AIDS And HIV Essay, Research Paper

AIDS and HIV

Introduction

Being one of the most fatal viruses in the nation, AIDS (Acquired

Immunodeficiency Syndrome) is now a serious public health concern in most major

U.S. cities and in countries worldwide. Since 1986 there have been impressive

advances in understanding of the AIDS virus, its mechanisms, and its routes of

transmission. Even though researchers have put in countless hours, and millions

of dollars it has not led to a drug that can cure infection with the virus or to

a vaccine that can prevent it. With AIDS being the leading cause of death among

adults, individuals are now taking more precautions with sexual intercourse, and

medical facilities are screening blood more thoroughly. Even though HIV ( Human

Immunodeficieny Virus) can be transmitted through sharing of non sterilize

needles and syringes, sexual intercourse, blood transfusion, and through most

bodily fluids, it is not transmitted through casual contact or by biting or

blood sucking insects.

Development of the AIDS Epidemic

The first case of AIDS were reported in 1982, epidemiologists at the

Center of Disease Control immediately began tracking the disease back wards in

time as well as forward. They determined that the first cases of AIDS in the

United States probably occurred in 1977.

By early 1982, 15 states, the District of Columbia, and 2 foreign

countries had reports of AIDS cases, however the total remained low: 158 men and

1 woman. Surprising enough more then 90 percent of the men were homosexual or

bisexual. Knowing this more then 70 percent of AIDS victims are homosexual or

bisexual men, and less then 5 percent are heterosexual adults. Amazing enough

by December of 1983 there were 3,000 cases of AIDS that had been reported in

adults from 42 states, the District of Columbia, and Puerto Rico, and the

disease had been recognized in 20 other countries. Recognizing the Extent of

Infection

The health of the general homosexual populations in the area with the

largest number of cases of the new disease was getting looked at a lot closer by

researchers. For many years physicians knew that homosexual men who reported

large numbers of sexual partners had more episodes of venereal diseases and were

at higher risk of hepatitis B virus infection than the rest of the population,

but conicidentally with the appearance of AIDS,. other debilitating problems

began to do appear more frequently. The most common was swollen glands, often

accompanied by extreme fatigue, weight loss, fever, chronic diarrhea, decreased

levels of blood platelets and fungal infections in the mouth. This condition

was labeled ARC (AIDS Related complex).

The isolation of HIV in 1983 and 1984 and the development of techniques

to produce large quantities of the virus [paved the way for a battery of tests

to determined the relationship between AIDS and ARC and the magnitude of the

carrier problem. Using several different laboratory tests, scientists looked

for antibodies against the HIV in the blood of AIDS and ARC patients. They

found that almost 100 percent of those with AIDS or ARC had the antibodies-they

were seriopostive. In contrast less then one percent of persons with no known

risk factors were seropositive.

Definition of AIDS

AIDS is defined as a disease, at least moderately predictive of defects

in cell-meditated immunity, occurring in a person with no known cause for

diminished resistance to that disease. Such diseases include Kaposi’s Sarcoma,

Pneumocystis carnii pneumonia, and serious other opportunistic infections.

After the discovery of HIV and the development of HIV-antibody test, the case

definition of AIDS was updated to reflect the role of the virus in causing AIDS,

but the scope of the definition remained almost the same. Transmission

HIV is primarily a sexually transmitted disease, it is transmitted by

both homosexual and bisexual and heterosexual activity. The first recognized

case was among homosexual and bisexual men. Many numbers of studies have shown

that men who have sexual partners and those who practice receptive anal

intercourse are more likely to be infected with HIV than other homosexual men.

Researchers found a strong connection between HIV infection and rectal trauma,

enemas before sex, and physical signs of disruption of the tissue lining the

rectum.

Homosexual women tend to have a very low incidence of venereal disease

in general, an AIDS is no exception. Female-to-female transmission is highly

uncommon, however it has been reported in one case and suggested in another. In

the reported case, traumatic sex practices apparently resulted in transmission

of HIV from a woman who had acquired the virus through IV drug abuse to her non-

drug-using sexual partner.

1983 was when the first heterosexual (Male to female; female to male)

transmission was reported. In 1985, 1.7 percent of the adult cases of AIDS

reported to the CDC (Center for Disease Control) were acquired through

heterosexual activity; projections suggest that by 1991 the proportion will rise

to 5 percent. Heterosexual contact is the only transmission category in which

women outnumber men with AIDS. Heterosexual contacts accounts for 29 percent of

AIDS cases among women in the United States, but for only 2 percent of cases

among men. Estimates of the risk of HIV transmission in unprotected intercourse

with a person known to be infected with HIV are 1 in 500 for a single sexual

encounter and 2 in 3 for 500 sexual encounters. The use of a condom reduces

these odds to 1 in 5,000 for a single encounter and to 1 in 11 for 500

encounters. Routes NOT Involved in Transmission of HIV

A study of more than 400 family members of adult and pediatric AIDS

patients demonstrate that the virus is not transmitted by any daily activity

related to living with or caring for an AIDS patient. Basically meaning that

personal interactions typical in family relationships, such as kissing on the

cheek, kissing on the lips, and hugging, have not resulted in transmission of

the virus. Patterns

There are three different geographic patterns of AIDS transmission. The

first one is characteristic of industrializing nations with large numbers of

reported AIDS cases, such as the United States, Canada, countries in Western

Europe, Australia, New Zealand, and parts of Latin America. In these areas most

AIDS cases have been attributed to homosexual or bisexual activity and

intravenous drug abuse. The second pattern is seen in areas of central, eastern,

and southern Africa and in some Caribbean countries. Unlike pattern one most

AIDS cases in these areas occur among heterosexuals, and the male-to-female

ratio approaches 1 to 1. The third pattern of transmission occurs in regions of

Eastern Europe, the Middle East, Asia, and most of the Pacific. It is believed

that HIV was introduced to these areas in the early to mid-1980s.

Any study associated with AIDS must begin with the understanding that

AIDS is only one outcome of infection with HIV-1. People infected with the

virus may be completely asymptomtic; they may have mildly debiliating symptoms;

or they may have life-threatening conditions caused by progressive destruction

of the immune system, the brain, or both.

One of the first signs of HIV-1 infection in some patients is an acute

fluelike disease. The condition lasts from a few days to several weeks and is

associated with fever, sweats, exhaustion, loss of appetite, nausea, headaches,

soar throat, diarrhea, swollen glands, and a rash on the torso.

Some of the symptoms of the acute illness may result from HIV-1 invasion

of the central nervous system. In some cases the clinical findings have

correlated with the presence of HIV-1 in the cerebrospinal fluid. Symptoms

disappear along with the rash and other sings of acute viral disease. When the

blood test for HIV-1 antibodies become available, researchers demonstrated the

lymphadenopathy was a frequent consequence of infection with the virus.

Scientist do not know what causes the wasting syndrome, but some experts believe

that it might result from the abnormal regulation of proteins called monokines.

Between 5 and 10 percent of patients with AIDS and HIV-related

conditions have bouts of acute aseptic meningtis. About two-thirds of AIDS

patients have a degenerative brain disease called subacute encephalitis. HIV

infection also have been associated with degeneration of the spinal cord and

abnormalities of the peripheral nervous system. Symptoms include progressive

loss of coordination and weakness. Involvement of the peripheral nervous system

may result in shooting pains in the limbs or in numbness and partial paralysis.

HIV destroys the body’s defense capabilities, opening itself to whatever

disease-producing agents are present in the environment. The diagnosis of

secondary infection in AIDS patients and others with HIV infection is

complicated because some of the standard diagnostic tests may not work. Often

such tests detect the immune response to a disease-producing microorganism

rather than the organism itself.

The most common life threatening opportunistic infection in AIDS

patients is Pneumocystis carinii Pneumonia, a parasitic infection previously

seen almost exclusively in cancer and transplant patients receiving

immunosuppressive drugs. The first signs of disorder are moderate to severe

difficulty in breathing, dry cough, and fever. Infection

Infection with HIV is a 2-step process consisting of binding and fusion.

The larger protein, glycoprotein120, is responsible for the binding activity.

Its target is a receptor molecule called CD4, found on the surface of some human

cells. The tight complex formed by glycoprotein120, and CD4 receptor brings the

viral envelope very close to membrane of the target cell. This allows the

smaller envelope protein, glycoprotein41, to initiate a fusion reaction. The

envelope of the virus actually fuses with the cell membrane, allowing the viral

core direct access to the inner mechanisms of the human cell. Once the viral

core is inside the cell, the viral RNA genome is reverse transcribed into DNA

and then integrated into the host genome cells.

Cells infected with HIV carry envelope proteins lodged in their membrane.

These cell-bound proteins can bind to CD4 receptors on uninfected cell. Fusion

of the two cell membranes allow partially formed viral particles to move from

the infected cell to the uninfected cell. Thus, HIV theocratically could spread

through the body without leaving host cells. Cell Death

HIV infects many different cell types, but it preferentially kills the

T4 lymphocyte. There have been suggestions the T4 cells are more vulnerable to

HIV-induced cell death than other cells because they have a higher

concerntration of CD4 receptors. There is speculation that cell death occurs

when viral envelope proteins lodged in the membrane of an infected cell bind to

CD4 receptors embedded in the same membrane. Multiple self fusion reactions

could destabilize the cell membrane and kill the cell.

The massive depletion of T4 cells involves the cell-to-cell fusion

reaction described above. A single infected cell with a high concentration of

viral envelope proteins on its surface can bind to hundreds of uninfected T4

cells. The fused cells form giant, mulitnucleated structures called syncytia,

which are extremely unstable and die within a day. One cell with a productive

viral infection can cause the death of up to 500 normal cells. Cell death might

be related to the presence of free-floating viral envelope proteins in the

bloodstream. These could bind to uninfected T4 cells, leading to their

elimination by the immune system. Other autoimmune mechanisms also may play a

roll in T-cell depletion.

HIV infection also may directly or indirectly suppress the production of

new T4 cells. Direct suppression would occur if HIV damaged T precursor cells

in the bone marrow. Indirect suppression would result if HIV interfered with

the production of specific growth factors. On the other hand, infected cells

may secrete a toxin that shortens the lifespan of T4 cells or other cells

required for their survival. Immune System

The Immune response to HIV infection, does not appear to halt the

progression of disease. Part of the explanation for this failure probably

relates to the structure of the envelope proteins. The most effective way to

stop HIV infection would be to block the binding reaction between the

glycoprotein120 and the CD4 receptor. However, antibodies from infected

patients rarely do this. Scientists speculate that 2 or 3 regions of the

glycoprotein120 molecule involved in the binding reaction may form a recessed

pocket. The inability of antibodies to get inside such a pocket could explain

the lack of protective immune response.

The envelope proteins also are heavily coated with sugar residues. The

human immune system does not recognize the sugar residues as foreign because

they are products of the host cell rather then the virus. The sugar residues

form a protective barrier around sections of the glycoprotein120 that might

otherwise elicit a strong immune response. Regulatory Genes

There has been recent studies that indicate HIV’s unusual regulatory

genes contributing to its ability to evade the immune system. In the simplest

retroviruses the replication rate is controlled by interactions between the host

cell and elements in the viral LTR. The virus itself has no way of regulating

when, here, or how much virus is produced. In contrast, the human

immunodeficiency viruses have elaborate regulatory control mechanisms in the

form of specific genes. Some of the genes permit explosive replication; other

appear to inhibit production of virus. Mechanisms that suppress the production

of certain viral proteins, such as the envelope proteins, may allow HIV to hide

inside infected cells for long periods without eliciting antibodies or other

host immune responses.

Conclusion

As stated above in the last few pages, AIDS is the leading cause of

death in homosexual, and bisexual adult men. However, these statistics were

from 1986, 11 years later it has grown to more, not just in homosexual and

bisexual men, but also in heterosexual sexual intercourse. At this point in

time there is no cure, nor is there a vaccination. However, there are ways to

prevent HIV, some of those ways are: abstinence, condoms, not sharing needles

used for IV drugs. Public concern is higher then it was 10 years ago, but

that’s because people are starting to realize that not everyone is immune to it,

as of right now the only ones immune to the HIV virus are baboons.