Structure
FIV is structured like other lentiviruses, which cause immune deficiency syndromes in mammals. The virion has a diameter from 80 to 100 nanometers and is pleomorphic. The viral envelope also has surface projections that are small, 8 nm, and evenly cover the surface.
The FIV virus genome is diploid. It consists of two identical single-strands of RNA in each case about 9400 nucleotides existing in plus-strand orientation. It has the typical genomic structure of retroviruses, including the gag, pol, and env genes as well as additional lentiviral genes vif, vpr, and rev. However it does lack the accessory genes tat, vpu, vpx, and nef. The gag polyprotein is proteolytically processed into major capsid proteins while the pol polyprotein is processed into virally encoded enzymes, and env into envelope glycoproteins. The capsid protein derived from the polyprotein gag is assembled into a viral core (the protein shell of a virus) and the matrix protein also derived from gag forms a shell immediately inside of the lipid bilayer. The env polyprotein codes for surface glycoproteins (SU) and transmembrane glycoproteins (TM). Both SU and TM glycoproteins are heavily glycosylated, a characteristic that scientists believe may mask the B-cell epitopes of the env glycoprotein giving the virus resistance to the virus neutralizing antibodies.
Read more about this topic: Feline Immunodeficiency Virus
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