Basic progression of AIDS.

On average it takes 7 - 10 years to develop AIDS

HIV (Human Immunodeficiency Virus), the cause of acquired immunodeficiency syndrome (AIDS), is an enveloped, double-stranded RNA virus, containing two identical RNA strands. Each of its 72 surface knobs contains a glycoprotein capable of binding to a CD4 receptor on the surface of certain host cells (e.g., T-helper cells). The "stalk" that supports the knob is a transmembrane glycoprotein which may also play a role in attachment to host cells. RNA is like the construction boss. Cells use RNA to tell enzymes how to build a specific part of a cell. To make a new protein, enzymes will copy a specific part of the DNA (blueprint for building living cells) into a piece of RNA. This RNA is then used by other enzymes to build a new protein or enzyme. The virus enters into the cells and begins to integrate into the chromosomes of the cell. The HIV virus works like a foreign enemy agent, who infiltrates the bloodstream and sneaks past cells.

HIV Life Cycle

Step 1: Binding

A virus consists of an outer envelope of protein, fat and sugar wrapped around a set of genes (in the case of HIV, genetic information is carried as RNA instead of DNA) and special enzymes. HIV has proteins on its envelope that are strongly attracted to the CD4+ surface receptor on the outside of the T4-cell. When HIV binds to a CD4+ surface receptor, activates other proteins on the cell's surface, allowing the HIV envelope to fuse to the outside of the cell.

Step 2: Reverse Transcription

HIV's genes are carried in two strands of RNA, while the genetic material of human cells is found in DNA. In order for the virus to infect the cell, a process called "reverse transcription" makes a DNA copy of the virus's RNA. After the binding process, the viral capsid (the inside of the virus which contains the RNA and important enzymes) is released into the host cell. A viral enzyme called reverse transcriptase makes a "proviral DNA."

Step 3: Integration

The HIV DNA is then carried to the cell's nucleus (center), where the cell's DNA is kept. Then, another viral enzyme called integrase hides the proviral DNA into the cell's DNA. Then, when the cell tries to make new proteins, it can accidentally make new HIVs.

Step 4: Transcription

Once HIV's genetic material is inside the cell's nucleus, it directs the cell to produce new HIV. The strands of viral DNA in the nucleus separate, and special enzymes create a complementary strand of genetic material called messenger RNA (instructions for making new HIV).

Step 5: Translation

The messenger RNA carries instructions for making new viral proteins from the nucleus to a kind of workshop in the cell. Each section of the messenger corresponds to a protein building block for making a part of HIV. As each messenger RNA strand is processed, a corresponding string of proteins is made. This process continues until the messenger RNA strand has been transformed or "translated" into new viral proteins needed to make a new virus.

Step 6: Viral Assembly

Finally, a new virus is assembled. Long strings of proteins are cut up by a viral enzyme called protease into smaller proteins. These proteins serve a variety of functions, some of which become structural elements of new HIV, while others become enzymes, such as reverse transcriptase. Once the new viral particles are assembles, they bud off the host cell, and create a new virus. this virus is then able to infect new cells. Each infected cell can produce a lot of new viruses.