Nontyphoidal strains of Salmonella enterica are a major cause of foodborne illnesses, and infection with these bacteria results in inflammatory gastroenteritis. Polymorphonuclear leukocytes (PMNs), also known as neutrophils, are a dominant immune cell type found at the site of infection in Salmonella-infected individuals, but how they regulate infection outcome is not well understood. Here, we used a co-culture model of primary human PMNs and human intestinal organoids to probe the role of PMNs during infection with two of the most prevalent Salmonella serovars: Salmonella enterica serovar Enteritidis and Typhimurium. Using a transcriptomics approach, we identified a dominant role for PMNs in mounting differential immune responses including production of pro-inflammatory cytokines, chemokines, and antimicrobial peptides. We also identified specific gene sets that were induced by PMNs in response to Enteritidis or Typhimurium infection. By comparing host responses to these serovars, we uncovered differential regulation of host metabolic pathways particularly induction of cholesterol biosynthetic pathways during Typhimurium infection and suppression of RNA metabolism during Enteritidis infection. Together, these findings provide insight into the role of human PMNs in modulating different host responses to pathogens that cause similar disease in humans.IMPORTANCENontyphoidal serovars of Salmonella enterica are known to induce robust recruitment of polymorphonuclear leukocytes (PMNs) in the gut during early stages of infection, but the specific role of PMNs in regulating infection outcome of different serovars is poorly understood. Due to differences in human infection progression compared to small animal models, characterizing the role of PMNs during infection has been challenging. Here, we used a co-culture model of human intestinal organoids with human primary PMNs to study the role of PMNs during infection of human intestinal epithelium. Using a transcriptomics approach, we define PMN-dependent reprogramming of the host response to Salmonella, establishing a clear role in amplifying pro-inflammatory gene expression. Additionally, the host response driven by PMNs differed between two similar nontyphoidal Salmonella serovars. These findings highlight the importance of building more physiological infection models to replicate human infection conditions to study host responses specific to individual pathogens.
Keywords: Salmonella; enteric pathogens; epithelial cells; innate immunity; neutrophils.