LA possesses a broad spectrum of inhibitory activity against SARS-CoV-2 variants
We then sought to investigate whether LA has the ability to inhibit SARS-CoV-2 variants by imaging SARS-CoV-2 N protein in Vero cells 24 h after the inoculation of authentic virus. The results showed that LA treatment impeded the infection of SARS-CoV-2 variants including Alpha, Beta, Delta, and Omicron with similar IC50 values of 3.37, 3.12, 2.23, and 2.45 μM, respectively (Figure 6a). Importantly, these values are comparable to that of ancestral virus (IC50: 2.62 μM) (Figure 2d), providing further corroborating evidence that LA can effectively hinder the infection of SARS-CoV-2, regardless of the types of S-mutation. Of note, remdesivir exhibited less effective and variable inhibitory activity toward SARS-CoV-2 variants (IC50: 4.06 ~ 7.40 μM) compared to LA (Figure 6b). Together, these results demonstrate that LA blocks the infection of SARS-CoV-2 variants as well as their ancestral virus with similar efficiency and thus implicate that LA can be a broad-spectrum antiviral agent, providing additional protection strategy against infection by SARS-CoV-2 variants