Provided are methods and compositions that can be used to treat subjects having a viral infection by provoking an immune response using newly discovered antigens that are non-naturally occurring variations on viral glycoproteins. For example, provided are viral glycoproteins or a fragments thereof, or, DNA constructs encoding for such viral glycoproteins or fragments thereof, wherein the glycoprotein or fragment comprises a glycosylation sequon that includes a non-templated aspartic acid residue.