March
2000
HIV/AIDS:
A Primer
By Angela Starks
|
|
|
Below are listed a few of the more common terms
that you might hear or read in reference to AIDS and HIV. It is by no
means an exhaustive glossary, so for more information, please refer
to a medical dictionary or your doctor.
AIDS (Acquired Immunodeficiency Syndrome)
AIDS is a disease of the immune system, characterized by increased
susceptibility to opportunistic infections (see below for examples),
certain cancers, and neurological disorders. AIDS is the clinical state
that results from prolonged infection with the human immunodeficiency
virus (HIV), which is transmitted chiefly through blood and blood products
that gain entry to the body’s bloodstream, especially through sexual
intercourse or contaminated hypodermic needles.
CD4 cells
Also called T4 cells, CD4 lymphocytes and T-helper lymphocytes.
The surfaces of these cells are studded with molecules named CD4. If
the virus chances upon such a cell and binds to these molecules, then
HIV gains entry. These cells are vital to the functioning of the immune
system, and are the principal target for HIV infection.
HIV Positive / Antibody Positive / Seropositive
A condition indicated by the presence of specific antibodies in
the blood. It means the person has been infected with the HIV virus
and is now a carrier; they can infect others even if they don’t
have noticeable AIDS symptoms. It does not automatically mean that they
have, or will go on to develop, full blown AIDS—though the likelihood
is that they will.
HIV (Human Immunodeficiency Virus) or AIDS Virus
The virus that is said to cause AIDS and AIDS-related complex. It
is a retrovirus, which copies its genetic code into the DNA of its host.
It spreads in the body by making millions of copies of itself each day,
invading and inactivating immune system cells called helper T cells.
Variants of the virus have been identified in several laboratories and
independently given different names, the name human immunodeficiency
virus (HIV) being subsequently proposed by an international classification
committee.
HIV-1 and HIV-2
There are actually two separate AIDS epidemics. The major one—which
has killed more than 16 million people—is caused by HIV-1. The
other epidemic is much smaller and concentrated in West Africa; it is
caused by HIV-2, a less virulent and less transmissible virus that nonetheless
can kill. While HIV-1 almost certainly comes from chimpanzees, HIV-2
has been traced to the sooty mangabey monkey. Scientists have discovered
at least 11 HIV-1 subtypes and 6 subtypes of HIV-2 (one of which—subtype
F—has only been found in one person).
New Variants
HIV has many different strains, called subtypes. The virus is still
mutating, creating new variants that can cause additional problems;
they might escape detection on tests and pass into the blood supply,
and also they might be able to evade drugs or a vaccine. Already, one
variant—subtype G—is resistant to at least two of the powerful
protease inhibitor drugs. HIV can average one alteration of its genetic
code every time it infects a new cell.
Two examples of new variants are:
Group O, discovered in 1991. It is so genetically distinct that
scientists believe that it did not evolve from the main strains of HIV
but represents a more direct transmission from chimps to humans. In
parts of Cameroon, it now accounts for about five percent of all HIV-1
infections. Group N, one of the newest HIV-1 variants, was discovered
in 1998. It is even more similar to the chimp strain than group O and
may further confirm cross-species transmission.
T Cells / T Lymphocytes
Immune cells, developed in the thymus gland that circulate in the
blood and lymph fluid and orchestrate the immune system’s response
to infected or malignant cells, either via secretions or by direct contact.
High numbers of HIV-specific T cells indicate that a person was exposed
to the virus.
Viral load
The quantity of HIV particles per milliliter of blood or any bodily
tissue.
Drugs
Drugs may help slow the progression of HIV and AIDS, and
prolong and/or improve the quality of life in some patients. But currently,
there is no pharmaceutical [or pharmacological – sic?] cure for
AIDS.
Antiretroviral
A drug that is active against retroviruses, usually HIV.
AZT
Trademark name of the AIDS drug azidothymidine; its brand name is
‘Retrovir’ and is also called ZDV (zidovudine). AZT is produced
by Glaxo Wellcome. It is antiretroviral, and belongs to a class of drugs
known as nucleoside analog reverse transcriptase inhibitors. It stops
HIV from multiplying by interrupting a crucial stage in the life-cycle
of the virus. It was the first drug approved by the FDA for use in AIDS
treatment, so it was initially used alone—a technique called monotherapy—but
AZT alone is no longer considered an effective treatment by most doctors.
AZT is manufactured from genetic materials in fish sperm or produced
synthetically.
Cocktail Therapy
A course of treatment usually involving a combination of three different
drugs, and is said to be responsible for a decline in AIDS-related deaths.
Preferred to monotherapy because some of the mutated viruses can more
easily develop resistance to one drug.
HAART (Highly Active Anti-retroviral Therapy)
A triple-drug therapy consisting of two nucleoside analogs and one
protease inhibitor. The patient must follow a vigorous treatment regime.
It has lowered some patients’ HIV to below detectable levels in
the blood, although it is not effective for everyone. HAART decreases
the chance of developing an AIDS-related illness, but the virus still
multiplies, albeit more slowly.
Protease Inhibitors
Seen as an essential part of effective cocktail therapy. HIV protease
is an enzyme that metabolizes proteins; it is essential for viral reproduction
and maturation. Inhibiting this protease does not prevent replication
but it does help prevent the virus from maturing into new infectious
particles.
AIDS-Related Illnesses and Disease-Causing
Organisms
Opportunistic diseases cause most of the fatalities of people with
AIDS. Autopsies reveal that close to 100 percent of AIDS patients are
found to have at least one opportunistic infection. It may be possible
that patients could continue to live with HIV if they remained free
of such illnesses, therefore targeting these illnesses may be important
in improving the prognosis of AIDS patients.
Candidiasis
Any yeast-like infection caused by Candida fungi, occurring most often
in the mouth, respiratory tract or vagina. May also affect the gastrointestinal
tract, lungs, skin, nails and other tissues.
Cryptosporidium
A type of protozoan that causes extreme inflammation and diarrhea.
Cytomegalovirus
A member of the Herpes family, this virus leads to severe eye infection
and gastrointestinal disease in the late stages of AIDS.
Epstein-Barr Virus
The cause of infectious mononucleosis and possibly other illnesses
in AIDS patients and other people with compromised immune systems.
Kaposi’s Sarcoma
A cancer of the skin and lymph nodes, characterized by painless,
purplish-red to brown nodules. It occurs in a particularly virulent
form among persons with AIDS and is a primary AIDS-defining illness.
Non-Hodgkin’s Lymphoma
A type of lymphoma (cancer of the lymph tissues) that is common
in AIDS.
Persistent Generalized Lymphadenopathy (PGL)
A specific AIDS-related syndrome characterized by chronic enlargement
of lymph nodes.
Pneumocystis Pneumonia
A severe lung infection caused by the organism pneumocystis carinii
occurring as an opportunistic disease in persons with impaired immune
systems such as in AIDS.
