Rationale: Wildfires are increasing in intensity, duration, and frequency with smoke plums affecting the lives of millions over large geographic areas. The immune modulatory effects of wildfire smoke are unclear. We previously showed that a major wildfire smoke component, ozone, inhibited dendritic cell lymph node homing (an essential process in vaccine immunity) by suppressing NK cell-derived IFN-γ expression in mice.
Methods: To study the hypothesis that wildfire smoke affects NK cell function and long-term immunity against SARS-CoV-2, we studied 52 healthy, non-smoker, age-and sex-matched 26-83-year-old subjects, participating in the Pfizer BNT162b2 vaccine trial. 28 subjects received the vaccine during heavy wildfire smoke (August-September 2020) and 24 received it in January-March 2021, during clean air conditions. Peripheral blood and serum samples were collected before, 1- and 6 months post-vaccination.
Results: 6 month post-vaccine, peripheral blood CD19+ B cells were significantly increased (p=0.015) and correlated with CD56+ NK-cell expression of IL-13 (r= 0.52, p=0.0146) in those who were vaccinated during wildfires compared to clean air. 6-month post-vaccine SARS CoV-2 S-RBD specific IgG levels were diminished with significant variability. Subjects who received vaccinations during wildfire smoke had a trend of decreased SARS-CoV-2 neutralizing antibody levels compared to recipients vaccinated
Conclusions: When COVID-19 vaccine immunizations occur during wildfire smoke exposures, we propose that IL-13+ NK cells play a novel role by activating CD19+ B cells while diminishing antigen specific IgG production.