Dual-subtype FIV vaccine (Fel-O-Vax FIV) protection against a heterologous subtype B FIV isolate

Abstract

Vaccine trials were undertaken to determine whether the Fel-O-Vax FIV, a commercial dual-subtype (subtypes A and D) feline immunodeficiency virus (FIV) vaccine, is effective against a subtype B FIV isolate. Current results demonstrate the Fel-O-Vax FIV to be effective against a subtype B virus, a subtype reported to be the most common in the USA.

Fig 1

The phylogenetic tree distribution (panel A), amino acid comparison (panel B), and recombination analysis (panel C) of the vaccine viruses and challenge virus used in current studies 1 and 2, and the virus (FIV_Bang) reported for prototype dual-subtype FIV vaccine studies (Pu et al 2001). The two vaccine viruses (boxes) and two challenge viruses (ovals), along with known FIV strains, are displayed in a phylogenetic tree of the FIV envelope (env). An unrooted phylogenetic tree was created using the BLOSUM matrix and neighbor-joining algorithm based on the Kimura two-parameter correction (Saitou and Nei 1987, Kimura 1980). Support at each internal node was assessed using 1000 bootstrap samplings and each tree was visualized using Tree View (Felsenstein 1989, Page 1996). All full-length isolates from NCBI data bank (Accession numbers M36968, X60725, M73964, L06312, X57002, M25381, L00607, D37813, X69496, X57001, X69494, D37811, D37815, AF474246, AF452126, D37812, D37816, D37814, E03581, AY621093, D37817, AY621094, U11820, AY620002) have been used with the exception of those based on partial sequences, which are designated in italics (CaBCpady02C, LP-24, LP-20, M2) (Accession numbers U02392, AB027304, AB027302, X69501). Isolates from Japan are designated with Jn, and isolates from USA are designated with the state abbreviation followed by the name of the virus. The amino acid (aa) sequence comparisons (panel B) between the vaccine and challenge strains used in our studies further demonstrate that both vaccine strains (FIV_Pet and FIV_Shi) had the greatest % aa difference from subtype B FIV_FC1 at all viral proteins (Gag, Pol, Env) analyzed. The recombination analysis (panel C) of structural and polymerase genes of the vaccine and challenge strains was based on phylogenetic tree distributions of the FIV group-specific antigen (gag, tree not shown), FIV polymerase (pol, tree not shown), and FIV env (panel A). FIV_Bang is a recombinant of subtypes A and B, and FIV_FC1 belongs to subtype B at gag, pol and env.