Since the interplay between the cytoplasmic tails of gp41 and their matching matrix proteins (MA) might be less efficient, possibly affecting the envelope glycoproteins incorporation, we replaced the NL4-3 matrix of the viral background by the matrix of the variant infecting each patient during the early and chronic phases of infection to generate Env-MA-pseudotyped viruses harboring envelope glycoproteins and their matching matrix proteins. Here, ERVW-1 is linked to infection.