Retroviruses are viruses that incorporate their genetic code (RNA) into host cells through means of enzymes called reverse transcriptase, which creates DNA from RNA (as opposed to the normal flow, RNA from DNA), and integrase, which makes the virus part of the cell's own genetic information. Retroviruses can be difficult to detect and are the root cause of AIDS (which is caused by the human immunodeficiency virus) and other conditions.
Features
Retroviruses, like most but not all viruses, code their genetic protein in ribonucleic acid (RNA), which is simpler in structure than DNA (found in humans and other eukaryotic organisms). This RNA is surrounded by a layer called the capsid, which is composed of proteins. Retroviruses are also characterized by having a lipid (fatty molecule) envelope; this layer both protects the virus and also contains proteins that enable the virus to sense and attach to appropriate host cells.
Effects
Also contained in the virus particle are two enzymes, reverse transcriptase and integrase. Reverse transcriptase is used by the virus to turn its RNA into DNA, thus making it easier to integrate into the genetic code of the host cell. Using integrase to combine its own newly formed DNA with that of the host cell, the virus turns the host cell into a reproduction factory of its own genetic code, effectively changing the nature of the cell into that of a virus particle. For more on this process, see Resources below.
Identification
Once retroviral RNA has become integrated into the host's cells, the virus is difficult to detect. This is why, in identifying a retrovirus (such as for diagnostic purposes), it is normal to detect antibodies to the infection (as opposed to the virus itself). There are tests that can detect retroviral genes (such as those of HIV). However, these tests are more expensive and are less widely used.
Types
The most commonly discussed human retrovirus is the human immunodeficiency virus, or HIV. HIV attacks the body's immune system, making it more difficult and eventually impossible for the infected person to fight off infections. Human T-lymphatic virus is another retrovirus that affects humans, causing both leukemia and lymphoma.
Treatment
A class of antiretroviral drugs is in use to combat retrovirus infection, in particular HIV. These are normally used in concert to attempt to control many different aspects of the infection. Because human retroviruses cause, directly or indirectly, other conditions, it may be possible to treat those conditions, but there is no cure for retroviral (or other viral) infection. Researchers are in the pursuit of new drugs or other therapies (including an HIV vaccine) to combat retrovirus infection.
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