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

Melgaço, Juliana G.; Azamor, Tamiris; Silva, Andréa M. V.; Linhares, José Henrique R.; dos Santos, Tiago P.; Mendes, Ygara S.; de Lima, Sheila M. B.; Fernandes, Camilla Bayma; da Silva, Jane; de Souza, Alessandro F.; Tubarão, Luciana N.; Brito e Cunha, Danielle; Pereira, Tamires B. S.; Menezes, Catarina E. L.; Miranda, Milene D.; Matos, Aline R.; Caetano, Braulia C.; Martins, Jéssica S. C. C.; Calvo, Thyago L.; Rodrigues, Natalia F.; Sacramento, Carolina Q.; Siqueira, Marilda M.; Moraes, Milton O.; Missailidis, Sotiris; Neves, Patrícia C. C.; Ano Bom, Ana Paula D.

The cellular immune response plays an important role in COVID-19, caused by SARS-CoV-2. This feature makes use of in vitro models’ useful tools to evaluate vaccines and biopharmaceutical effects. Here, we developed a two-step model to evaluate the cellular immune response after SARS-CoV-2 infection-induced or spike protein stimulation in peripheral blood mononuclear cells (PBMC) from both unexposed and COVID-19 (primo-infected) individuals (Step1). Moreover, the supernatants of these cultures were used to evaluate its effects on lung cell lines (A549) (Step2). When PBMC from the unexposed were infected by SARS-CoV-2, cytotoxic natural killer and nonclassical monocytes expressing inflammatory cytokines genes were raised. The supernatant of these cells can induce apoptosis of A549 cells (mock vs. Step2 [mean]: 6.4% × 17.7%). Meanwhile, PBMCs from primo-infected presented their memory CD4(+) T cells activated with a high production of IFNG and antiviral genes. Supernatant from past COVID-19 subjects contributed to reduce apoptosis (mock vs. Step2 [ratio]: 7.2 × 1.4) and to elevate the antiviral activity (iNOS) of A549 cells (mock vs. Step2 [mean]: 31.5% × 55.7%). Our findings showed features of immune primary cells and lung cell lines response after SARS-CoV-2 or spike protein stimulation that can be used as an in vitro model to study the immunity effects after SARS-CoV-2 antigen exposure.