We would like to block write permissions to USB drives. We will allow user read-only permissions to the USB drive.
By doing that, do we still allow the Antivirus to scan the USB drive and delete, if needed, the potential virus found?
No. If the USB port only allows reading, then Anti-virus cannot delete the file from the drive.
But it might not have to. AV can simply block the file from being run. The virus will still be there, but it will not infect the machine.
Alternatively, there is software that will block users from USB. So you could run AV as a permitted user.