Aids + Hiv Essay, Research Paper

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.