Dual-subtype feline immunodeficiency virus vaccine provides 12 months of protective immunity against heterologous challenge

The duration of immunity of the dual-subtype feline immunodeficiency virus (FIV) vaccine, Fel-O-Vax FIV, for protection against subtype-B FIV was assessed in this study. Vaccinated cats along with controls were challenged with FIVFC1, a subtype-B FIV strain, 54 weeks after the final vaccination, and monitored for 46-48 weeks for provirus and viral RNA in peripheral blood, provirus in lymphoid organs, and CD4:CD8 ratios. Results of provirus detection in peripheral blood and lymphoid organs and plasma viral RNA loads showed that 10/14 vaccinated cats were fully protected for 48 weeks against infection with FIVFC1 whereas 5/5 controls were persistently infected with FIVFC1. CD4:CD8 inversions were noted in association with FIV infection and viral loads were not significantly different between FIV infected controls and the unprotected vaccinated animals.