Stable pseudotyped lentiviral particles and uses thereof

A method for obtaining stable lentiviral particles pseudotyped with an endogenous retroviral syncytin (ERV syncytin) and packaging a heterologous gene of interest, which have a high physical and/or infectious titer(s), comprising the following steps:

• a) transfecting four plasmids in appropriate cell lines, wherein said four plasmids comprise a first plasmid comprising the heterologous gene of interest, a second plasmid comprising the lentiviral rev gene, a third plasmid comprising the gag and pol genes, and a fourth plasmid comprising a nucleotide sequence coding for an envelope glycoprotein, wherein the envelope glycoprotein consists of an ERV syncytin selected from the group consisting of HERV-W, HERV-FRD, murine syncytin-A and murine syncytin-B;
• b) incubating the transfected cells obtained in a), so that they produce the stable lentiviral particles pseudotyped with an ERV syncytin, and packaging the heterologous gene of interest;
• c) harvesting the stable lentiviral particles obtained in b) 24 hours after the transfection, before fusion of the transfected cells, and
• d) concentrating the stable lentiviral particles harvested in c) to obtain a preparation of concentrated stable lentiviral particles having a high infectious titer higher than 1×106 TU/mL or a high physical titer higher than 1.5×10 5 ng p24/mL after freezing and thawing of the preparation.