A vector for eliciting an immune response to a host comprising a gene encoding the gp140 protein of the primary isolate of HIV-1, BX08, under the control of a promotor for expression of the protein in the host, specifically plasmids pCMV.gp140.BX08, pMP83, pMP84 and pMP88. Murine and human MHC class 1-restricted binding motifs contained in BX08 are identified.