Project Summary We are in the midst of an unprecedented, modern pandemic as a result of the evolution of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2019. SARS-CoV-2 is one of three known coronaviruses that can replicate in the lower respiratory tract and cause pneumonia and acute respiratory distress syndrome, which can be fatal. However, people are not equally susceptible to development of severe SARS-CoV-2 infection disease (COVID-19). Some risk factors are known, including male sex and comorbidities related to metabolic disease. This pandemic has occurred during an endemic exposure to a class of chemicals called per- and polyfluoroalkyl substances (PFAS) in the United States. Daily exposures occur via PFAS contaminated food, drinking water, dust and air, resulting in nearly universal detection in people examined. What we do not know is how PFAS exposure may influence susceptibility to SARS-CoV-2 infection and COVID-19. SARS-CoV-2 infects airway epithelial cells, triggering a Th1-polarizing pro- inflammatory response. Resolution of the infection is driven by CD8+ T cell-mediated clearance of infected cells and inactivation of the free virus by antibody-binding. Disease severity is associated with lymphopenia and reduced IFN-γ production by CD4+ T cells. PFAS are well-known immunosuppressive agents in rodent models, and PFAS are associated with reduced antibody titers following vaccinations in humans. Our data, and others, show that PFAS are agonists for nuclear receptors, including peroxisome proliferator activated receptor α (PPARα), constitutive androstane receptor (CAR) and pregnane X receptor (PXR) and that their respective transcriptional programs are upregulated following in vivo exposure. Intriguingly, activation of at least PPARα and PXR in T cells results in Th2-skewing, reduced IFN-γ production, and lymphopenia. Here, we propose to examine the interaction between exposure to legacy (perfluorooctanoic acid, PFOA) and replacement (perfluoro(2-methyl-3-oxahexanoic) acid, GenX) PFAS and infection with SARS-CoV-2. We will test the hypothesis that PFAS exposure enhances susceptibility to SARS-CoV-2 infection via interaction with nuclear receptors. First, there are critical, species-specific differences in proteins regulating susceptibility to SARS- CoV-2 infection (angiotensin-converting enzyme 2 (ACE2)) and the biological effects of PFAS (PPARα). In Aim 1 we will generate a novel hACE2/hPPARα transgenic mouse and examine the effects of SARS-CoV-2 infection in mice with human relevant steady-state body burdens of PFAS. Second, efficient CD4+ T cell function is essential for minimizing risk of developing COVID-19. PFAS activate multiple nuclear receptors known to regulate immune function and T cell function. In Aim 2, we will use adeno-associated virus-mediated transduction of PPARα, CAR and PXR shRNA in vivo, to test the necessity for each receptor in enhancing susceptibility to SARS-CoV-2 and how PFOA’s effects are modified. The results will provide essential information on how concurrent exposures to environmental chemicals enhance the risk of severe COVID-19.

Project Narrative SARS-COV-2 has cost more than 100,000 Americans their lives, but not everyone is equally susceptible to the disease caused by the infection (COVID-19). Americans also are exposed daily to mixtures of perfluoroalkylated substances (PFAS) in their drinking water, food and air, and these chemicals are known to suppress the immune system. Here, we propose to investigate how exposure to PFAS enhances susceptibility to severe COVID-19.