UC Riverside

The relationship between electronic cigarette (EC) use and SARS-CoV-2 infection is poorly understood and contradictory with claims that vaping both increases and decreases the likelihood of contracting COVID-19. The objective of this dissertation was to determine how EC fluids and aerosols affect SARS-CoV-2 infection of human cells and tissues. Responses of human bronchial epithelial cells to EC fluids and aerosols and their individual constituents were evaluated using submerged cultures, air liquid interface (ALI) exposure in a cloud chamber, and ALI exposure in a Cultex® system, which produces authentic heated EC aerosols. Both monolayers of BEAS-2B cells and 3D organotypic cultures of EpiAirway tissues were studied. Results were generally in agreement across the three exposure platforms and the two cell models. EC aerosols made from fluids with nicotine, BLU™ EC aerosols, and pure nicotine increased ACE2 (the viral receptor) and TMPRSS2 activity, a protease essential for viral entry. In contrast to BLU™ EC, aerosols from JUUL™ “Virginia Tobacco” decreased TMPRSS2 activity. Using SARS-CoV-2 viral pseudoparticles, we demonstrated that exposure to EC fluids or aerosols with nicotine or to pure nicotine increased infection dose dependently. PG/VG also increased infection but only when aerosols were made in the Cultex® exposure system, suggesting reaction products contributed to increased infection. Aerosols produced at both low (8 watt) and high (20 watt) powers increased nicotine-enhanced infection. EC fluid ingredients and aerosol nicotine dosimetry modulated the response of human bronchial epithelial cells to infection. Specifically, inclusion of benzoic acid reduced EC fluid pH, which reduced TMPRSS2 activity, providing protection against the enhanced infection produced by PG/VG and nicotine. This protection lasted at least 48 hours. Finally, JUUL™ “Virginia Tobacco” aerosols, which contain benzoic acid, protected against pseudoparticle infection, while BLU™ EC aerosols, which lack benzoic acid, did not. Our investigation demonstrates that the effect of ECs on SARS-CoV-2 infection are complex, and infection can either be increased or not affected depending on the ingredients and the pH of EC fluids, TMPRSS2 activity, and nicotine concentration.