Novel virulence factor dupA of Helicobacter pylori as an important risk determinant for disease manifestation: An overview

Abstract

Helicobacter pylori (H. pylori) is a microaerophilic, Gram-negative, human gastric pathogen found usually in the mucous lining of stomach. It infects more than 50% of the world's population and leads to gastroduodenal diseases. The outcome of disease depends on mainly three factors: Host genetics, environment and bacterial factors. Among these, bacterial virulence factors such as cagA, vacA are well known for their role in disease outcomes. However, based on the global epidemiological results, none of the bacterial virulence (gene) factors was found to be associated with particular diseases like duodenal ulcer (DU) in all populations. Hence, substantial importance has been provided for research in strain-specific genes outside the cag pathogenicity island, especially genes located within the plasticity regions. dupA found within the plasticity regions was first demonstrated in 2005 and was proposed for duodenal ulcer development and reduced risk of gastric cancer in certain geographical regions. Due to the discrepancies in report from different parts of the world in DU development related to H. pylori virulence factor, dupA became an interesting area of research in elucidating the role of this gene in the disease progression. In this review, we shed light on the detailed information available on the polymorphisms in dupA and their clinical relevance. We have critically appraised several pertinent studies on dupA and discussed their merits and shortcomings. This review also highlights dupA gene as an important biomarker for DU in certain populations.

Keywords: Duodenal ulcer; Gastric cancer; Helicobacter pylori; Plasticity region; dupA gene.

Figure 1

Schematic representation of the jhp0917, jhp0918 and jhp0919 gene in strain J99 and that of the dupA alleles in the clinical isolates. The long type dupA (2499 nt) in some clinical isolates contained an additional 615 nt in 5' region before jhp0917 gene and ended 5 bp after the start codon of jph0919 gene. The short type dupA (1884 nt) in some clinical isolates starts from the 5' region of jhp0917 gene and ended 5 bp after the start codon of jph0919 gene.

Figure 2

Organization of three types of type IV secretion system in the Helicobacter pylori compared to Agrobacterium tumefaciens prototype type IV secretion system. Genes are not drawn to scale. H. pylori: Helicobacter pylori; A. tumefaciens: Agrobacterium tumefaciens; T4SS: Type IV secretion system.