Virology, Nebraska Center for


Date of this Version



2004, American Society for Microbiology. All Rights Reserved.

DOI: 10.1128/JVI.78.4.2158–2163.2004


JOURNAL OF VIROLOGY, Feb. 2004, p. 2158–2163 Vol. 78, No. 4


Rigorous phylogenetic analyses were used to compare the nucleotide sequences of feline immunodeficiency virus strains isolated from Texas and throughout the world. The envelope V3-V4 sequences and capsid gene of the Texas isolates formed a cluster between subtypes B and E. Statistical comparisons with other published sequences confirmed that the Texas group is a unique cluster, possibly a new subtype, arising from subtype B.

Feline immunodeficiency virus (FIV) was initially isolated in 1987 from a cat in California with severe immunodeficiency and has been recognized as a common worldwide feline pathogen (11, 14, 19, 20, 33). FIV-infected cats exhibit a progressive impairment of cellular immunity, leaving the animals susceptible to opportunistic infections (17, 23, 24). Similar to other lentiviruses, genetic variations may occur as a result of point mutations or recombination (1, 2). Since genetic variation and associated disease characteristics are similar between FIV and human immunodeficiency virus, FIV is a practical model for T-tropic lentiviral infection, especially for vaccine development and the design of antiviral therapies (3, 4, 11, 12, 14, 17, 21, 27, 29, 33, 34).

A number of FIV strains have been identified throughout the world, and their corresponding genomes have been partially sequenced (1, 5, 6, 10, 13, 15, 18, 19, 22, 27, 32). Studies developed on the basis of the nucleotide sequences from the envelope gene separated FIV strains into five distinct phylogenetic subtypes designated A to E (1, 2, 10, 13, 22, 27). Although geographic isolation could be a major factor in the evolution of FIV, individual subtypes are found in more than one part of the world (1, 2, 5, 13, 19, 27). For example, subtypes A and B have been isolated from cats in the United States, Europe, Japan, and Australia, and subtype C-infected cats have been identified in North America, Europe, and Taiwan. Consequently, recombinant strains have also been described (notably between subtype A and B subtypes and between B and D subtypes) (1, 2). The isolation and characterization of new FIV isolates with a broad feline representation, including high-risk feral cats, are critical for better understanding of ongoing genetic diversity.