This invention relates to polynucleotides comprising a nucleotide sequence encoding a PPT1 polypeptide or a fragment thereof, vectors (viral or non-viral vectors) comprising the same, and methods of using the same for delivery of the open reading frame to a cell or a subject and to treat infantile neuronal lipofuscinosis (infantile Batten disease). The polynucleotides comprise an optimized CLN1 open reading frame.