Campylobacter jejuni Demonstrates Conserved Proteomic and Transcriptomic Responses When Co-cultured With Human INT 407 and Caco-2 Epithelial Cells

Abstract

Major foodborne bacterial pathogens, such as <i>Campylobacter jejuni</i>, have devised complex strategies to establish and foster intestinal infections. For more than two decades, researchers have used immortalized cell lines derived from human intestinal tissue to dissect <i>C. jejuni</i>-host cell interactions. Known from these studies is that <i>C. jejuni</i> virulence is multifactorial, requiring a coordinated response to produce virulence factors that facilitate host cell interactions. This study was initiated to identify <i>C. jejuni</i> proteins that contribute to adaptation to the host cell environment and cellular invasion. We demonstrated that <i>C. jejuni</i> responds to INT 407 and Caco-2 cells in a similar fashion at the cellular and molecular levels. Active protein synthesis was found to be required for <i>C. jejuni</i> to maximally invade these host cells. Proteomic and transcriptomic approaches were then used to define the protein and gene expression profiles of <i>C. jejuni</i> co-cultured with cells. By focusing on those genes showing increased expression by <i>C. jejuni</i> when co-cultured with epithelial cells, we discovered that <i>C. jejuni</i> quickly adapts to co-culture with epithelial cells by synthesizing gene products that enable it to acquire specific amino acids for growth, scavenge for inorganic molecules including iron, resist reactive oxygen/nitrogen species, and promote host cell interactions. Based on these findings, we selected a subset of the genes involved in chemotaxis and the regulation of flagellar assembly and generated <i>C. jejuni</i> deletion mutants for phenotypic analysis. Binding and internalization assays revealed significant differences in the interaction of <i>C. jejuni</i> chemotaxis and flagellar regulatory mutants. The identification of genes involved in <i>C. jejuni</i> adaptation to culture with host cells provides new insights into the infection process.