Baric Transcribed Interview (Redacted) — page 132

DC.Scheduling@LexitasLegal.com asymptomatic. It's an enteric disease. It's when you lose the furin cleavage site that it becomes a fulminant, deadly disease that is 100 percent fatal in cats. So loss-of- function of that furin cleavage site kills you dead, the cat. In mouse hepatitis virus, a couple of researchers had removed the furin cleavage site and said what happens to the pathogenesis? There was no change. Another group, taking pseudoviruses, had introduced furin sites into the SARS-coronavirus 2003 strain, and the only thing they found was slightly increased infectivity. Nothing big. Nothing that said "eureka." So now let's compare SARS from 2003 and SARS-2, and let's ask the question, what experiments were done to prove that the furin cleavage site drove severe disease in SAR-2 pathogenesis. What they did was a loss-of-function experiment. They deleted those four residues that were introduced by whatever means, and they asked what happened to the virus. It was less pathogenic, and it was less transmissible. Eureka. Furin cleavage site causes that phenotype. Except when you look at the other figures in the paper, where it shows that it also knocked down the ability of other proteases to cleave at that S1/S2 boundary. So it wasn't a furin cleavage site-specific knockout.