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HIV/AIDS Glossary

Glossary Terms

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Acquired Immunodeficiency Syndrome (AIDS)
A disease of the body's immune system caused by the human immunodeficiency virus (HIV). AIDS is characterized by the death of CD4 cells (an important part of the body's immune system), which leaves the body vulnerable to life-threatening conditions such as infections and cancers.

Also known as immunoglobulin. A protein produced by the body's immune system that recognizes and fights infectious organisms and other foreign substances that enter the body. Each antibody is specific to a particular piece of an infectious organism or other foreign substance.

Antiretroviral Therapy (ART)
Treatment with drugs that inhibit the ability of retroviruses (such as HIV) to multiply in the body. The antiretroviral therapy recommended for HIV infection is referred to as highly active antiretroviral therapy (HAART), which uses a combination of medications to attack HIV at different points in its life cycle.

CD4 Cell
Also known as helper T cell or CD4 lymphocyte. A type of infection-fighting white blood cell that carries the CD4 receptor on its surface. CD4 cells coordinate the immune response, signaling other cells in the immune system to perform their special functions. The number of CD4 cells in a sample of blood is an indicator of the health of the immune system. HIV infects and kills CD4 cells, leading to a weakened immune system

CD4 Cell Count
A measurement of the number of CD4 cells in a sample of blood. The CD4 count is one of the most useful indicators of the health of the immune system and the progression of HIV/AIDS. A CD4 cell count is used by health care providers to determine when to begin, interrupt, or halt anti-HIV therapy; when to give preventive treatment for opportunistic infections; and to measure response to treatment. A normal CD4 cell count is between 500 and 1,400 cells/mm3 of blood, but an individual's CD4 count can vary. In HIV-infected individuals, a CD4 count at or below 200 cells/mm3 is considered an AIDS-defining condition.

Clinical Trial
A research study that uses human volunteers to answer specific health questions. Carefully conducted clinical trials are regarded as the fastest and safest way to find effective treatments for diseases and conditions, as well as other ways to improve health. Interventional trials use controlled conditions to determine whether experimental treatments or new ways of using known treatments are safe and effective. Observational trials gather information about health issues from groups of people in their natural settings.

Infection with more than one virus, bacterium, or other micro-organism at a given time. For example, an HIV-infected individual may be co-infected with hepatitis C virus (HCV) or tuberculosis (TB).

Human Immunodeficiency Virus (HIV)
The virus that causes Acquired Immunodeficiency Syndrome (AIDS). HIV is in the retrovirus family, and two types have been identified: HIV-1 and HIV-2. HIV-1 is responsible for most HIV infections throughout the world, while HIV-2 is found primarily in West Africa.

Immune System
The collection of cells and organs whose role is to protect the body from foreign invaders. Includes the thymus, spleen, lymph nodes, B and T cells, and antigen-presenting cells.

Investigational Drug
Also known as experimental drug. A drug that has not been approved by the FDA to treat a particular disease or condition. The safety and effectiveness of an investigational drug must be tested in clinical trials before the manufacturer can request FDA approval for a specific use of the drug.

The time period when an infectious organism is in the body but is not producing any noticeable symptoms. In HIV disease, latency usually occurs in the early years of infection. Also refers to the period when HIV has integrated its genome into a cell's DNA but has not yet begun to replicate.

A natural or man-made substance that kills microbes. Researchers are studying the use of microbicides to prevent the transmission of sexually transmitted diseases (STDs), including HIV infection.

Opportunistic Infections (OIs)
Illnesses caused by various organisms that occur in people with weakened immune systems, including people with HIV/AIDS. OIs common in people with AIDS include Pneumocystis carinii pneumonia; cryptosporidiosis; histoplasmosis; toxoplasmosis; other parasitic, viral, and fungal infections; and some types of cancers.

T Cell
A type of lymphocyte (disease-fighting white blood cell). The "T" stands for the thymus, where T cells mature. T cells include CD4 cells and CD8 cells, which are both critical components of the body's immune system.

Therapeutic HIV Vaccine
Any HIV vaccine used for the treatment of an HIV-infected person. Therapeutic HIV vaccines are designed to boost an individual's immune response to HIV infection in order to better control the virus. This therapeutic approach is currently being tested in clinical trials

A substance that stimulates the body’s immune response in order to prevent or control an infection. A vaccine is typically made up of some part of a bacteria or virus that cannot itself cause an infection. Researchers are testing vaccines both to prevent and treat HIV/AIDS; however, there is currently no vaccine approved for use outside of clinical trials.