Efficient　expression　of　HIV-1　structural　gene　involves　regulation　by　viral　Rev　and　Rev-responsive　elements　(RRE).　Messenger　RNAs　of　wild-type　HIV-1　structural　genes　are　either　retained　in　the　nucleus　or　degraded　rapidly　in　the　absence　of　Rev/RRE;　therefore　little　protein　can　be　expressed.　Modifying　HIV-1　genes　is　an　excellent　approach　to　circumvent　this　problem,　but　it　is　a　laborious　and　costly　process.　Using　certain　vectors　to　deliver　wild-type　genes　may　be　a　promising　approach.　In　this　study,　the　wild-type　and　modified　gag　genes,　derived　from　Chinese　HIV-1　isolates,　were　separately　constructed　in　both　plasmid　DNA　and　recombinant　Sendai　virus　vectors　(rSeV).　The　expression　and　immunogenicity　of　the　wild-type　and　modified　gag　genes　were　compared.　The　results　showed　that　efficient　expression　of　the　modified　gag　gene　could　be　achieved　by　transfection　with　DNA　and　infection　with　rSeV,　but　the　efficient　expression　of　wild-type　gag　could　only　be　achieved　by　rSeV.　In　addition,　the　rSeV　expressing　wild-type　gag　elicited　similar　Gag-specific　immune　responses　with　modified　gag　in　both　SeV/SeV　and　DNA-prime/rSeV-boost　schemes.　However,　SeV/SeV　failed　to　produce　Gag-specific　responses　as　robust　as　DNA/rSeV.　Then　the　SeV-specific　humoral　and　cellular　immune　responses　were　evaluated　just　before　the　second　rSeV　vaccine　immunization.　It　was　found　that　anti-SeV　neutralizing　antibody　was　very　low　but　the　SeV-specific　cellular　response　was　strong.　Efficient　expression　of　wild-type　HIV-1　structural　genes　may　make　the　SeV　vector　a　useful　tool　for　the　HIV-1　vaccine　research,　but　the　strong　SeV-specific　cellular　immune　responses　may　impair　the　efficacy　of　SeV-SeV　vaccination　scheme.