Hsien-Jue Chu

Efficacy and safety of a feline immunodeficiency virus vaccine

Abstract Fel-O-Vax FIV is an inactivated virus vaccine designed as an aid in the prevention of infection of cats, 8 weeks or older, by feline immunodeficiency virus (FIV). It contains two genetically distinct FIV strains. The efficacy of this vaccine was demonstrated in a vaccination–challenge study designed to meet various regulatory requirements for registering the vaccine. Eight-week-old kittens were vaccinated with an immunogenicity vaccine which contained minimal release levels of FIV antigens formulated with a proprietary adjuvant system. Twelve months later, all vaccinates and controls were challenged with a heterologous FIV strain. Following the vigorous challenge exposure, cats were monitored for FIV viremia. It was found that 16% of the vaccinated cats developed viremia while 90% of the controls became persistently infected with FIV, which demonstrated that the vaccine was efficacious and the protective immunity lasted for at least 12 months. The safety of the vaccine was demonstrated by a field safety trial in which only 22 mild reactions of short duration were observed following administering 2051 doses of two pre-licensing serials of Fel-O-Vax FIV to cats of various breeds, ages and vaccination histories. Thus, Fel-O-Vax FIV is safe and efficacious for the prevention of FIV infection in cats.

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.