HIV stands for human immunodeficiency virus. It is a virus that attacks the body's immune cells (called CD4 cells), gradually weakening it so that it can no longer defend the body against illnesses, infections and certain other antigens (foreign invaders).
HIV replicates in the body, making thousands of copies of itself each and every day. The amount of virus that is found in a blood sample is called the viral load. It is measured in the number of copies of the HIV virus per ml^3 of the virus.
While suppressing the body's immune defenses, HIV attacks a specialized type of immune cell called CD4 cells. HIV attacks these types of cells and uses them to make more copies of HIV. And in doing so, HIV weakens the immune system, making it unable to protect the body from illness and infection.
Normally, your immune system works to protect you; however, HIV works to destroy the immune system, leaving an HIV infected person defenseless. However, good treatment has changed this. Read about HIV treatment for more information.
HIV belongs to a family of viruses called retroviruses. Retroviruses use RNA, rather than DNA, as their genetic material. Retroviruses also contain an enzyme called reverse transcriptase, which allows the retrovirus's genetic material to imitate the host cell's genetic material. Retroviruses mutate quite quickly.
HIV Replication Cycle (Youtube Video)
HIV attaches itself to a receptor site on a healthy CD4 cells. These receptors are called CCR5 and CXCR4. It binds itself using a protein in the viral envelope called gp120. Once it attaches, many changes begin that allow HIV to make thousands of copies of itself.
HIV inserts its own genetic material called RNA (ribonucleic acid) into the CD4 cell. This process is called reverse transcription which uses a protein called reverse transcriptase. This is important because your CD4 cell has DNA (deoxyribonucleic acid), which is double-stranded; RNA on the other hand is single-stranded. It is spliced by another protein called integrase which assists the RNA integration into DNA. This process occurs inside the nucleus. The DNA then becomes what is known as "pro-virus".
HIV provirus may lie dormant in that cell for a period of time, but once activated human enzymes transform them into messenger RNA. It is then transported outside the nucleus of the cell. These are now the blueprints to create new HIV virus. The above processes are called transcription and translation.
Once this process has taken place, assembly, budding and maturation takes place. Among the messenger RNA created are copies of HIV genetic material. The enzyme called protease helps this process along by chopping up longer strands of RNA into smaller ones. These become mature viral cores - new HIV. Essentially, a new cell will "pinch off" or bud from the infected CD4 cell.