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

Abstract

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.

CLEC5A expression can be triggered by spike glycoprotein and may be a potential target for COVID‐19 therapy

“…Notably, CLEC5A on nonclassical monocytes was extremely elevated, and significantly different compared to mild COVID‐19 cases and has a significant association with severity. Inflammatory monocytes are commonly related to the pathogenesis of COVID‐19, 32 and we previously demonstrated that nonclassical monocytes can be activated by SARS‐CoV‐2 using in vitro assays 19 . As expected, vaccinated people had low expression of CLEC5A on monocytes, which could be explained by mild infection with minor signs and symptoms without hospitalization or death after full vaccination (two or three doses of a COVID‐19 vaccine) (Supporting Information: Table ), as mentioned by others 38,39 .…”

“…Monocytes have an important role in the innate immune response against COVID-19, as these cells are directly affected by SARS-CoV-2 replication 19,[31][32][33][34] and involved in the activation of the inflammatory cascade, that is, the phenomenon known as the cytokine storm, which is related to severity and lethality. 31,32,35,36 Inflammatory monocytes are commonly related to the pathogenesis of COVID-19, 32 and we previously demonstrated that nonclassical monocytes can be activated by SARS-CoV-2 using in vitro assays.…”

“…Monocytes have an important role in the innate immune response against COVID‐19, as these cells are directly affected by SARS‐CoV‐2 replication 19,31–34 and involved in the activation of the inflammatory cascade, that is, the phenomenon known as the cytokine storm, which is related to severity and lethality 31,32,35,36 . Although the function of monocytes is very well described by literature, there is a gap in the information about C‐type lectin receptors expressed by these cells during SARS‐CoV‐2 infection.…”

Molecular docking and molecular dynamics study Lianhua Qingwen granules (LHQW) treats COVID-19 by inhibiting inflammatory response and regulating cell survival

“…Melgaço et al. showed that stinging viral proteins lead to activation of CD4 T helper cell and CD8 T to produce IFNG ( Melgaço et al., 2021 ). Therefore, inhibition of IFNG or IL-17 seems to improve clinical status of critically ill patients.…”

“…Th1 and Th17 perform their effector functions by producing inflammatory cytokines (including IFNG and IL-17). Melgaco et al showed that stinging viral proteins lead to activation of CD4 T helper cell and CD8 T to produce IFNG (Melgaco et al, 2021). Therefore, inhibition of IFNG or IL-17 seems to improve clinical status of critically ill patients.…”