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Transcript
Clinical finding:
Infection with HIV-1 is associated with a progressive decrease of the
CD4+ T cell count and an increase in viral load (the level of HIV in the
blood). The stage of infection can be determined by measuring the
patient's CD4+ T cell count and viral load.
The clinical picture of HIV infection can be divided into three stages: an
acute stage, latent stage, and immunodeficiency stage.
Infection with HIV generally occurs by introduction of bodily fluids from
an infected person into the body of an uninfected person. A period of
rapid viral replication ensues, leading to an abundance of virus in the
peripheral blood. During primary infection, the level of HIV may reach
several million virus particles per milliliter of blood.
This response is accompanied by a marked drop in the numbers of
circulating CD4+ T cells. This acute viremia is associated in virtually all
patients with the activation of CD8+ T cells, which kill HIV-infected cells,
and subsequently with antibody production, or seroconversion. The
CD8+ T cell response is thought to be important in controlling virus
levels, which peak and then decline, as the CD4+ T cell counts rebound. A
good CD8+ T cell response has been linked to slower disease progression
and a better prognosis, though it doesn't eliminate the virus.
During this period most individuals (80 to 90%) develop an influenza or
mononucleosis-like illness called acute HIV infection, the most common
symptoms of which may include fever, lymphadenopathy, pharyngitis,
rash, myalgia, malaise, mouth and esophageal sores, and may also
include, but less commonly, headache, nausea and vomiting, enlarged
liver/spleen, weight loss, thrush, and neurological symptoms (figure 3).
Infected individuals may experience all, some, or none of these
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symptoms. The duration of symptoms varies, averaging. This acute stage
resolves spontaneously in about 2 weeks. Antibodies to HIV typically
appears 3-4 weeks after infection.
Because of the nonspecific nature of these symptoms, they are often not
recognized as signs of HIV infection. Even if patients go to their doctors
or a hospital, they will often be misdiagnosed as having one of the more
common infectious diseases with the same symptoms. As a
consequence, these primary symptoms are not used to diagnose HIV
infection, as they do not develop in all cases and because many are
caused by other more common diseases. However, recognizing the
syndrome can be important because the patient is much more infectious
during this period.
Figure(3): the main symptoms of HIV acute infection.
In the second stage, a long latent period, measured in years ensues. The
patient is asymptomatic, and a large amount of virus is produced by
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lymph node cells but remains sequestered within the lymph nodes
(which typically become persistently swollen, in response to large
amounts of virus that become trapped in the follicular dendritic cells
(FDC) network). Individuals who are in this phase are still infectious. A
syndrome called AIDS-related complex (ARC) can occur during the latent
period. The most frequent manifestations are persistent fever, fatigue,
weight loss, ad lymphadenopathy. ARC often progress to AIDS.
The late stage of HIV infection is AIDS, manifested by a decline in the
number of CD4 cells to below 400/mm3 and increase in the frequency
and severity of opportunistic infections. Syndrome associated with this
period include the following features:
1) Constitutional disease: fever, diarrhea, weight loss, skin rashes.
2) Neurological disease: dementia, peripheral neuropathy.
3) Immunodeficiency: Increased susceptibility to opportunistic
infections.
4) Rare malignancies: Kaposi sarcoma, lymphomas.
Diagnosis:
The diagnosis of HIV infection is made by the detection of antibodies by
ELISA. Because there are some false-positive results with this test, the
definite diagnosis is made by Western blot analysis. The PCR is very
sensitive technique that detect HIV DNA within infected cells.
During the first months after infection, antibody tests are frequently
negative. In view of this, the diagnosis of acute HIV infection typically
cannot be made using serological tests. The presence of HIV can be
detected during that period by either viral culture, p24 antigen test, or
PCR assay.
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Treatment:
The treatment of choice for advanced disease is a regimen consisting of
two nucleoside inhibitors ( Azidothymidine and Lamivudine) and a
protease inhibitors ( Indinavir). This combination is known as HAART
(highly active antiretroviral therapy). It is effective in prolonging life,
improving quality of life, and reducing viral load but doesn't cure the
chronic HIV infection. Another regimen especially in children, is the
combination of azidothymidine, lamivudine, and non-nucleoside reverse
transcritase inhibitor, efavirinez.
Azidothymidine (AZT) inhibits HIV replication by interfering with proviral
DNA synthesis. Strains of HIV resistant to AZT have been isolated from
patient receiving long-term AZT therapy. Dideoxyinosine (ddI) is
recommended for patient who are intolerant of AZT or whose disease
has progressed while they were taking AZT.
Prevention:
 The risk of contracting HIV increases with the number of sexual
partners. A change in the lifestyle would obviously reduce the risk.
 The spread of HIV through blood transfusion and blood products
had virtually been eliminated since the introduction of blood
donor screening in many countries.
 AZT had been shown to be effective in preventing transmission of
HIV from the mother to the fetus. The incidence of HIV infection in
the baby was reduced by two-thirds.
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