Temporal Control of the Helicobacter pylori Cag Type IV Secretion System in a Mongolian Gerbil Model of Gastric Carcinogenesis Aung Soe Lin, a Mark S. McClain, b,c Amber C. Beckett, a Rhonda R. Caston, a M. Lorena Harvey, a Beverly R. E. A. Dixon, b Anne M. Campbell, b Jennifer H. B. Shuman, a Neha Sawhney, b Alberto G. Delgado, b John T. Loh, b M. Blanca Piazuelo, b Holly M. Scott Algood, a,b,c,d Timothy L. Cover a,b,c,d a Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA b Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, USA c Vanderbilt Institute for Infection, Immunology, and Inflammation, Vanderbilt University Medical Center, Nashville, Tennessee, USA d Veterans Affairs Tennessee Valley Healthcare System, Nashville, Tennessee, USA Aung Soe Lin and Mark S. McClain contributed equally to this work. Author order was determined by mutual agreement. ABSTRACT The Helicobacter pylori Cag type IV secretion system (T4SS) translocates the effector protein CagA and nonprotein bacterial constituents into host cells. In this study, we infected Mongolian gerbils with an H. pylori strain in which expression of the cagUT operon (required for Cag T4SS activity) is controlled by a TetR/tetO sys- tem. Transcript levels of cagU were significantly higher in gastric tissue from H. pylori-infected animals receiving doxycycline-containing chow (to derepress Cag T4SS activity) than in tissue from infected control animals receiving drug-free chow. At 3 months postinfection, infected animals receiving doxycycline had significantly increased gastric inflammation compared to infected control animals. Dysplasia (a premalignant histologic lesion) and/or invasive gastric adenocarcinoma were de- tected only in infected gerbils receiving doxycycline, not in infected control animals. We then conducted experiments in which Cag T4SS activity was derepressed during defined stages of infection. Continuous Cag T4SS activity throughout a 3-month time period resulted in higher rates of dysplasia and/or gastric cancer than observed when Cag T4SS activity was limited to early or late stages of infection. Cag T4SS ac- tivity for the initial 6 weeks of infection was sufficient for the development of gastric inflammation at the 3-month time point, with gastric cancer detected in a small pro- portion of animals. These experimental results, together with previous studies of cag mutant strains, provide strong evidence that Cag T4SS activity contributes to gastric carcinogenesis and help to define the stages of H. pylori infection during which Cag T4SS activity causes gastric alterations relevant for cancer pathogenesis. IMPORTANCE The “hit-and-run model” of carcinogenesis proposes that an infectious agent triggers carcinogenesis during initial stages of infection and that the ongoing presence of the infectious agent is not required for development of cancer. H. pylori infection and actions of CagA (an effector protein designated a bacterial oncopro- tein, secreted by the Cag T4SS) are proposed to constitute a paradigm for hit-and- run carcinogenesis. In this study, we report the development of methods for control- ling H. pylori Cag T4SS activity in vivo and demonstrate that Cag T4SS activity contributes to gastric carcinogenesis. We also show that Cag T4SS activity during an early stage of infection is sufficient to initiate a cascade of cellular alterations lead- ing to gastric inflammation and gastric cancer at later time points. KEYWORDS Helicobacter pylori, type IV secretion system, gastric cancer, Citation Lin AS, McClain MS, Beckett AC, Caston RR, Harvey ML, Dixon BREA, Campbell AM, Shuman JHB, Sawhney N, Delgado AG, Loh JT, Piazuelo MB, Algood HMS, Cover TL. 2020. Temporal control of the Helicobacter pylori Cag type IV secretion system in a Mongolian gerbil model of gastric carcinogenesis. mBio 11:e01296-20. https://doi.org/10.1128/mBio .01296-20. Editor Craig R. Roy, Yale University School of Medicine Copyright © 2020 Lin et al. This is an open- access article distributed under the terms of the Creative Commons Attribution 4.0 International license. Address correspondence to Timothy L. Cover, timothy.l.cover@vumc.org. This article is a direct contribution from Timothy L. Cover, a Fellow of the American Academy of Microbiology, who arranged for and secured reviews by Robert Maier, University of Georgia, and Karen Ottemann, University of California, Santa Cruz. Received 19 May 2020 Accepted 26 May 2020 Published RESEARCH ARTICLE Host-Microbe Biology crossm May/June 2020 Volume 11 Issue 3 e01296-20 ® mbio.asm.org 1 30 June 2020 Downloaded from https://journals.asm.org/journal/mbio on 23 February 2022 by 54.242.133.186.