Abstract
Helicobacter pylori is a Gram-negative bacterium that causes chronic atrophic gastritis and peptic ulcers and it has been associated with the development of gastric adenocarcinoma and mucosa-associated lymphoid tissue (MALT). One of the more remarkable characteristics of H. pylori is its ability to survive in the hostile environment of the stomach. H. pylori regulates the expression of specific sets of genes allowing it to survive high acidity levels and nutrient scarcity. In the present study, we determined the expression of virulence associated protein D (VapD) of H. pylori inside adenocarcinoma gastric (AGS) cells and in gastric biopsies. Using qRT-PCR, VapD expression was quantified in intracellular H. pylori-AGS cell cultures at different time points and in gastric mucosa biopsies from patients suffering from chronic atrophic gastritis, follicular gastritis, peptic ulcers, gastritis precancerous intestinal metaplasia and adenocarcinoma. Our results show that vapD of H. pylori presented high transcription levels inside AGS cells, which increased up to two-fold above basal values across all assays over time. Inside AGS cells, H. pylori acquired a coccoid form that is metabolically active in expressing VapD as a protection mechanism, thereby maintaining its permanence in a viable non-cultivable state. VapD of H. pylori was expressed in all gastric biopsies, however, higher expression levels (p = 0.029) were observed in gastric antrum biopsies from patients with follicular gastritis. The highest VapD expression levels were found in both antrum and corpus gastric biopsies from older patients (>57 years old). We observed that VapD in H. pylori is a protein that is only produced in response to interactions with eukaryotic cells. Our results suggest that VapD contributes to the persistence of H. pylori inside the gastric epithelial cells, protecting the microorganism from the intracellular environment, reducing its growth rate, enabling long-term infection and treatment resistance.
Highlights
Helicobacter pylori infection is the most common chronic infection around the world, since different epidemiological studies have shown that approximately 50% of the human population is infected with the bacterium [1]
Our results suggest that virulence associated protein D (VapD) contributes to the persistence of H. pylori inside the gastric epithelial cells, protecting the microorganism from the intracellular environment, reducing its growth rate, enabling long-term infection and treatment resistance
Our results suggested that virulence-associated protein D (vapD) is a gene capable of being induced and transcribed only when H. pylori comes into contact with gastric cells but it is not expressed when H. pylori is grown in culture medium, because it could not be necessary for its survival outside eukaryotic cell
Summary
Helicobacter pylori infection is the most common chronic infection around the world, since different epidemiological studies have shown that approximately 50% of the human population is infected with the bacterium [1]. The cag pathogenicity island (cagPAI) has a variable structure and a different chromosomal arrangement; in some strains it presents as a single uninterrupted unit, or can be divided into two regions by IS605 (cagI and cagII), be split into cagI and cagII by a large segment of chromosome, or it can consist of partially deleted segments of cagI, cagII or both [6]. Another distinctive hallmark is the presence of strain-specific genes [7,8], which are found within plasticity zones where the highest diversity among H. pylori strains can be seen
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