A biomimetic model composed of injectable 3D-muscle like tissue, stromal and immune cells for recapitulating the rapid immune signature predictive of mRNA vaccine immunogenicity

Marilena Paola Etna¹Claudia Fuoco²Martina Severa¹Daniela Ricci¹Alessandro Sinigaglia³Camilla Lucca³Giada Cairo¹Barbara Bottazzi⁴Cecilia Garlanda⁴Anna Teresa Palamara¹Luisa Barzon³Cesare Gargioli^2*Eliana Marina Coccia^1*

• ¹National Institute of Health (ISS), Rome, Italy
• ²Universita degli Studi di Roma Tor Vergata, Rome, Italy
• ³Universita degli Studi di Padova, Padua, Italy
• ⁴IRCCS Humanitas Research Hospital, Rozzano, Italy

Background: System vaccinology identified an early innate signature associated with vaccine-mediated protection whose induction is likely to involve both immune and non-immune cells. Methods: To dissect muscle and stromal cell contribution, we in vitro simulated anti-COVID19 BNT162b2 mRNA vaccine intramuscular administration in human primary cell systems composed of 3D muscle-like tissue (3D-MT), fibroblasts and peripheral blood mononuclear cells (PBMC). Results: BNT162b2 vaccine was recognized by all cell types, although fibroblasts only translated the spike antigen. Factors from vaccine-injected 3D-MT stimulated monocyte and macrophage recruitment and promoted inflammatory macrophage activation, while stromal factors improved dendritic cell frequency and activation. Conditioned media from vaccine exposed 3D-MT and fibroblasts elicited in PBMC the expression of an early innate immune module previously associated with protective responses in BNT162b2 vaccinees. Conclusion: Thus, models combining human PBMC, stromal and muscle cells could be employed for the in vitro validation of system vaccinology findings and non-animal vaccine pre-clinical testing.