Diet driven differences in host tolerance are linked to shifts in global gene expression in a common avian host-pathogen system

As humans alter the landscape, wildlife have become increasingly dependent on anthropogenic resources, altering interactions between individuals and subsequently disease transmission dynamics. Further, nutritional quantity and quality greatly impact an individual host’s immune capacity and ability to mitigate damage caused by infectious disease. Thus, understanding the impact of dietary nutrition on immune function is critical for predicting disease severity and transmission as human activity both facilitates the dispersal of pathogens and alters dietary options for wildlife. Here, we use transcriptomics to explore the previously unstudied molecular mechanisms underpinning diet-driven differences in pathogen tolerance using a widespread avian bacterial pathogen, Mycoplasma gallisepticum (MG). MG is an ideal model for understanding the dietary drivers of disease as the human supplementation that wild birds commonly rely on, bird feeders, are also an important source for MG transmission. Significant diet-driven differences in the expression of many genes encoding immune response and translational machinery proteins are seen both in the absence of MG and during the recovery period. Prior to infection, protein-fed birds are more transcriptionally primed for infection than lipid-fed birds which translates to greater tolerance in protein-fed birds during the recovery period. Given the significant importance of human supplemented food in wildlife disease systems, the molecular mechanisms by which interactions between diet and infection emerge provide insight into the ecological and immunological consequences of human behavior and wildlife disease.