Novel evidence of Thymosin α1 immunomodulatory properties in SARS-CoV-2 infection: Effect on innate inflammatory response in a peripheral blood mononuclear cell-based in vitro model.

In vitro experimental study using human peripheral blood mononuclear cells (PBMC) and ex vivo analysis of patient samples

“Here, we interrogated peripheral blood mononuclear cell (PBMC) cultures stimulated with SARS-CoV-2 to disclose Tα1 properties on the main cell players of early response to infection, namely monocytes and myeloid dendritic cells (mDC).”

Healthy donors, asymptomatic SARS-CoV-2 infected individuals, and hospitalized COVID-19 patients

“Six hospitalized COVID-19 [CP-H; 2 females/4 males; median age ± Standard Deviation (SD) 51.5 ± 23.3 years (yrs)] and eight asymptomatic [CP-AS; 4 females/4 males; 58.5 ± 10.4 yrs] patients matched to five HD [3 females/2 males; 53 ± 12.5 yrs] were enrolled and provided written informed consent.”

19 total participants (6 hospitalized, 8 asymptomatic, 5 healthy donors)

“Six hospitalized COVID-19 [CP-H; 2 females/4 males; median age ± Standard Deviation (SD) 51.5 ± 23.3 years (yrs)] and eight asymptomatic [CP-AS; 4 females/4 males; 58.5 ± 10.4 yrs] patients matched to five HD [3 females/2 males; 53 ± 12.5 yrs] were enrolled and provided written informed consent.”

24 hours for in vitro cell stimulation

“PBMC were pre-incubated for 1 h at 37 ˚C with infectious SARS-CoV-2 at a multiplicity of infection (MOI) of 0.02 and then cultured at 2x106 cells/ml in RPMI 1640 (GIBCO) in presence of P/S (100 U/mL) (GIBCO), L-glutamine (2 mM) (GIBCO) and 10% FBS (Euroclone) for 24 h.”

SARS-CoV-2 stimulation increased the frequency of inflammatory and atypical monocytes and activated myeloid dendritic cells in both ex vivo patient samples and in vitro cultures.

“Moving from ex vivo data showing an enhancement in the frequency of inflammatory monocytes and activated mDC in COVID-19 patients, a PBMC-based experimental setting reproduced in vitro a similar profile with an increased percentage of CD16+ inflammatory monocytes and mDC expressing CD86 and HLA-DR activation markers in response to SARS-CoV-2 stimulation.”

Treatment with Thymosin alpha 1 (Tα1) reduced the expression of activation markers CD86 and HLA-DR on monocytes and myeloid dendritic cells in SARS-CoV-2-stimulated cultures.

“Interestingly, the treatment of SARS-CoV-2-stimulated PBMC with Tα1 dampened the inflammatory/activation status of both monocytes and mDC by reducing the release of pro-inflammatory mediators, including TNF-α, IL-6 and IL-8, while promoting the production of the anti-inflammatory cytokine IL-10.”

Tα1 treatment decreased the release of pro-inflammatory cytokines TNF-α, IL-6, and IL-8 while increasing the production of the anti-inflammatory cytokine IL-10.

“The release of these inflammatory factors from SARS-CoV-2 stimulated PBMC was significantly mitigated by Tα1 pre-treatment (Fig. 7 A and B).”