FIV vaccine development and its importance to veterinary and human medicine: a review FIV vaccine 2002 update and review

Abstract

Feline immunodeficiency virus (FIV) is a natural infection of domestic cats that results in acquired immunodeficiency syndrome resembling human immunodeficiency virus (HIV) infection in humans. The worldwide prevalence of FIV infection in domestic cats has been reported to range from 1 to 28%. Hence, an effective FIV vaccine will have an important impact on veterinary medicine in addition to being used as a small animal AIDS model for humans. Since the discovery of FIV reported in 1987, FIV vaccine research has pursued both molecular and conventional vaccine approaches toward the development of a commercial product. Published FIV vaccine trial results from 1998 to the present have been compiled to update the veterinary clinical and research communities on the immunologic and experimental efficacy status of these vaccines. A brief report is included on the outcome of the 10 years of collaborative work between industry and academia which led to recent USDA approval of the first animal lentivirus vaccine, the dual-subtype FIV vaccine. The immunogenicity and efficacy of the experimental prototype, dual-subtype FIV vaccine and the efficacy of the currently approved commercial, dual-subtype FIV vaccine (Fel-O-Vax FIV) are discussed. Potential cross-reactivity complications between commercial FIV diagnostic tests, Idexx Snap Combo Test and Western blot assays, and sera from previously vaccinated cats are also discussed. Finally, recommendations are made for unbiased critical testing of new FIV vaccines, the currently USDA approved vaccine, and future vaccines in development.

Fig. 1

FIV immunoblot and commercial FIV test results of cats immunized with the dual-subtype FIV vaccine or experimentally infected with FIV_PET (20 CID₅₀). Sera tested for FIV antibodies were from cats (two each) experimentally immunized with two different sources of dual-subtype FIV vaccine (immunoblot/Snap Combo lanes A, B, C and D) or experimentally infected with FIV (immunoblot/Snap Combo lanes E and F). These sera were tested for the presence of FIV antibodies using immunoblot analysis and commercial Idexx Snap^TM Combo (FeLV and FIV) Test Kit. The immunoblot analysis was performed at serum dilution of 1:100 using a published method (Pu et al., 2001) and the Snap test was performed as recommended by the Idexx Laboratories, Inc. Dual-subtype FIV vaccine produced by Fort Dodge Animal Health commercial company (USDA approved product) (lanes A and B) and those produced by our laboratory (lanes C and D) are shown for comparison. Immunogenicity and efficacy of our dual-subtype FIV vaccine has been previously reported (Pu et al., 2001). Both Snap test and immunoblot results demonstrate that vaccinated cats will develop antibodies reactive to current FIV diagnostics. Both vaccinations induced antibodies to the full spectrum of FIV antigens, including antibodies to the envelope (gp95). Interestingly, the cats immunized with the USDA approved dual-subtype FIV vaccine had more consistent and long-lasting antibodies to the envelope compared to cats immunized with our experimental dual-subtype FIV vaccine (2 of 2 cats vs. 1 of 2 cats positive after 1 year post-vaccination).