Phylogenetic analysis of feline immunodeficiency virus and the development of a prophylactic genetic vaccine

Feline immunodeficiency virus (FIV) is a natural pathogen of domestic and wild cats. This study investigates the use of DNA vectors capable of expressing FIV gag and envelope genes, fused to trafficking proteins, to induce strong mucosal immunity. The DNA was delivered intravenously in a polyethylenimine-macroaggregated albumin (PEI-MAA) associated complex. Fifty percent of the vaccinated cats were protected when challenged vaginally with cell-associated FIV. When stimulated with FIV proteins and peptides, all vaccinated cats were responsive and had stimulation indices up to 230, while unvaccinated animals were not responsive. Anti-FIV antibodies were not detected post-immunization and were only detected post-challenge in unprotected animals. These findings indicate that PEI-MAA delivered DNA plasmids are capable of inducing protection against vaginal challenge.; A second aspect of this study was to determine the cladistics of FIV isolated from feral cats in Texas. A phylogenetic analysis of eleven strains of FIV isolated from Texas cats was performed using envelope, V3–V4, and capsid nucleotide sequences. Phylogenetic analysis revealed that the Texas isolates clustered near the B and E clades, but was isolated to a distinct branch outside these characterized viral strains. This new and unique cluster shows an increase in the heterogeneity of the United States of America (U.S.A.) strains and likely indicates the emergence of a fourth U.S.A. subtype designated F.; Finally, data indicate that FIV from within the U.S. forms four viral clusters, A, B, C, and TX. Also shown is the geographical isolation of the strains, where clade A is predominantly found on the West coast and clade B is found predominantly on the East coast. However, clade B is found throughout the U.S.A. and represents the dominant subtype. Of the 36 viral isolates sequenced, 8 were found to cluster to the A branch, 16 were found to cluster to the B branch, and 12 were found to cluster to a unique branch, TX or branch F. This study shows a more complete and conclusive analysis of FIV isolates from within the U.S.A. and may be an essential basis for the development of an effective multi-clade vaccine.