Characteristics of Helicobacter pylori attachment to human primary antral epithelial cells

Conventional cell lines are commonly used to study infection characteristics of the human gastric pathogen Helicobacter pylori. We sought to investigate bacterial attachment to human antral primary epithelial cells, a cell model that more closely resembles the human stomach than transformed cell lines. Primary cells were infected for 24 and 48 h with H. pylori. Morphological appearance of both the pathogen and the cells as well as features of colonization, attachment and internalization were evaluated by electron microscopy and compared to features observed with cultured AGS cells. H. pylori exhibited various shapes during colonization including the spiral, U-shaped, donut, and coccoid forms. The prevalence of each form seemed to be dependent on the infected donor tissue but, in general, changed with time to the coccoid form. Bacterial cell membranes progressively enlarged and appeared at times to be connected with microvilli. Bacterial attachment occurred to cells that were either unchanged, or had formed cup-like structures. Simultaneously, outer membrane vesicles were increasingly secreted from the bacteria, coinciding with increased cellular damage. We conclude that bacterial shape conversion, adherence and secretion of outer membrane vesicles are features of H. pylori infection. Primary gastric cell cultures closely imitate the antral environment and present an appropriate and useful model to study H. pylori pathogenesis.