Analysis of recombinant HCoV-229E nsp6 mutants.

<p>(<b>A</b>) Predicted topological structure of HCoV-229E nsp6 indicating the location of K22 resistance mutations. Concerning transmembrane domains VI and VII two proposed topologies are shown. (<b>B-C</b>) Recombinant nsp6 mutant viruses are resistant to K22. MRC-5 cells were inoculated with nsp6 recombinant HCoV-229E^H121L, HCoV-229E^M159V, HCoV-229E^H121L/M159V or wild-type HCoV-229E at a moi of 0.05 for 45 min at 4°C, and K22 (10 µM) was added at specific time points relative to the end of inoculation period. The infectious cell culture medium and cells were harvested after 24 h of incubation at 37°C, and copy numbers of cell-associated (CA) or extracellular (EX) viral RNA was determined. Data shown are means (±SD) of duplicate determinations from two independent experiments. (<b>D-F</b>) Replication kinetics of recombinant nsp6 mutant viruses. MRC-5 cells were inoculated with nsp6 recombinant HCoV-229E^H121L, HCoV-229E^M159V, HCoV-229E^H121L/M159V or wild-type HCoV-229E at an moi of 0.05 for 1 h at 4°C. The infectious cell culture medium and cells were harvested at specific time points relative to the end of inoculation period, and copy numbers of cell-associated (CA; <b>D</b>) or extracellular (EX; <b>E</b>) viral RNA and infectivity (<b>F</b>) was determined. Data shown are means (±SD) of duplicate determinations from two independent experiments.