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The Lentivirus is a virus responsible for notable diseases like HIV. The Lentivirus is unique in that it has been the basis of research using viruses in gene therapy. To be effective in gene therapy, there must be insertion, alteration and/or removal of host cell genes. To do this scientists can use the Lentivirus' mechanisms of infection, that it would normally use, to achieve a desired outcome to gene therapy.

Mechanisms of Infection
Mechanisms of infection include the parts of the virus that make it able to function as it's genome codes for. The Letivirus is classified in Group VI of the Baltimore classification system, this means it has a single stranded RNA genome with a reverse transcriptase enzyme. an viral envelope with protruding glycoproteins found to aid in attachment to the host cell's outer membrane, these act as antigens for the virus and binding sites. As stated before it contains a reverse transcriptase molecule found to perform transcription of the viruses genetic material upon entering the cell. The act of the transcription of the viral RNA into DNA creates a more stable molecule inside the host cell. With in the viral genome are DNA sequences that code for specific enzymes effecting the incorporation of the viral DNA into the host cell genome. The "gag" domain codes for the structural components of the virus like the capsid,the matrix, nucleoproteins. The "pol" domain codes for the reverse transcriptase and integrase enzymes. Lastly, the "env" domain of the viral genome encodes for the glycoproteins and envelope on the surface of the virus.

Lentivirus as a Virus
To understand the capabilities of the Lentivirus as a vector, the biology of the infectious process must be understood. As discussed above the Lentivirus has many mechanisms of infection. The first of which the virus uses is the glycoproteins for attachment to the outer surface of a cell, more specifically, the CD40 ligand glycoproteins on the surface of the T-Lymphocyte cells. The viral material is then injected into the host cell's cytoplasm. Within the cytoplasm is where the viral reverse transcriptase performs transcription of the viral RNA genome to create a viral DNA genome. The viral DNA is then sent into the nucleus of the host cell where it is then incorporated into the host cell's genome with the help of the viral enzyme integrase. From there the host cell performs translation and transcription to create viral particles and assemble virions which then burst from the host cell when enough are made.

Lentivirus as a Vector
Some of the common uses for the Lentivirus vector have been in the treatment of gene therapy with diseases like Diabetes mellitus, Murine haemophilia A, prostate cancer, chronic granulomatous disease, and vascular gene therapy. Therapy requires manipulation of the lentivirus genes and structure for proper indications.

Studies
In a study designed to enhance the outcomes of vascular transplant through vascular endothelial cell gene therapy, the third-generation of Lentivirus showed to be effective in the delivery of genes to moderate venous grafts and transplants in procedures like coronary artery bypass. Because the virus has been adapted to loose most of it's genome, the virus becomes safer and more effective in transplanting the required genes into the host cell. A draw back to this therapy is explained in the study that long-term gene expression may require the use of promoters and can aid in a greater trans-gene expression.

In chronic granulomatous disease immune functioning is deficient as a result of the loss of nicotinomide adenine dinucleotide phosphate oxidase (NADP) in phagocyte cells, which aides in lipid and nucleic acid synthesis. If this becomes deficient, the bodies immune responses become weakened. Study performed in mice emphasizes the use of lineage-specific lentiviral vectors for the production of NADP. Scientists developed this strain of lentivirus by transinfecting 293T cells. The viral vector's responsibility was to increase the gene synthesis and production of NADP in these phagocytic cells.

With prostate cancer, the lentivirus is transformed by being bound to trastuzumab to attach to androgen-sensitive LNCaP and castration-resistant C4-2 human prostate cancer cell lines. These two cells are primarily responsible for secretion of excess human epidermal growth factor receptor 2 (HER-2), which is a hormone linked to prostate cancer. By attaching to these cells and changing their genomes, the lentivirus can slow down, and even kill, the cancer causing cells.

Haemophilia A has also been studied in gene therapy with a lentaviral vector in mice. The vector targets the haematopoietic cells in order to increase the amount of factor VIII, which is affected in haemophilia A. But this continues to be a subject of study as the lentavirus vector was not completely successful in achieving this goal.

Studies have also found that injection of a lentiviral vector with IL-10 expressing genes in utero in mice can suppress, and prevent, rheumatoid arthritis and create new cells with constant gene expression. This contributes to the data on stem cells and in utero inoculation of viral vectors for gene therapy.

Like many of the in utero studies, the lentiviral vector gene therapy for diabetes mellitus is more effective in utero as the stem cells that become affected by the gene therapy create new cells with the new gene created by the actual viral intervention. The vector targets the cells within the pancreas to add insulin secreting genes to help control diabetes mellitus.