This result was surprising because VLPs were previously observed using vaccines encoding Env and Gag of MelARV [6,7] and HERV-K (unpublished results, patent no. WO2019043127) (Supplementary Figure S1E), and because of the reported association of the used HERV-W Gag sequence with the formation of particles in patients with multiple sclerosis [39,40]. This evidence concerns the gene ERVW-1 and multiple sclerosis.