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• AIDS HIV Terms

AIDS-HIV Related Terms

- P -

• P24

(p24) A bullet-shaped core made of another protein that surrounds the viral RNA within the envelope of HIV. The p24 antigen test looks for the presence of this protein in a patient's blood. A positive result for the p24 antigen suggests active HIV replication. p24 found in the peripheral blood is also thought to correlate with the amount of virus in the peripheral blood. Measurement of p24 levels in the blood has been used to monitor viral activity, although this is not considered a very accurate method due to the existence of the p24 antibody that binds with the antigen and makes it undetectable. See Branched DNA Assay.



• Package Insert

A document, approved by the FDA and furnished by the manufacturer of a drug, for use when dispensing the drug (i.e., inserted into the package). The document indicates approved uses, contraindications, and potential side effects.



• Palliative

A treatment that provides symptomatic relief but not a cure.



• Palliative Care

Palliative care is an approach to life- threatening chronic illnesses, especially at the end of life. Palliative care combines active and compassionate therapies to comfort and support patients and their families who are living with life-ending illness. Palliative care strives to meet physical needs through pain relief and maintaining quality of life while emphasizing the patient's and family's rights to participate in informed discussion and to make choices. This patient- and family-centered approach uses the skills of interdisciplinary team members to provide a comprehensive continuum of care including spiritual and emotional needs.



• Pancreas

A gland situated near the stomach that secretes a digestive fluid into the intestine through one or more ducts and also secretes the hormone insulin.



• Pancreatitis

Inflammation of the pancreas that can produce severe pain and debilitating illness. Its onset can be predicted by rises in blood levels of the pancreatic enzyme, amylase.



• Pancytopenia

Deficiency of all cell elements of the blood.



• Pandemic

A disease prevalent throughout an entire country, continent, or the whole world. See Epidemic.



• Pap Smear

A method for the early detection of cancer and other abnormalities of the female genital tract, especially of the cervix.



• Papilloma

1. A benign tumor (as a wart, condyloma, or polyp) resulting from an overgrowth of epithelial tissue on papillae of vascularized connective tissue (as of the skin). 2. An epithelial tumor caused by a virus. See Condyloma; Epithelium; JC Virus.



• Parallel Track

A system of distributing experimental drugs to patients who are unable to participate in ongoing clinical efficacy trials and have no other treatment options. See Clinical Trial.



• Parasite

A plant or animal that lives and feeds on or within another living organism (host), causing some degree of harm to the host organism.



• Parenteral

A route other than in or through the digestive system. For example, parenteral can pertain to blood being drawn from a vein in the arm or introduced into that vein via a transfusion (intravenous), or to injection of medications or vaccines through the skin (subcutaneous) or into the muscle (intramuscular).



• Paresthesia

Abnormal sensations such as burning, tingling, or a 'pins-and-needles' feeling. Paresthesia may constitute the first group of symptoms of peripheral neuropathy, or it may be a limited drug side effect that does not worsen with time. Circumoral paresthesia affects the area around the mouth.



• Passive Immunity

Also referred to as acquired immunity. Resistance resulting from previous exposure to an infectious agent or antigen may be active or passive. Passive immunity can be acquired from the transfer of antibodies from another person or from an animal, either naturally-as from mother to fetus or to the newborn via breast milk-or by intentional inoculation (vaccination).



• Passive Immunotherapy

Process in which individuals with advanced disease (who have low levels of HIV antibody production) are infused with plasma rich in HIV antibodies or an immunoglobulin concentrate (HIVIG) from such plasma. The plasma is obtained from asymptomatic HIV-positive individuals with high levels of HIV antibodies.



• Pathogen

Any disease-producing microorganism or material.



• Pathogenesis

The origin and development of a disease.



• PBMC

See Peripheral Blood Mononuclear Cell.



• PCP

See Pneumocystis carinii Pneumonia.



• PCR

See Polymerase Chain Reaction.



• Pediatric AIDS Clinical Trial Group (PACTG)

This is the pre-eminent organization in the world for evaluating treatments for HIV-infected children and adolescents, and for developing new approaches for the interruption of mother-to-infant transmission. It has set the standards of care for children infected with HIV and for the interruption of vertical transmission. Internet address



• Pelvic Inflammatory Disease

Gynecological condition caused by an infection (usually sexually transmitted) that spreads from the vagina to the upper parts of a woman's reproductive tract in the pelvic cavity. PID takes different courses in different women, but can cause abscesses and constant pain almost anywhere in the genital tract. If left untreated, it can cause infertility or more frequent periods. Severe cases may even spread to the liver and kidneys, causing dangerous internal bleeding and death.



• Peptide

(Also polypeptide.) Biochemical formed by the linkage of up to about 50 amino acids to form a chain. Longer chains are called proteins. The amino acids are coupled by a peptide bond, a special linkage in which the nitrogen atom of one amino acid binds to the carboxyl carbon atom of another. Many peptides, such as the hormones vasopressin and ACTH, have physiological or antibacterial activity.



• Perianal

Around the anus.



• Perinatal

Events that occur at or around the time of birth.



• Perinatal Transmission

Transmission of a pathogen, such as HIV, from mother to baby before, during, or after the birth process. Ninety percent of children reported with AIDS acquired HIV infection from their HIV-infected mothers.



• Peripheral Neuritis

Inflammation of terminal nerves or the nerve endings, usually associated with pain, muscle wasting, and loss of reflexes.



• Peripheral Neuropathy

Condition characterized by sensory loss, pain, muscle weakness, and wasting of muscle in the hands or legs and feet. It may start with burning or tingling sensations or numbness in the toes and fingers. In severe cases, paralysis may result. Peripheral neuropathy may arise from an HIV-related condition or be the side effect of certain drugs, some of the nucleoside analogs in particular.



• Persistent Generalized Lymphadenopathy

Chronic, diffuse, noncancerous lymph node enlargement. Typically it has been found in persons with persistent bacterial, viral, or fungal infections. PGL in HIV infection is a condition in which lymph nodes are chronically swollen in at least two areas of the body for 3 months or more with no obvious cause other than the HIV infection.



• Person With AIDS (PWA)

Person with AIDS. Also known as PLWA, person living with AIDS.



• PGL

See Persistent Generalized Lymphadenopathy.



• Phagocyte

A cell that is able to ingest and destroy foreign matter, including bacteria.



• Phagocytosis

The process of ingesting and destroying a virus or other foreign matter by phagocytes. See Macrophage; Monocyte.



• Pharmacokinetics

The processes (in a living organism) of absorption, distribution, metabolism, and excretion of a drug or vaccine.



• Phase I Trials

Involve the initial introduction of an investigational new drug into humans. Phase I trials are closely monitored and may be conducted in patients or in healthy volunteers. The studies are designed to determine the metabolism and pharmacologic actions of the drug in humans, safety, side effects associated with increasing doses, and if possible, early evidence of effectiveness. The trials also can include studies of structure-activity relationships, mechanisms of action in humans, use of the investigational drug as research tools to explore biological phenomena, or disease processes. The total number of patients included in Phase I studies varies but is generally in the range of 20 to 80. Sufficient information should be obtained in the trial to permit design of well-controlled, scientifically valid Phase II studies.



• Phase Ii Trials

Include controlled clinical studies of effectiveness of the drug for a particular indication or indications in patients with the disease or condition under study, and determination of common, short-term side effects and risks associated with the drug. Phase II studies are typically well controlled, closely monitored, and usually involve no more than several hundred patients.



• Phase Iii Trials

Expanded controlled and uncontrolled studies. They are performed after preliminary evidence of drug effectiveness has been obtained. They are intended to gather additional information about effectiveness and safety that is needed to evaluate the overall benefit-risk relationship of the drug and to provide an adequate basis for physician labeling. These studies usually include anywhere from several hundred to several thousand subjects.



• Phase Iv Trials

Post-marketing studies, carried out after licensure of the drug. Generally, a Phase IV trial is a randomized, controlled trial that is designed to evaluate the long-term safety and efficacy of a drug for a given indication. Phase IV trials are important in evaluating AIDS drugs because many drugs for HIV infection have been given accelerated approval with small amounts of clinical data about the drugs' effectiveness.



• Phenotypic Assay

A procedure whereby sample DNA of a patient's HIV is tested against various antiretroviral drugs to see if the virus is susceptible or resistant to these drugs. See Resistance.



• Photosensitivity

Heightened skin response to sunlight or ultraviolet light (rapid burning when exposed to the sun).



• PHS

See Public Health Service.



• Pituitary Gland

Small, oval endocrine gland that lies at the base of the brain. It is called the master gland because the other endocrine glands depend on its secretions for stimulation.



• Placebo

An inactive substance (may look like the real medication) against which investigational treatments are compared for efficacy and safety. See Placebo Controlled Study.



• Placebo Controlled Study

A method of investigation of drugs in which an inactive substance (placebo) is given to one group of patients, while the drug being tested is given to another group. The results obtained in the two groups are then compared to see if the investigational treatment is more effective in treating the condition.



• Placebo Effect

A physical or emotional change, occurring after a substance is taken or administered, that is not the result of any special property of the substance. The change may be beneficial, reflecting the expectations of the patient and, often, the expectations of the person giving the substance.



• Plasma

The liquid part of the blood and lymph that contains nutrients, electrolytes (dissolved salts), gases, albumin, clotting factors, wastes, and hormones.



• Plasma Cells

Large antibody-producing cells that develop from B cells. See Antibodies; B Lymphocytes.



• Platelets

Active agents of inflammation that are released when damage occurs to a blood vessel. The platelets stick to the vascular walls, forming clots to prevent the loss of blood. Thus, it is important to have adequate numbers of normally functioning platelets to maintain effective coagulation (clotting) of the blood. Some persons living with HIV develop thrombocytopenia, a condition characterized by a platelet count of less than 100,000 platelets per cubic millimeter of blood.



• PML

See Progressive Multifocal Leukoencephalopathy.



• Pneumocystis Carinii Pneumonia (PCP)

An infection of the lungs caused by Pneumocystis carinii, which is thought to be a protozoa but may be more closely related to a fungus. P. carinii grows rapidly in the lungs of persons with AIDS and is a frequent AIDS-related cause of death. P. carinii infection sometimes may occur elsewhere in the body (skin, eye, spleen, liver, or heart).



• POL

(pol) A gene of HIV that codes for the enzymes protease, reverse transcriptase, and integrase.



• Polymerase

Any of several enzymes that catalyzes the formation of DNA or RNA from precursor substances in the presence of preexisting DNA or RNA acting as templates (i.e., patterns).



• Polymerase Chain Reaction (PCR)

A laboratory process that selects a DNA segment from a mixture of DNA chains and rapidly replicates it to create a large, readily analyzed sample of a piece of DNA. As related to HIV: a sensitive laboratory technique that can detect and quantify HIV in a person's blood or lymph nodes (also called RT-PCR). It is an FDA-approved test to measure viral load.



• Polyneuritis

Inflammation of many nerves at once.



• Polypeptide

See Peptide.



• Polyvalent Vaccine

A vaccine that is active against multiple viral strains.



• Post-Exposure Prophylaxis (PEP)

As it relates to HIV disease, a potentially preventative treatment using antiretroviral drugs to treat individuals within 72 hours of a high-risk exposure (e.g., needlestick injury, unprotected sex, needle sharing).



• Ppd Test

See Purified Protein Derivative.



• Preclinical

Refers to the testing of experimental drugs in the test tube or in animals-the testing that occurs before trials in humans may be carried out.



• Pre-Conception Counseling

Recommended by the American College of Obstetrics and Gynecology for all women of childbearing age as a component of their primary medical care. The purpose of preconception care is to identify risk factors for adverse maternal or fetal outcome, provide education and counseling targeted to the patient's individual needs, and treat or stabilize medical conditions prior to conception in order to optimize maternal and fetal outcomes.



• Precursor Cells

Cells that, via natural processes, form other cells.



• Prenatal

Prenatal is the time period preceding birth. Prenatal care includes all the obstetric exams, services, tests, medications, vitamins and supplements that a woman receives while pregnant. Antiretroviral therapy for HIV infected pregnant women has been shown to decrease the risk of transmitting HIV to the unborn child.



• Prevalence

A measure of the proportion of people in a population affected with a particular disease at a given time.



• Primary HIV Infection

See Acute HIV Infection.



• Primary Isolate

HIV taken from an infected individual (as opposed to grown in laboratory cultures).



• Proctitis

Inflammation of the rectum.



• Prodrome

A symptom that indicates the onset of a disease.



• Prodrug

An inactive or partially active drug that is metabolically changed in the body to an active drug.



• Progressive Multifocal Leukoencephalopathy (PML)

A rapidly debilitating opportunistic infection caused by the JC virus that infects brain tissue and causes damage to the brain and the spinal cord. Symptoms vary from patient to patient but include loss of muscle control, paralysis, blindness, problems with speech, and an altered mental state. PML can lead to coma and death.



• Prophylactic Drug

A drug that helps to prevent a disease or initial infection. See Prophylaxis.



• Prophylaxis

Treatment to prevent the onset of a particular disease ('primary' prophylaxis), or the recurrence of symptoms in an existing infection that has been brought under control ('secondary' prophylaxis, maintenance therapy).



• Protease

An enzyme that breaks down proteins into their component peptides. HIV's protease enzyme breaks apart long strands of viral protein into the separate proteins making up the viral core. The enzyme acts as new virus particles are budding off a cell membrane. Protease is the first HIV protein whose three-dimensional structure has been characterized. See Proteins.



• Protease Inhibitors

Antiviral drugs that act by inhibiting the virus' protease enzyme, thereby preventing viral replication. Specifically, these drugs block the protease enzyme from breaking apart long strands of viral proteins to make the smaller, active HIV proteins that comprise the virion. If the larger HIV proteins are not broken apart, they cannot assemble themselves into new functional HIV particles.



• Protease-Sparing Regimen

An antiretroviral drug regimen that does not include a protease inhibitor.



• Proteins

Highly complex organic compounds found naturally in all living cells. Proteins are a source of heat and energy to the body. They are essential for growth, the building of new tissue, and the repair of injured tissue.



• Protocol

The detailed plan for conducting a clinical trial. It states the trial's rationale, purpose, drug or vaccine dosages, length of study, routes of administration, who may participate (see Inclusion/Exclusion Criteria), and other aspects of trial design.



• Protozoa

Large group of one-celled (unicellular) animals, including amoebas. Some protozoa cause parasitic diseases in persons with AIDS, notably toxoplasmosis and cryptosporidiosis. See Pneumocystis carinii Pneumonia.



• Provirus

Viral genetic material, in the form of DNA that has been integrated into the host genome. HIV, when it is dormant in human cells, is in a proviral form.



• Pruritus

Itching.



• Pseudo-Cushing's Syndrome

Also referred to as lipodystrophy; syndrome characterized by changes in bodily fat distribution that could be a side effect of HAART therapy, especially when HAART includes protease inhibitors.



• Pseudovirion

A virus-like particle.



• Pubmed

A service of the National Library of Medicine, it provides access to over 11 million MEDLINE citations back to the mid-1960's and additional life science journals. PubMed includes links to many sites providing full text articles and other related resources. Internet site



• Pulmonary

Pertaining to the lungs.



• Purified Protein Derivative (PPD)

Material used in the tuberculin skin test (TST); the most common test for exposure to Mycobacterium tuberculosis, the bacterium that causes tuberculosis (TB). PPD is sometimes used synonymously with TST. In the PPD test, a small amount of protein from TB is injected under the skin. If patients have been previously infected, they will mount a delayed-type hypersensitivity reaction, characterized by a hard red bump called an induration.