The Autobot plague ship is an Autobot starship, long lost and derelict following an ancient disaster that befell its crew.
At some point as it traveled through space, Cybonic plague spread through the ship's crew and they all died, leaving the ship flying without control. It eventually crashed on Earth in a remote area. Centuries later, Team Prime detected the ship's emergency beacon, and Optimus Prime and Ratchet cut their way into the ship to search for potential survivors. They found only bodies, but the unstable ship moved as they walked through it, causing infected energon to drip onto Optimus and resulting in him catching the plague