Enabling risk-based testing through characterization of environmentally induced immune dysregulation and susceptibility to the SARS-CoV2 virus and COVID-19

Investigators

Abstract

In FY 23 we continued to focus the immunotoxicology research program within the the Division of Translation Toxicology (DTT) on in vitro approaches. A major effort involved investigating how interindividual susceptibility factors and environmental risk factors impact the response to viral infection, using an in vitro human whole blood culture system. Endpoints include lymphocytotoxicity, cytokine release, and Natural Killer cell activity. We have screened >200 individual samples to date and are analyzing in vitro data to examine how intrinsic factors such as age, gender and ethnicity influence the response of peripheral blood leukocytes to influenza and SARS-CoV-2 antigens. Preliminary results demonstrate an association between sex and NK activity with males having higher NK activity in peripheral blood than females. Immunophenotyping data are being analyzed to determine if this effect is due to males having higher abundance of NK cells or more active NK cells than females. A second phase of this study is investigating the responses to these antigens following in vitro exposure to known immunotoxicants, including PACs and how exposure to these environmental agents may affect susceptibility to viral infection. The PAC data will be referenced against mouse in vivo data previously collected in the PAC-MAP mixtures studies and serve to anchor human relevance and strengthen the data that can be generated using the in vitro system. As proof of concept, whole blood cultures were unstimulated or stimulated with anti-CD3/CD28 or viral peptide pools in the presence of dexamethasone, a known immunosuppressive drug. DEX treatment resulted in inhibition of NK activity, cytokine production, and T-cell activation following stimulation with the positive control anti-CD3/CD28. Importantly, DEX treatment also inhibited the production of cytokines stimulated by SARS-CoV-2 antigen pool in a concentration related manner. This work demonstrated that the in vitro immunotoxicity platform was capable of detecting immune suppression and alterations in responses to SARS-CoV-2 peptides. A second proof of concept study using the PAC Benzo(a)pyrene is ongoing and exposure to this compound in the present of metabolizing enzymes resulted in potent suppression in the immune endpoints measured to date. BRT is currently working on development of additional in vitro tools for this culture system that will facilitate interrogation of humoral antibody mediated immunity and T-cell driven immunity. This in vitro toolbox will be critically important to provide direct human relevance in the methods used to identify chemicals that have the potential to modulate immune function, and will reduce the use of animals in toxicology testing.