AIDS, HIV and The Immune
System
Studies Research
Recently, there is a private college student, Andi is 20 years old positively affected by HIV / AIDS. His life is often free, rah-rah in the association. He was a drug addict, they do it when the time is empty and hour lecture, and without thinking of all treasures, and wears out the money for a party drug. soon it was several years suddenly he felt strange to her complaints she was experiencing symptoms similar to HIV / AIDS that is often quickly exhausted, limpe gland enlargement (neck, armpits, and groin) is accompanied by the decrease of weight suddenly.
She assumed that ordinary pain and many days more and more strange that the illness did not heal despite treatment. and Andi also felt his illness got worse and he too the hospital to consult with doctors and check his body, and blood tests suggested doctor anti body to the hospital laboratory to confirm what diseases suffered by andi body. after blood test (anti-bodies), the doctor said that suffer andi positive HIV / AIDS. Andi feels sadness and despair he considers his life soon.
Introduction
The virus responsible for the condition known as AIDS
(Acquired Immunodeficiency Syndrome), is named HIV (Human Immunodeficiency
Virus). AIDS is the condition whereby the body's specific defense system
against all infectious agents no longer functions properly. There is a focused
loss over time of immune cell function which allows intrusion by several
different infectious agents, the result of which is loss of the ability of the
body to fight infection and the subsequent acquisition of diseases such as
pneumonia. We will examine the virus itself, the immune system, the specific
effect(s) of HIV on the immune system, the research efforts presently being
made to investigate this disease, and finally, how one can try to prevent
acquiring HIV.
The Virus
HIV is one member of the group of viruses known as
retroviruses. The term "retrovirus" stems from the fact that these
kinds of viruses are capable of copying RNA into DNA. No other organism so far
discovered on earth is capable of this ability. The virus has two exact copies
of single-stranded RNA as its basic genetic material (genome) in the very
center of the organism. The genome is surrounded by a spherical core made of
various proteins in tightly-packed association with one another. The core is
itself surrounded by a membrane (called an "envelope", made of fat
[lipids] and various membrane-bound proteins). One of the membrane-bound proteins
can bind to a particular protein on the surface of certain immune cells, called
T-cells (we'll talk about these in a minute) which results in the virus
becoming physically attached. Upon binding, the virus is brought inside of the
T-cell (cells do this kind of thing all of the time), and the envelope is
removed by enzymes normally present inside the cell. The internal core is thus
exposed, and it too is broken-down. This last phase results in exposure of the
virus's RNA genetic material. An enzyme attached to the RNA, known as
"reverse transcriptase", begins to make a complimentary base-pair
single-strand copy of the RNA into DNA (please see What
the Heck is PCR? ). The single strand of DNA is also copied by the
same enzyme to form double-stranded DNA. This DNA inserts somewhere into one of
the 46 chromosomes within our cells, and there it is used as a template for
production of all of the things necessary to form new virus particles (
replication of the virus). These new virus particles can be subsequently
released from the infected cell, and
can infect adjacent cells.
The Immune System
The immune system is a system within all vertebrates
(animals with a backbone) which in general terms, is comprised of two important
cell types: the B-cell and the T-cell. The B-cell is responsible for the
production of antibodies (proteins which can bind to specific molecular
shapes), and the T-cell (two types) is responsible either for helping the
B-cell to make antibodies, or for the killing of damaged or
"different" cells (all foreign cells except bacteria) within the
body. The two main types of T-cells are the "helper"T-cell and
the cytotoxic T-cell. The T-helper population is further divided into
those which help B-cells (Th2) and those which help cytotoxic T-cells (Th1).
Therefore, in order for a B-cell to do its job requires the biochemical help of
Th2 helper T-cells; and, for a cytotoxic T-cell to be able to eliminate a
damaged cell (say, a virally-infected cell), requires the biochemical help of a
Th1 helper T-cell.
Whenever any foreign substance or agent enters our body, the immune
system is activated. Both B- and T-cell members respond to the threat, which
eventually results in the elimination of the substance or agent from our
bodies. If the agent which gains entry is the kind which remains outside of our
cells all of the time (extracellular pathogen), or much of the time (virus
often released) the "best" response is the production by B-cells of
antibodies which circulate all around the body in the bloodstream, and
eventually bind to the agent. There are mechanisms available which are very
good at destroying anything which has an antibody bound to it. On the other
hand, if the agent is one which goes inside one of our cells and remains there
most of the time (intracellular pathogens like viruses or certain bacteria
which require the inside of one of our cells in order to live), the
"best" response is the activation of cytotoxic T-cells (circulate in
the bloodstream and lymph), which eliminate the agent through killing of the
cell which contains the agent (agent is otherwise "hidden"). Both of
these kinds of responses (B-cell or cytotoxic T-cell) of course require
specific helper T-cell biochemical information as described above. Usually,
both B-cell and cytotoxic T-cell responses occur against intracellular agents
which provides a two-pronged attack. Normally, these actions are wonderfully
protective of us. The effect of HIV on the immune system is the result of a
gradual (usually) elimination of the Th1 and Th2 helper T-cell sub-populations.
How HIV Specifically Affects the Immune System
Remember about the proteins which are part of the
envelope of HIV? Well, one of these proteins, named gp 120, (a sugar-containing
protein called a glycoprotein, of approximately 120,000 molecular weight),
"recognizes" a protein on helper T-cells named CD4, and physically
associates with it. The CD4 [Cluster of Differentiation Antigen No. 4] protein
is a normal part of a helper (both Th1 and Th2) T-cell's membrane. Thus, CD4
is a specific receptor for HIV. This virus however, can also infect other
cells which include macrophages and certain other kinds of cells which can
engulf substances through a process known as phagocytosis. As a consequence of
the interaction with CD4 on helper T-cells, HIV specifically infects the
very cells necessary to activate both B-cell and cytotoxic T-cell immune
responses. Without helper T-cells, the body cannot make antibodies properly,
nor can infected cells containing HIV (an intracellular pathogen) be properly
eliminated. Consequently, the virus can: multiply, kill the helper T-cell in
which it lives, infect adjacent helper T-cells, repeat the cycle, and on and
on, until eventually there is a substantial loss of helper T-cells.
The fight between the virus and the immune system for supremacy is
continuous. Our body responds to this onslaught through production of more
T-cells, some of which mature to become helper T-cells. The virus eventually infects
these targets and eliminates them, too. More T-cells are produced; these too
become infected, and are killed by the virus. This fight may continue for up to
ten years before the body eventually succumbs, apparently because of the
inability to any-longer produce T-cells. This loss of helper T-cells finally
results in the complete inability of our body to ward-off even the weakest of
organisms (all kinds of bacteria and viruses other than HIV) which are normally
not ever a problem to us. This acquired condition of immunodeficiency is
called, AIDS.
Research
This virus has been under intense scrutiny for several
years, now (since approximately 1985), and an astonishing amount of information
has been gathered. One must wonder, "why isn't there a cure?" There
isn't a cure primarily because there isn't a cure for most viruses. We do not
yet know how to specifically kill a virus which spends most of the time hiding
inside of our cells. The substances which we know can directly harm such a
virus, unfortunately can also harm our own cells. Unlike our immune system, we
do not yet know how to direct an attack on only those cells which are
infected with the virus. Our knowledge so far allows us only to attack all
of our cells (much like we do in chemotherapy for cancer treatments). We can't
even sort-of focus an attack, as one can do with radiation treatment - if
radiation treatment were used for HIV infections, this treatment would
significantly hurt our immune system's ability to function, which is the
opposite of what we want. To date, the most effective treatment against viruses
is to develop a vaccine - which stimulates our own immune system to enable our
immune system to better fight the virus. Thus, we have vaccines against
poliovirus, smallpox virus, measles virus, influenza viruses, and others. The
vaccine per se does not fight the virus, but instead causes an immune
response specifically directed against the particular virus from which the
vaccine is made - this response directly increases the number of specific B-
and T-cells available to respond against a live virus infection encountered at
some later time. Unfortunately, the fact that HIV is a retrovirus causes
serious problems in vaccine development. The enzyme which generates RNA and DNA
copies of the virus's RNA genetic material, makes errors. These errors are
sometimes not lethal to the virus, but instead result in a different strain of
a given virus - a different "looking" virus. Indeed, HIV is
approximately 65-times more likely to undergo such changes as influenza virus
(before HIV, the greatest variant producer - Please see The
Flu Season is Upon us).
Our immune system's ability to recognize any foreign substance or
agent, depends entirely upon how the substance or agent
"looks" with respect to the molecular shapes displayed - just as your
elbow looks different than someone else's elbow - even though each are clearly
elbows. Therefore, while an individual may become infected with a single strain
of HIV, over several years of many, many viral generations, an individual may
have 10 different strains of HIV present. Further, to date no two people have
been identified to have been infected with the same strain of HIV.
Consequently, against which strain should a population be immunized? In such
cases, one tries to identify molecular shapes which are common to all known
strains - in this way, all strains would theoretically be recognizable by our
immune system. Sadly, this research has failed to provide an effective vaccine.
This virus is subtle, and can do some very covert things using biochemical
mechanisms we do not yet understand. Because of recent basic research in the
field of immunology (the discipline which develops an understanding of the
intricate workings of the immune system), based upon years of previous basic
research in this and other fields however, some light is beginning to emerge
which may help us.
It is becoming clear that the two helper T-cell types identified
only a few years ago may be significantly more important than first assumed.
Remember, the Th1 helper-cell helps generate a cytotoxic T-cell response, and
the Th2 helper-cell helps generate an antibody response. As it turns out,
certain intracellular pathogens primarily elicit a Th2 response in certain
in-bred strains of mice, while in a different in-bred mouse strain, the same
pathogen primarily elicits a Th1 response. In this example, all mice
which respond primarily with antibody (B-cell; Th2 help), die; and, all
mice which primarily respond with a cytotoxic T-cell response (Th1 help), live!
Such is not the case for every intracellular pathogen - some responses are very
balanced with respect to B-cell and cytotoxic T-cell contributions, and others
are imbalanced in one or the other direction. The balance in contribution of
these two paths to an immune response, appears to not only depend upon the
particular infectious organism, but also upon the particular genetic background
of the infected animal. Thus, one can imagine that one may be able to find a
way to tip the balance towards the most effective response path against a given
organism, e.g., either antibody production by B-cells, or development of
cytotoxic T-cells. This research is one of the prime areas under investigation
with regard to HIV. There are very limited data to date; but, those individuals
who have had HIV for a really long time, but have not yet acquired AIDS (there
are indeed now a number of such individuals), appear to have their immune
response shifted towards the cytotoxic side (Th1 help). This limited
information on HIV, in combination with basic research information on several
different diseases using animal models (mice), has generated a quick response
within the research community. Consequently, there are efforts currently
underway to identify the biochemical substances which are involved in directing
a response along the Th1 path, and efforts to determine how the immune system
might be manipulated to direct a response along a given path. Such
experimentation is long and difficult, and requires money, skill, unflinching
commitment, and an abiding faith that this problem can be solved.
How One Can Try Not to Become HIV-Infected
HIV can enter one's body by several different routes:
indirectly through eye, oral, anal, vaginal, or urethral (female/male urine
canal) contact, and directly through the bloodstream via any opening in the
skin. The walls of all tissue (the eye, upper and lower respiratory, genital,
urethral, intestinal) except the skin, which are exposed to the environment are
lined with mucosal tissue. Within and beneath this tissue are cells which can
engulf anything which invades the tissue. After engulfment of an agent, these
particular cells travel to a regional area where B- and T-cells are concentrated
and organized into a complex arrangement of tissue called a lymph node. Also,
the engulfment process may generate a local inflammatory response, which in
turn calls on the arrival of B- and T-cells from the bloodstream, across the
endothelial wall of the blood-vessel, and into the tissue at the focus of the
inflammatory response. If an agent enters the bloodstream via a direct
injection into a vein (needle puncture made through intravenous illicit drug
use, or by receipt of needed blood products, e.g., transfusion), it will enter
the spleen (an organized tissue primarily containing B- and T-cells, and also
various lymph nodes via lymphatic and blood vessels connected to the spleen).
It is in these ways that HIV eventually associates with helper T-cells. Any
abrasion in the skin or mucosal tissue provides access to the tissue and
bloodstream by any infectious agent.
Under normal circumstances, the design of the immune system's
various tissues and connections, allows the agent to be focused within a regional
lymph node, which greatly improves the probability of an effective defensive
response. In the case of HIV, however, this ability either brings the target
cells to the virus, or brings the virus to the target cells. Consequently, the
only way to prevent exposure to the virus, is to avoid situations which allow
the potential for entry of the virus. Such situations are overwhelmingly
associated with sexual intercourse, intravenous drug use, and exposure of a cut
in one's skin to the bodily fluids (secretions, blood) of an HIV-infected
individual. Such situations do not include hugging, touching, or other
nonfluid-exchange expressions of caring for someone infected with HIV.
Oral, vaginal,
and anal intercourse can lead to tiny abrasions of the mucosal tissue in these
areas; and, within the tissues of the mouth (gums in particular) there will
almost always be tiny abrasions present under any circumstances. These openings
provide access by the virus to the blood and lymphatic streams, as well as to
cells within the tissue. If a person is infected with HIV, there will be virus
within the secretions of the person (particularly the seminal fluid of males),
and in the blood of the person. Consequently, the direct exposure to bodily
fluids (secretions, blood) can potentially occur between both partners
(female/female, male/male, female/male) during any kind of sexual intercourse,
whether or not ejaculation by a male partner occurs. While the body may be able
to ward-off a small amount of virus, repeated exposure to such amounts places a
person, particularly women having vaginal intercourse, and men and women having
anal intercourse with an HIV-infected partner, at significant risk of HIV
infection. Under any circumstance, there is a risk of HIV infection through
only one sexual intercourse encounter. The use of a condom for the male
partner, in combination with chemical substances which kill viruses, is
recommended. Multiple sexual partners, unprotected sexual intercourse, anal
sexual intercourse, the presence of other sexually-transmitted disease, and intravenous
drug usage significantly increase the risk of HIV infection.
One can be tested for the presence of HIV through an appointment
with one's local Health Department (state-supported). Health department test
results are completely confidential and inaccesible to anyone but the patient
and testing physician at the public-health clinic. While a personal physician's
records are also confidential, these records are however, subject to
examination at any time by the health insurer(s) of the physician. No matter
where one chooses to be examined, one will be required to undergo a pre-test
and post-test psychological counseling session.
An AIDS researcher
examines a test sheet. There is no known cure for the disease, caused by the
retrovirus HIV, but researchers are constantly investigating ways to attack it.
Bill Branson
Nutrition for HIV/AIDS
In the absence of a cure, it is important to control symptoms,
support the immune system, and lower the levels of HIV circulating in the
blood. To lower the level of HIV in the blood, patients take a prescribed
combination of antiviral drugs . The role nutrition plays will vary
along the disease continuum (disease progression over many years), with
consideration given to the patient's age, gender, behaviors, current
medication, drug history, socioeconomic status , and associated health
concerns.
In all cases, adequate hydration (fluid intake) and increased
calorie and protein intake are necessary to fight
the infection. Proper nutrition must begin immediately to support nutritional
deficiencies (including vitamin A and E, the B vitamins , magnesium,
and zinc ) that occur early in the disease process. These nutritional
deficiencies contribute to decreased immunity and disease progression. Ellen
Mazo and Keith Berndtson, in The Immune Advantage , suggest that once
the patient has been diagnosed with HIV infection, more protein and complex carbohydrates , along with moderate
amounts of fats, should be consumed. The diet
should include lean meat, fish, beans, seeds and nuts, whole-grain
breads and cereals, and fruits and vegetables. Moderate amounts of fat for energy
and calories can be acquired through foods such as nuts, avocado dip,
peanut butter, and seeds.
The diet should include each of the five major food groups (dairy,
vegetable, meat, fruit, and bread). The sixth group (fats and sugars) should be
used sparingly. Patients with a poor appetite should eat six or more small
meals throughout the day, rather than three large ones. In prolonged cases of
appetite depression, a physician may prescribe an appetite stimulant (e.g.,
megesterol acetate). It is important to keep all foods refrigerated, to avoid
eating rare meats, to practice proper hand washing, and to use soap and hot
water to clean sinks and utensils. Food-borne illnesses pose serious threats
for HIV/AIDS patients.
HIV/AIDS Complications
Some symptoms will require additional attention beyond general
nutritional recommendations. For example, diarrhea will rapidly reduce the
water content of the body, causing severe alterations in the body's metabolism and electrolyte balance.
Electrolytes may be replaced with products such as Pedialyte or Gatorade.
Proteins and calories should be increased to prevent weight loss, and dairy
products, alcohol, caffeine, and spicy and fatty foods should be avoided.
A second complication is that of weight loss and wasting. According
to Derek Macallan, in Wasting HIV Infection and AIDS, wasting may be
either acute (associated with a secondary disease) or chronic (associated
with gastrointestinal disease), and is the result of a variety of
processes, including drug use, medications, concurrent disease, and HIV itself.
HIV infection causes abnormal protein and fat metabolism. During episodes of
acute wasting the patient may require a prescription for steroids , to
help support tissue maintenance and tissue development, in combination with
optimal protein and calories in the diet.
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REFERENCES
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