Genetic screens to identify factors pertinent to host defence against bacterial infection

Student thesis: Doctoral Thesis

Abstract

Antibiotic resistance is a growing concern for healthcare providers across the world. Indeed, resistance is now being found to those 'last-ditch' antibiotics reserved for antibiotic-resistant infections. There is great need for research into alternative therapies for globally important pathogens, as well as those that pose a bioterror threat due to their infectivity and high morbidity (e.g. Francisella tularensis). Host-directed therapy as a concept for infection treatment seeks either to block bacterial invasion and growth within host cells or enhance host bactericidal activity. This approach has the potential to treat a broad range of bacterial infections, as well as to reduce the likelihood of developing resistance. As a first step, we explored a host infection response network (including the gene PCDH7) defined on the basis of results from a previous HEK-293 host infection screen. Cellular knockout of human PCDH7 showed reduced intracellular Salmonella enterica serotype Typhimurium (STM) and Shigella sonnei burden in vitro, suggesting resistance to bacterial growth. To identify further targets, a 'gene trap' mutation library was generated in a macrophage-like human cell line, U937, which was then differentiated and infected with STM and F. tularensis LVS in independent screens. RNA-Seq was performed on the infected and control populations to identify functionally vital host defence gene mutations. The most statistically significant gene mutations were assessed using pathway analysis tools and literature searches. Multiple pathway analyses converged on electron transport chain subunits MT-ND5, MT-ND6 and MT-CO1, the trapped versions of which were identified as protective in the STM screen. Furthermore, another trapped protective hit, SLC7A11, shows promise from initial validation using a CRISPR knockout (lower intracellular STM burden) as well as pharmacological modulation with the inhibitor sulfasalazine. This work has provided a starting point for the investigation of human genes and cellular processes that might be amenable to pharmacological manipulation to provide protection against, or recovery from, bacterial infection. Therefore host-directed therapies merit further exploration as a novel route to counter the potentially devastating impact of bacteria largely resistant to current antimicrobial drugs.
Date of Award4 Aug 2021
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorBen Pickard (Supervisor) & Craig Roberts (Supervisor)

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