How Retrovirus Infect Organism?

A retroviral infection begins when a virus comes into contact with a suitable host cell.In the initial stages of an HIV infection, for example, the hosts are T cells—white blood cells that belong to the human immune system.

Other common retrovirus targets include connective tissue cells, which form muscle, cartilage, or bone. On encountering a host cell, the retrovirus attaches itself to receptors on the surface of the host cell’s membrane.In this two-way process, the retrovirus’s glycoproteins and the host cell’s receptors bind together, locking the virus in place. The outer envelope of the retrovirus then fuses with the host cell membrane, enabling the viral capsid to enter the cell itself.

Once inside the cell, the capsid opens, releasing RNA and reverse transcriptase into the cell’s cytoplasm, a watery fluid that is rich in proteins and other chemicals. Using the cell’s chemical resources, reverse transcriptase builds up a double-stranded DNA molecule that mirrors the information stored in the viral RNA.

Initially, this DNA molecule is circular, but it is later spliced apart and inserted into the DNA of the host cell. From this moment onward, the viral DNA, known as a provirus, behaves like the host cell’s own genes.

The only difference is that the provirus contains instructions for assembling replicated viruses, rather than instructions for building or controlling a living cell.

As viral replication proceeds, the provirus directs the host cell to manufacture all the parts needed for more viruses, including capsids and viral RNA. These viral parts spontaneously self-assemble to form new viruses, and the new viruses migrate toward the exterior of the cell.

The newly formed viruses bud away from the host cell, taking with them small areas of the cell membrane, which the viruses use to form outer envelopes. The host cell may survive this viral breakout, but in many infections it becomes so weakened that it dies.

As viruses replicate and infect more cells, the number of cell deaths lead to tissue destruction and disease.