Tissue tropism

Factors influencing viral tissue tropism include: • The presence of cellular receptors permitting viral entry. • Availability of transcription factors involved in viral replication. • The molecular nature of the viral tropogen or virus surface, such as the glycoprotein, which interacts with the corresponding cell receptor. The cellular receptors are the proteins found on a cell or viral surface. These receptors are like keys, allowing the viral cell to fuse with or attach itself to a cell. The way that these proteins are acquired is through a similar process to that of an infection cycle. ==How 'tropic' tissue is acquired==

Tissue tropism develops in the following stages: • Virus with GPX enters body (where GP - glycoprotein and X is the numeric value given to the GP) • Viral cell "targets" cell with a GPX receptors • Viral cell fuses with the host cell and inserts its contents into the host cell • Reverse transcription occurs • Viral DNA is incorporated with host DNA via viral enzyme • Production of RNA and viral protein • Viral particle is assembled • Viral particle buds out of the cell, taking a chunk of the cell membrane with it and acquiring a new tissue with all the receptors it needs to continue tissue tropism Example: HIV has a gp120, which is precisely what the CD4 marker is on the surface of the macrophages and T cells. Thus HIV can enter T cells and macrophages. ==See also==