Cell type-specific adaptation of the SARS-CoV-2 spike

Area of Science:

• Virology
• Molecular Biology
• Evolutionary Biology

Background:

• Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infects diverse human tissues, primarily through angiotensin-converting enzyme-2 (ACE2) receptor interaction.
• Understanding SARS-CoV-2 evolution in various cellular contexts is crucial for predicting viral tropism and pathogenesis.

Purpose of the Study:

• To investigate the adaptive evolution of the SARS-CoV-2 spike protein in distinct cellular environments.
• To identify mutations conferring cell-type-specific phenotypic changes and assess their impact on viral entry and fitness.

Main Methods:

• Experimental evolution of a spike-expressing recombinant vesicular stomatitis virus (VSV) across four human cell lines with varying entry factor levels.
• Sequencing to identify adaptive spike mutations after twenty passages.
• VSV pseudotyping assays to evaluate entry efficiency, ACE2 affinity, spike processing, TMPRSS2 usage, and entry pathway utilization.
• Cell-cell fusion assays to assess spike fusogenicity.
• Recombinant VSV fitness assays to determine the advantage of selected mutations.

Main Results:

• Sixteen adaptive spike mutations were identified, exhibiting cell-type-specific effects on viral entry and replicative fitness.
• Mutations L48S and A372T, selected in low ACE2 conditions, enhanced receptor affinity, syncytia formation, and entry efficiency.
• The impact of mutations varied significantly across different cell types, highlighting cellular context-dependent adaptation.

Conclusions:

• The SARS-CoV-2 spike protein demonstrates specific adaptive capabilities to different host cell types.
• These findings provide insights into SARS-CoV-2 tissue tropism, viral evolution, and potential mechanisms of adaptation to diverse cellular environments.