Air pollution exposure induces a decrease in type II interferon response: A paired cohort study

Background While air pollution is a major issue due to its harmful effects on human health, few studies focus on its impact on the immune system and vulnerability to viral infections. The lockdown declared following the COVID-19 pandemic represents a unique opportunity to study the large-scale impact of variations in air pollutants in real life. We hypothesized that variations in air pollutants modify Th1 response represented by interferon (IFN) y production.Methods We conducted a single center paired pilot cohort study of 58 participants, and a confirmation cohort of 320 participants in Nice (France), with for each cohort two samplings at six months intervals. We correlated the varia-tions in the production of IFNy after non-specific stimulation of participants' immune cells with variations in key regulated pollutants: NO2, O3, PM2.5, and PM10 and climate variables. Using linear regression, we studied the effects of variations of each pollutant on the immune response. Findings In the pilot cohort, IFNy production significantly decreased by 25.7% post-lockdown compared to during lockdown, while NO2 increased significantly by 46.0%. After the adjustment for climate variations during the study period (sunshine and temperature), we observed a significant effect of NO2 variation on IFNy production (P=0.03). In the confirmation cohort IFNy decreased significantly by 47.8% and after adjustment for environmental factors and intrinsic characteristics we observed a significant effect of environmental factors: NO2, PM10, O3, climatic condi-tions (sunshine exposure, relative humidity) on variation in IFNy production (P=0.005, P<0.001, P=0.001, P=0.002 and P<0.001 respectively) but not independently from the BMI at inclusion and the workplace P=0.007 and P<0.001 respectively).Interpretation We show a weakening of the antiviral cellular response in correlation with an increase of pollutants exposition.