Video showing the internalization of VLP-Wuhan^del-1:(E, S, N, M&M-mCherry&M-pHluorin) into A549. This VLPs allow the simultaneous tracking of the pH of the VLP together with its membrane dynamics. pHluorin emits bright fluorescent light in pH≥8 but its intensity sharply decreases at pH<7.5, completely disappearing at pH<5.As the M protein C-terminal domain lies inside the VLPs, the fused pHluorin serves as a real-time indicator of the intra-VLP pH. When added to the medium (pH8), pHluorin-labelled VLPs emitted a bright green signal  and mCherry emits bright red signal which renders the visible signal as yellow. However, shortly after binding to the membrane of the A549 cells, the intensity rapidly disappeared, due to drop into pH during internalization and only the mCherry (Red) one is still present.

A549

A549 cells are lung carcinoma epithelial cells.

No cell labelling,

SASR-CoV-2 VLPs Del-1

SARS-CoV-2 virus-like particles containing an inframe 30-bp deletion which spanned genome coordinates 2035–2064 of the spike region. This region is the S1/S2 junction and attenuated the particles entry into cells.

M-mCherry M-pHluorin, Part of the M protein of the particle is tagged with mCherry and part with M-pHluorin. This allows us to track simultaneously the membrane of the particle and the the change of the pH under the microscope.

No treatment