Studies of AIDS vaccination using an ex vivo feline immunodeficiency virus model: protection conferred by a fixed-cell vaccine against cell-free and cell-associated challenge differs in duration and is not easily boosted

Abstract

Cats immunized with cells infected with a primary isolate of feline immunodeficiency virus (FIV) and fixed with paraformaldehyde were challenged with cell-free or cell-associated homologous virus obtained ex vivo. Complete protection was observed in animals challenged with cell-free virus 4 months after completion of vaccination (p.v.) or with cell-associated virus 12 months p.v. In contrast, no protection was observed in cats challenged with cell-free virus 12 or 28 months p.v or with cell-associated virus 37.5 months p.v. Prior to the 28-and 37.5-month challenges, the animals had received a booster dose of vaccine that had elicited a robust anamnestic immune response. These results show that vaccine-induced protection against ex vivo FIV is achievable but is relatively short-lived and can be difficult to boost.

FIV vaccine development and its importance to veterinary and human medicine: a review

“…When placed in a free-roaming shelter for 22 months with natural FIV-infected cats, this single-subtype vaccine protected the vaccinated group of cats (0/12 FIV infection rate) whereas 5/14 of the unvaccinated control group became infected . A major limitation of inactivated infected-cell vaccines is the short duration of vaccine immunity compared to inactivated whole virus vaccines (Matteucci et al, 1997;Tellier et al, 1998). Since the level of the FIV exposure during natural transmission remains unknown, the ef®cacy evaluation using a contact challenge system represents the ultimate test for any commercial FIV vaccine.…”

“…Among these FIV vaccine designs, VN antibody induction was more consistent in cats immunized with conventional inactivated virus vaccine followed by recombinant vectored vaccine (Tellier et al, 1998;Giannecchini et al, 2001;Pu et al, 2001). Although, inactivated infectedcell vaccine may induce higher VN antibody levels compared to inactivated whole virus vaccine, the duration of protection may be shorter in the inactivated infected-cell vaccine group (Matteucci et al, 1997). Unlike human AIDS research which test HIV vaccine antibodies for their ability to neutralize both labora-tory and clinical isolates, FIV vaccine researchers have not tested their vaccine antibodies against nonadapted clinical isolates (Matteucci et al, 1997;Pu et al, 2001).…”

“…Although, inactivated infectedcell vaccine may induce higher VN antibody levels compared to inactivated whole virus vaccine, the duration of protection may be shorter in the inactivated infected-cell vaccine group (Matteucci et al, 1997). Unlike human AIDS research which test HIV vaccine antibodies for their ability to neutralize both labora-tory and clinical isolates, FIV vaccine researchers have not tested their vaccine antibodies against nonadapted clinical isolates (Matteucci et al, 1997;Pu et al, 2001). FIV laboratories now test the crossneutralizing ability of sera from naturally and experimentally infected cats against clinical and laboratory isolates (Inoshima et al, 1998;Pu et al, 2001).…”

FIV as a Model for AIDS Vaccine Studies

“…Confirmation of the efficacy of vaccines containing FIV-infected cells was provided by Matteucci et al 47 A vaccine based on paraformaldehydeinactivated cells of the MBM feline lymphoblast line infected with FIV-M2 protected cats when challenged with ex vivo, cell-free virus 4 months after vaccination. No significant protection was recorded when the cats were challenged 12 or 28 months after vaccination, indicating that the duration of immunity was short.…”

FIV as a Model for HIV: An Overview

“…528 Duration of WKV and FC vaccineinduced protection has been another concern, with some vaccine studies revealing a breakthrough in vaccine-induced protection a year after vaccination despite boostering the primary immunization. 529,530 Another concern relates to differences in WKV or FC vaccine-induced protection observed against similar challenge viruses but delivered by different routes of exposure, including parenteral and mucosal delivery. 526 Collectively these findings suggest that WKV vaccines demonstrate significant potential for development of lentivirus vaccines, but that multiple issues including WKV vaccine-induced enhancement still require attention for achievement of optimal protection.…”