Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY AIDS, recent advances in research and treatment

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brings about a greater increase of antibodies and a greater

decrease of fulminant HIV than either type of drug alone.

Although patients improve on a regimen of mixed drugs, they

are not cured due to the persistence of inactive virus left in the

body. Researchers are looking for ways to flush out the

remaining HIV. In the battle against AIDS, researchers are also

attempting to develop a vaccine. As an adjunct to the classic

method of preparing a vaccine from weakened virus, scientists

are attempting to create a vaccine from a single virus protein.

In addition to treatment, the battle against AIDS

includes preventing transmission of the disease. Infected indi-

viduals pass HIV-laden macrophages and T lymphocytes in

their bodily fluids to others. Sexual behaviors and drug-related

activities are the most common means of transmission.

Commonly, the virus gains entry into the bloodstream by way

of small abrasions during sexual intercourse or direct injection

with an infected needle. In attempting to prevent HIV trans-

mission among the peoples of the world, there has been an

unprecedented emphasis on public healtheducation and social

programs; it is vitally important to increase public under-

standing of both the nature of AIDS and the behaviors that put

individuals at risk of spreading or contracting the disease.

See alsoAIDS, recent advances in research and treatment;

Antibody and antigen; Blood borne infections; Centers for

Disease Control (CDC); Epidemics, viral; Human immunode-

ficiency virus (HIV); Immunodeficiency disease syndromes;

Immunodeficiency diseases; Immunological analysis tech-

niques; Infection and resistance; Infection control; Latent

viruses and diseases; Sexually transmitted diseases; T cells or

T lymphocytes; Viral genetics; Viral vectors in gene therapy;

Virology; Virus replication; Viruses and responses to viral

infection

AIDS, RECENT ADVANCES IN RESEARCH

AND TREATMENTAIDS, recent advances in research and treatment

Acquired Immune Deficiency Syndrome (AIDS) has only been

known since the early years of the 1980s. Since that time, the

number of people infected with the causative virus of the syn-

drome and of those who die from the various consequences of

the infection, has grown considerably.

In the 1980s and 1990s, researchers were able to estab-

lish that the principle target for the maladies associated with

AIDS is the immune system. Since then, much research has

been directed towards pinpointing the changes in the human

immune system due to infection, seeking ways of reversing

these changes, or supplementing the compromised immune

system to hold the infection in check.

The particular immune system component that has been

implicated in the progression of AIDS is a type of T cell called

the CDC4 T cell. This cell, which is activated following

recognition of the virus by the immune system, functions in

the destruction of the cells that have been infected by the

virus. Over time, however, the number of CDC4 cells

declines. If the decline decreases the T cell count to below 200

per microliter of blood, the number of infective virus particles

goes up steeply and the immune system breaks down. This

loss of the ability to fight off foreign organisms leaves the

patient open to life-threatening illnesses that normally would

be routinely defeated by an unimpaired immune system.

Until 2001, the prevailing view was that the decline in

the number of CDC4 cells was due to a blockage of new T cell

production by the infecting virus. However, the conclusions

from studies published in 2001 now indicate that the produc-

tion of new T cellsis not blocked, but rather that there is accel-

eration in the loss of existing T cells. Even though the result is

the same, namely the increased loss of the specialized AIDS-

fighting T cells, the nature of the decline is crucial to deter-

mine in order to devise the most effective treatment strategy.

If the reasons for the accelerated loss of the T cells can be

determined, perhaps the loss can be prevented. This would

better equip patients to fight the infection.

Since 1998, a multi-pronged strategy of AIDS therapy

has been established. Highly Active Anti-Retroviral Therapy

(HAART) consists of administering a “cocktail” of drugs tar-

geted to the AIDS virus to a patient, even when the patient

shows no symptoms of AIDS. The drug mixture typically con-

tains a so-called nucleoside analog, which blocks genetic

replication, and inhibitors of two enzymesthat are critical

enzyme in the making of new virus (protease and reverse tran-

scriptase).

HAART has greatly reduced the loss of life due to AIDS.

But, this benefit has come at the expense of side effects that can

often be severe. Also, the treatment is expensive. But now,

research published toward the end of 2001 indicates that the use

of HAART in a “7-day-on, 7-day-off” cycle does not diminish

treatment benefits, but does diminish treatment side effects.

Costs of treatment has become more reasonable, as well.

Another advancement in AIDS treatment may come

from the finding that the inner core of the AIDS virus, which

is called the nucleocapsid, is held together by structures

known as “zinc fingers.” There are drugs that appear to break

apart these supports. This stops the virus from functioning.

Furthermore, evidence supports the view that the nucleocapsid

does not change much over time. Thus, a drug that effectively

targeted the nucleocapsid could be an effective drug for a long

time. The drawback to this approach at the present time is that

other structures in the body utilize zinc fingers. So, an anti-

AIDS zinc finger strategy will have to be made very specific.

In the mid 1980s, there was great optimism that a vac-

cinefor the AIDS virus would be developed within two years.

However, this optimism soon disappeared. In late 2001, how-

ever, preliminary clinical trials began on a candidate vaccine.

Traditional vaccines rely on the administration of a protein to

stimulate the production of an antibodythat confers protection

against the disease-causing organism. The candidate vaccine

works by targeting what is called cell-mediated immunity.

This type of immunity does not prevent infection, but rather

clears the virus-infected cells out of the body. Such a vaccine

would be intended to prolong and enhance the quality of the

lives of AIDS-infected people. Studies in monkeys have been

encouraging. However, studies must still rule out the possibil-

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