Regarding envelope proteins from Orthomyxoviridae family viruses, a lentiviral vector pseudotyped with Hemagglutinin (HA) and neuraminidase (NA) envelope proteins from influenza viruses is considered as an alternative and attractive source for the study of influenza virology, in order to evaluate neutralizing antibodies and viral entry [258,259]. This evidence concerns the gene ERVW-1 and influenza.