Utilizing Cellular GWAS as a Springboard to Understand Complex Host-Pathogen Interactions

Abstract

If nothing else, the 2019 Coronavirus pandemic has made it abundantly clear that understanding the mechanisms of infectious disease is imperative to the survival of our species. While the last fifty years of developments in molecular biology has accelerated our ability to study microbial pathogens, limitations in pathogen tropism, microbial survival in laboratory conditions, uneven sampling of human cohorts across geographical and socioeconomic lines, and heterogeneous complexity during human infection have limited our ability to study complex mechanisms of human susceptibility to infectious disease. In this work, I build on recent developments in utilizing High-throughput Human in vitro Susceptibility Testing (Hi-HOST) to not only (a) identify novel sites in the human genome that contribute to natural variation in infectious disease susceptibility based on highly quantifiable cellular phenotypes, but (b) use these sites as a springboard to understand the entire, complex host-pathogen interaction. From this perspective, I paired the model pathogen Salmonella enterica and the Hi-HOST system to identify that natural variation in the mammalian gene arhgef26 contributes to susceptibility to Salmonella invasion. I used this finding as a starting point to fully explore the role of ARHGEF26 during infection, redefining its role in invasion, inflammation, and its interaction with host and bacterial proteins during the process. Similarly, I used prior Hi-HOST findings that methionine metabolism influences the host response to Salmonella enterica serovar Typhimurium (S. Typhimurium) as a launching point to investigate the impacts of host and bacterial metabolism on the virulence of S. Typhimurium. I found that the metabolite methylthioadenosine is a potent inhibitor of S. Typhimurium type III secretion, motility, and invasion. Finally, I mechanistically explain some of these findings by linking methionine metabolism to DNA methylation using a novel approach to integrate the Salmonella Typhimurium methylome and transcriptome. In sum, these findings demonstrate the ability for cellular GWAS to serve as a launching point to understand complex host-pathogen interactions.