Lentiviruses

Lentivirus is primarily a research tool used to introduce a gene product into <a href="https://en.wikipedia.org/wiki/In_vitro" title="In vitro" >in vitro</a> systems or animal models. Large-scale collaborative efforts are underway to use lentiviruses to block the expression of a specific gene using <a href="https://en.wikipedia.org/wiki/RNA_interference" title="RNA interference" >RNA interference</a> technology in high-throughput formats. The expression of <a href="https://en.wikipedia.org/wiki/ShRNA" class="mw-redirect" title="ShRNA" >short-hairpin RNA (shRNA)</a> reduces the expression of a specific gene, thus allowing researchers to examine the necessity and effects of a given gene in a model system. These studies can be a precursor to the development of novel drugs which aim to block a gene-product to treat diseases. Conversely, lentivirus are also used to stably over-express certain genes, thus allowing researchers to examine the effect of increased gene expression in a model system.

Another common application is to use a lentivirus to introduce a new gene into human or animal cells. For example, a model of mouse <a href="https://en.wikipedia.org/wiki/Hemophilia" class="mw-redirect" title="Hemophilia" >hemophilia</a> is corrected by expressing wild-type platelet-<a href="https://en.wikipedia.org/wiki/Factor_VIII" title="Factor VIII" >factor VIII</a>, the gene that is mutated in human hemophilia. Lentiviral infection has advantages over other gene-therapy methods including high-efficiency infection of dividing and non-dividing cells, long-term stable expression of a <a href="https://en.wikipedia.org/wiki/Transgene" title="Transgene" >transgene</a>, and low immunogenicity. Lentiviruses have also been successfully used for <a href="https://en.wikipedia.org/wiki/Transduction" class="mw-disambig" title="Transduction" >transduction</a> of diabetic mice with the <a href="https://en.wikipedia.org/wiki/Gene" title="Gene" >gene</a>-encoding <a href="https://en.wikipedia.org/wiki/PDGF" class="mw-redirect" title="PDGF" >PDGF</a> (platelet-derived growth factor), a therapy being considered for use in humans. These treatments, like most current gene therapy experiments, show promise but are yet to be established as safe and effective in controlled human studies. <a href="https://en.wikipedia.org/wiki/Gammaretrovirus" title="Gammaretrovirus" >Gamma retroviral</a> and lentiviral vectors have so far been used in more than 300 clinical trials, addressing treatment options for various diseases.

Viruses are small obligate intracellular parasites with either a RNA or DNA genome that are surrounded by a protective protein coat and transfer their genetic material to infected cells.

Lentivirus represents a genus of slow viruses with long incubation period (months, even years) and a propensity to induce a wide range of pathologies in different animal species. Due to their rather flexible genome and a potential of transducing many forms of nondividing cells, lentiviruses have become one of the most widely used vectors for gene transfer.

According to the recent classification of International Committee on Taxonomy of Viruses (ICTV), Lentivirus genus belongs to the family Retroviridae and currently comprises of nine species: seven animal lentiviruses and two human lentiviruses.

Animal lentiviruses are bovine immunodeficiency virus (BIV), caprine arthritis encephalitis virus (CAEV), equine infectious anemia virus (EIAV), feline immunodeficiency virus (FIV), puma lentivirus (PLV), simian immunodeficiency virus (SIV) and visna/maedi virus (VMV). Human species are well-known human immunodeficinecy virus 1 (HIV-1) and human immunodeficiency virus 2 (HIV-2).

Lentiviruses

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