FIG. 1.

The V1CSF-Petaluma envelope chimeras. Fragments representing specific regions of the FIV envelope gene (env) were removed from the Petaluma molecular clone (34TF10A) and replaced with equivalent sequences from V1CSF that were amplified and cloned from genomic DNA from V1CSF-infected feline PBMC. The resulting chimeras included viruses encoding the entire envelope (FIV-Ch), the SU (FIV-ChSU) or TM (FIV-ChTM) glycoprotein alone, or only the V3-to-V5 region of the SU (FIV-ChV35) from V1CSF.