HRH3 and infection: The results showed that histamines at concentrations of 8, 40, and 200μM potently inhibited SARS-CoV-2 PsV infection, while neither the HRH2antagonist nizatidine nor the HRH3 antagonist betahistine mesylate could preventviral infection, even at a drug concentration of 100 μM (Fig. 2A through C).