What is the basis for the antiviral activity of hydroxychloroquine?

The antiviral activity of hydroxychloroquine is primarily based on its ability to interfere with viral entry into the host cell. Hydroxychloroquine is known to raise the pH within the endosomal compartments of cells, which is critical for the fusion of the viral envelope with the host cell membrane. When this fusion is inhibited, the virus is unable to enter the host cell effectively, thereby preventing it from initiating the infection process.

This mechanism is significant because preventing the entry of the virus is a crucial step in controlling viral infections. By blocking the initial phase of infection, hydroxychloroquine can help mitigate the spread of the virus within the body. The other proposed mechanisms, such as inhibiting the release of virions, interrupting replication or transcription of viral RNA, do not accurately describe the primary action of hydroxychloroquine, as its foremost role is to prevent the virus from gaining access to host cells in the first place.