IDENTIFICATION OF 3 FELINE IMMUNODEFICIENCY VIRUS (FIV) ENV GENE SUBTYPES AND COMPARISON OF THE FIV AND HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1EVOLUTIONARY PATTERNS
Dl. Sodora et al., IDENTIFICATION OF 3 FELINE IMMUNODEFICIENCY VIRUS (FIV) ENV GENE SUBTYPES AND COMPARISON OF THE FIV AND HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1EVOLUTIONARY PATTERNS, Journal of virology, 68(4), 1994, pp. 2230-2238
Feline immunodeficiency virus (FIV) is a lentivirus associated with AI
DS-like illnesses in cats. As such, FIV appears to be a feline analog
of human immunodeficiency virus (HIV). A hallmark of HIV infection is
the large degree of viral genetic diversity that can develop within an
infected individual and the even greater and continually increasing l
evel of diversity among virus isolates from different individuals. Our
goal in this study was to determine patterns of FN genetic diversity
by focusing on a 684-nucleotide region encompassing variable regions V
3, V4, and V5 of the FIV env gene in order to establish parallels and
distinctions between FIV and HIV type 1 (HIV-1). Our data demonstrate
that, like HIV-1, FIV can be separated into distinct envelope sequence
subtypes (three are described here). Similar to that found for HIV-1,
the pairwise sequence divergence within an FIV subtype ranged from 2.
5 to 15.0%, whereas that between subtypes ranged from 17.8 to 26.2%. H
owever, the high number of synonymous nucleotide changes among FIV V3
to V5 env sequences may also include a significant number of back muta
tions and suggests that the evolutionary distances among FIV subtypes
are underestimated. Although only a few subtype B viruses were availab
le for examination, the pattern of diversity between the FIV A and B s
ubtypes was found to be significantly distinct; subtype B sequences ha
d proportionally fewer mutations that changed amino acids, compared wi
th silent changes, suggesting a more advanced state of adaptation to t
he host. No similar distinction was evident for HIV-1 subtypes. The di
versity of FIV genomes within individual infected cats was found to be
as high as 3.7% yet twofold lower than that within HIV-1-infected peo
ple over a comparable region of the env gene. Despite these difference
s, significant parallels between patterns of FIV evolution and HIV-1 e
volution exist, indicating that a wide array of potentially divergent
virus challenges need to be considered in FIV vaccine and pathogenesis
studies.