Km. Lockridge et al., Protective immunity against feline immunodeficiency virus induced by inoculation with vif-deleted proviral DNA, VIROLOGY, 273(1), 2000, pp. 67-79
To determine whether live-attenuated feline immunodeficiency virus (FIV) pr
oviral DNA will induce protective immunity, a plasmid clone constructed wit
h a FIV provirus containing a deletion in the viral accessory gene vif (FIV
-pPPR-Delta vif) was inoculated as proviral DNA into four cats by the intra
muscular route. After 43 weeks, these cats were boosted with the same provi
ral plasmid. Analysis of peripheral blood mononuclear cells at several time
points after the primary and booster inoculations revealed no detectable v
irus or proviral DNA. Al 6 weeks after the booster, immunized cats and addi
tional naive control cats were challenged with a cell-free preparation of t
he infectious biological isolate FIV-PPR by the intraperitoneal route. Viru
s was detected after challenge in unvaccinated control cats but not in any
of the FIV-pPPR-Delta vif-immunized cats. Both FIV Gag- and Env-specific cy
totoxic T lymphocyte (CTL) activities were detected in peripheral blood cel
ls of control cats after challenge infection, whereas only one of four cats
immunized with FIV-pPPR-Delta vif DNA exhibited a measurable CTL response
to Env following challenge. Although anti-Gag antibodies were not detected
after both proviral DNA inoculation and challenge, anti-Env antibodies were
found in FIV-pPPR-ilvif-immunized cats after vaccination as well as after
challenge. These findings indicate that inoculation with FIV-pPPR-Delta vif
proviral DNA induced resistance to challenge with infectious FIV and that
a vif deletion mutant may provide a relatively safe attenuated lentiviral v
accine. (C) 2000 Academic Press.