Changes

==Agent==

==Agent==

FIV is a member of the lentivirus genus of the Retroviridae family. The Retroviridae are enveloped viruses which contain a single-stranded RNA genome within an icosahedral nucleocapsid. Glycoprotein surface spikes are located on the envelope. Unusually, Retroviruses have a diplod genome: two identical copies of their positive-sense ssRNA are found on the virion^viro. During viral replication, reverse transcriptase converts the ssRNA genome to ssDNA. This process is inherently error-prone, and the high rate of mutation gives rise to a wide genetic diversity of virus^viro. A dsDNA can then be made from the ssDNA template. This provirus DNA then becomes integrated into the host genome by the actions of the viral enzyme integrase, and remains latent until transcription is initiated by the host cell machinery^viro. Proviral DNA then serves as a template for the production of progeny ssRNA genomes and messenger RNA.  

FIV is a member of the lentivirus genus of the Retroviridae family. Retrovirus virions are are sensitive to heat, lipid solvents, and detergents but are relatively resistant to damage caused by ultraviolet light^viro. The Retroviridae are enveloped viruses which contain a single-stranded RNA genome within an icosahedral nucleocapsid. Glycoprotein surface spikes are located on the envelope. Unusually, Retroviruses have a diplod genome: two identical copies of their positive-sense ssRNA are found on the virion^viro. During viral replication, reverse transcriptase converts the ssRNA genome to ssDNA. This process is inherently error-prone, and the high rate of mutation gives rise to a wide genetic diversity of virus^viro. A dsDNA can then be made from the ssDNA template. This provirus DNA then becomes integrated into the host genome by the actions of the viral enzyme integrase, and remains latent until transcription is initiated by the host cell machinery^viro. Proviral DNA then serves as a template for the production of progeny ssRNA genomes and messenger RNA. Once the proviral DNA has been transcribe and translated, the virions assemble and are release by budding through the host cell membrane. This does not always cause lysis^viro.

Once the proviral DNA has been transcribe and translated, the virions assemble and are release by budding through the host cell membrane. This does not always cause lysis^viro.

 

Many Retrovirus genomes contain oncogenes which may be expressed when integrated to the host genomes. However, oncogenes are not a requirement for tumour induction, and some Retroviruses can cause tumours without carrying oncogenes. The Retroviral genome has four coding regions. The "gag" region codes for the matrix protein, nucleoprotein and capsid, and "pro" encodes a protease^viro. Reverse transcriptase is coded by the "pol" region, whereas "env" gives rise to the envelope and receptor binding. An additional, specific cellular transporter RNA is required for replication and present within the virion.

 

    * Many retroviruses carry oncogenes (e.g., Rous sarcoma virus in chickens), while others do not (e.g., human T-cell lymphotrophic virus). However, some retroviruses may cause tumors without carrying oncogenes.

    * All retroviral genomes consist of two molecules of ssRNA, (+)sense, have 5' cap and 3' poly-(A) (equivalent to mRNA) and four characteristic coding regions (gag-pro-pol-env). Gag (group specific antigen: matrix protein, nucleoprotein, capsid) genes; pro (protease) gene; pol (reverse transcriptase and RNase-H); and env (envelope, receptor binding) genes (see Fig.15.2). These vary in size from ~8-11 kb. They are the only viruses that are truly diploid. Additionally, there is a specific type of cellular transporter RNA (tRNA) (usually trp, pro or lys) - required for replication that is present in the virion.

    * The virions are sensitive to heat, lipid solvents, and detergents but are relatively resistant to ultraviolet light damage.

==Transmission and Epidemiology==

==Transmission and Epidemiology==