AIM:　To　explore　the　possibility　of　the　replacement　of　the　gag　gene　between　human　immunodeficiency　virus　and　bovine　immunodeficiency　virus,　to　achieve　chimeric　virions,　and　thereby　gain　a　new　kind　of　AIDS　vaccine　based　on　BHIV　chimeric　viruses.　METHODS:　A　series　of　chimeric　BHIV　proviral　DNAs　differing　in　the　replacement　regions　in　gag　gene　were　constructed,　and　then　were　transfected　into　293T　cells.　The　expression　of　chimeric　viral　genes　was　detected　at　the　RNA　and　protein　level.　The　supernatant　of　293T　cell　was　ultra　centrifuged　to　detect　the　probable　chimeric　virion.　Once　the　chimeric　virion　was　detected,　its　biological　activities　were　also　assayed　by　infecting　HIV-sensitive　MT4　cells.　RESULTS:　Four　chimeric　BHIV　proviral　DNAs　were　constructed.　Genes　in　chimeric　viruses　expressed　correctly　in　transfected　293T　cells.　All　four　constructs　assembled　chimeric　virions　with　different　degrees　of　efficiency.　These　virions　had　complete　structures　common　to　retroviruses　and　packaged　genomic　RNAs,　but　the　cleavages　of　the　precursor　Gag　proteins　were　abnormal　to　some　extent.　Three　of　these　virions　tested　could　attach　and　enter　into　MT4　cells,　and　one　of　them　could　complete　the　course　of　reverse　transcription.　Yet　none　of　them　could　replicate　in　MT4　cells.　CONCLUSION:　The　replacement　of　partial　gag　gene　of　HIV　with　BIV　gag　gene　is　feasible.　Genes　in　chimeric　BHIVs　are　accurately　expressed,　and　virions　are　assembled.　These　chimeric　BHIVs　(proviral　DNA　together　with　virus　particles)　have　the　potential　to　become　a　new　kind　of　HIV/AIDS　vaccine.　(C)　2005　The　WJG　Press　and　Elsevier　Inc.　All　rights　reserved.