Reproduction Cycle
After successfully entering a host cell, the virus envelope and capsid disassociates within the infected host cell, releasing the viral RNA and enzymes. Shortly after, the reverse transcriptase begins translating the viral RNA into cDNA molecules (complementary DNA). The viral enzyme integrase uses the cDNA molecules to enter the nucleus of the infected host cell undetected. After entering the host nucleus, the integrase enzyme then binds the cDNA molecules to the host DNA, creating provirus DNA. This DNA can lie dormant for years.
After integrating itself into the host, the virus can begin to replicate by transcribing its viral DNA into viral mRNA, which is the spliced by the host and exits the nucleus into the cytoplasm. In the cytoplasm, the mRNA is translated to TAT’s and REV’s, viral proteins that catalyze viral production and bind to the viral mRNA, allowing unspliced RNA strands to leave the binding site.
After this stage, GAG and ENV proteins are also created from the translation of the full length RNA. The GAG proteins bind to the full length RNA to create a tightly bounded package. The ENV (gp120) proteins are transported to the golgi apparatus of the infected host cell where they are cleaved off by furins to form two new proteins: gp41 and gp120. The new proteins travel across the plasma membrane, where they are attached to the virion. Gp41 associated itself with the virion capsid to form the membrane of the virion, and gp120 anchors itself to the virion and the inner membrane of the host cell.
The virion is now completely formed, and the virus begins to bud from the infected host cell. However, the virus is still immature until the nucleocapsid, capsid, and the matrix of the virus are cleaved properly by the protease of the virus. Once they have been cleaved properly, the virion takes a small portion of the outer membrane of the infected host cell as its own, causing significant damage to the infected host cell. After the HIV virion buds out completely, the HIV virus is able to spread to other macrophages and T-cells.
