ERVW-1 and coinfection: It was generally evident that gp and env transgene expression by the FPgp or FPenv single recombinants and by the FPgpCIITA or FPenvCIITA double recombinants was lower than after co-infection with the FPgp+FPCIITAH6 or FPenv+FPCIITAH6 single recombinants.