Typhoidal Salmonella Dendritic Cell Survival Mechanism Revealed by Dual RNA sequencing

Salmonella enterica represent a major disease burden worldwide. While non-typhoidal Salmonella (NTS) serovars trigger self-limiting diarrhoea, leading to occasional secondary bacteraemia, S. enterica serovar Typhi is responsible for potentially life-threatening Typhoid fever. Dendritic cells (DCs) are key professional antigen presenting cells of the human immune system. The ability of pathogenic bacteria to subvert DC functions and prevent T cell recognition contributes to their survival and dissemination within the host. Here, we adapted Dual RNA-sequencing to define how different Salmonella pathovariants remodel their gene expression in tandem with that of infected DCs. We find DCs harness iron handling pathways to defend against invading Salmonellas, which, the human pathogen S. Typhi is able to circumvent. We show that S. Typhi mounts a robust response to host oxidative stress to avoid host iron-mediated defence mechanisms. In parallel, we provide evidence that invasive non-typhoidal Salmonella employs several strategies to impair DC functions and undertake alternative nutrient scavenging strategies to survive in the hostile intracellular environment. Dual RNA-seq of mini-bulks (20'000 cells) of human monocyte derived dendritic cells infected with S. Typhimurium strain LT2 or D23580 or S. Typhi strain Ty2 or left uninfected