and caga polymorphisms were found between the Chinese, Malays and Indians. Significantly more non-Chinese patients carried vaca s1/m1 strains versus Chinese patients (p<0.05). All 9 Malay patients, 11/15 (73.3%) Indians and 31/80 (38.8%) Chinese patients carried H. pylori strains with the vaca s1/m1/i1. Significantly more Chinese patients carried isolates with East Asian caga EPIYA motifs versus nonChinese patients (p<0.05). 79/80 (98.8%) of the Chinese isolates, 2/15 (13%) of Indian isolates, and 5/9(55.6%) of Malay isolates possessed caga with the East Asian ABD type motif. Conclusion:Results from the current study demonstrated marked differences in the polymorphisms of vaca and caga EPIYA motifs in strains isolated from Chinese versus non-Chinese patients. Epidemiologically, the Chinese are at the highest risk of developing gastric cancer. Work is ongoing to determine if differences found in the caga EPIYA motifs of isolates from the Chinese patients can contribute to a subject's risk of developing gastric cancer.

In view of recent revised recommendations for human immunodeficiency virus (HIV) confirmatory testing, the performance of 3 HIV confirmatory assays was compared. Using the HIV Blot 2.2 (MP-WB), the INNO-LIA HIV I/II Score (INNO), and the Geenius HIV 1/2 Confirmatory Assay (Geenius), we tested 199 HIV-1 positive, 161 HIV negative, 65 HIV western blot indeterminate, 26 HIV seroconversion, 34 early HIV infection and 4 HIV-2 positive archived specimens. We show that all 3 assays had comparable test sensitivity in the detection of HIV-1 positive cases. However, less non-specific reactivity was observed with the INNO and Geenius assays, where both of them were able to resolve MP-WB indeterminate cases. When early HIV cases were considered, INNO and Geenius were more likely to confirm an early-stage infection as positive. Nevertheless, overall poor sensitivity (25.5% - 44.7%) of these assays for the detection of early cases was observed, likely because these cases had very low or non-detectable levels of HIV antibodies. Hence, further testing by a nucleic acid test or a p24 antigen test of specimens reactive on screening with a fourth generation Ag/Ab assay that are negative on confirmatory testing for HIV-specific antibody, may be useful. In conclusion, INNO and Geenius had comparable test performance, although the ease of use and shorter assay time for Geenius may make it the preferred choice for laboratories. In that regard, of note is our observation of non-specific reactivity of lipaemic specimens to the HIV-2 gp140 band in the Geenius assay, which should prompt caution when interpreting results of such specimens.