E-Poster with pre-recorded video presentation Lorne Infection and Immunity 2021

Tracking variability in the antimicrobial zinc toxicity response of human macrophages against Escherichia coli (#267)

Jessica B von Pein 1 2 3 4 , Claudia J Stocks 1 2 3 4 , Stacey B Andersen 1 5 6 , Minh Duy Phan 3 7 , Kate M Peters 3 7 , Nicholas D Condon 1 2 , Ronan Kapetanovic 1 2 3 4 , Mark A Schembri 3 7 , Matt J Sweet 1 2 3 4
  1. University of Queensland, St Lucia, Brisbane, Queensland, Australia
  2. Institute for Molecular Bioscience (IMB), University of Queensland, St Lucia, Queensland, Australia
  3. Australian Infectious Diseases Research Centre, University of Queensland, St Lucia, Queensland, Australia
  4. IMB Centre for Inflammation and Disease Research, University of Queensland, St Lucia, Queensland, Australia
  5. Genome Innovation Hub, University of Queensland, St Lucia, Queensland, Australia
  6. IMB Sequencing Facility, University of Queensland, St Lucia, Queensland, Australia
  7. School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, Queensland, Australia

Uropathogenic E. coli (UPEC) are the primary cause of urinary tract infections, one of the most common bacterial infections in humans. Understanding effective host defence pathways could facilitate the development of new therapeutics to treat infections caused by UPEC, which are frequently antibiotic-resistant. During infection, innate immune cells, including macrophages, can restrict essential trace elements from pathogens in a phenomenon termed ‘nutritional immunity’. Conversely, these cells can also toxify microorganisms with high concentrations of trace elements. Innate immune cells use both zinc starvation and zinc toxicity as antimicrobial strategies, but molecular mechanisms underlying the latter pathway are poorly understood. Here, we show differences between human monocyte-derived macrophages (HMDM) differentiated with CSF-1 versus GM-CSF in the deployment of these two antimicrobial responses against E. coli. Intramacrophage bacterial gene expression analyses as well as intracellular survival assays for specific E. coli mutants revealed that CSF-1-derived HMDM preferentially employ zinc toxicity, whereas GM-CSF-derived HMDM are more effective at zinc starvation. However, each population could still deploy both zinc toxicity and zinc starvation, suggesting that there may be variability in engagement of these responses at a single cell level. Using an E. coli strain that reports zinc stress, we demonstrate variation of zinc toxicity responses between individual cells within CSF-1-derived HMDM. To further delineate the heterogeneity of macrophage zinc toxicity responses, we are currently using single-cell RNA sequencing methods to determine both host and pathogen transcriptomes associated with the zinc toxicity response in macrophages. To this end, we have optimised reporter tools and protocols that will allow for single-cell bacterial and mammalian transcriptome sequencing. Together, our study shows the deployment of zinc toxicity is likely affected by heterogeneity between and within macrophage populations. Mapping macrophage transcriptional profiles that align with bacterial zinc stress at the single cell level should enable the identification of host genes and pathways that mediate the zinc toxicity response. Such knowledge may ultimately guide the development of host-derived therapies for the treatment of antibiotic-resistant bacterial infections.