Impact of the SARS-CoV-2 Spike Protein on the Innate Immune System: A Review

The Spike protein enables the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection by binding to multiple receptors, including the angiotensin-converting enzyme 2 (ACE2). Scientific studies also indicate that Spike is involved in severe forms of coronavirus disease 2019 (COVID-19), "long-haul COVID diseases" - also known as "long COVID syndromes" or "post-acute sequelae of SARS-CoV-2 infection" (PACS) - or, recently, in adverse reactions to lipid nanoparticle-messenger ribonucleic acid (mRNA) vaccines or other anti-COVID19 products. Numerous mutations, notably within the subunit 1 of Spike (S1), prevent neutralization by antibodies, but more generally, the virus has developed numerous strategies to avoid immune system surveillance, especially type-I interferons (IFN-I). Meanwhile, a "hyperinflammatory" state, named "cytokine storm," sets in. However, what role does the Spike protein play in the immune escape mechanisms? Can its inflammatory activities affect IFN-I? Does Spike block IFN-I or hijack them for the virus benefits? What are the other potential consequences? This article was written to provide an up-to-date and more general overview of the impact of the Spike protein on the innate immune system and its effectors at the molecular level.