SARS-CoV-2 spike (S) mediates viral entry into cells and is critical for vaccine development against COVID-19.
Structural studies have revealed distinct conformations of S, but real-time information that connects these structures, is lacking. In this paper it’s applied single-molecule Fluorescence (Förster) Resonance Energy Transfer (smFRET) imaging to observe conformational dynamics of S on virus particles.
Virus-associated S dynamically samples at least four distinct conformational states. In response to human receptor Angiotensin-Converting Enzyme 2 (hACE2), S opens sequentially into the hACE2-bound S conformation through at least one on-path intermediate.
Conformational preferences observed upon exposure to convalescent plasma or antibodies suggest mechanisms of neutralization involving either competition with hACE2 for binding to the receptor-binding domain (RBD) or allosteric interference with conformational changes required for entry.
These findings inform on mechanisms of S recognition and conformations for immunogen design.
6 Comments
Havewala
It is not clear how …
smFRET imaging …
showed that ….
exposure to convalescent plasma or antibodies …
suggest mechanisms of neutralisation …
involving allosteric interference.
PIER MARIA FORNASARI
the SARS-CoV-2 virus once attached to ACE receptor is strongly activated by proteolytic enzymes and this can be the point of action of new drugs (like convalescent plasma antibodies or proteases inhibitors) to control infection
Havewala
Before saying what might sound criticism, it needs to be underlined your smFRET imaging is phenomenal work which deepens our knowledge.
Convalescent plasma /antibodies could allosteric-ally interfere with the proteolytic enzymes. But it is not clear how the smFRET imaging described in your paper supports this conclusion.
PIER MARIA FORNASARI
You must open the paper and look at Figure 4.
This is the legenda
Figure 4. Spike-conformational preferences of RBD-directed monoclonal
antibodies and convalescent patient plasma.
(A, B) Bar graphs of a virus capture assay (VCA) showing that convalescent plasma from
SARS-CoV-2-positive patients S006 and S002 can bind to SARS-CoV-2 S on viral particles not
to SARS-CoV-1 in reference to a cross-reactive SARS-CoV-1 monoclonal antibody CR3022.
(B) The competition VCA depicts sensitivity of S006 binding to S to soluble ACE2. p values
derived from unpaired t-test; * corresponds to p < 0.05. Plasma from healthy donors HD1542 and HD1545 as controls. S006, S002, HD1542, and HD1542 represent plasma. Virus capture experiments were repeated three times and represented as mean ± s.d. (C) The binding affinity of both S006 and S002 towards SARS-CoV-2 RBD in comparison to plasma from heathy donors by anti-RBD IgG ELISA. (D–J) FRET histograms of CR3022 (D) at 200 µg/ml, convalescent patient plasma from S006 (E) and S002 (F) at 1:100 dilution, and RBD-directed monoclonal antibodies VHH72 (G), H4 (H), 2- 43 (I), and 2-4 (J) at 200 µg/ml. (K) Three-dimensional presentations of FRET histograms of spikes on the retrovirus under different conditions (D–I) in reference to ligand-free (Figure 2B). FRET histograms represent mean ± s.e.m., determined from three randomly assigned populations of FRET traces. For state occupancies see Table S1.
Havewala
BINGO !
Your smFRET imaging is phenomenal work which deepens our knowledge.
PIER MARIA FORNASARI
Thanks. Follow the website and please recommend it to your friends