The theosopher James Morgan Pryse
published a groundbreaking book in 1914, titled "The Restored New Testament" (see wiki link). He makes a good case indeed that the gospels are but disfigured copies from Eleusinian initiation rites
Very good stuff indeed. His vast knowledge of Ancient Greek culture and language, coupled to a deep understanding of mythology and metaphysics is impressive. A good example for other theosophers to follow!
You can also find the book (part one) on my Gnosis site