AIDS. A current disease.

Last 1^st of December we celebrated the World Day Against AIDS, a disease which kills more than 30 million people in the world.

The HIV virus, or human immunodeficiency virus, which belongs to retrovirus family, causes this disease. HIV virion (about 100 nm in diameter) has two copies of its own single-strain RNA protected by a protein layer, the nucleocapsid. It also has more layers, but the important one is its lipidic bilayer, which comes from the infected cell but including viral glycoproteins such as GP120 or GP41, the important ones to infect new T cells using their receptors for these glycoproteins. When T cells get infected, the virus destroys them, reducing our immune system capabilities.

Human immunodeficiency virus structure.

Internally, there are many enzymes which cause many awful effects to humans. First of all, proteases degrade all the layers covering the virus so the RNA can penetrate to the host cell. Another one is inverse transcriptase which synthesizes double strained DNA from single strained viral RNA. This fact is essential for the replication process. Finally, retroviral integrase integrates viral DNA into the cell's genome and then, all viral proteins can be synthesized to assemble the new copies of the virus so they can keep on infecting new cells.

Then, a virus sticks to a T cell by recognizing cell receptors (like a key opening its lock) in a process called fixation (1); that's the reason about losing immune system capabilities. After that, the two layers (T cell and virus ones) merge so the viral genome penetrates (2) into the cell. In the cytoplasm the protease can play its paper degrading the nucleocapsid. At this moment, inverse transcriptase joins to the free viral RNA and begins to transcribe RNA into DNA (3) which is integrated to the cell genome by the retroviral integrase after (4). Integrating the virus genome allows it to use available cell replication tools to replicate and transcribe viral DNA to synthesize the proteins (5) to build new viral particles which will infect another cells (6 & 7).

HIV life cycle.

When HIV gets to the blood it is recognized as an antigen so macrophages destroy them and they promote antibody synthesis. By this time, the person is already infected but it is not possible to detect these specific antibodies until 3 months later, a period known by as "window period". If the infected one is in this period of the disease, all tests will conclude wrongly that this person is not infected, although he or she is actually infected (false negative). The infected will go through three different phases of symptoms: during the 2-4 first weeks he/she will mainly have fever and rash in the arms and legs; in the second phase, the infected one will not suffer any important disease: it is the asymptomatic phase, which can last for months to years. During this second phase viral particles replicate themselves into the lymph nodes. Finally, infection will develop into AIDS after 10-12 years. AIDS is actually the name of the third phase in which VIH wins the battle against immune system so the body's defenses are reduced and the infected one suffers many serious illnesses. In this period of time CD4 T cells population falls below 400 cell /μl. Kaposi's sarcoma is a very important symptom in this period.

VIH Infection phases.

This disease has no cure despite all the investigation groups that study it in the world. There are antiretroviral drugs which can reduce viral population to insignificant rates but they don't cure it. They only make patients' life easier. The best therapy against HIV is to use condom during sex. It would prevent almost 90% transmission cases.

Nowadays, HIV is a pandemic, especially in underdeveloped countries (Africa leads the ranking with more than 16 million infected people) because of lack of information, mankind, and poor health service. In countries like Spain where we are overcrowded of information, there are still new infections every year. Without scientists and doctors efforts, which fight against the disease, we would be lost. People who know how to stop this pandemic have to do something, something like writing to inform about the danger. Just something…