Roll of CD4 cells on HIV/ AIDS

CD4 T-cells & HIV

CD4 is a glycoprotein found on the surface of immune cells such as T helper cells, monocytes and macrophages cells. CD4 cells (sometimes called T-cells, T-lymphocytes, or helper cells) are white blood cells that play an important role in the immune system. Your CD4 cell count gives you an indication of the health of your immune system – your body’s natural defence system against pathogens, infections and illnesses.

CD4 T-cells are considered "helper" cells because they do not neutralize infections but rather triggers the body's response to infections. In response, CD8 T-cells—classified as such because of the type of glycoprotein on their surface—play a part as so-called "killer" cells by producing antiviral substances (antibodies) that help fight off foreign invaders.

Structure of CD 4 cells:

Like many cell surface receptors/markers, CD4 is a member of the immunoglobulin super family

It has four immunoglobulin domains (D1 to D4) that are exposed on the extra cellular surface of the cell:

• D₁ and D₃ resemble  immunoglobulin variable (IgV) domains.
• D₂ and D₄ resemble immunoglobulin constant (IgC) domains.

CD4 uses its D₁ domain to interact with the β₂-domain of MHC class II  molecules. T cells expressing CD4 molecules (and not CD8) on their surface, therefore, are specific for antigens presented by MHC II and not by MHC class II (they are MHC class II-restricted). MHC class I contains Beta-2 macroglobulin.

How HIV Affects CD4 Cells:

As a retrovirus, HIV do not have own enzymes necessary for protein & nuclic acid synthesis and so depend upon synthetic machinery oh host cells. Therefore, HIV needs to infect certain "host" cells in order to make copies of itself. CD4 cells are the prime targets for this in the course of an infection.

During infection, HIV attaches to surface of CD4 cells, emptying its genetic material within so that the host's genetic coding can be altered to produce other HIV virions.

How Do We Measure CD4 T-Cells

By determining how many functioning CD4 cells are circulating in the blood, a doctor can determine the status of a person's immune system. A simple blood tested called the CD4 COUNT estimates the number of functioning CD4 cells in a cubic millimetre of blood. The higher the CD4 count, the stronger the immune function.

Your CD4 cell count is the measurement of the number of blood cells in a cubic millimeter of blood (a very small blood sample). It is not a count of all the CD4 cells in your body.

• The CD4 cell count of a person who does not have HIV can be anything between 500 and 1500.
• People living with HIV who have a CD4 count over 500 are usually in pretty good health.
• People living with HIV who have a CD4 cell count below 200 are at significant risk of developing serious illnesses. While HIV treatment is recommended for all people living with HIV, it is especially important for people with low CD4 counts.

If you have HIV and do not take HIV treatment, your CD4 count will fall over time. The lower the CD4 cell count, the greater the damage to the immune system and the greater the risk of illness.

When you take HIV treatment, your CD4 count should gradually increase

HIV POSITIVE Vs AIDS

HIV POSITIVE Vs AIDS

AIDS (Acquired immune deficiency syndrome or acquired immunodeficiency syndrome) is a syndrome caused by a virus called HIV (Human Immunodeficiency Virus). This virus attack on cells of the immune system & destroying or impairing their function which lead to progressive deterioration of the immune system, leading to "immune deficiency.” As the immune system weakens, the person is at risk of getting life-threatening infections and cancers and finally person have symptoms of AIDS.

 

Human Immunodeficiency Virus (HIV):

It belongs to the Lentivirus sub-group of Retroviridac family. HIV is an RNA retrovirus. The unique morphologic feature oh HIV is its cylindrical nucleotide in mature virion.The virus contain the 3 genes required for a replicating retrovirus – gap,pol and env. The virus has outermost envelope rich in glycoproteins (gp41,gp120,gp160) & inner core with two component protein (p18 ,p24).while the enzyme reverse transcriptase capable of the retrograde transcription of viral RNA to viral DNA mark its special feature. The incubation period seem to be long, ranging from 6 months to more than 2 years.

Inactivation of HIV:

10 minutes, treatment at 37 C can inactivate this virus, with 10% household bleach, 50% ethanol, 35% isopropanol, 0.5% Lysol & 0.3% hydrogen per oxide.

How is HIV transmitted?

The virus is transmitted person-to-person in any of the following ways:

• Unprotected sexual intercourse (vaginal or anal), and oral sex with an infected person.
• Transfusion of contaminated blood.
• Sharing of contaminated needles, syringes or other sharp instruments.
• Mother and her infant during pregnancy, childbirth and breastfeeding.

Listed below are health problems common in people with AIDS:

AIDS is characterized by pronounced suppression of immune system, the development of unusual neoplasm especially Kaposi’s sarcoma or wide variety of sever opportunistic infections. Other symptom include:-

• Loss of vision
• Coughing and shortness of breath
• Problems swallowing
• Severe and constant diarrhea
• Nausea, stomach cramps, and vomiting
• Fever
• Weight loss
• Feeling very tired all the time
• Seizures
• Pneumonia
• Coma
• Cancers of the skin or immune system

Treatment

There is no cure for HIV but some drugs are used in the treatment and prevention of HIV infection which is called antiretroviral therapy (ART), they fight HIV by stopping or interfering with the reproduction of the virus in the body, reducing the amount of virus in the body.

In the past, people with HIV infection would start antiretroviral treatment after their CD4 count dropped or they developed HIV complications. Today, HIV treatment is recommended for all people with HIV infection, even if their CD4 count is still normal.

If the CD4 count already dropped before treatment was started, it will usually slowly go up. HIV complications often disappear as the immune system recovers.

How is AIDS different from HIV positive?

HIV positive can be defined as when You have HIV but not have any symptoms that’s  mean HIV alive  in your body but they do not attack on your immune system i.e CD-4 cells  and some HIV tests will not show a positive result for as long as 3 months after infection. This is referred to as the  HIV test window period, and has to do with how HIV tests detect the virus.

Some people recently infected with HIV will experience some "flu-like" symptoms. These might include: Fever, Severe Fatigue, A non-itchy rash, swollen glands/lymph nodes, Muscle aches, Sore throat. Night sweats. These symptoms are called Acute Retroviral Syndrome and last from a few days to a few weeks.

After the acute phase, the virus typically becomes less active in the body for as long as 10 years, during which you might have no symptoms at all. An HIV test will still detect the virus during this period. This is one of the reasons that it's important for sexually active people to routinely get tested regularly - the signs of HIV infection are easy to miss or misinterpret.

AIDS can be defined as disease that later develops in people with HIV when HIV attack on CD 4 cells (immune cell) & continuing to replicate, leading to a gradual decline of CD4 cells and result in person are not able to protect himself from other infectious disease. Today, drugs make it possible for people with HIV infection to live a very long time before ever getting AIDS. How long you have the HIV infection before developing AIDS depends on a few things. Some of these things you can control, like taking your medicine on time every day.