Soluble SARS-CoV-2 Spike glycoprotein: considering some potential pathogenic effects

Area of Science:

• Immunology
• Virology
• Pathology

Background:

• The soluble S1 subunit of SARS-CoV-2 Spike protein (SP) is implicated in COVID-19 pathogenesis.
• NK cells play a role in immune responses to viral infections and may be affected by SARS-CoV-2.
• Post-acute sequelae of COVID-19 (PASC) and post-vaccination side effects present complex clinical challenges.

Purpose of the Study:

• To explore the hypothesis that soluble SP directly activates human NK cells.
• To elucidate the pathogenic role of NK cells in COVID-19 and post-vaccination syndromes.
• To explain the heterogeneity of clinical outcomes in severe COVID-19, PASC, and post-vaccine adverse events.

Main Methods:

• Review of existing literature on SARS-CoV-2 Spike protein interactions with immune cells.
• Analysis of proposed mechanisms involving toll-like receptors (TLR) 2 and 4.
• Discussion of the biological activities of circulating SP and their impact on cellular processes.

Main Results:

• Soluble SP may directly bind and activate NK cells via TLR2 and TLR4 in vitro.
• This activation contributes to NK cell dysfunction and a novel pathogenic role in COVID-19 and post-vaccination effects.
• Soluble SP triggers multiple cellular responses, including decreased interferon, altered autophagy/apoptosis, cytokine release, and endothelial damage.

Conclusions:

• Circulating SP's diverse biological activities may explain varied clinical manifestations of COVID-19, PASC, and post-vaccine events.
• Factors like SP levels, age, and antibody response influence pathological activity.
• Systematic analysis of excessive SP production is needed to identify at-risk individuals and develop safer vaccines.