Two-Step In Vitro Model to Evaluate the Cellular Immune Response to SARS-CoV-2

Area of Science:

• Immunology
• Infectious Diseases
• Cell Biology

Background:

• The cellular immune response is critical in COVID-19 pathogenesis and vaccine efficacy.
• In vitro models are essential for studying SARS-CoV-2 interactions and evaluating interventions.
• Understanding the differential immune cell responses in COVID-19 is crucial.

Purpose of the Study:

• To develop and validate a two-step in vitro model for evaluating cellular immune responses to SARS-CoV-2 infection or spike protein stimulation.
• To compare the immune cell activation and supernatant effects in peripheral blood mononuclear cells (PBMCs) from unexposed and COVID-19 convalescent individuals.
• To assess the impact of PBMC-derived supernatants on lung cell line (A549) apoptosis and antiviral activity.

Main Methods:

• Developed a two-step in vitro model using peripheral blood mononuclear cells (PBMCs) and A549 lung cell lines.
• Stimulated PBMCs from unexposed and COVID-19 convalescent individuals with SARS-CoV-2 or spike protein.
• Analyzed PBMC-derived supernatant effects on A549 cell apoptosis and antiviral gene expression.

Main Results:

• In unexposed individuals, SARS-CoV-2 induced cytotoxic natural killer cells and inflammatory monocytes; their supernatant increased A549 cell apoptosis.
• In previously infected individuals, PBMCs showed activated memory CD4+ T cells with high IFNG production.
• Supernatants from convalescent PBMCs reduced A549 cell apoptosis and enhanced antiviral activity (iNOS).

Conclusions:

• The developed two-step in vitro model effectively characterizes distinct cellular immune responses to SARS-CoV-2 antigens.
• This model can be utilized to study immune effects following SARS-CoV-2 antigen exposure and evaluate vaccine or biopharmaceutical efficacy.
• Findings highlight differential immune cell activation and protective effects in convalescent individuals relevant for therapeutic strategies.