HIV/AIDS

Biology of HIV

HIV budding from an infected cell. Credit: NIAID

HIV belongs to a class of viruses known as retroviruses. Retroviruses are viruses that contain RNA (ribonucleic acid) as their genetic material. After infecting a cell, HIV uses an enzyme called reverse transcriptase to convert its RNA into DNA (deoxyribonucleic acid) and then proceeds to replicate itself using the cell's machinery.

Within the retrovirus family, HIV belongs to a subgroup known as lentiviruses, or "slow" viruses. Lentiviruses are known for having a long time period between initial infection and the beginning of serious symptoms. This is why there are many people who are unaware of their HIV infection, and unfortunately, can spread the virus to others.

Similar versions of HIV infect other nonhuman species, such as feline immunodeficiency virus (FIV) in cats and simian immunodeficiency virus (SIV) in monkeys and other nonhuman primates. Like HIV in humans, these animal viruses primarily infect immune system cells, often causing immune deficiency and AIDS-like symptoms. These viruses and their hosts have provided researchers with useful, although imperfect, models of the HIV disease process in people.

Learn More

• Structure of HIV
• HIV Replication Cycle
• HIV Evolves to Evade the Immune System
• HIV Devastates the Immune System
• HIV Hides from the Immune System
• Clinical Progression of HIV
• Factors that Affect Disease Progression

To learn more about NIAID’s HIV basic research activities, visit the HIV Basic Research Page.