Extracellular vesicles carry SARS‐CoV‐2 spike protein and serve as decoys for neutralizing antibodies

Abstract

In late 2019, a novel coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) emerged in Wuhan, China. SARS‐CoV‐2 and the disease it causes, coronavirus disease 2019 (COVID‐19), spread rapidly and became a global pandemic in early 2020. SARS‐CoV‐2 spike protein is responsible for viral entry and binds to angiotensin converting enzyme 2 (ACE2) on host cells, making it a major target of the immune system – particularly neutralizing antibodies (nAbs) that are induced by infection or vaccines. Extracellular vesicles (EVs) are small membraned particles constitutively released by cells, including virally‐infected cells. EVs and viruses enclosed within lipid membranes share some characteristics: they are small, sub‐micron particles and they overlap in cellular biogenesis and egress routes. Given their shared characteristics, we hypothesized that EVs released from spike‐expressing cells could carry spike and serve as decoys for anti‐spike nAbs, promoting viral infection. Here, using mass spectrometry and nanoscale flow cytometry (NFC) approaches, we demonstrate that SARS‐CoV‐2 spike protein can be incorporated into EVs. Furthermore, we show that spike‐carrying EVs act as decoy targets for convalescent patient serum‐derived nAbs, reducing their effectiveness in blocking viral entry. These findings have important implications for the pathogenesis of SARS‐CoV‐2 infection in vivo and highlight the complex interplay between viruses, extracellular vesicles, and the immune system that occurs during viral infections.

Generation of Spike-Extracellular Vesicles (S-EVs) as a Tool to Mimic SARS-CoV-2 Interaction with Host Cells

“…Indeed, we deeply characterized at a single EV level the S-EVs showing variable co-expression of all three tetraspanins (CD9, CD63 and CD81) in about half of the isolated EVs, suggesting that the spike incorporated in a specific subset of EVs. This study parallels a recent study showing the neutralizing effect of spike carrying EVs obtained from HEK transfected cells [ 15 ]. The analysis of the obtained EGFP-bound spike EVs by nanoflow cytometry showed 85% of CD9 co-expression, whereas CD81 was mainly negative.…”

“…This discrepancy could be due to the different sensitivity of the detection systems used. However, the authors showed that the spike protein was incorporated predominantly as the S2 subunit with rarer full-length glycoproteins [ 15 ]. At variance, in our study, we detected by western blot analysis mainly the full-length form of the spike protein.…”

“…Moreover, spike expressing EVs were shown to act as decoy targets for convalescent patient serum-derived Abs, reducing their effectiveness in blocking viral entry [ 15 ]. Therefore, it is conceivable that the generation of spike expressing EVs that are naturally released from infected cells may participate in the disease with different mechanisms of viral dissemination and immune system downregulation [ 15 ].…”

“…Another work showed the possibility of using EVs modified with the receptor-binding domain of the viral spike protein that recognizes ACE2 receptor as a target delivery system in vivo of potential anti-viral agents [ 14 ]. Recently, Troyer Z et al showed that EVs containing SARS-CoV-2 spike interact with the humoral immune system and reduce serum neutralizing antibodies of convalescent patients [ 15 ].…”

Use of Early Donated COVID-19 Convalescent Plasma Is Optimal to Preserve the Integrity of Lymphatic Endothelial Cells

“…Krishnamachary et al also found correlations between severity of the disease and EVs-associated proteins as well as EVs-mediated endothelial apoptosis [ 54 ]. EVs can also serve as decoys for neutralizing antibodies and modulate immunity [ 55 ]. A review article from Askenase focuses on the involvement of exosomes in convalescent plasma for COVID-19 therapy [ 56 ].…”