It is estimated that 50-100 million people (~5% of the global population) died from the 1918 influenza pandemic. While influenza infections usually do not cause such severe disease, ~30 million are infected every year in the United States alone (2014-2015). However, there are broad differences in influenza susceptibility and severity, with outcomes from asymptomatic infections (~16%) to death (0.2% in 2014-2015). These differences arise from the complex interplay of exposure, environment, influenza genetics, and human genetics. The overall goal of my lab is to understand how human genetic diversity regulates susceptibility and severity of infections. Famous examples of genetic differences that profoundly impact susceptibility include sickle cell allele protection against malaria and CCR5 deletion protection against HIV. Such genetic differences can lead to insights on pathogenesis, drug targets (e.g. CCR5 inhibitors), and more personalized care. For influenza, common genetic variation has been most convincingly shown to influence flu severity at a single locus (IFITM3) that regulates a single step (cytosolic entry) in the complex influenza life cycle. We hypothesize that other human genetic differences affect influenza infection and can be identified through measuring inter-individual variation in cellular infection phenotypes. To facilitate identification of SNPs that affect cellular infection phenotypes, we developed and validated a cell-based GWAS approach called Hi-HOST. SNPs identified as important for influenza infection by Hi-HOST can then be examined for relevance in human infection using already completed human flu challenge studies and population-based studies. We propose that the intersection of human subject and cell line data facilitates discovery of novel pathways and genetic determinants of susceptibility. This project will generate a high resolution analysis of how human genetic variants impact transcription, cellular phenotypes, and human disease following influenza exposure. We will accomplish this through 1) identifying human SNPs that confer resistance/susceptibility to cellular and molecular phenotypes of flu infection, including entry, replication, cell death, cytokine levels, and host transcriptional responses, 2) determining the impact of SNPs on host transcription during influenza challenge of healthy volunteers, and 3) integrating the generated cellular and human challenge datasets to generate and test hypotheses linking transcriptional response and cellular susceptibility. Understanding these differences could lead to new diagnostic approaches in identifying at-risk individuals and novel therapeutic strategies for treatment.
Influenza is responsible for millions of respiratory infections every year and three global pandemics in the last century that caused tens of millions of deaths. This proposal is an integrated effort to identify natural human genetic variation regulating influenza infection through GWAS of variation in cellular entry, replication, and host gene expression and studies of human flu challenge. Successfully carrying out this work will identify specific genetic differences that regulate influenza infection and may also reveal new targets for host-directed therapies.
