AIDS  (Acquired Immune Deficiency Syndrome)
"AIDS is an epidemic disease, a potentially preventable, deadly infection for which there is no cure, no vaccine, and it is not under control."                                                                                                            -   National Commission on AIDS, 1993

 

More than 40 million people worldwide, are infected with HIV/AIDS and more than 3.1 million AIDS-related deaths occurred worldwide each year. Women are more affected by the virus than men. The Incidence of AIDS is higher in South Africa and the World AIDS Day campaign (December 1st) is aimed to raise awareness about AIDS. AIDS is the clinical manifestations or disease symptoms occurring due to HIV infection. Immune compromised stage of the infected person manifests this end stage.

H.I.V. = Human Immunodeficiency Virus. 
The Virus infection causes AIDS, the time interval between exposure to the virus and appearance of symptoms and manifestations of AIDS depends upon various factors, like: treatment, immunity of the exposed person, Cell mediated Immunity. 

A.I.D.S. = Acquired Immune Deficiency Syndrome. 

Please remember the World's AIDS day is on the 1st December every year

The HIV virus can spread through : 

Sex with HIV infected person.

Blood

Shared needles

HIV positive mother to her child

Some people infected with HIV may not develop AIDS for ten years or longer, but during this period, the infected person might not feel sick but can still pass the virus to other people. 

The course of HIV infection and disease progression may span for a decade.

Stages of HIV infections include :

1) Primary infection

2) Dissemination of virus to lymphoid organs

3) Clinical latency

4) Induction of HIV expression

5) Clinical disease

6) Death

The duration between primary infection and progression to clinical disease averages about 10 years. 

Death usually occurs within 2 years after the onset of clinical symptoms.

Following primary infection, viral replication occurs and the virus in blood (viremia) is detectable for about 8-12 weeks. 

Virus is widely disseminated throughout the body during this time, and the lymphoid organs become affected.

Since the epidemic began, an estimated 21.8 million people have died of AIDS (17.5 million adults and 4.3 million children under 15). 

An estimated 5.3 million new HIV infections occurred in 2000. During 2000, HIV- and AIDS-associated illnesses caused deaths of an estimated 3 million people, including 500,000 children under the age of 15. 

HIV eventually destroys many of the white blood cells, which protect us against disease. 

HIV infection leaves people helpless against many other serious infections and cancers. 

Different viruses invade different kinds of cells. HIV invades and destroys helper T cells, the very cells that direct the body's defenses. By destroying helper T cells, HIV disables the entire immune system that protects us against disease.

Lymphoid organs play a central role in HIV infection.

Know Our Body's Defense System: The immune system is made up of many different kinds of white blood cells. White blood cells work together to protect us against disease-causing germs. White blood cells defend against germs. 

Blood and body fluids contain many small cells circulating around body called Red Blood Cells and White Blood Cells.

The RBC carries heme and iron that help in carrying oxygen around the body. The WBC fights against infection and there are many sub-types of WBC.

Macrophages identify germs - When a germ invades our bodies, macrophages gobble up the germ and display its surface shape, or antigen, for other immune cells to see.

Helper T cells direct the defense - Helper T cells spot the foreign antigen on the macrophage and begin to multiply. They alert other white blood cells and direct the body's defense.

Killer T cells destroy germs Alerted by helper T cells; killer T cells multiply and destroy the invading germs.
B cells make antibodies - B cells start to make chemicals called antibodies. Antibodies lock onto foreign antigens making it easier for other immune cells to destroy them.

Working together, our white blood cells can usually destroy invading germs. 

T-cells and HIV infection - 

There is a significant drop in number of circulating CD4 T cells at this early stage. 

An immune response to HIV occurs 1 week to 3 months after infection, when the levels of CD4 cell increases. But the immune response is unable to clear the infection completely, and HIV-infected cells persist in the lymph nodes. 

This period of clinical latency may last for as long as 10 years. Although very few infected cells are in the blood.

HIV found in patients with late-stage disease is usually much more virulent and harmful than the strains of virus found early in infection. 

Decrease of CD4 T-lymphocytes causes a decrease in Immune response and affects the lymphoid and non-lymphoid cell functions. 

Further Reading :

HIV and B-Cell function : 

AIDS infected persons show an abnormal B cell function. 

It produces an inability to mount an adequate immunoglobulin M (IgM) response against the HIV.

Monocytes and HIV : 

Monocytes and macrophages play a major role in the spread and pathogenesis of HIV infection. 

These phagocytic cells can engulf the virus. 

Monocytes express the CD4 surface antigen and therefore bind to the envelope of HIV.

The infectivity of monocytes with HIV suggests that the monocyte serves as a major reservoir for HIV in the body.

Neural cells and HIV :

Neurologic abnormalities are common in AIDS 

HIV encephalopathy, myelopathy, peripheral neuropathies, and most serious, AIDS dementia complex.

gp120, may be involved in tissue damage without actual infection of all cells.

It is speculated that gp120 may activate macrophages, microgilia, and astrocytes and cause the release of cytokines and neurotoxins that injure neighboring neuronal cells.

In HIV infected individual, a wide range of invivo antigenic stimuli seems to serve as cellular activators.
Other concomitant viral infections - EB virus, Cytomegalo virus, Herpes simplex virus, or hepatitis B virus can act as cofactors for AIDS.

The immune system recognizes HIV by its antigen shape. But, just when the immune system recognizes one shape, HIV may multiply and change the shape of its antigen.

HIV can "hide" from the immune system for a long time.

When HIV infects a cell the virus may make more viruses and infect more cells or lie quietly in a cell for a long time. If HIV doesn't reproduce, the immune system can't find it and destroy it.

HIV destroys the immune system. The Immune system consists of Innate Immunity and Humoral Immunity Innate Immunity is Non-specific Immunity, whereas Humoral Immunity is specific Immunity. T-cells produce Cell-Mediated Immunity and B-cells produces Humoral Mediated Immunity.

As HIV destroys more and more helper T cells, the immune system begins to break down. 

Finally the immune system can no longer kill HIV or any other invading germs and a person infected with HIV is diagnosed with AIDS.