replication cycle

HIV is a member of the group of viruses known as retroviruses, which share a unique life cycle (Fig. 4). Once HIV binds to a host cell, the viral envelope fuses with the cell membrane, and the virus's RNA and enzymes enter the cytoplasm. HIV, like other retroviruses, contains an enzyme called reverse transcriptase. This allows the single-stranded RNA of the virus to be copied and double-stranded DNA (dsDNA) to be generated. The enzyme integrase then facilitates the integration of this viral DNA into the cellular chromosome. Provirus (HIV DNA) is replicated along with the chromosome when the cell divides. The integration of provirus into the host DNA provides the latency that enables the virus to evade host responses so effectively.

Production of viral proteins and RNA takes place when the provirus is transcribed. Viral proteins are then assembled using the host cell's protein-making machinery. The virus's protease enzyme allows for the processing of newly translated polypeptides into the proteins, which are then ultimately assembled into viral particles. The virus eventually buds out of the cell. A cell infected with a retrovirus does not necessarily lyse the cell when viral replication takes place; rather, many viral particles can bud out of a cell over the course of time.