WHAT IS FELINE LEUKEMIA
virus evolved from a virus of ancestral rats and cats. During the
evolutionary process, three subgroups emerged. FeLV-A is the only
subgroup that is contagious between cats, making it the most clinically
significant. FeLV-B and FeLV-C are able to infect cats, but only
if the cat is already infected with FeLV-A (4).
Feline leukemia virus is a virus
that belongs to the
Retroviridae family, Oncovirinae
subfamily. It is a gamma-
It has a genome
comprised of a single strand of
surrounded by a protein
core and encased within
THE FELINE LEUKEMIA VIRAL GENOME
leukemia RNA codes for only a few
proteins. The protein that is detected
clinically is p27. This is a
group-associated antigen (gag), indicating that all subgroups
have the same protein. p27 is responsible
for viral infectivity, virulence, and subsequent disease.
Free p27 can be found in plasma, tears, and
saliva. The polymerase
gene codes for reverse transcriptase. Envelope
(env) genes encode envelope
proteins gp70 and p15e.
gp70 defines the different subgroups. An
anti-gp70 antibody is able to neutralize
subgroups. Envelope protein p15e is
responsible for immunosuppression in
LEUKEMIA VIRAL REPLICATION
are unique from other viruses
in that they carry with them an enzyme called reverse
(RT). Once the virus has infected a cell,
the single-stranded viral RNA is
released into the cellular cytoplasm. RT
makes a DNA copy of the RNA.
The DNA copy is called a provirus,
which randomly inserts into the host cell’s DNA (6).
the host cell replicates its DNA, the viral DNA is replicated as well,
followed by protein synthesis. The cell
synthesizes its own cellular proteins along with viral proteins. The newly synthesized viral proteins come
together to form new virions, each with a single strand of viral RNA
inside them. FeLV leaves the cell by
budding out (3).
It takes a little bit of the
cell’s plasma membrane and uses it to envelope itself.
This process is non-cytopathic and the cell remains alive.