Feline Leukemia Virus (FeLV) is a retrovirus characterized in the domestic cat and originally isolated in 1964. The following subgroups have been detected from a sequence variation in the viral surface env-like Surface glycoprotein (Chen et al. 1998 and references therein):
- FeLV-A is an ecotropic virus present in all natural isolates.
- FeLV-B is a polytropic virus concurrent with FeLV-A, which is over-represented in the lymphosarcomas of infected but otherwise healthy cats.
- FeLV-C is also polytropic, although more infrequent and related to FeLV-A or FeLV-A/plus/FeLV-B. It is known that this variant induces aplasmatic anemia in cats, and it has been speculated that this subgroup might be a variant of FeLV-A.
The "FeLV-A Rickard" strain is taken as a representative. Its genomic structure is 8.4 Kb size including LTRs of 0.5 Kb. The internal region displays a Primer Binding Site (PBS) complementary to a tRNAPro, a single Open Reading Frame (ORF) encoding the gag-pol polyproteins, an ORF for the env, and also a Polypurine Tract (PPT) adjacent to the 3′LTR (Chen et al. 1998).
Figure not to scale. If present, long terminal repeats (LTRs) have been highlighted in blue. Amino acid motifs noted with lines indicate the conserved residues in each protein domain, abbreviations below mean:
||DU or DUT=dUTPase
||TAV or IBMP=transactivator/viroplasmin or inclusion body matrix protein
||PBS=primer binding site
||ATF=aphid transmission factor
||VAP=virion associated protein