Using a PCR-based de novo gene synthesis method, a plant optimized HIV-1 gag gene was constructed. The gene was expressed in Nicotiana benthamiana using a modified tobacco mosaic virus-based transient expression system and leaf accumulation of the 55 kDa Gag protein was confirmed. Sucrose gradient sedimentation showed that the full-length Gag protein migrated at a density corresponding to that reported for Gag VLPs. Furthermore, examination of leaf material and the extract in transmission electron microscopy showed budding of 100-nm VLPs. Stable lines harboring the gag gene were created and were shown to accumulate the Gag protein. The dgp41 gene was then transiently expressed in these stable lines, and expression was confirmed with western blotting using anti-2F5 Abs. Preliminary evidence based on sucrose gradient sedimentation suggests that the two proteins may assemble into eVLPs.