Codon optimization of the immunogenic genes is an effective strategy for improving the protection efficacy of DNA vaccine.It is well known that different species have different bias in using the codons for protein expression.Equine infectious anemia virus(EIAV)differs greatly from mammalian in utilizing codons bias.Using over-lapping extension PCR techniques and restriction enzyme digestion,we constructed membrane-bound and secreted EIAV env gene with mammalian codons.The genes were inserted into pCAGGS and...