BACTERICIDAL (Bacteriocidal):
Capable of killing bacteria.
BACTERIOSTATIC:
Capable of inhibiting reproduction of bacteria.
BACTERIUM:
A microscopic organism composed of a single cell. Many bacteria can cause disease in humans.
BACULOVIRUS:
A virus of insects used in the production of some HIV vaccines. See Vaccine.
BASELINE:
1. Information gathered at the beginning of a study from which variations found in the study are measured. 2. A known value or quantity with which an unknown is compared when measured or assessed. 3. The initial time point in a clinical trial, just before a volunteer starts to receive the experimental treatment undergoing testing. At this reference point, measurable values such as CD4 count are recorded. Safety and efficacy of a drug are often determined by monitoring changes from the baseline values.
BASOPHIL:
A type of white blood cell, also called a granular leukocyte, filled with granules of toxic chemicals that can digest microorganisms. Basophils, as well as other types of white blood cells, are responsible for the symptoms of allergy.
B CELL LYMPHOMA:
See Lymphoma.
B CELLS:
See B Lymphocytes.
bdna TEST:
(bDNA) See Branched DNA Assay.
BETA 2 MICROGLOBULIN (B2M):
Protein tightly bound to the surface of many nucleated cells, particularly those of the immune system. Elevated B2M levels occur in a variety of diseases. While elevated B2M is not specific to HIV, there is a correlation between this marker and the progression of HIV disease. See Immune System.
BILIRUBIN:
A red pigment occurring in liver bile, blood, and urine. Its measurement can be used as an indication of the health of the liver. Bilirubin is the product of the breakdown of hemoglobin in red blood cells. It is removed from the blood and processed by the liver, which secretes it into the digestive tract. The normal value is 0.1 to 1.5 milligrams per liter of blood. An elevated level of bilirubin in blood serum is an indication of liver disease or drug-induced liver impairment.
BINDING ANTIBODY:
As related to HIV infection: An antibody that attaches to some part of HIV. Binding antibodies may or may not adversely affect the virus.
BIOAVAILABILITY:
The extent to which an oral medication is absorbed in the digestive tract and reaches the bloodstream.
BIOLOGICAL RESPONSE MODIFIERS (BRMs):
Substances, either natural or synthesized, that boost, direct, or restore normal immune defenses. BRMs include interferons, interleukins, thymus, hormones, and monoclonal antibodies.
BIOPSY:
Surgical removal of a piece of tissue from a living subject for microscopic examination to make a diagnosis (e.g., to determine whether abnormal cells such as cancer cells are present).
BIOTECHNOLOGY:
1. Use of living organisms or their products to make or modify a substance. These include recombinant DNA techniques (see genetic engineering) and hybridoma technology. 2. Industrial application of the results of biological research, particularly in fields such as recombinant DNA or gene splicing, which permits the production of synthetic hormones or enzymes by combining genetic material from different species.
BLINDED STUDY:
A clinical trial in which participants are unaware as to whether they are in the experimental or control arm of the study. See Double Blind Study.
BLOOD-BRAIN BARRIER:
A selective barrier (obstacle) between brain blood vessels and brain tissues whose effect is to restrict what may pass from the blood into the brain. Certain compounds readily cross the blood-brain barrier; others are completely blocked.
B LYMPHOCYTES (B CELLS):
One of the two major classes of lymphocytes, B lymphocytes are blood cells of the immune system, derived from the bone marrow and spleen, and involved in the production of antibodies. During infections, these cells are transformed into plasma cells that produce large quantities of antibody directed at specific pathogens. When antibodies bind to foreign proteins, such as those that occur naturally on the surfaces of bacteria, they mark the foreign cells for consumption by other cells of the immune system. This transformation occurs through interactions with various types of T cells and other components of the immune system. In persons living with AIDS, the functional ability of both the B and the T lymphocytes is damaged, with the T lymphocytes being the principal site of infection by HIV.
BODY FLUIDS:
Any fluid in the human body, such as blood, urine, saliva (spit), sputum, tears, semen, mother's milk, or vaginal secretions. Only blood, semen, mother's milk, and vaginal secretions have been linked directly to the transmission of HIV.
BONE MARROW:
Soft tissue located in the cavities of the bones where blood cells such as erythrocytes, leukocytes, and platelets (see entries for these terms) are formed.
BONE MARROW SUPPRESSION:
A side effect of many anticancer and antiviral drugs, including AZT. Leads to a decrease in white blood cells, red blood cells, and platelets. Such reductions, in turn, result in anemia, bacterial infections, and spontaneous or excess bleeding.
BOOSTER:
A second or later dose of a vaccine given to increase the immune response to the original dose.
BRANCHED DNA ASSAY:
(bDNA test) A test developed by the Chiron Corporation for measuring the amount of HIV (as well as other viruses) in blood plasma. The test uses a method that creates a luminescent signal whose brightness depends on the amount of viral RNA present. Test results are calibrated in numbers of virus particle equivalents per milliliter of plasma. The bDNA test is similar in results but not in technique to the PCR test. bDNA testing is currently being used to evaluate the effectiveness of drug treatment regimens and to gauge HIV disease progression. Newer versions, or generations, of these assays are being developed; they will be able to detect smaller numbers of copies of HIV in a blood sample. See Viral Burden.
BREAKTHROUGH INFECTION:
An infection, caused by the infectious agent the vaccine is designed to protect against, that occurs during the course of a vaccine trial. These infections may be caused by exposure to the infectious agent before the vaccine has taken effect, or before all doses of the vaccine have been given.
BRONCHOSCOPY:
Visual examination of the bronchial passages of the lungs through the tube of an endoscope (usually a curved flexible tube containing fibers that carry light down the tube and project an enlarged image up the tube to the viewer) that is inserted into the upper lungs. Can be used for extraction of material from the lungs. See Endoscopy.
BUDDING:
See Assembly and Budding.
BUFFALO HUMP:
See Lipodystrophy
BURKITT'S LYMPHOMA:
See Lymphoma.
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