Well if I understand it correctly, he creates this messenger RNA code with the poem encrypted in it packs that in a retrovirus which implants his code onto the DNA of the cell. The gene that he packs in the virus and then is grafted onto the host DNA codes for a certain string of amino acids that create a protein. That protein is the poem itself since he assigns every letter and a space to an amino acid. So a protein string that read Leucine, Glycine, Proline, Proline produces the word Glee. So it's synthetic in that it's not natural to any cell and works kind of like a flu vaccine.
