Fig. 3.

Coronavirus immunity cycle. Following SARS-CoV-2 uptake in the endosome and virion degradation the viral antigens are presented in (1) the exogenous pathway, (2) cross-presentation pathway and (3) endogenous pathway; partial genome transcription may provide a source of antigen for priming T-cells by MHC class-1 antigen processing following endogenous pathway. Viral pathogen-associated molecular patterns (PAMPs), using endosomal or cytosolic PRRs, as well as the production of cytokines such as IFN-1, can promote potent cellular mediated immune responses. Structural or nonstructural proteins might be recognized by TLR-4 or inflammasome, leading to the activation of proinflammatory cytokines. Abbreviations: APC, antigen-presenting cells; IFN-1, interferon 1; ssRNA, single-stranded RNA; TBK1, TANK-binding kinase 1.