We measured serum IgG responses to the native full-length Env protein expressed on the surface of cancer cells using flow cytometry, and since the SU sequence is the same in both of our vaccines, and it is the most distal and accessible part of the protein, it is possible that serum antibodies primarily bound the SU, masking any differences in responses to the Ecto-region. Here, ERVW-1 is linked to cancer.