HIV Structure
The basics section of this page gave an overview of viral structure and replication. However, the process is more complicated than was stated before. The HIV virus is actually made up of layers. The outermost layer of the HIV virus is composed of fats and is called the envelope. Through this envelope proteins protrude. These proteins have a special chemical structure that allows the virus to attach itself to certain receptors on T4 helper cells. Inside the envelope, is a structure made of proteins called the matrix. This structure surrounds the most important part of the virus: the core. The core is made up of two strands of RNA and some viral enzymes (which are once again surrounded by a protein coat). The core is the most important part of the virus, for without it, the virus could not function.
The first step in the replication of any virus is to attach to a cell. In the case of HIV, the virus attaches itself to the T4 helper cells of the immune system. Once the virus has attached itself to a cell, the envelope is absorbed into the cell's membrane. This pushes the matrix and the core of the virus into the cell. Then the matrix is stripped away leaving the core. The core begins to migrate toward the nucleus of the cell, which is where all of the cell's genetic material is located, with the goal of integrating its genetic material with that of the cell. This, however, poses a problem for the virus since its genetic material is composed of RNA and the genetic material of the cell is, of course, DNA. Therefore, the virus must change its RNA into DNA. It uses an enzyme, which is present in the core of the virus, called Reverse Transcriptase to do this. Barring any mutations, this process results in two strands of DNA, which contain all of the information needed to make another virus. Once the transformation is complete, the virus inserts its DNA into the cell's nucleus and inserts it into the genetic material of the cell, in a process called integration. Once the viral DNA has been integrated into the cell's DNA, it can stay dormant for a long time. However, once the cell is activated, the viral DNA is turned back into RNA through a process called transcription. Some of the RNA copies of the viral DNA will be used as genetic material for the new viruses, while others will be modified and used to make the viral proteins. All of the components for the new set of viruses gather near the cell membrane where they assemble themselves. Once the inner layers of the virus are assembled, the virus passes through the cell membrane, using some of the membrane to form the viral envelope, and escapes the cell. Once the virus escapes the cell, it matures and is ready to infect other cells. Below is a diagram of the life-cycle of a HIV virus.
The first symptoms of AIDS can appear anywhere from a few months to a decade after the initial infection with the virus. However, in some cases, infection can be followed by flu-like symptoms which appear about a month after infection. These symptoms usually disappear after several weeks and are usually misdiagnosed. During the dormant period, the virus is infectious and is weakening the immune system of the patient. As the immune system continues to deteriorate, the body becomes more and more susceptible to diseases. This leads to what are called "opportunistic infections." These infections are caused by microbes that would not cause disease in a healthy person, but are manifest because of the weakened state of the patient's immune system. These opportunistic infections are what actually cause people to die. Another effect that the weakening of the immune system has is that it reduces the body's ability to fight diseases. Because of this, common diseases, such as colds, the flu, etc., last longer and are more severe. AIDS also causes symptoms such as weight loss, a lack of energy, skin rashes, and several other symptoms.
As stated before, opportunistic infections are infections that either occur only in patients with HIV or that are made worse by the HIV infection. Each infection has its own symptoms, but opportunistic infections can generally produce symptoms such as weight loss, nausea, vomiting, abdominal cramps, fever, vision loss, coma, and even death. Currently, two opportunistic infections are causing a lot of trouble in different parts of the world. Outbreaks of AIDS related cases of diseases like TB are causing massive epidemics in countries such as South Africa. In fact, TB is the most common opportunistic infection. Another reason that AIDS related TB is so deadly is that it is an airborne virus, which means that it can be transmitted through coughing, sneezing, etc.. Thus, any outbreak of TB in AIDS patients will quickly spread through an entire population. In America, the opportunistic infection causing doctors the most trouble is Hepatitis. Since there are about 40 different opportunistic infections, they will not all be mentioned here. In order to see a list of opportunistic infections and to get information on them, click
HERE.